Renix Pinging

[5-90]

What? 5-90, me, and a bunch of others have completley blocked off the EGR with no ill effects. I think 5-90 says it actually made his put out less emissions. There have been absolutely no side effects to it other than a more reliable engine..

Like I said earlier, there is something extremely wrong about stangrcr1's engine. Maybe distributor play like that other guy said?

Also that's the first time I've heard of "Renix is known to run lean and thats why the exhaust manifolds crack". As far as I know, the manifolds crack on every single XJ (87-01) just as commonly.

Not trying to be offensive or condensending, this is just my experiences/what I've heard..

Stangrcr1, perhaps you have a big vacuum leak? That can cause a motor to run lean. You don't get any high idles do you?

Hey, when's the last time you changed your timing chain?

I have got to dig up those "before/after" tests on my 87 from right after I got it - it damned sure did run cleaner with the failed EGR valve...

And, as I understand it, the common "header cracks" in the XJ and MJ are more often due to failed/failing engine mounts, and the lack of a flexible section in the downpipe (between the collector flange and the first exhaust hanger at the crossmember.) This is per "reports from the field," and nothing official.

 

[8Mud]

What? 5-90, me, and a bunch of others have completley blocked off the EGR with no ill effects. I think 5-90 says it actually made his put out less emissions. There have been absolutely no side effects to it other than a more reliable engine..

Like I said earlier, there is something extremely wrong about stangrcr1's engine. Maybe distributor play like that other guy said?

Also that's the first time I've heard of "Renix is known to run lean and thats why the exhaust manifolds crack". As far as I know, the manifolds crack on every single XJ (87-01) just as commonly.

Not trying to be offensive or condensending, this is just my experiences/what I've heard..

Stangrcr1, perhaps you have a big vacuum leak? That can cause a motor to run lean. You don't get any high idles do you?

Hey, when's the last time you changed your timing chain?

I've run without an EGR with no ill affects I've noticed. It probably makes a difference under certain and specific vacuum conditions. Likely on the high side of the torque curve under load.
Exhaust manifold cracks are likely due to hot and cool down cycles, expansion and contraction. With some vibration and the design of the cross over section thrown in. I once found an exhaust manifold with about double the wall thickness of any other I've seen. It's still going strong (no cracks) after a couple of hundred thousand miles on two XJ's.
The Renix will compensate some for vacuum leaks. It may be leaking some vacuum and not raise the idle much. Though it may hunt at idle with the idle constantly changing (cycling every few minutes) a couple of hundred RPM. There is a tip over point though if the vacuum leak is bad enough. It's likely to get a vacuum leak that mostly affects a cylinder two, this often manifests as a rich idle and bone white plugs on a couple of cylinders at after a high speed run.

Common causes for pinging are a lean motor (either the whole motor or a couple of cylinders), hot (wrong) plugs, timing isn't retarding enough, low octane fuel (way low). I've run one step colder plugs on occasion, usually when I've worked far from home and done repeated hundred mile an hour runs up the interstate (autobahn). Pinging has really never been an issue with any of my Renixs, the octane here is fairly low with the standard grade gas.

You can often see warn timing chains and distributors with a timing light. Just point it at a dark spot and watch the rhythm of the pulses. It usually jumps around a lot, when the distributor or timing chain is seriously worn.

Is it possible your oil isn't making it to the top of your motor in sufficient quantities to dump enough oil on the rockers. I had one 4.0 with a partial blockage in an oil passage, the valve train sure enough rattled..

