1987 Renix High Idle Issue

N

NicksRenix04

NAXJA Forum User
Hi Folks, I'm new here. I'm 19, and I inherited my Grandpa's 1987 Renix Wagoneer about a year ago. Since then, I've learned a LOT about cars and it's been a fairly reliable daily driver since roughly last August. Now that most of the major things are ironed out on the thing, I'm slowly improving it and bettering the small things, such as dash rattles, interior, etc. One of the things I'm working on currently is its high idle that's driving me nuts! The idle isn't crazy high, but it's more than it should be. In Park and Neutral, its running about 1100RPM fully warmed up, and in Drive/Reverse it runs fantastically at about 8-850RPM fully warm. When I start the Jeep cold, it may surge to about 1100, then quickly make its way down to about 6-700ish. Throughout warming up, the Idle will lope and eventually make its way up to around 1k-1100RPM. I have no serious drivability issues though, and the thing never skips a beat. No random surges or drops, when warm It just lopes consistently around 1k-1100RPM in Park and Neutral when warmed up. If I turn the car off, and back on, it goes straight back to idling where it was, no funky ' idle resetting' or anything like that. The problem is consistent and I can count on it to do the exact same thing each day.

Some things I've replaced/ or done that may be relevant to the issue include:
-Replaced 2 main Vacuum Harnesses
-Replaced PCV grommet and line
-Replaced CPS & properly adjusted it (from Napa)
-Replaced TPS (from Napa) (Ground checked, around an ohm)
- New 195Tstat (Napa)
-Replaced 02 Sensor (Bosch 12009, great 0-5v swing on REM)
-Cleaned Throttle body & replaced gasket (stop screw doesn't seem to have been tampered with, gap between bore and butterfly is .003", left it alone)
- Replaced injectors with Bosch 823 Injectors & new O-rings
-Did Cruiser54's Tip 31, permanent Map line fix
-Snugged Intake bolts
-Thoroughly cleaned C101 (When I say thoroughly, I spent over 2hrs cleaning it)
-Reset the ECU (I know it doesn't store codes, but I've heard it stores fuel trim)
-Cleaned major grounds in engine bay
-New Fuel Filter, properly gapped plugs (.035), rotor, cap, and plug wires

I also did a vacuum leak test. I got one of those EVAP smoke testers from Amazon. I discovered a few Vacuum leaks.
-Two at the lower part of the airbox (cracked airbox, new one has been found, don't have it yet)
-One at the Map line Grommet (has since been fixed thanks to Cruiser's tip)
-One at the TPS? (looks like its coming from behind the TPS? IAC has a new O-ring.)
-One huge one at the EGR. (I did some poking, and the leak is NOT coming from the diaphragm part of the EGR where the vacuum line connects)

My main hobby besides working my Jeep is fixing old tube radios, so I know my way around a multimeter if need be. I also have a Renix Engine Monitor, if anyone would like some of the Data from that, I can provide it. I hope some of the knowledgeable people here can help guide my young soul in fixing this strange problem.
Thank you!
 
Welcome!! It's great to hear you're committed to getting the ol' XJ in tip top running shape. Perhaps we should all be committed! :)

I have an '88.

A few things. Sounds like you do have a vacuum leak. The one "behind the TPS", may be a worn shaft on the throttle shaft. Check out this video for clues and, if you determine that's it, how to fix it. One trick it to spray some starter fluid at the shaft, or use an UNLIT propane torch and douse that area with propane. If the idle drops, then that would indicate the leak is there. (Did I say unlit?)


Next, you mention the EGR. These are tricky little buggers. Do you have the transducer connected? Looks like a small saucer shaper plastic disk with 3 vacuum connections. Your EGR valve itself should have 2. The EGR looks like this:

egv608_front.jpg


This is the one in my '88. So the vac line from the solenoid next to the ballast resistor goes into the transducer, then the transducer connects to the EGR valve. Not sure it would contribute to a high idle, but can still cause some funky idle if it's not sealing properly. You can remove the egr valve and clean the ports if needed.

