Restoring my 4.0’s lost power, where to begin? (LONG)

[Maz]

I am the original owner of my 1989 Pioneer. 4.0L, AW4, 231, 3.54, 215/75/15, bone stock, 280K miles. She has been on Penzoil 10-30 and Fram filter diet (which I'll switch with the next oil change) all her life, with an average of 3.5K oil and filter change intervals.

She sat for 18 months, and I recently got her started so I could get a smog certificate and renew registration. She was getting 18mpg, mostly freeway, before being side-lined.

She is a far cry from being "jack the rabbit" she was in her glory days. I am trying to find out if the engine is just too old and tired (therefore requiring a rebuild), or, if there are things I can do to bring her back to the best she "can" be, given her age. I am not looking for performance mods as I think it would be a waste of money on a tired engine. I am looking for advice on the logical sequence of things to R&R from cheapest (most likely to re-fresh) to most expensive being "don’t waste your money, she is dead." I am also trying to find out if her lack of power is engine-related or tranny-related, so I can focus on one or the other.

Here is the best I can explain the sluggishness. She accelerates fine (normal) on both flat roads, or climbing hills. She will get up to 80mph, climbing hills. However, if I step on her, she will only climb up to 3000 rpm. If I really-really floor the gas, she will spike to 3500 rpm, for 1 second, and then jump back down to 3000. The older days guts is not there.

She also makes a very loud "growling" noise, which is more pronounced under load. I am only including the noise here, in case there is a relationship between slugishness and it. The best I can describe this noise is that it resembles a bearing going bad but very muted sound. To me it appears to come from injectors and is not the typical ticing noise.

Here is a long list of her condition, based on lots of search and readings; anticipating your questions. TIA for reading my long thread and I welcome all, or part feedback, with suggestions.

I figured first order of the business would be a compression test. This is how I did it. Fully charged battery, engine warm, all spark plugs out, throttle fully open (gas pedal fully depressed), fuel pump relay out.

Readings:

(PSI) Cyl 6 to 1 (back to front)

Dry test, 2-3 cranks:
120, 107, 145, 110, 137, 127
Dry test, 5 cranks:
130, 110, 155, 120, 150, 135

Wet test (a bit of 10-40 oil in each cyl), 2-3 cranks
127, 125, 140, 130, 155, 140
Wet test, 5 cranks
130, 140, 160, 155, 170, 160

Factory specs call for 120-150 PSI with no more than 30PSI variation between 2 adjacent Cyls.

Oil pressure is:
42 psi cold idle
20 psi warm idle
45 psi highway speed (65mph)

Do I need to do a leak-down test? Do I have worn rings? I know the numbers say she is tired, but that shouldn’t limit the engine speed to 3500 rpm, should it?

Oil consumption:
She loses about 0.5 quart every 3000 miles. For the longest time I thought it was the combination of the rear/front seals and some oil burning. But after checking behind the valve cover, there is a lot of goop there. There is no smoke when she is warmed up.

Crankcase ventilation system (original)
I don't know if she has "blow-by". There is a bit of oil at the edge of the air filter.

IDLE
She’s never had high idle problem; if anything, she has a low (rough) idle. Cold idle is 750 rpm. When warm, the engine speed fluctuates 600-750 rpm, with a variable engine hum (is this called hunting?), with some engine vibration.

Maintenance history (with R&R mileage). I am trying to give all pertinent info.

FUEL:
-Fuel filter, changed every 2 years (10K miles since last change)
-Fuel pump (original), pressure: 35 psi, regulated
-TB, never taken off, or cleaned, it’s black in there.
-No FI cleaner has run through the fuel system
-Replaced injectors (106K miles)
-Corroded FI harness ends (see pic)

-Throttle valve cable (never adjusted, see pic)

-Fuel pump ballast resistor (original)

Note: She won’t start 1 out 5 tries until I wiggle the harness at No.6 FI. The dealer was unable to fix that (without explanation) and I’ve lived with it for well over 10 years.

