Riccccardo

My Cherokee starting stalling once in a blue moon about a year ago.

All I had to do was to wait for about 1-2 minutes, and it would start back up, sometimes with 2000-2500rpm and the drop to idle after a minute or two.

Last week it died on me at a busy intersection. I would start back up and as soon as it would reach idle RPMs it would stall and die.

Some friendly bystanders helped me push it out of the way. I checked the oil, and it was right at the low mark (shame on me), so I had my son pick me up and we came back later, added a quart of new oil, and it started right up.

It rand fine for a few days with the oil at the full mark when hot, so I figured I'm good to go. So yesterday, it dies on me at work when I'm trying to leave. I had already started to read about this issue on these forums and came across the TPS checks and adjustment procedure and throttle cleaning procedure.

Being stuck at work, last one out, I resorted to tapping on the throttle assy with a screwdriver handle, cracked it up and it ran. I made it about halfway home, 10 min, 8 miles roughly, when it died on me close enough to a grocery store for me to roll into the parking lot. This time, not matter what I did, it wouldn't start. Had son pick me up again and came back later after dark and it fired right up and got me 1.5 miles closer to home. Rinse and repeat the next morning and we get it to the house where I can work on it.

So, first thing I checked was the TPS, and it was bad, good input voltage, no output on the 3pin connector. Replaced the TPS, but the problem remained even after adjusting it to factory specs.

I replaced my negative battery cable to the block with a brand new one, cleaned the post, cleaned the sensor wire terminals, and for good measure, I added a ground from this same block ground to the firewall ground since I was not able to remove the block side end of the braided cable to replace it with something better. I cleaned all the surfaces with a brillo pad until everything was shiny, added a touch dielectric grease, and tightened it all up. The battery post connectors are now marine quality brass. I also replaced the battery charging wire from the terminal near the relay panel to the battery post since one end looked horrible.

When I went to O'Reilleys to buy all the parts to do the above (and below), I had my battery checked, and it is fine and strong. It's an O'Reilley brand battery (I forget what the brand name is, but it can crank the engine about 30-40 time no problem, that's without charging it)

I noticed some cracks and cuts in two of the spark plug wires, so I got a new Borg Warner wire set, and a new rotor and distributor cap by same company. Again, dielectric grease on all the contacts. I checked 3 of the the spark plugs, and they are light tan in color and still look good, so I left them alone since I'm low on funds.

Using throttle body cleaner I cleaned the throttle body assy, I used Qtips on the butterfly to scrub the edges, and I sprayed the IAC and its port (am I correct in assuming the IAC is right next to the TPS?).

I also replaced two vacuum lines from the manifold vacuum port just forward of the throttle body. the two little hard plastic lines going into the big vacuum disconnect block kept falling out of the block with minimal tugging, so i bypassed the disconnect with new hose going from the port to their respective two locations, one to the air cleaner box, and one to the elbow on the outboard side of the big disconnect block. This second line goes to the EGR solenoid. The line that goes to the MAP sensor has a second opening in the rubber grommet on the throttle body. I could not find any other lines that may go there, so I plugged that hole with golf tee for now.

So I started it up, and it ran fine, so I let it idle and warm up, and it seemed to run fine while warming up, even revving it here and there... I was happy with how much better it started up and it seemed to run a bit smoother from what I could tell.

Once it was up to temp, about 200 or so, I started revving the engine just a little, and presto, it stalled. I try to start it back up, it cranks, gets up to almost idle RPM, stalls and dies. Even after reading all the "stall" posts I could find on these forums I'm still a little lost.

Ideas anyone?

Here are my vehicle specs:

1988 Cherokee Laredo (2 door, short wheel base)
Renix I6 4.0l
4x4
Automatic
275600+ miles
Original engine and tranny.
Most everything on this Jeep is original (except for some of the hoses, spark plugs, other consumables etc) and what I replaced above.

I use Castrol GTX 10w-40 (or if I can afford it, AMSOIL Synthetic, whatever they recommend on their charts at time of order), currently Castrol, oil is light brown, close to oil change.

cruiser54

Test your CPS. It may be getting hot soaked.
Did you adjust that new 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

Riccccardo

Cruiser,

in your CPS instructions above, you mention that "you can have intermittent crank/no-start conditions" but I don't have a crank or start problem.