IMG_0028.JPG


When mine sits for a day or so (not a DD) and I go to start it, mine will also jump to a high idle at first, but then come back down to normal. When I first start it, I can hear the vents doors moving. If I shut down and restart (or restart an hour or so later) it goes to proper idle right away. I'm sure mine is due to loosing vacuum in the reservoir (located behind the front bumper) over time and the initial start results in sucking the air out if the HVAC system resulting in the momentary high idle. So are your vent doors working OK? Does it blow air out the right vents based on the setting on the HVAC control?

Cruiser54 is no longer with us (RIP) but there are a bunch of us RENIX guys still around. Glad you got the Nickintime monitor. He's been OOS for quite a while now.
 
Saudade said:
Welcome!! It's great to hear you're committed to getting the ol' XJ in tip top running shape. Perhaps we should all be committed! :)

I have an '88.

A few things. Sounds like you do have a vacuum leak. The one "behind the TPS", may be a worn shaft on the throttle shaft. Check out this video for clues and, if you determine that's it, how to fix it. One trick it to spray some starter fluid at the shaft, or use an UNLIT propane torch and douse that area with propane. If the idle drops, then that would indicate the leak is there. (Did I say unlit?)


Next, you mention the EGR. These are tricky little buggers. Do you have the transducer connected? Looks like a small saucer shaper plastic disk with 3 vacuum connections. Your EGR valve itself should have 2. The EGR looks like this:

View attachment 12006


This is the one in my '88. So the vac line from the solenoid next to the ballast resistor goes into the transducer, then the transducer connects to the EGR valve. Not sure it would contribute to a high idle, but can still cause some funky idle if it's not sealing properly. You can remove the egr valve and clean the ports if needed.

View attachment 12007


When mine sits for a day or so (not a DD) and I go to start it, mine will also jump to a high idle at first, but then come back down to normal. When I first start it, I can hear the vents doors moving. If I shut down and restart (or restart an hour or so later) it goes to proper idle right away. I'm sure mine is due to loosing vacuum in the reservoir (located behind the front bumper) over time and the initial start results in sucking the air out if the HVAC system resulting in the momentary high idle. So are your vent doors working OK? Does it blow air out the right vents based on the setting on the HVAC control?

Cruiser54 is no longer with us (RIP) but there are a bunch of us RENIX guys still around. Glad you got the Nickintime monitor. He's been OOS for quite a while now.
Click to expand...
Thanks for the warm welcome! Looks like you're here in SoCal too! Thank you for the information regarding the worn throttle shaft, I think thats a good possibility. With the help of a friend, I've been able to determine that at a minimum, my EGR diaphragm is not working. My EGR does not open nor close with vacuum (mouth tested with a rubber hose). So it will need to be replaced regardless. My EGR, does not have the UFO transducer-looking thingy. However, I have located a used & hopefully working EGR through a friend (it has the transducer and looks more like yours). Funny enough, I had a vacuum problem with the HVAC (only blowing out of defrosters), two of the lines going to that vacuum canister were broken, but patching those seems to have fixed my vents. It seems to hold vacuum for a while, haven't tested how long. I talked to Cruiser a few weeks ago regarding Injectors, the news hit hard.. I'm sure he's living it up with the Renix gods up above. I'm guessing that if the EGR doesn't do it, then the throttle shaft will be the next place for me to look.
 
Grab a wrench and check to make sure the intake manifold bolts haven't backed off. My '90 had a high idle problem that took me months to track down. Seems the original bolts had worn to the point where they could wiggle loose after a couple of hundred miles. I had to regularly tighten them and eventually, ordered a new set of bolts from NAPA and replaced them all. No issues since.
 
tjmotter said:
Grab a wrench and check to make sure the intake manifold bolts haven't backed off. My '90 had a high idle problem that took me months to track down. Seems the original bolts had worn to the point where they could wiggle loose after a couple of hundred miles. I had to regularly tighten them and eventually, ordered a new set of bolts from NAPA and replaced them all. No issues since.
Click to expand...
Thanks for the suggestion. I will double-check them when I replace the lower portion of my Airbox. I think I'm onto something with my EGR vacuum leak. I will keep the thread updated.
 