IGNITION:
-Spark plugs (Champion), cap (OEM), rotor (OEM), wires (OEM), all changed every 2 years (10K since last change).
-Distributor (original, never taken off).

-CPS, (8K miles)
-Throttle Position Sensor (TPS, 201K miles), voltages:
-Manifold Absolute Pressure (MAP) sensor (original)
-Inlet Air Temp sensor (original)
-Engine knock sensor – (original)
-Idle Air Controller motor (original)
-Oxygen sensor (79K miles)
-Coolant Temperature Sensor (12K miles)
-Manifold Air Temperature Sensor (original)
-Cam Position Sensor (original)

TRANSMISSION:
-Fluid changed every 2 years (40K-45K miles).
-Filter changed every 4 years.
-She has had ATF (non-DEX) fluid most of her life. That’s what I get for trusting shops to know what the correct fluid should be.
-I replaced the fluid with Chevron DEX-III, last week.
-TPS / TCU ground by the dip stick is clean
-Fresh 7.5 amp TRANS fuse in the fuse box

-Catelytic Converter (79K miles), there is no rattle when I hit it.
-Muffler (84K miles)
-Air filter (10K miles)
-EGR Solenoid (brand new)
-Vac lines, (some original, some about 190K)

From my research, the possible causes of my engine/tranny behavior can be:
1. A plugged catalytic converter and/or muffler (easy fix)
2. Bad/out-of-calibration TPS (easy fix)
3. Throttle valve cable adjustment (easy fix)
4. Bad torque converter (completely clueless here)
5. Worn out distributor (completely clueless here)

I know Martin will tell me to replace all sensors. I will if ypu guys tell me there is life left in her. I also need to R&R the entire crankcase ventilation system as well as the vac lines.

At minimum, I am going to start her on BG44K/MMO/Seafoam fuel injection cleaning diet, and internal engine flushing using the synth oil method.

So guys, where do I start? Engine or tranny, and what do I do, and in what order?

Thanks a million for staying with me on this long thread.

_Maz

 

[Dr. Dyno]

Your cylinder compression numbers do indicate that there's some piston ring blowby but it looks pretty mild and your engine could easily go another 20-30,000 miles before needing a rebuild.
I think the most likely reason for the lack of performance is a plugged cat. I know you said it doesn't rattle but it's old so replace it anyway. It might just be the magic pill that your 4.0 needs. You can find a carsound high-flow cat cheaply on e-bay.
Adjust the TPS to factory spec and run some Seafoam or Mopar Combustion Chamber Cleaner down the TB to clean the engine's insides.
Let us know what the results are from these measures.

 

[5-90]

I agree with the good Doctor on the compression results - besides, what you are looking for mostly is consistency rather than absolute compression. You have a problem when there's a variation from cylinder to cylinder of more than 10% from mean.

Your air filter is cleaner than mine - so don't feel bad there.

Check the TPS as mentioned - after you adjust it, backprobe the pins and make sure that it changes value smoothly throughout the full range - it may have developed a "flat spot" over the last sixteen years. If it needs replacing, make sure you get the right one - the RENIX AW4 wanted a "double" TPS - the 3-pole goes to the ECM, the 4-pole goes to the TCU.

While you're at it, backprobe the MAP sensor - same check. It's a standard GM part, so it's easy to find. Ditto the IAT sensor and the CTS - which should probably be replaced out of hand at this point.

Change the HEGO sensor as well - 16 years of 1200*F isn't good for much of anything beyond a plain pipe. The RENIX HEGO sensor is a variable resistance type, which is a non-standard part. Make sure it's the right listing - but I usually use ACDelco or Bosch rather than OEMR (which is probably Bosch, but pricey.)

Mainly, you'll want to look into anything to do with fuel metering and timing, and renew that. The compression is nominal, I'd not worry about it too much. You are a candidate for a re-ring, but it's not critical yet.

