88 cherokee starting/stalling problem

[Edbrooks]

6-4.0/auto. Suspected CPS but resistance readings (235 ohms) are correct. MAT resistance readings correct. MAP operating correctly.
When first started, drive off cold and the vehicle will hesitate or die completely. If it dies, the starter cranks, but won't start. Sounds like CPS, right? However, pumping gas pedal a bit will get it started. Sounds like TPS? Voltage readings on TPS are correct. When vehicle is warm, SO FAR there has been no problem. Two years ago I replaced the sensor in the distributor to correct a transmission problem (which it did.) Recently replaced O2 sensor. Coolant sensor tests OK.

Possibly connected: When first started, idles smoothly, after brief (two minute) warmup, appears to miss. Even when restarted hot, will run smoothly for approx 2 minutes, then return to idle miss. Fine at above idle. Suspected O2 sensor but it made no difference. O2 relay is operating.

Probable bad injector, so new set arriving and will be installed in a few days. Fuel pressure regulator tests OK. Fuel pressure within range, but bleeds off more rapidly than it should, and leaky injector is suspect. Plan to first replace all injectors and o-rings. If problem persists afterward, next step is TPS. Noted that Autozone does not sell TPS and CPS is special order. Any other sources of dual TPS other than the platinum ones at Jeep dealers?
Thanks

[Whitehouse813]

Mine was doing the same thing and the CPS fixed the stalling, and one new injector fixed hesitation, and just so you know, autozone does sell CPS's; thats where i got mine for my 96 Cherokee Classic. i dont know about TPS's though.

the one suggestion i can make it to put a noid light on each of the injector connectors to make sure the computer and electrical is all good up to the injector itself.
good luck

[Saudade]

AZ carries the TPS
http://www1.autozone.com/servlet/UiB...+UP%7C%7E00136

[viper1861]

Do a search for Tommy's Hi-Tech auto. Tommy is a Master mechanic and likes troubleshooting Jeeps. Not sure if they have a website but it's worth a shot.

Good luck

[stokleyjm]

my 4.0/auto 88 cherokee is doing something like that. It has been in three dealerships and had almost every sensor replaced , all the injectors,even the starter in an atempt to get more cranking rpm. the only way it will start somtimes is with a large helping of starting fluid.
The first sensor replaced was the cps it has never been right is there a likelyhood it was defective and i've just been sinking money in this pig($7,000)all a nickel and a dime at a time pluse the new motor and trans. I am about to dig a big hole and cut my losses any ideas

[viper1861]

I just added up all the charges for the problem I had with my Jeep and it was about $1500. Four times into the shop for the same symptoms with towing expenses and rental car fees.
Finally, I said screw this and had the car towed to a shop that actually diagnosed the problem and it was a $16.25 part.

It's all about finding someone talented enough to diagnose the problem. That generally means someone with an analytical mind and the ability to test circuits.

[bayouwolf]

Originally Posted by viper1861

It's all about finding someone talented enough to diagnose the problem. That generally means someone with an analytical mind and the ability to test circuits.

Finding a reputable shop is a hassle any more. It is almost worth spending 1600 bucks for the test equipment and finding out the problems yourself.

[viper1861]

With all the on-line diploma mills these days I would guess that one could complete a good portion of an automotive degree on-line.

Pay for the equipment by repairing a few cars and one would be set.

[Saudade]

With all the troubleshooting and repair guides available, I don't even think a "course" is needed unless you need to work on basic skills.

However, changing a part and diagnosing the bad parts are 2 different things. Given the sophisticated technology for diagnosing "modern" cars, it seems like working on the older, pre-ODBII cars is becoming a lost art.

[Edbrooks]

Yes Autozone carries the dual-section TPS (69.95) and the CPS (53.99) so I have ordered both. CPS is special order, but promises to ship in five business days. Thanks for the clues.

I spoke with a very nice ASE L-1 mechanic (whatever an L1 is!!) who advised me that it was indeed the CPS. He told me rather than paying him $180 to get and replace it, go do it myself, and save the bucks. Neat guy! Cost me nothing for that info. And quite a bit more, as we sat over coffee in his very clean shop and talked for a good half hour about my Jeep.

The TPS that is on the vehicle now can be set according to Chilton's setup procedure, and runs through the voltage smoothly, using a digital VOM. Did the same with an analog meter, but I decided to replace it anyway.

It is indeed hard to find a mechanic today. Every job I have paid a mechanic to do in the last 20 years I have - honestly - had to re-do myself. Every time. No exceptions, and with different mechanics and shops. I hope this one I found is a good one.

He advised me, though, that unless the vehicle is acting wrong at the specific time he hooks it up to the computer, it cannot be diagnoses. That bit of info for those of you planning to have your vehicles diagnosed.

Ed

[viper1861]

The Crankshaft position sensor sells even lower than that. I got one from the dealer for $45. It's hard to get to though so figure on getting your hands dirty. Also make sure you clip the wire to the spring clip on the bell housing so the CPS wire doesn't rest up against the manifold.

[Edbrooks]

FOUND IT! Nope, not the CPS, not the TPS. I have purchased both, and can't return electrical parts, so will toss them into the vehicle to carry in case I'm a "long ways from home."

Had the Jeep out yesterday, trying to locate problem. CluesHopefully this will help someone else)

Was dying about every 150 feet. Would restart easily. On some restarts, though, it ran very rough, had low power, top speed only about 20 mph. Stop, turn off, restart, and it was OK, but would then die in a couple hundred feet. During one of the rough-running episodes I decided to keep going, needed to get home. It ran, and did not die. But I was now doing about 20 mph, not 35.

I live on back dirt roads. Ah ha! Something Loose!! CPS connector? This morning I started it up, took a wooden dowel, poked firmly all around the engine compartment. It just kept on idling.

And then I hit the MAP. It died. Restarted it, and tapped on the MAP with just my finger. It ran rough. Tapped again and it died. Restarted. thumped the MAP, engine died. No wonder it ran fine on paved roads (the few times I could get to paved roads with it!) but died dozens of times on my roads at home.

AZ has the MAP for 33 bucks. I'll put one on tomorrow and if it does NOT solve the problem, I'll be back!

Ed