Well, the new EGR didn't do it. Did another smoke test, this time into the brake booster line rather than the throttle body boot, and the vacuum leak at the throttle body shaft has just about disappeared (might have been getting a false positive there when injecting the smoke into the throttle body boot, I'm thinking the smoke was building up pressure at the TB butterfly, and therefore leaking anywhere it normally wouldnt), and the leak at the new EGR is minimal, probably an amount that one may expect. Still Idling in Park/Neutral at around 1100RPM, and in Drive around 800. With the Jeep warmed up, I can see the pintle/reed in the EGR moving when giving the Engine a good rev, so I'm pretty sure it's working. Running out of ideas...
 
At least your egr works now.

So you can get a can of starter fluid or an UNLIT propane torch and spray the fluid/gas around the intake manifold, TB, FPR, air box, the vacuum harness junction, etc., and see if the idle changes. Don't firehose it with starter fluid, just a few quick spurts at each place. If there's a vacuum leak, it will suck in the fluid instead of air and the idle should drop momentarily. Same for for the propane but you can leave it on (did I say UNLIT!!). Same principle applies.

Or you can just start disconnecting and capping the vac lines not needed to run the engine. Cap the EGR off at the solenoid. Cap the vac port on the intake for the HVAC. Plug the line that goes to the top of the airbox. Cap/plug the brake booster line. and so on.

Double check your TPS adjustment. On my '88 I had to deviate from the spec to get mine to idle. You might have to as well, but first verify you have no vacuum leaks.
 
Saudade said:
At least your egr works now.

So you can get a can of starter fluid or an UNLIT propane torch and spray the fluid/gas around the intake manifold, TB, FPR, air box, the vacuum harness junction, etc., and see if the idle changes. Don't firehose it with starter fluid, just a few quick spurts at each place. If there's a vacuum leak, it will suck in the fluid instead of air and the idle should drop momentarily. Same for for the propane but you can leave it on (did I say UNLIT!!). Same principle applies.

Or you can just start disconnecting and capping the vac lines not needed to run the engine. Cap the EGR off at the solenoid. Cap the vac port on the intake for the HVAC. Plug the line that goes to the top of the airbox. Cap/plug the brake booster line. and so on.

Double check your TPS adjustment. On my '88 I had to deviate from the spec to get mine to idle. You might have to as well, but first verify you have no vacuum leaks.
Click to expand...
I opted to try the latter test. I unplugged many vacuum lines and plugged them with some Torx bits. In particular: The vacuum source that goes to the EGR solenoid, the hose on the intake that goes all the way to the vacuum ball, the brake booster line, as well as the vacuum source for the bi-metal temp sensor in the airbox. I ran the engine with all of them plugged, and there's no difference, still idles high around/above 1000. According to my REM, the TPS is at 17%, so it's correct. Whatever the issue is, it stays consistent. I can count on it to act the same way tomorrow. The engine starts up around 700rpm cold, then as it warms up, the RPM lopes/fluctuates consistently until it reaches around 1000-1100. Once it reaches that threshold, it continues to lope and cycle back and forth between 1000-1100. Rather, when in drive, it doesn't lope/cycle, and stays rock solid at about 800RPM.
 
90xj06 said:
maybe check and clean the IAC its next to the tps sensor. it might be stuck or not working. that's what actually adjusts the idle.
Click to expand...
Thanks for the suggestion, IAC is clean and not dirty, as I thoroughly cleaned the TB last week. On my REM, I can see the IAC drop from about 130 to 0 throughout the course of warm-up.
 
Saudade said:
Welcome!! It's great to hear you're committed to getting the ol' XJ in tip top running shape. Perhaps we should all be committed! :)

I have an '88.

A few things. Sounds like you do have a vacuum leak. The one "behind the TPS", may be a worn shaft on the throttle shaft. Check out this video for clues and, if you determine that's it, how to fix it. One trick it to spray some starter fluid at the shaft, or use an UNLIT propane torch and douse that area with propane. If the idle drops, then that would indicate the leak is there. (Did I say unlit?)


Next, you mention the EGR. These are tricky little buggers. Do you have the transducer connected? Looks like a small saucer shaper plastic disk with 3 vacuum connections. Your EGR valve itself should have 2. The EGR looks like this:

View attachment 12006


This is the one in my '88. So the vac line from the solenoid next to the ballast resistor goes into the transducer, then the transducer connects to the EGR valve. Not sure it would contribute to a high idle, but can still cause some funky idle if it's not sealing properly. You can remove the egr valve and clean the ports if needed.

