Guess what?? another renix low rough idle.

[AKghandi]

Soooooo I am an idiot.

I hooked the ground jumper to the 5v sensor wire at the O2........

corrected it and we are back to square one. no more super surging idle but, we still have a low-er idle and a miss.


so what I did was force open loop. now whats strange is that when it was like that after fully warm it idled very smooth just very low.

that leads me to think its a sensor thats causing atleast part of my issue.

I suspect Knock even though its not hooked up I think its picking up interference. So I think I will cut the Knock wire at the ecu and wrap it in foil and tape.

either way that should eliminate it as a possible issue.

I am also going to check the timing with a timing light and see if I can learn anything. maybe i indexed wrong.

then i am going to double check the tps adjustment. i have checked it a thousand times but i keep reading i should adjust from the transmission side and get 4.82 volts.

 

[Ecomike]

Have you read my RenX files thread yet? Have you disconnected the battery to clear the ECM memory since you fixed the ECM-O2 power feed wire mistake?

Leave the Knock sensor wire alone IMHO. Timing light is waste of time IMHO. Did you change the throttle body idle setting? Maybe need to reset them again? Did you check the fuel injectors, and connections and wires to them for any loose joints, and check for stable fuel pressure while the idle screws up?

There is some awesome info on TPS testing in my RenX files thread here (search Ecomike RenX files), that is no where else. Check it out. You need to test both sides with an ohm meter. power off, then adjust one side, and test the wires to both sides and grounds on both sides and power feeds to both sides!!! The Renix TPS is 2 independent sets of wires and two sensors in one!!! Either side can muck up, but only the ECU side, 3 wire flat connector affects idle.

 

[AKghandi]

Have you read my RenX files thread yet? Have you disconnected the battery to clear the ECM memory since you fixed the ECM-O2 power feed wire mistake?

Leave the Knock sensor wire alone IMHO. Timing light is waste of time IMHO. Did you change the throttle body idle setting? Maybe need to reset them again? Did you check the fuel injectors, and connections and wires to them for any loose joints, and check for stable fuel pressure while the idle screws up?

There is some awesome info on TPS testing in my RenX files thread here (search Ecomike RenX files), that is no where else. Check it out. You need to test both sides with an ohm meter. power off, then adjust one side, and test the wires to both sides and grounds on both sides and power feeds to both sides!!! The Renix TPS is 2 independent sets of wires and two sensors in one!!! Either side can muck up, but only the ECU side, 3 wire flat connector affects idle.

I have not reset the ECM but I am not sure it really matters i keep hearing it either way.

I may just depin the knock wire from the ecu. i just want to eliminate ignition interference from the field.

I have wiggled all conections and the whole harness. no difference.

I want to hook up the timing light because i want to see if its related to the idle miss

 

[AKghandi]

Well I read through the renix files and decided to check my tps again.

.77v Bingo. set it to .828 and fired it up. it did the high idle thing so i unpluged and restarted and replugged and restarted and it was idling right at 750!!!

so i went for a drive. nice bump in power, but that may just be a mental thing.

got home and parked and let it
idle..750....700....650....600...550.....500....450...400...350.... MO********ER.

Well I am getting very near the end of my patience with this truck..:banghead::explosion

 

[Ecomike]

I have not reset the ECM but I am not sure it really matters i keep hearing it either way.

IT MATTERS!!! I HAVE PROVED THIS MANY TIMES ON MY RENIX RIGS. Just disconnect the battery for 5 minutes. Or cycle the on/ off key about 6 times, on for about 15 seconds, then off about 15 seconds. No need to crank it.

I may just depin the knock wire from the ecu. i just want to eliminate ignition interference from the field.

WASTE OF TIME, I HAVE 2 RENIX RIGS, 8 AND 11 YEARS WITH YEARS OF RUNNING WITH NO KNOCK SENSOR AND NO PROBLEMS WITH IDLE FROM THE DANGLING WIRE.

I have wiggled all connections and the whole harness. no difference.

GOOD!!!

I want to hook up the timing light because i want to see if its related to the idle miss

EVEN IF THE TIMING CHANGES WITH AN IDLE CHANGE IT PROVES NOTHING AND CAN NOT BE ACTED ON AS THE COMPUTER CONTROLS THE TIMING, NOTHING ELSE.

Better to put a dozen cheap $5 harbor freight ohm/volt meters all over the place to read voltages of sensors, alternator etc while the engine runs and watch for one that goes haywire when the idle swings low.

Have you checked the MAP sensor vacuum hose at the throttle body for any slop, loose connection?

Do not trust new parts!!!! 80% of new parts I bought at Auto zone the last 3 years croaked in days, weeks or hours if they worked at all. Not having much better luck with other sources either. Suspect everything and start over, checking everything.

I am under the impression that the current problem is a steady idle that suddenly drops and recovers, right?

Don't overlook wiring and parts like the fuse block and ignition switch!!!

 

[Ecomike]

Well I read through the renix files and decided to check my tps again.

.77v Bingo. set it to .828 and fired it up. it did the high idle thing so i unpluged and restarted and replugged and restarted and it was idling right at 750!!!

so i went for a drive. nice bump in power, but that may just be a mental thing.

got home and parked and let it
idle..750....700....650....600...550.....500....450...400...350.... MO********ER.

Well I am getting very near the end of my patience with this truck..:banghead::explosion

You need to check the TPS voltage at idle at those rpms!!!! Is the TPS voltage or ECM supply voltage changing when the idle changes!!

Also disconnect the idle speed controller again and see if the idle speed keeps changing.

