ProblemJeepIsRedundant

Hello everyone. I am new here and have been reading over a lot of your posts to find the answer to some problems I am having with my 1990 Cherokee 4x4 with automatic transmission. I should finally have some time to work on it this weekend, so lets see how well this goes.

Problem: Jeep decides randomly not to start in park and sometimes not in neutral. Reverse lights do not work at all.
Soultion: All indications are that the Neutral Safety Switch is bad. I will try the rebuilt first. Thanks to the links y'all have posted, that should go very quickly.

Problem: Jeep idles really low, around 500 rpms. Idles low warm and cold. When I am driving and I let off the gas completely, the Jeep will idle down and then stall out. Jeep still has plenty of power when I am on the gas. Gas mileage is also very poor. I have noticed that the spark plugs have a significant amount of carbon build up, but nothing unreasonable. I also noticed a small amount of black liquid spray from the exhaust. I could not tell if this was a small amount of oil or if it was gas mixed with carbon deposits as it had dried on my friends driveway before I noticed it. I have already tested the entire fuel system with the exception of the injectors. Fuel pressure is great and regulator is working properly. There are no known vaccum leaks.
Solution: I plan to check the IAC and the TPS to see if either is bad. I also plan to do a compression check. I'll start there and see where that gets me.

Any further suggestions that anyone has would be greatly appreciated.

This is my first Cherokee and I have had it for about a year. I used to own a 1972 Jeep CJ5. She had an 8 point roll cage, a 14" lift and was sitting on 44" tires. That thing chewed through rear-ends quicker than kids chew through candy. Man I loved that Jeep.

Willys55

Idle air control motor is the problem..........Welcome to CF

ProblemJeepIsRedundant

The NSS repair went pretty well. The directions were extremely helpful. I also had to repair some wiring for the left side reverse light as the towing wiring harness was poorly installed by a previous owner.

I purchased a new IAC ($62) and installed it. This did not change the way the engines runs at idle.

I was in the process of testing the TPS when my multimeter broke. I'll have to get a new one tomorrow.

Does anyone have any ideas as to what else might be causing the low idle or stalling?

Thanks

mike albo

map sensor maybe

ProblemJeepIsRedundant

I removed the throttle body and cleaned it up really well. Reinstalled that and replaced a few questionable vaccum lines. My Cherokee runs a little better now. She idles in the 600 to 800 rpm range, only occasionally dropping to around 500 rpms. Unfortunately, she still isn't running right.

I have not checked the map sensor yet.

113Cherokee

any check eng. light or anything. mine runs a lil rough at idle because the O2 sensor is going bad. mine is also throwing a code for it though.

ProblemJeepIsRedundant

Actually, the Emission Maintenance light came on shortly after I made that post yesterday. The brake light is also on, but that is probably because the park brake is broken.

I had a power steering leak a couple months ago. I fixed the leak, but the pump was already damaged. I am replacing the pump today, then gonna try some more to figure out the rest of this.

XJ Stryker

You seem to not mind reading and looking at stuff.

Try this link since you own Renix I always look here when I have engine problems.

http://www.lunghd.com/Tech_Articles/...iagnostics.htm


My guess is a worn CPS since it causes all kinds of problems and is always the culprit

ProblemJeepIsRedundant

Thanks for the Link. It looks like it could be very helpful.

The power steering pump was less than fun to replace. The pully broke when trying to remove it from the old pump. The old pully was made of plastic or some such crap. The new one is good ol steel.

ProblemJeepIsRedundant

So, without reason, my Jeep was running great on Tuesday. No stalling, not dropping in rpm's, nothing at all. I was confused, but certainly wasn't going to complain.

On Thursday I go to drive the Jeep to work... it won't start. She just keeps cranking over. I have not had a chance to see what the problem is yet.

It is never a dull moment when you own a Jeep (for one reason or another).

pbudzy

or filter.

ProblemJeepIsRedundant

Sorry for bringing this thread back up, but my problems have resurfaced. I was using my jeep just for towing and hauling stuff around until recently, when some old lady decided to smash the hell out of my mazda. The Jeep's problems were not bad enough to concern me too much before. Now, I have taken to driving the Cherokee daily and the problems are making my commute difficult.

It is a 1990 Jeep Cherokee Laredo, 4.0L, I6, Automatic, 4x4

She starts fine but idles really low and rough when engine is cold. I have to tap the gas pedal to get it to start. I can drive fine, but she has extremely low power when accerating from a stop (I have to get the RPMs to about 1800 to go more than 5 mph). I have to feather the gas while breaking and stopping or she stalls out on me. She always restarts without an issue, but if the engine is up to temperature she will stall again right away unless I give it some gas. Fuel mileage it absurdly low under these conditions.

I checked the fuel pressure again yesterday and did a leak down test. Fuel pressure was perfect and fuel pressure regulator is working well. I am going to replace the fuel filter later today because it is past due.

I was laid off recently and am going back to school now, so I don't have the money to just replace parts until I find the problem. Any help figuring out this problem would be greatly appreciated. Thanks

ProblemJeepIsRedundant

Just finished messing with the jeep a little, trying to figure out what is wrong with it. New fuel filter is in and didn't change anything.
The IAC tested good.
The TPS tested good.
The MAP sensor tested bad. Repair manual says the voltages should be 4-5 volts across A and B with ignition on, actual voltage was 2. Voltage across A and B with engine running should be 2 volts, actual voltage was 1. Voltage across A and C with ignition on should be 4-5 volts, actual voltage was 2.
I guess I will have to shell out the money for a new MAP sensor.
Has anyone else experienced this kind of a problem from a faulty MAP sensor?
Other possible problems I have been told to check are the CPS, the O2 sensor, and the EGR valve. I was not able to get those tested yet.
Thoughts?

laidoff

You sound like you are having the same problem I've had. My Jeep is 1991 Cherokee 4.0 4x4 MT. I have done all you had (except the NSS) come to find out, in my case and maybe your worst case scenario, was that my "Camshaft sprocket Key" and the gear it's self had worked loose causing my chain to "skip". Offsetting the timing by 2 teeth, or however many degrees that is in real mechanic talk. So, after some Dremel grinding and a dab of welding I got the key in place along with a new chain. After, getting it all put back together I changed the oil and smelled a large about of gas in my oil. If I was a smarter man, I would have changed the oil first, noticed the gas and looked deeper into the mechanical timing. Instead, I was insistent it was a computer and/or sensor issue and ended up spending far to much money chasing sensors and electrical problems. But, Hey! I'll be ready for the Emissions test.

So, my advice to you would be, even if you have already done an oil change. Would be to drain some oil. Does it have a gas smell? Does it have water in it? If either of these do turn up try looking into the engines mechanical workings before you keep chasing down an electrical problem.

ProblemJeepIsRedundant

Thanks for the heads-up laidoff. I checked the oil level while I was working on the jeep earlier and the oil on the stick looked good. I can't say about gas smell because I had gas on my hands from the fuel filter. I will check that out tomorrow.