 

[stangrcr1]

Less than 1k miles ago, I installed a new front and rear main seals, rod and main bearings, oil pump and Cloyes double roller timing chain installed straight up, no advance or retard.
Oil pressure never goes below 30 even when hot. Plenty of oil on top when looking in the fill plug while running.
Ignition timing is as stated in first post, 14 degrees advance at idle(800rpm) and 30 degrees at 2500rpm. I think this is a bit much and the cause of my issues.
My exhaust manifold was cracked and that is why it now has the modified header. The stock manifold was cracked where #5 and #6 pipes went into the main pipe. I am sure this was from expansion\contraction issues, along with both motor mounts broken.
All the spark plugs I pulled out look the same, Black soot near the threads, clean ceramic and some tan deposits around the electrode tip and the ground post.
I have tried blocking off all the vacuum hoses at the intake manifold looking for leaks along with spraying carb cleaner anywhere I thought a leak might be. No leaks found.
The only reason I changed the knock sensor is I broke the old one while replacing the exhaust header.
Distributor is tight. I just replaced the sync sensor and checked while I had it apart.

I have been in the "throw parts at it till its fixed" mode for a few months now.

My biggest question now is "Could it be the new injectors making more noise when the computer calls for bigger pulse width?" As far as I know, the orange top injectors were made for a higher fuel pressure than what we run, and if it is low, could the injectors be starving at higher loads?

 

[mattbred]

My biggest question now is "Could it be the new injectors making more noise when the computer calls for bigger pulse width?" As far as I know, the orange top injectors were made for a higher fuel pressure than what we run, and if it is low, could the injectors be starving at higher loads?

Didn't you say it made the same noise even with the older injectors?

Damn man, sounds like you've completley rebuilt the entire front end. I'm not sure what to tell you other than it just shouldn't be pinging.

 

[8Mud]

Less than 1k miles ago, I installed a new front and rear main seals, rod and main bearings, oil pump and Cloyes double roller timing chain installed straight up, no advance or retard.
Oil pressure never goes below 30 even when hot. Plenty of oil on top when looking in the fill plug while running.
Ignition timing is as stated in first post, 14 degrees advance at idle(800rpm) and 30 degrees at 2500rpm. I think this is a bit much and the cause of my issues.
My exhaust manifold was cracked and that is why it now has the modified header. The stock manifold was cracked where #5 and #6 pipes went into the main pipe. I am sure this was from expansion\contraction issues, along with both motor mounts broken.
All the spark plugs I pulled out look the same, Black soot near the threads, clean ceramic and some tan deposits around the electrode tip and the ground post.
I have tried blocking off all the vacuum hoses at the intake manifold looking for leaks along with spraying carb cleaner anywhere I thought a leak might be. No leaks found.
The only reason I changed the knock sensor is I broke the old one while replacing the exhaust header.
Distributor is tight. I just replaced the sync sensor and checked while I had it apart.

I have been in the "throw parts at it till its fixed" mode for a few months now.

My biggest question now is "Could it be the new injectors making more noise when the computer calls for bigger pulse width?" As far as I know, the orange top injectors were made for a higher fuel pressure than what we run, and if it is low, could the injectors be starving at higher loads?

Run it up to TDC number one. Use a compression gage to get you close and make sure you are on the true number compression stroke. Put a couple of bends in a piece of welding rod and stick it on top of the piston, find true TDC piston all the way up. Turn the balancer with a wrench, make sure your last movement is clockwise facing the motor. May take a few tries and some fine finger tip feeling. But you will eventually get near true piston top, then check your timing mark alignment, it should be pretty darned close. You can also use a dial gage on the number one rockers to compare if need be, though taking off the valve cover again may be a last resort.
You may have to degree your cam/timing chain.
Though seriously, the ECU will adjust timing over a pretty broad range when out of a true TDC intial setup. I've had mine run pretty darned good with the distributor off by one tooth.

Does your motor ever buck a few times at certain RPM's. There was a TSB about re indexing the early 4.0 Renix distributors, they would run out of retard (or advance, i forget which) on occasion and buck. Some cams were ground a little off spec.

 

[stangrcr1]

TDC verifed when I put the timing chain in. Not sure about the cam, except the marks lined up. It did make the same pinging with the old injectors, and I do have a very early 87 as it was made 10/86.