View attachment 12007


When mine sits for a day or so (not a DD) and I go to start it, mine will also jump to a high idle at first, but then come back down to normal. When I first start it, I can hear the vents doors moving. If I shut down and restart (or restart an hour or so later) it goes to proper idle right away. I'm sure mine is due to loosing vacuum in the reservoir (located behind the front bumper) over time and the initial start results in sucking the air out if the HVAC system resulting in the momentary high idle. So are your vent doors working OK? Does it blow air out the right vents based on the setting on the HVAC control?

Cruiser54 is no longer with us (RIP) but there are a bunch of us RENIX guys still around. Glad you got the Nickintime monitor. He's been OOS for quite a while now.
Click to expand...
"When I first start it, I can hear the vents doors moving." That is usually caused by a broken vacuum tube near or that goes to the firewall under the coolant bottle.
 
How are your PCV lines? Maybe a vacuum leak there?
 
NicksRenix04 said:
Hi Folks, I'm new here. I'm 19, and I inherited my Grandpa's 1987 Renix Wagoneer about a year ago. Since then, I've learned a LOT about cars and it's been a fairly reliable daily driver since roughly last August. Now that most of the major things are ironed out on the thing, I'm slowly improving it and bettering the small things, such as dash rattles, interior, etc. One of the things I'm working on currently is its high idle that's driving me nuts! The idle isn't crazy high, but it's more than it should be. In Park and Neutral, its running about 1100RPM fully warmed up, and in Drive/Reverse it runs fantastically at about 8-850RPM fully warm. When I start the Jeep cold, it may surge to about 1100, then quickly make its way down to about 6-700ish. Throughout warming up, the Idle will lope and eventually make its way up to around 1k-1100RPM. I have no serious drivability issues though, and the thing never skips a beat. No random surges or drops, when warm It just lopes consistently around 1k-1100RPM in Park and Neutral when warmed up. If I turn the car off, and back on, it goes straight back to idling where it was, no funky ' idle resetting' or anything like that. The problem is consistent and I can count on it to do the exact same thing each day.

Some things I've replaced/ or done that may be relevant to the issue include:
-Replaced 2 main Vacuum Harnesses
-Replaced PCV grommet and line
-Replaced CPS & properly adjusted it (from Napa)
-Replaced TPS (from Napa) (Ground checked, around an ohm)
- New 195Tstat (Napa)
-Replaced 02 Sensor (Bosch 12009, great 0-5v swing on REM)
-Cleaned Throttle body & replaced gasket (stop screw doesn't seem to have been tampered with, gap between bore and butterfly is .003", left it alone)
- Replaced injectors with Bosch 823 Injectors & new O-rings
-Did Cruiser54's Tip 31, permanent Map line fix
-Snugged Intake bolts
-Thoroughly cleaned C101 (When I say thoroughly, I spent over 2hrs cleaning it)
-Reset the ECU (I know it doesn't store codes, but I've heard it stores fuel trim)
-Cleaned major grounds in engine bay
-New Fuel Filter, properly gapped plugs (.035), rotor, cap, and plug wires

I also did a vacuum leak test. I got one of those EVAP smoke testers from Amazon. I discovered a few Vacuum leaks.
-Two at the lower part of the airbox (cracked airbox, new one has been found, don't have it yet)
-One at the Map line Grommet (has since been fixed thanks to Cruiser's tip)
-One at the TPS? (looks like its coming from behind the TPS? IAC has a new O-ring.)
-One huge one at the EGR. (I did some poking, and the leak is NOT coming from the diaphragm part of the EGR where the vacuum line connects)

My main hobby besides working my Jeep is fixing old tube radios, so I know my way around a multimeter if need be. I also have a Renix Engine Monitor, if anyone would like some of the Data from that, I can provide it. I hope some of the knowledgeable people here can help guide my young soul in fixing this strange problem.
Thank you!
Click to expand...
I also own a 1987 Wagoneer, now at about 293,000 miles, and my fathers old radio tube gear, including his army surplus, WWII US Army Air core Ham radio gear. Congrats. Lets stay in touch?
 