Silly, but also check the torque on the manifold bolts. They like to get loose over time. You'll want to get a 9/16" "universal" socket to reach some of the rear ones on the underside - but the job is usually a half-hour to an hour well spend. It helps to get the airbox out when you go after the lower rear bolts.

And, cleaning isn't a bad idea - I've not used Seafoam, but I've heard good things about it. I usually use Berryman's B-12, which works well and can be used in the fuel, the oil, and the transmission fluid without trouble.

Electronic faults with RENIX control are rare - the only failed RENIX ECM I've heard of (blown injector drivers) is in a box under my desk - I got it from South Africa. The controls were made by Bendix/King Avionics under contract to Renault, and are the most solid damn things I've seen in automotive electronics. All four of my XJ's (87/88/89/89) still have solid control electronics - the lowest mileage I've got is about 150Kmiles on the second 89... I'm getting ready to restore the first.

Check the connection at the CPS sensor (11:00 on the bellhousing, looking forward) and make sure it's clean. Clean if not. Also check the wiring at the rear of the engine bay - especially the CPS and #6 injector. It gets hot back there.

I'd not worry about the FI connector you pictured - that's not corrosion, just old rubber. If you are really worried, Motormite/Help! makes a replacement connector that you can replace the old one with.

The only sensor I can think of that I'm not addressing here is the SYNC sensor in the distributor - but I've not heard of one of those failing just yet. To replace it, you have to pull the distributor, pull the gear off the bottom, slip the shaft out, and THEN you can pull the sensor. Technicall simple - probably about two hours' work!

Nice touch with the plug pic - they don't look too bad - just a little fouling. How many miles?

OH - VERY IMPORTANT!
If you have over 150Kmiles on your RENIX, and the injectors are still original, KEEP A CLOSE EYE ON THEM or REPLACE THEM NOW. Everytime we hear of an engine bay fire here, it's a RENIX 4.0 with lots of miles, and it was traced to a leaking fuel injector.

The RENIX injectors are known for leaking at the body seams over time, and since they are right over the hot exhaust, they're a great way to start a fire when they leak.

It will only take you about an hour to replace them, and you can use Ford 302 injectors without any trouble. Pulls are easy to find from people who have upgraded - get 19# or 20# injectors for your replacements. New orings are easily had from the dealer - a kit of 13 will run you somewhere between $10 and $15 (the odd oring goes on the fuel pressure regulator - it comes out the front of the fuel rail, and you should just go ahead and change that seal while you're about it.) Soak the new orings in clean fuel for 10-15 minutes before installing them. Don't forget to get a new QD kit if you take one apart - two if you do both - they WILL leak if you don't use a new set of seals. Expect those to go for about $10 per kit - and I'm working on an idea to be quit of those in favour of -4AN or -6AN fittings...

If you have any more RENIX questions, I'll be happy to answer. Given the choices, I'll take the RENIX over the OBD or OBD-II any time With four RENIX XJ's, I guess my preference is clear... Got another one you'd like to part with?

5-90

 

[8Mud]