It reminds me of an old Vega 4 cylinder that wouldn't go any faster with more pedal, only make more noise. My Jeep is the same as once the pinging gets bad, it only makes more noise, no more power, usually over 3k rpm. Is my cam that far advanced? Has really good power off the line but then gets weaker the higher the rpm. Really flat over 3k and pinging bad by then. The timing set does have 3 notches to advance/retard the cam 4 degrees and then straight up. Should I try retarding the cam?

I am about to give up and just drive it till it blows/breaks.

 

[8Mud]

Even if you've tested the basics once, it really won't hurt to double check TDC and the basic setup again. Piston to the top, timing marks aligning, push rods as low as they will go, rotor somewhat before the center of one at the distributor cap (somebody jump in if I have this one wrong, it's been awhile since I've done a distributor setup). I cut a hole in an old distributor cap just so I could see the alignment of the rotor in relation to the number one electrode in the cap.
More than one person has said, setting the static (motor not running) timing at 14 degrees will align the *center* of the rotor to the number one cap electrode (if I understood correctly) I haven't tried it myself though.
I had to re index the distributor on my 87, it would occasionally buck and would run out of torque above 3400 RPM's or so. I finally got a TSB recommending re indexing the distributor, which seemed to cure the problem. I had almost the exact same symptoms on my 88, but that turned out to be the wiring for the O2 sensor cooking on the exhaust manifold near the front of the motor. I'm guessing lean and timing have much the same symptoms. The lean burn O2 sensor thing (bucking) seemed to mostly disappear at WOT on my 88, but the motor would still crap out around 3000-3500 RPM, until I got the O2 sensor and wiring sorted out.
The torque setting for the knock sensor is supposed to be important, if I ever have to replace one I'm going to try and torque it to specs. A buddy put an HO in his Renix, our solution to the knock sensor, was to weld a threaded piece of flat steel onto the block at the stock location. Seemed to work just fine, so maybe the installation torque isn't as important as it's made out to be, or maybe we just got lucky..

 

[stangrcr1]

That is exactly what I did when I set it up the first time. TDC/pushrods/distributor on #1.

I am going to try the water misting tonight and if it doesn't help, time to delve deeper into the engine again.

 

[8Mud]

That is exactly what I did when I set it up the first time. TDC/pushrods/distributor on #1.

I am going to try the water misting tonight and if it doesn't help, time to delve deeper into the engine again.

Blowing all that junk through my motor by misting water down the TB makes my sphincter pucker. Speaking of misters,
I had a Holly mister (water injector) on my supercharged Dodge 360, worked great. Distilled water is a lot cheaper now than it used to be. The distilled water was a whole lot cheaper than octane booster and worked just as well if not better.

 

[stangrcr1]

I have already tried Seafoaming it twice without luck. Looking into the cylinders with a bore scope, it has some carbon buildup, but not enough, IMO, to be an issue. Still going to mist it and see what happens.

I am still curious on the injectors. I know the orange top Ford injectors fit, but were they designed for different fuel pressure? Different operating voltages? Different pulse widths? They seem to work well, but.....

 

[stangrcr1]

Well, I tried misting with water. A whole quart of water misted into the throttle body with the engine at 2000 rpm. Barely got anything out of the exhaust. No change in the pinging.

Screw it. I am just going to drive it as is and turn up the stereo.

 

[mattbred]

Can you get a video of the sound?

 

[stangrcr1]

I don't have a vid camera, or even a tape recorder that works. I am still in the 8-track days and a cheap bastard.

Just imagine constant pinging under load, and all the time over 2500 rpm. At cruise below 2500 rpm, it is nice and quiet. Light throttle and she is quiet. Reving it in the driveway with my ear near the injectors, it is hard to tell if the noise is the injectors themselves or inside.

 

[89CherokeePioneer]

On the knock sensor connecter, terminal A is ground-pin D8 on the ECM harness is where it goes. Terminal B is 'sensor input' at D16 (the bottom left) on the harness.

