Low Idle Renix Questions

I'll tell ya. There's a braided strap from the back of the head to the firewall. Remove it from the firewall and scrape the paint from under it. It's a POS anyway, so I recommend also adding at least a #4 gauge cable from the firewall to an easily accessed bolt on the intake manifold.

There are 3 grounds at the engine dipstick tube stud. They are the ground for very important sensors. Remove the nut, clean the wire terminals and before bolting everything back on tightly, make sure the stud is clean and shiny with no grease and no paint.

I also like to add a #4 wire from the negative battery cable to the radiator support. Make sure you scrape down to bare metal where you bolt it.
 
korn9613 said:
ive got an 89 xj and it has an adjustment for idle. right where the throttle plate sits at an idle is a screw, pushing the plate further away ( faster idle) or bringing it closer ( lower idle)
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I think we found "Uncle Bob". :roflmao:
 
cruiser54 said:
That's not for setting the idle. That screw should be backed out il the butterfly is totally closed. Then it should be slowly turned in til the butterfly just begins to move. It's there to keep the hard steel butterfly from beating itself into the soft material of the throttle body, not for idle speed adjustment. Just as bending the tab is not to be used for idle adjustment. Old man offers good advice here.^^^^^^^
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EXACTLY!

The technical name for that 3/32 Allen screw is: "the little Allen screw that keeps the steel throttle plate from slamming closed against the alloy throttle body and damaging the throttle body itself screw."

Set it correctly and leave it ALONE.
 
Your target idle speed, checked with an external tach, is 700-750 RPM AFTER 20 minutes of driving, i.e., when the engine (and auto transmission if so equipped) are fully warmed up.

The idle speed is CONTROLLED by the ECU/PCM that sends extend and retract signals to the IAC--idle air controller--which is a simple stepper motor.

If the sensors are not giving accurate data to the ECU/PCM there will be some wonky results. If the TPS is out of adjustment or bad the ECU/PCM will start making bad decisions.

Look out for "Uncle Bob"--he really gets around.
 
There are ground straps!?! Holy Sh*t! I think the only ground straps my XJ has is from hood to firewall and block to battery. lol

Voltage goes everywhere on the dash depending on hvac settings and headlights (Anywhere from 10-14.8v)

Mine must be grounding through the shifter or something... Ask me how I know to look there..

Got to add that Block to firewall ground ASAP!
 
Thanks for all the tips, I've got to deal with a more dangerous issue (first injector is spewing gas) first, then I'll check all the grounds.

Yeah, it may not be 200rpm, but it just sits on the first hash mark when its warm.

I'll report back with my findings
 
The first hash mark on the gauge is pretty low. With an OEM temperature thermostat you should be running about 205-210 degrees. OEM thermostat is 195 degrees.

That low of an engine temperature is going to have the CTS telling the ECU the engine is still in warm up and the ECU will extend the duration of the injector firing pulse to enrich the mixture--too rich of a mixture = lower idle speed.
 
joe_peters said:
The first hash mark on the gauge is pretty low. With an OEM temperature thermostat you should be running about 205-210 degrees. OEM thermostat is 195 degrees.

That low of an engine temperature is going to have the CTS telling the ECU the engine is still in warm up and the ECU will extend the duration of the injector firing pulse to enrich the mixture--too rich of a mixture = lower idle speed.
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Hmm, I must disagree on that one. I have run 165 to 180 F thermostats on Renix, both 87 and 89, for 6 and 3 years, and they both have good idle speeds, no idle speed problems, and both run closed loop in less than 30 seconds of start up. The 165 F used a little more fuel than the 180 F, and the MPG is a little better in summer than winter, which I attribute to higher intake manifold temperatures thinning out the air density.
 
Ecomike said:
Hmm, I must disagree on that one. I have run 165 to 180 F thermostats on Renix, both 87 and 89, for 6 and 3 years, and they both have good idle speeds, no idle speed problems, and both run closed loop in less than 30 seconds of start up. The 165 F used a little more fuel than the 180 F, and the MPG is a little better in summer than winter, which I attribute to higher intake manifold temperatures thinning out the air density.
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Hmmmm...

I'm certain you aren't implying that your rigs' terminal temperatures were 160/180 degrees respectively.
 
joe_peters said:
Hmmmm...

I'm certain you aren't implying that your rigs' terminal temperatures were 160/180 degrees respectively.
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Once they were warmed up in winter, they operated at 165-170 F (the 87 with the 160, or 165 F thermostat. I forget the exact value).

In the summer, at idle, with AC running, 100 F ambient, I try to keep mine under 200 F peak. They are both Renix.

The 89 gets 20 to 24 mpg, and has been running between 180 F and 200 F, winter to summer, with a 180 F thermostat for years.

But my point was that I have tested the Renix, two of them, and they go closed loop in less than a minute, even in cold weather. They do not need to be hot to go closed loop. I hear that the HO wants hot signals from the CTS to go closed loop.
 
Just a up date on mine, I got a new iacv and cleaned all my grounds, and added one more and everything is much better next it to clean the egr
 
rockcrusher said:
Just a up date on mine, I got a new iacv and cleaned all my grounds, and added one more and everything is much better next it to clean the egr
Click to expand...

The grounds are super important but most people just blow off that suggestion as being some kind of BS for some reason. Truth is, those of us who lived with these rigs when new at the dealership have seen the benefits of the factory recommended ground refreshing.
 
rockcrusher said:
Just a up date on mine, I got a new iacv and cleaned all my grounds, and added one more and everything is much better next it to clean the egr
Click to expand...

I wish that was all I needed to fix mine! I've done all of that and then some. My O2 was going out during all of this which did not help any but it idles worse and is getting worse mileage with the new O2:helpme:

I started a book about my troubles;http://www.naxja.org/forum/showthread.php?t=1056135
 
Ground refreshing, C101 cleaning and connection tightening, engine sensor connector cleaning and tightening,and ECU connector cleaning and tightening are often overlooked.

Sad part is it costs nothing out of pocket and very little time to perform these procedures. People just resist believing something so simple could solve their complicated running problems.
 
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