I´ll give a list of things that I´ve found on my 88, that seemed to help in order of effectivness.
First was a new 02 sensor, then again, when I figured out the new one I´d bought, was flacky (wouldn´t idle correctly).
Cleaning most all of the connectors (except the 101), found one, with a 1 volt loss to the TPS and another with a bent pin. At the same time, I fixed the 02 sensor, engine temp, sensor and knock sensor harness, it was kind of melted and toasty.
TPS adjusment to about 86%, works for me. Tranny shifts just a little later (a couple of hundred RPM´s in the higher gears) than a stock setting. Leave the tranny switch in the sport setting.
Changed from ATF to Dexron, but it does take a few changes to get most of it out. Tranny seems to shift better after every change.
Grounds, added two, battery ground to front clip and oil dipstick holder to the firewall. One of the more noticable improvements was when I cleaned the paint from behind the firewall ground, from the head to the firewall.
Had a high resisitance coil to cap wire. Which made for a slightly rough idle.
Reindexed the distributor, which did seem to add a little top end, but not as much as the 02 sensor did. Was probably not necessary.
Changed the fuel filter out, to a Honda FI filter, which is about double the diameter, for a motor with half the cubes. My old filter was pretty dirty, I saved the fuel and junk (there was quit a bit) that came out in a jar, just for a look see.
Periodic loads of fuel injector cleaner.
TB cleaning, pay extra attention to cleaning the idle air adjustment oririfice and the MAP vacuum orifice, both of which were mostly plugged on mine.
K&N OEM replacement air filter, which was probably not necessary.
High flow cat. the old one, was still good, but I had it on a shelf and it fit with a little welding. Noticed a little improvement in accelaration.
Front whell Hub, grinding, which sounded like it was coming from the transfer.
Very slight vacuum leak at the MAP pick, up at the TB (the rubber stopper shrunk, where it plugs into the TB). A little dab of silicon fixed that and helps keep it from popping out on bumpy roads
Popped the sealed cap off of the idle adjustment screw and adjusted idle to 850 RPM (motor hot). A by product of this adjustment, is my voltmeter stays pretty much centered, volts were a touch low at idle.
Replaced most of the leaky gaskets and cleaned the top of the head, when doing the valve cover gasket. Which surprisingly quieted the motor a bit.
I´m doing body work now, but my next trip into the motor, I´m gonna replace the intake/exhaust gasket and fix my leaky exhaust manifold.
My compression is a little better than yours (not a lot, just a little) and my old iron is pretty zippy, runs good.
Replaced the radiator, with a 2 row GDI aluminum, which I bought, just because the parts place had it priced wrong (cheap). Kept the closed system. The radiator didn´t do much for performance, but along with a OEM themrostat, does keep a pretty constant temperature, which helps with some sensor tests and troubleshooting. Just as a side note, my closed system, actually works a little better, than the wifes 96, with an open system (also with a fairly new radiator).
Hope my list helps you out some, I imagine many of my problems are common.

 

[Maz]

I think the most likely reason for the lack of performance is a plugged cat. You can find a carsound high-flow cat cheaply on e-bay.

Adjust the TPS to factory spec and run some Seafoam or Mopar Combustion Chamber Cleaner down the TB to clean the engine's insides.
Let us know what the results are from these measures.

8Mud and 5-90, thanks for the long list of things to refurbish, check , and replace. I'll turn your recommendations into a check-list and go through all of it this summer. Most of tem seem easy enough.

I am glad to hear that there is a bit of life left in my 4.0. I am surprised that there was no comment about the fuel pump, and the throttle cable adjustment.

Dr. Dyno, thanks for the diagnosis steps. Here is an update:

Measured the TPS voltage:
Readings were; input 4.66 volts, output 4.00 volts, resulting in 86% which were outside the spec in my '89 FSM. The TPS torx bolts were loose. I adjusted the output to 3.82 volts, giving me 82%, per factory instructions. The test drive showed a bit of better responsiveness, but she still won't go above 3500rpm.

Next I fed the intake 3/4 of a can of Seafoam, through the brake booster hose, and let it sit over night. Started her the next morning, and I saw the humongo smoke cloud out the tail pipe, as I expected to see.
BUT, what I didn't expect to see was a cloud of smoke coming out of the manifold area in the engine bay. That tells me I have an exhaust leak either at the gasket, or, a busted manifold. I have to remove the bloody heat shield so I can see where it's coming from. I suspect the growling noise of the engine is because of this leak. BTW, cleaning the intake didn't help my situation (not getting over 3500rpm). It only stabilized the idle speed to somewhere around 850-900 rpm. I am happy about that.

