Starts fine, drives fine, bucks, sputters and dies randomly?

[Keithmania]

Here is a random thought. Could it be the battery? I had a friend with a Lincoln Mark V and when driving would randomly shut off, sometimes sputter till it died or just die. Turned out the battery had a bad cell...

 

[cruiser54]

One of my favorite things to do on these old Jeeps is to grab a can of good electronics cleaner and unplug every engine management connector in the engine bay one at a time and spray/flush each one and plug it back in.

 

[tayman]

Chris, are they old and used stock injectors? or are they new? I think for this stuff I should go with new ones to avoid the "oh it's not that, crap maybe it is" way of thinking.

BigBuilt: it's not acting like CPS issue. Been there twice on my own rig and a time or two on a friends...

Ecomike: I think that replacment is probably the way to go with my jeep. It IS my DD, and I'd rather not have another 21 year old sensor die when I"m 300 miles from home on a trail somewhere... That being said, it WOULD be good to know exactly which fix fixes the issue. I think I'll start with a TPS and FPR and go from there?

Keithmania: Battery is a deep cycle blue top Optima. 800amp I believe. Holds a good charge, I seriously don't think that's the problem here.

 

[Keithmania]

. I think I'll start with a TPS and FPR and go from there.

Right on.

Was also thinking though: do the old Renix systems have crankshaft position sensors? If its failing intermittently would it give the same results as a failing TPS?

 

[Ecomike]

Right on.

Was also thinking though: do the old Renix systems have crankshaft position sensors? If its failing intermittently would it give the same results as a failing TPS?

You can start the Renix with no TPS attached. The CPS must work to get a spark and fuel. No CPS signal, no spark, and no fuel. How well the CPS works is the next question, same for the TPS. The TPS is high wear rate, moving contacts part, the CPS is not, it does not wear out. The CPS in the Renix (87-90) is a different style sensor than the HO models (91-up). The Renix CPS has been known to give early symptoms of going completely bad. I had a brand new one for 4 months that gave early signs of going bad, but was unable to confirm the cause until it complete died, it went completely open circuit inside.

 

[tayman]

You can start the Renix with no TPS attached. The CPS must work to get a spark and fuel. No CPS signal, no spark, and no fuel. How well the CPS works is the next question, same for the TPS. The TPS is high wear rate, moving contacts part, the CPS is not, it does not wear out. The CPS in the Renix (87-90) is a different style sensor than the HO models (91-up). The Renix CPS has been known to give early symptoms of going completely bad. I had a brand new one for 4 months that gave early signs of going bad, but was unable to confirm the cause until it complete died, it went completely open circuit inside.

As previously stated, the CPS is still "relatively" new... I've replaced it because the old one went bad. What tells me that it's probably not the CPS is that it starts right back up after it dies.

 

[tayman]

Interesting thought that I just realized... Could this be due to something as simple as TPS being slightly out of adjustment? I just remembered that I took it off a while ago to clean it, and got it back to operational just "by feel" of what worked best.

I think the reason for cleaning though, was the occasional dying when cold, after a sudden backing off of the throttle. Now it dies when warm, and under power too...

 

[cruiser54]

Oh yeah. Adjust it before chasing any other possibilities.

 

[Ecomike]

If you cleaned the TPS with water or soap, you ruined it!!!! Even solvent cleaning may ruin it!!!!
This part "occasional dying when cold, after a sudden backing off of the throttle." may have been due to a sticking IAC in the throttle body, Idle Air control stepper motor, that controls idle air flow rates!!!

You must adjust the idle position on the TPS on Renix jeeps!!! Needs to be about .82 volts at idle. Also check the TPS ground wire!!!!!!! Needs to be less than 1 ohm to the negative battery post (power off)!

 

[fulltimer]

so true , just sprayed the crud out of mine with gumout and the motor now idles at 700 steady and it idles smooth as new now , used to idle at around 300 and a little rough , guess the iac is workin smooth again.

 

[Ecomike]

so true , just sprayed the crud out of mine with gumout and the motor now idles at 700 steady and it idles smooth as new now , used to idle at around 300 and a little rough , guess the iac is workin smooth again.

For those that are following here, now and in the future, it was IAC and NOT the TPS he used Gumout on!!!! Gumout would ruin a TPS!!!!!

It is also a good idea to add some lube back into the thread area of the IAC after cleaning with a strong solvent!!!!

Myself, I would not use gumout or a carb cleaner, as the toluene and MEK in those solvents can damage the varnish on the motor windings. Chlorinated brake cleaner or electrical part safe cleaner is needed for the job!!!

 

[tayman]

If you cleaned the TPS with water or soap, you ruined it!!!! Even solvent cleaning may ruin it!!!!
This part "occasional dying when cold, after a sudden backing off of the throttle." may have been due to a sticking IAC in the throttle body, Idle Air control stepper motor, that controls idle air flow rates!!!

You must adjust the idle position on the TPS on Renix jeeps!!! Needs to be about .82 volts at idle. Also check the TPS ground wire!!!!!!! Needs to be less than 1 ohm to the negative battery post (power off)!

I just wiped it off with a shop towel, no solvent I swear! same with the CPS as previously stated. I think I'll get a new TPS anyhow, to prevent future issues, and Get the new one adjusted properly. Hopefully Napa has one in stock.

 

[tayman]

Alright, the TPS is now adjusted. It wasn't correct before. I'm going to drive it a bit and see if it did anything.

I DID buy one from NAPA today, so whether it's bad or not, it's getting replaced.

 

[tayman]

OK: tested a couple more things: CPS is good, and I *THINK* the O2 is good. I didn't really find a simple explanation of how to test the sensor.

Anyway, I replaced the intake/exhaust manifold gasket today, so that also got rid of my #1 cyl exhaust leak.

Like I said before, the TPS is now adjusted properly, so I'll give it a few days and see what happens.

 

[f-a-t-b-o-y]

I have a 93 4.0 aw4 231. About a year ago i had the same issue. It did everything you were saying in your original post. After replacing various items, I realized i had a bad coil and a loose ground to the brain box. I fixed both at the same time, then never had a problem again. She purred like a kitten.

 

[tayman]

Brain box meaning ECU?

 

[cruiser54]

More than likely. Never hurts to remove the ECU plug, spray out both sides of the connector with a good electronics cleaner. While you're there, use a small pick to tweak the connectors so they grab the pins on the ECU a little tighter.........

 

[f-a-t-b-o-y]

*sorry ECU=brain box. That's just what i call it.

 

[1990JEEPXJ]

when my renix was randomly dying and stumbling it ended up being the coil. had spark, but not enough to run. replaced it and never had another problem. i would have that checked out as well.

 

[tayman]

when my renix was randomly dying and stumbling it ended up being the coil. had spark, but not enough to run. replaced it and never had another problem. i would have that checked out as well.

Will do. Anyone know how to test this?