Like I said before, bad TPS, bad variable grounds, dying ICM, worn dizzy cap and rotor, fouled plugs, variable vacuum leaks, bad or dirty Air intake temp sensor (can also cause hard starts depending on temps), bad CPS connection, multiple O2 sensor circuit/sensor issues, in some cases a cracked exhaust manifold, leaking intake manifold gasket, to name a few can cause idle speed issues. So can leaking puel pressure regulator they usually cause hard starts as well.

Is this idle problem temperature sensitive?

 

[Ecomike]

I once had low idle issues when I connected the O2 sensor or TPS wires backwards.

 

[AKghandi]

Well I decided to go further down the rabbit hole.

I pulled the ecm and checked what voltage the ecm was seeing from the tps.

at the ecm it was reading .70v so I ran a jumper wire from the tps straight to the ecm. then readjusted tps

reads .835 at the ecm now.

still idles low. so then i adjusted the idle bleed screw all the way out. perfect 750 idle.

took it for a drive and there is a definite gain in power but when I got home same story as before. but this time it idled perfectly for a while then after I shut it down and waited a bit and restarted, it went right back to the low idle.

Tps voltage stays in the 4.8x range.


every thing in the ignition side is new. cap rotor plugs wires icm coil even ignition switch.

intake manifold gasket is only a few months old and all bolts are tight.

fuel pump and regulator are new. injectors are used but in very good shape. I suspect they are only a few years old.


I depinned the knock input wire because my harness is not pristine. there was a small engine fire before I owned the truck. I took the entire harness apart and did not see any burnt or melted wires. so I re-loomed it. I just want to cover my bases. my missfire could easily be from interference pulling timing intermittently.



The current issue is that the idle will get lower and lower until its just above the first mark on the tach, and will bounce about 100 rpm. I'm not super concerned with the bounce it happens at 350 or 750.

I have worked at both oriellys and autozone. I buy napa or dealer parts if I can. if I cant, then I buy BWD from oriellys. no duracrap on my truck.

 

[AKghandi]

Reset ECM. no change.

One day I'll figure this out.maybe.hopefully.mightbuyatoyota..

 

[AKghandi]

https://www.youtube.com/watch?v=pK4KHe3sCnY

this shows the issue. which has remained through everything I have done.

 

[mtbxj87]

One of the things that helped mine when I had a low idle was getting the valve cover sealed up correctly. The gasket started to leak right around the time the low idle started. New gasket and filler cap, installed a different breather elbow, cleaned and sealed the vacuum line grommet. Mostly Took care of my low idle. Cleaning the IAC port and IAC pintle then using a little dielectric grease on the pintle helped a lot too. I know you've done that already.

 

[Ecomike]

One of the things that helped mine when I had a low idle was getting the valve cover sealed up correctly. The gasket started to leak right around the time the low idle started. New gasket and filler cap, installed a different breather elbow, cleaned and sealed the vacuum line grommet. Mostly Took care of my low idle. Cleaning the IAC port and IAC pintle then using a little dielectric grease on the pintle helped a lot too. I know you've done that already.

Now that you mention it, an entirely new vacuum harness and valve cover gasket did help solve the last low idle dip issue on the 89 Cherokee. Seemed odd too as the 87 has a leaky Vacuum harness in spots like the large supply line to the front of the valve cover. Also I controlled my low idle on the 87 at last by using a custom, hand made orifice size on the rear valve cover line. I experimented till I got what I wanted.

 

[Ecomike]

Regarding the video, possible sticking, partly plugged injector(s) unplugging then replugging, but that seems to be a stretch if the jeep drives and runs fine at higher engine rpms, and the idle is the only problem.

Sounds like too little air flow to me? Then a jump as the ECM tries to compensate and over does it. What does it do with the IAC disconnected?

 

[AKghandi]

I forgot to mention I revved the truck up in that video. it will sit at 300rpm all day long.. unless I have headlight and heater on.. then the battery will slowly die. which is the main reason I want to get this solved.

I will check what happens with the IAC unhooked tomorrow

valve cover gasket is new. I have a pretty good seal on the cap and elbow. brand new factory orifice tube.

i tried a larger orifice a while back. same issue.

only thing i have found to actually bring the idle up and keep it there is adjusting the throttle stop

noticed something interesting. sometimes when i rev it the rpms come down really quick and sometimes they just come down.

the only think i can compare it to is like a lightweight flywheel vs stock.

not sure if it correlates to the low or normal idle yet.


I have a whole intake manifold a new vacuum harness egr valve solenoid and tube to get my EGR working again. I may just swap it tomorrow. but then again it is like 15 degrees out there..


there are no restrictions in the intake, actually its better than stock with the cowl intake. so it would have to be sensor or maybe mechanical. the truck sounds like it has a rod or lifter noise.

 

[blondejoncherokee]

is the idle bypass screwed orifice all clogged? side of the throttle body, not the IAC?

 

[AKghandi]

is the idle bypass screwed orifice all clogged? side of the throttle body, not the IAC?

the entire TB is squeaky clean.

 

[AKghandi]

sort of off topic but i just rebuilt my egr valve

the rusty one is the one from my truck, the other is from the new intake manifold ill be installing.

the right one is from the new one, but the nipple is broken.
the left is the rusty one.

so i put the rusty cap with the good nipple onto the nice clean egr with a bit of high temp rtv.

obviously i cleaned all the rust out of the cap

nice and sealed and works like new.

saved myself $80 :greensmok


now i can get back to replacing my intake manifold.

 

[mtbxj87]

let us know if that helps your low idle issue

 

[Ecomike]

Many times I have adjusted the throttle stop and then the TPS to get the proper base idle.

 

[AKghandi]

well i'd say that was a waste of effort but we wont know till i run a tank through and see if atleast the mpgs improved.

idle is still the same. its not missing as much though much smoother.

not sure if the egr circut is working yet. ill have to look into testing procedures.