Well, it's been a few months, and I thought I'd update the thread. The slightly high idle issue persists and has not changed one bit, It simply remains, only noticeable in Park and Neutral. I kinda gave up on it months prior and am considering giving it a revisit. I will say that I am rather skeptical of the IAC. The reason I say this is because the Jeep has never idled high to warm up the engine from a cold start, Which I think it is supposed to do? Someone correct me if I'm wrong. (Idles high to warm up, and drops Idle when warm?). Anyways, rather strange. Pretty sure the IAC is original too, but I guess it could also be a B+ Latch Relay issue (unless the IAC is sticking).

In the past few months, I did some small repairs. I re-ran the CPS wiring after having a Crank-No-Start issue (hasn't come back since I fixed it), and while I was in that area of the engine bay, I did Cruiser54's Tip #6 Sensor Ground upgrade, as well as installed a new set of cables from Jeep Cables. No changes in idle regarding the latter two repairs.

To answer some questions,
Bent- I got my 'new' (used) EGR valve from a friend in a non-smog state
Rarreola- I will keep this in mind. However, I think mine's fine since I'm able to adjust it to 17%?
Mewz99- PCV hoses are all brand new, Dorman parts from Napa
Ecomike- Very nice, lots of Miles on that thing! Very cool! Absolutely, We'll Stay in Touch.

If anyone has any more thoughts, suggestions, or things I can try. I'm more than open to hearing it.
 
In general, high idle must be too much air. Where that air is coming from, who knows. The fact that your REM shows IAC constantly decreasing means the ECU is trying to close off the air and lower the idle, but for some reason you're still getting too much. Looking at the Arduino code I don't think the ECU/REM reports IAC shorts, so this could be due to an IAC wiring or motor problem, or it could be elsewhere.

Check the throttle body idle air adjustment screw, maybe it got opened too far at some point in the past (it's behind a cap on the driver's side of the TB).

I'd get vacuum caps (I know you tried plugging with torx bits but caps should work a little better) and directly cap every vacuum port on the intake and see if it idles lower (don't leave the PCV/CCV capped long, but it should be ok for just a quick test at idle). Then use process of elimination to find the leak. Your Jeep should idle and drive just fine with only PCV/CCV and brake booster connected to vacuum. [Edit: and FPR]

If capping every vacuum port doesn't improve things, look for other areas that could be leaking - check the intake bolts like tjmotter said, check your TB gasket and bolts, check the EGR gasket...maybe even completely cap the EGR for testing only (the EGR plate from boxyjeep is $30 if you want an easy way to do that).
 
Last edited:
I have an 88 as well, and when I bought it and was bringing it up to specs doing all of Crusier's tips, (before I got a REM, should have done that first..LOL) I also got the CCV kit from NAPA and the idle was fine 650 in neutral (I'm a manual). I had been doing the Crusier MAP upgrade and broke the rear CCV plastic line and replaced it with a little larger rubber vacuum line, no big deal.. LOL. Spent the next 2 months chasing why my idle went to 850, and never thought about the larger line from rear CCV. Well put the correct size line on and BOOM back to 650, man are these RENIX finicky. So if you have put a different line from the rear CCV grommet, check there. FYI my permanent fix for the rear CCV was to put an 1/8" compression fitting into the rubber grommet and ran it to an 1/8" compression fitting in the manifold, the 1/8 copper tubing is the correct I.D. for flow and won't crack or break anymore. Just a thought for extra air causing high RPM?
 
Thanks guys. I will see about getting some vacuum caps. Looks like Amazon has some. I may try this over Thanksgiving break or early next month when college finals are done. Some other notes. I didn't find any of the intake bolts to be loose, all were tight. EGR gasket is also new, as well as the TB gasket. I'm a bit doubtful that both EGR's I own would have any significant vacuum leaks that cause the Jeep to idle high, no difference between the 'new' and the old.

On a bit of a different note. Out of curiosity, I decided to test the B+ latch this morning and make sure it is working properly. I determined that it is working, however, the 'time-delay' function does not seem to be working. If I am understanding this correctly. When the Jeep is turned off, power will remain applied to the B+ Latch Relay's coil for a few seconds (3-5sec)? This keeps the relay switched on, to feed power to the ECU in order to reset the IAC? Well, checking with my meter, the instant that the Jeep is turned off, the relay immediately switches off, it does not remain on for 3-5 seconds.
 
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