My engine fires up fine, even when hot, I can hear at least a few cylinders firing before it dies again, so I'm confused what this would have to do with the stalling engine issue.

I also spoke with three different mechanics about this problem before I posted this thread. They are no Renix experts, but without leading my questions, they all three mentioned the Manifold O2 sensor, which I don't have on this 88, but I do have the MAT sensor. According to the manual it should be 4000 Ohms or less at operating temps, but I didn't want to burn the gas to get it back up to operating temps today as it was 95% humidity and hot and I didn't want to overheat my body. By the time I got to measure it, it was 85 ambient and it measured 2007 Ohms.

I also had all three mechanics and two of my co-workers mention the MAP sensor. I checked what the manual claims to be the correct meter readings and I'm right on. I don't have a vacuum pump to check that part, tho.

Now, back to your CPS checks. Are you telling me that the CPS quits working alltogether when the engine reaches operating temps? That doesn't make any sense. Could you or someone on the forum explain to me how the engine can start and run fine with this sensor flaky, but then consistently die at 200+ operating temps?

Keep in mind, I am an Aircraft E&E (Electrical and Environmental [HVAC]) specialist and very familiar with laws of physics, especially electrical, hydraulic and pneumatic controls.

Something doesn't jive here... or I am missing some vital piece of information.

No offense, but I would like to get a little more details before I spend some more money I don't have (yes, $33+tax is killing my budget right now, we are eating bologna sandwiches because of all the other parts I replaced).

I did check the CPS and it reads .1 VAC when cranking, so it meets your replacement criteria, but the consistent engine temp shut down point doesn't make any sense to me, the CPS is connected to the bell housing which should moderate the temp swings, but then why does it shut down at night with ambient temps in the 60, but the engine reaches 200+ and it dies? The tranny bell housing should be different temps at 60 ambient vs. 85 ambient and air flowing across the tranny...

What am I missing?

Thanks

cruiser54

Electrical components can fail due to heat soak and/or high temps. It's the straw that breaks the camel's back so to speak. Work great cold, fail when hot. You need a CPS. Replace it after drilling the upper hole per my instructions. Gotta eliminate the known issue first, as your CPS is performing at 20% of what it's supposed to be . And that's before it gets hot. .

Riccccardo

I'm picking up a CPS on my way home. I'll let you know how I fare.

cruiser54

Gonna drill it?

Riccccardo

I don't know yet. I crawled under there and I don't know if I can even get to old one out, tight area to work in, and its 94F with 90% humidity. I can't hack that. Been like this all week.

I work in 62 air conditioned office/server space all day, anything above 80F is swelteringly hot to me.

Any suggestions on making the R&R easier when you don't have ramps or a pit?

cruiser54

It's a bear no matter what. I disconnect the front driveshaft so I can get my arms up in there. Either way, drill the CPS.

Riccccardo

How the heck do you get the CPS off without dropping the transmission down?

I can't get to the top bolt, and even the bottom one would be a challenge to get off. I'll have to take it to a mechanic to do this, I don't have the means drop half the drive train just to change this stupid sensor.

And guess what? I don't' have the money to take it to the mechanic, as all three of my mechanics charge $75-125 just to look at it.

I guess I'm screwed unless you can suggest some means of getting this thing out?

Riccccardo

I'm on my own with this and I also have vertigo, so when I shift positions I have to pause and wait 10-15 minutes before I can do anything.

Removing the drive shaft and possibly dropping the tranny down isn't an option for me.

Thanks for all your help, but I will be junking this car over this damn sensor.

cruiser54

Post up in your local area on CF for some help then.

Blue Angel

Where you located man?

peep

To reach those CPS fasterners, gotta use deep socket, three to four extensions, and a swivel on your ratchet. It's a pita but can be reached with trans in.

Riccccardo

I'm located in Moore, OK, near 27th and Santa Fe

Riccccardo

Cruiser,

I need to apologize. I have been under immense stress lately and I'm close to busting a gasket in my head, but that isn't an excuse for saying what I did above.

I do have the health issues mentioned above and struggle with that and a few other things, including not being able to handle this heat.

I will try to get my 17 year old son to help with this. He is skinnier than me and can get under there better.

If anyone else has suggestions or ideas or have change this sensor and have some techniques, please keep it coming.

Thanks all for being so forthcoming and helpful.