I looked into hi flow CAT. I can get either Carsound or CATCO, both direct fit, from Summit. I am not an e-Bayer, and I don't mind paying extra to get the Cat from Summit. Is there a preference for one or the other?

I guess my next step is the overhaul of the entire exhaust side.

Again, thanks for all the advice. 5-90, tell me more about this universal socket. Got a pic?

_Maz

 

[Maz]

Why are my pics coming out huge. I resize them to about 200+ KB.

Sorry about this.

_Maz

 

[Dr. Dyno]

Re: Restoring my 4.0’s lost power, where to begin? (LONG)

I looked into hi flow CAT. I can get either Carsound or CATCO, both direct fit, from Summit. I am not an e-Bayer, and I don't mind paying extra to get the Cat from Summit. Is there a preference for one or the other?

Either will get the job done Maz. I'd say there's at least a 95% chance that the new cat will cure the problem of the engine not wanting to go above 3500rpm. The stable idle suggests that the fuel pump is probably OK but if the new cat isn't the cure, you might wanna check the fuel pump flow rate. It should be at least 1.0 liter per minute, with 1.5LPM being the nominal flow rate (90LPH or 24GPH). If that checks out OK, replace the fuel filter (I suggest you do that anyway).

 

[XJXJ]

CAT is a good idea and the O2 sensor can be checked for strong/rapid switching signal with a DVM when HOT. TPS adjustment is critical too and easy to goof-up if you don't understand why to adjust that AFTER the throttle plate idle position is set HOT with IAC closed.

Throw a vacuum gauge on there for grins too and make certain there are no leaks.

 

[old_man]

I agree with the cat, but there is another thing that might help the power once the cat is done. Injectors clog and carbon builds up over time. Run a can of BG44k through the gas. It will clean the injectors and loosen carbon. It might really help with those compression numbers. It runs around $20 a can but is well worth it. Don't even bother with the STP and similar junk. BG44k is in a catagory all to itself.

 

[Maz]

It might really help with those compression numbers. It runs around $20 a can but is well worth it.

Thanks "old-man" (Sure sounds funny calling you that)

Anyways, I am a bit surprised by your comment on improving compression numbers by cleaning injectors. Do you mind elaborating a bit?

Remember, the truck was driven less than 50 miles, after sitting for 18 months, when the compression was measured.

Would FRAM filter on there affect the compression numbers?

Would sludge build-up (she was on Penzoil all her life) affect compression numbers?

I'll take new measurements once I am done with most of the R&R's

Thanks a bunch for all the comments.

BTW, I finally found BG44K at a local gas station. They reluctantly sold me 2 cans for $14+tax, each. It was like I was taking gold away from them.

_Maz

 

[old_man]

The product not only cleans the injectors but removes carbon in the combustion chamber. I've done the tests with a bore scope. The stuff really works. When I built my stroker, it was running crappy. The injectors were used and had been sitting unused for about a year. I put in a can and before I got home, about 10 miles, the injectors had been cleaned and it ran perfectly. I run a can in each of my vehicles about every 10k miles. I have 200k on my Exploder 5.0L and it runs as good today as when I bought it.

I scoped an engine that had significant carbon buildup on the pistons and the back of the valves. After running a can, I scoped it again and the difference was simpy amazing. If I hadn't seen it with my own eyes, I wouldn't have believed it.

 

[5-90]

All it is is a socket that has the universal joint built into it - like this:

This gives you the little bit of flex you need to get around things, but the inbuilt joint shortens the thing by at least an inch, and really makes the whole thing go a lot easier.

All the big tool names have them, but everyone is at least twice as much as Sears - and the Sears one is just fine.

The two sizes that you'll want to have around are 7/16" or 11m/m (pretty much the same size - they swap back and forth like 3/4" and 19m/m) for the CPS, and 9/16" for the manifold bolts (it really helps on the lower back bolts!)