It only mentions testing with a DRB II. You use it to check the knock units, and it displays in number what it's getting for a knock signal. It may be worth checking the wiring between the knock sensor and the ECM-though some of us run no knock sensors and the ECM advances timing anyway with no ping.

Probably not spark knock at all.

 

[stangrcr1]

I don't have a DRB II, but I do have a Snap-On MT2500 that reads the computer. All the sensors show correct inputs to the computer. The knock sensor does show input, usually a 1 or 2.

I am thinking it is not pinging, but injector noise. Or something else entirely.

 

[Ecomike]

Some fresh ideas. Was the head ever milled thus increasing the compression??

Could the exhaust be partly blocked?

What is the history on the dizzy? Has it even been removed? Could it be off by one tooth?????

We have toyed with the idea of biasing the Renix O2 sensor towards a leaner fuel ratio by adding a resistor in series to the wiring, but I have conflicting FSM and Bosch Factory data as to whether that would make it run leaner, or richer. If it makes it run leaner, than a poor ground wire in the O2 sensor circuit, or poor connection in the harness connector might make it run leaner, unknowingly by adding resistance to the circuit.

How hot is the coolant system running?

What about a bad, biased CTS sensor. I don't recall seeing what all you replaced sensor wise. Also, a poor ground on the ECU to CTS / MAP / IAC / TPS sensor network might be involved. THey share a common sensor ground.

I can assure you it is not the fuel injectors making it run lean from your descriptions, as the O2 sensor and ECU, when working properly will compensate.

 

[stangrcr1]

I think the head was off at least once before I bought the jeep, but I have not had it off. No idea on if it had been milled.

Exhaust is all new from header, to high flow cat, to Magnaflow cat-back and out.

Distributor was much cleaner than the rest of the motor when I first saw it, but it has been verified to be in the proper position. TDC=rotor at #1 and sync sensor cam just entering sync sensor as described in the FSM.

I have added 2 ground straps from the battery, one to the engine (which now has 3), and one to the shock tower near the battery. I have the following ground wires installed: battery to engine (stock), battery to engine alternator bracket, battery to shock tower, and cylinder head bolt to firewall. All connections were cleaned and cables are new or tested.

Thermostat is a 180 degree unit due to the previous owner trying to overcome the stock cooling system and a worn out cap on the expansion tank on the firewall. I have since converted it all over to the newer 93up system without the expansion tank. On the temp gage, it never gets over the 200 mark. Just barely gets out of the blue range on the gage and sits there no matter how long it idles, etc.

I am not thinking the injectors are making it run lean, just that they make a lot of noise at higher loads.

 

[5-90]

Stupid question - have you gone over the engine with a mechanic's stethoscope to isolate the source of the noise? I don't think you've mentioned if you have (if you have, I've certainly missed it!)

Let me know if you think about getting quit of that MT2500 - I've been looking for one that won't break the bank for a while.

 

[stangrcr1]

Considering the noise happens mostly while I am driving.... I had thought about having the wife drive while I was under the hood listening but.... The noise is from the injectors, or the valves/rockers/etc. as it is right at the top of the motor, drivers side.

The MT2500 would not be cheap as I have a lot of newer cartridges (think I am only a couple years behind new now). Not for sale anyway.

 

[Ecomike]

At this point it sounds like your not sure it is pinging, so I would go get 3 or 4 other opinions from others, local mechanics and or local XJ members in your area to determine what the noise is.

If it really is pinging, I would get a knock sensor on there working first, then maybe look at cutting the tab on the dizzy and trying a setting between the dizzy gear teeth limits. Also, check all the sensors while the engine is hot for proper ohm & voltage readings, new sensor(s) or not and do the checks at the ECU to see if the ECU is getting good data or not. IF you find a bad one, back up to the sensor to see if it is wiring or the sensor causing the problem.

I have seen two or three styles of aftermarket knock sensors offered for the Renix, I suspect any one of them will work properly! Cheapest one I found was at Advance Auto.