jdjonesdr

Well, not exactly.

The Cherokee (90) has been doing pretty well since I got it up and running.

The only problems I've had is the occasional fast idle. First start in the morning it starts then dies, and the second attempt, it starts and keeps running. Sometimes with fast idle, other times with low idle.

When it has a fast idle, I shut it off and restart, and voila, slow idle. If I shut it off again and restart, fast idle again. I can do that time and time again, and it always reacts the same. Fast, slow, fast, slow. Weird.

But, other than that, it seems to run just fine.

Yesterday morning on my drive to work, I started and drove about 5 minutes, and it died, doing about 50. Pulled over, it turned over fine, but wouldn't start. Waited for 3-4 minutes, tried again, and it started.

Same thing happened today. Started it up to drive into town, drove about 5 minutes, and it died, going about 35 mph. (it was raining, btw)

Same thing. Turned over, but wouldn't start. After 3-4 minutes, tried again, and it started right up.

It's almost like there's a breaker that overheats, kicks off, and when it's cool, works again.

What do you think guys?

cruiser54

Probably a bad CPS and maybe a TPS.

:
Renix CPS Testing and Adjusting
　
　




Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.

Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.

The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.

Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.

You should get a reading of .5 AC volts.

If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.

Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.

A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.









　

　

Revised 01-26-2013

cruiser54

The above said, I would click on the "pink link" in my signature and do the outlined procedures in posts # 1, 3, 4, and 5.

jdjonesdr

Hi Cruiser, thanks for the response.

I've long since done the grounding renovation, and have good grounds all over the place.

The throttle Position Sensor is new, and I'm not sure what the CPS is, but if it's what's next to the Throttle position sensor, it's new too.

I've changed all the sensors except for the one down by the flywheel as part of my attempts to rejuvenate the beast.

Oddly enough, I have not had a repeat of the engine quitting in midflight, but the problem with the idle continues. Fast, slow, fast, slow.

It may be deteriorating though. I find that if I turn the engine off, and start it to have a slow idle, the idle is creeping up while I drive.

So, I can do the fast,slow,fast,slow routine, start driving with the idle around 500, and after a couple of minutes driving, the idle will be closer to 1000 rpms, and if I continue, it will inch it's way up to about 1300 rpm.

Shut off and restart, it's back to 500 rpm.

Edit: Found a picture, the CPS is the crank position sensor. The one down by the bell housing. I'm going to check it out, and let everyone know what's up.

Edit again: If I understand correctly, the CPS would give me the engine dying problem, but not the variable idle problem. Do I need to read some more?

cruiser54

Test the CPS. #7 in my link. Correct, will not cause the idle issues. would be good to get a reading from it. Takes just a minute.

Did you adjust the TPS?
Have you ever checked your intake manifold bolts to see if they're loose?
Ever cleaned your throttle body?
Ever replaced the oxygen sensor?

jdjonesdr

Yep, cleaned the throttle body. Replaced the Oxygen sensor. Intake bolts are all nice and tight. I did all of that when I first bought the beast. The air intake temp. sensor was not changed, because I can't find one to buy.

I just checked the TPS. It's not giving me the correct voltage perimeters now.

When I was checking it now, I remembered I had a shifting issue when I first bought the truck, so I threw in a used TPS. I did the voltage levels test, it was reading properly, so I made a mental note that it would need to be replaced with a new one down the road. Of course I forgot about it.

So now, a new CPS and TPS are on the way. I'll stick them in, and I'm betting the problem will go away.

Thanks for walking through this with me.

cruiser54

Adjust the new tPS on the engine side per my write-up. That's using the flat 3 wire connector.

I would do the drill mod on the new CPS also.

jdjonesdr

You can bet your sweet bippy it will happen. I'll let ya know once the parts arrive and are installed.

Thanks, big guy.

cruiser54

Rowan and Martin's Laugh-In. Goldie Hawn's launching pad.........

jdjonesdr

Yep. Some of us here ain't young'uns....