5-90

 

[Maz]

All it is is a socket that has the universal joint built into it
5-90

Thanks 5-90. Now I know what you are talking about. I have a metric set (Craftsman) that I bought when I did my Toyota pickup's intake gasket. Yes you are right, the are *very* handy to have.

_Maz

 

[Maz]

Throw a vacuum gauge on there for grins too and make certain there are no leaks.

Went to a friend's shop. Here is vac measurement for the grins:

17.5 - 18 in-HG, with the gauge needle mostly on 18 in-HG. He said the reading is good

Fuel pressure:
Regulated: 30 psi
Vac line at the fuel regulator disconnected: 39 psi

About the smoke from engine bay, i.e., when I fired her up with Seafoam in the intake, my friend said it's normal, and that, from all the cracked headers he has seen on Jeeps, mine doesn't sound cracked. But he couldn't really explain where all the smoke came from.

He played with the vac gauge while reving the engine up and down, and said that the CAT is not clogged. I'm going to go ahead with the CAT replacement, anyway.

Reporting the latest _ Maz

 

[8Mud]

Mine had a dead spot in the throttle at around 2000 RPM. it would stutter a bit and actually felt like the torque convertor couldn´t make up it´s mind to lock or unlock. It also would not rev any higher than 3500 or there abouts. A new 02 sensor cured that and changed my plug color to a light tan. It was running a little lean, under certain vacuum and RPM ranges (ran lean and crapped out at around 3500). It seemed to be running a little rich at idle and the IAC, was constantly changing the idle a couple of hundred RPM´s, in cycles.
You might want to get a new TB gasket and take off the TB and do a serious cleaning next time, the IAC seats, the idle air orifice and the MAP orifice. I had a lot of build up, in hard to get to places and some of it was really baked on there. I´ve given up trying to clean the TB with anything on there, I remove it all, the IAC, the TPS. I wraped one TPS in plastic and still managed to get some spray solvent into it, which required a replacement. I always tell my son, not to take shortcuts, I should listen to my own advice. If it´s running good now, I wouldn´t do a detailed cleaning of the TB (if it ain´t broke don´t fix it) but maybe next time.
Mine runs a little better with around a 86% TPS adjustment, but all XJ´s probably aren´t exactly the same. Seems to have better throttle responce. Remember the TPS, is two halves, one for the tranny and one for the ECU. Changing the TPS for tranny sperc.´s also changes the ECU/motor imputs. Most of the factory adjustments are for smog and fuel efficiency reasons.
When you get everything running well, a little TPS tweaking might be benefitial.
I don´t know if the heat shield actually does anything or not, but I remove mine, the first chance I get. Dremel, sharp cold chisel, whatever it takes (I would`t pull the fuel rail with old O rings). It really makes taking the manifold off, much easier and exhaust manifold inspection partialy possible. I´ve removed it on two other Renix models, never seemed to hurt anything. The newer models, don´t have it anymore, I think it´s mostly cosmetic.
Was 18 inches peak vacuum or vacuum at idle? Vacuum at idle, is most times, more important. a fairly steady needle with little or no pulsing.

 

[Maz]

Mine had a dead spot in the throttle at around 2000 RPM. it would stutter a bit and actually felt like the torque convertor couldn´t make up it´s mind to lock or unlock. It also would not rev any higher than 3500 or there abouts....... It seemed to be running a little rich at idle and the IAC, was constantly changing the idle a couple of hundred RPM´s, in cycles.

Sure sounds familiar. I am planning on the 02 sensor change along with the CAT change.

You might want to get a new TB gasket and take off the TB and do a serious cleaning next time, the IAC seats, the idle air orifice and the MAP orifice.

I want to do that as soon as I get a chance to buy a new TB gasket. It must be very dirty in there. 16 years, 280K miles, and nothing was ever cleaned in there. It took 1/2 hour to clear the smoke mushroom from using Seafoam. I'll also get a new TPS, regardless, and keep the current as spare. The IAC seat, and the orfices you mention, are they withing the TB?

I always tell my son, not to take shortcuts, I should listen to my own advice.

Part of being a parent. If you don't, your kids will keep you honest with your own advice

I don´t know if the heat shield actually does anything or not,

I really-really want to remove mine so that I can inspect the exhaust side. the growling noise on accelaration is driving me nuts. But my mechanic friend strogly advised against removing it. I suspect it is there for partial leak protection against fuel hitting the hot manifold.

Was 18 inches peak vacuum or vacuum at idle? Vacuum at idle, is most times, more important. a fairly steady needle with little or no pulsing.

18 inches of vacuum was at idle. The needle was not steady and was pulsing betwwen 18 and 17.5; but stayed on 18 most of the time. It fluctuated with the engine rpm.

The smooth idle (800rpm) that I achieved yesterday by using Seafoam has dropped down to about 600-650 rpm again. The smoothness was temporary.

Thanks 8Mud for all the detailed advice.

Cheers _Maz

 

[8Mud]

Sure sounds familiar. I am planning on the 02 sensor change along with the CAT change.



I want to do that as soon as I get a chance to buy a new TB gasket. It must be very dirty in there. 16 years, 280K miles, and nothing was ever cleaned in there. It took 1/2 hour to clear the smoke mushroom from using Seafoam. I'll also get a new TPS, regardless, and keep the current as spare. The IAC seat, and the orfices you mention, are they withing the TB?



Part of being a parent. If you don't, your kids will keep you honest with your own advice



I really-really want to remove mine so that I can inspect the exhaust side. the growling noise on accelaration is driving me nuts. But my mechanic friend strogly advised against removing it. I suspect it is there for partial leak protection against fuel hitting the hot manifold.



18 inches of vacuum was at idle. The needle was not steady and was pulsing betwwen 18 and 17.5; but stayed on 18 most of the time. It fluctuated with the engine rpm.

The smooth idle (800rpm) that I achieved yesterday by using Seafoam has dropped down to about 600-650 rpm again. The smoothness was temporary.

Thanks 8Mud for all the detailed advice.

Cheers _Maz

There is a cut out in the top of the TB for the idle air adjustment, then it goes down, through the hole/orifice by an adjusting screw and out the bottom. Some of the idle air adjusters are adjusted all the way in, so it won´t pass air. I´m not sure were the MAP vacumm orifice is inside the TB, I blew mine clean from the outside in, with solvent.
The IAC has a piston (rubber?) and a brass seat in the TB, the opening is (rather large, hard to miss) on the top of the TB in the Renix TB. Pretty easy to look down the hole (with a flashlight) and watch the IAC work the piston some, when working the throttle slightly. Removing the IAC isn´t a big deal, three torx fasteners /they have been known to freeze, remove with feeling or you may snap one off), but the "O" ring has also been known to give some trouble, be carefull how you install it again. And it´s best not to mess with the piston much (on the IAC), it can pop out of there if pulled too far (the book says it´s then an expensive throw away).
I´m jealous, 18 inches of vacuum at idle, is pretty darned good. Just for the heck of it, the next time you check your vacuum at idle, check with and with out the paper element.

 

[Maz]

.I´m jealous, 18 inches of vacuum at idle, is pretty darned good. Just for the heck of it, the next time you check your vacuum at idle, check with and with out the paper element.

Will do. I take it, from your statement, that the vacuum is good.

8Mud, I sure appreciate you staying with me on this with all the detailed how2's and education.

I will post back with the results of the CAT and 02 replacement. The more I drive her, the more she seems to be loosening up. Just an hour ago I ordered 2 TB gaskets and will take the TB apart for good cleaning, and to see if I can remove the heat shield with TB out of the way. I don't want to mess with the injectors yet. I took all the heat shield bolts out this morning just too see how it moves. I think by cutting it in half I can remove it.

Thanks again for all the good advice.

_Maz