Cherokee_of_Tennessee

Sorry if this is a similar issue discussed somewhere else, but I searched the forums and could not find this situation.

Here are the facts:
1999 jeep Cherokee, 4.0 liter inline six cylinder
New fuel pump about 4 months ago
new upstream O2 sensor about 4 months ago
new #2 cylinder fuel injector and cleaned throttle body and IAC valve about 3 weeks ago
new battery positive and negative 4 gauge wires, new starter wire 4 guage, and new alternator wire 4 guage about 2 months ago.

Here are the symptoms:
Ever since I owned this jeep , the idle speed has always seemed low. Stays at 550 to 600 rpms. My other jeep, 1998 xj with 4.0 liter, always stays at about 800 rpm. About six weeks ago, the rpms were getting very erratic, would drop to 200 then surge to 1200. Engine light came on and the code said injector 2 was bad. I replaced the injector with one from autozone. All was well, but still had some slight stuttering and hesitation when pulling out. This morning, was on my way back home from physical training at about 6:45 am. I got up to about 55mph after engine was running for about 10min, and it started bucking and sputtering really bad. RPMs started dropping. When I stopped at a red light it died on me. Shifted to N and got it to start back up. Had to be very easy on the gas to keep it running. I also had to keep shifting into N. Seems like it wanted to die in Drive. Runs just fine with no hesitation or missing in N or Park. Put it in drive and it bucks like crazy. So I limped it home. Died on me 3 times. I pulled over and disconnected the upstream O2 sensor. No change. When I got home, I disconnected the downstream O2 sensor, no change. Last time this happened about 3 months ago, I disconnected the upstream sensor, and it quit acting up. Changed the sensor, and all was well until recently.

So after researching here, I tested the TPS with an analog meter and my $300 true rms meter. I got the following results:

1. Across the voltage supply wire and ground wire I get 5.17 Volts
2. From the PCM input to the ground wire I get 0.847 Volts at no throttle.
3. From the PCM input to the ground wire I get 3.970 Volts at wide open throttle. Check this 3 times, got 3.870 on 2nd try, and 3.840 on 3rd try.
4. With the analog meter, I get a smooth transition with no dips in the needle from 0 throttle to wide open throttle.

The TPS seems to be in spec according to the numbers I researched here. Supposed to be between .200 and 0.999 volts at 0 throttle, and 3.00 to 4.00 at wide open throttle, right? or did I read that wrong?

Then I sprayed brake cleaner around the throttle body and the fuel injectors. No surge in RPMs.

I am stumped. The issue gets worse when I turn left or right at low speeds, or backing up the hill in my drive way. Its as if when I put a greater load on the engine it makes it worse.

If anyone has any ideas, please help. This is my daily driver and I can't afford to have it broke down or undependable. Thanks!!

EDIT #1: I am getting a fuel pressure gauge from a friend tonight. But I really don't think it is a fuel issue.
EDIT #2: No engine codes show up when these symptoms occur

Cherokee_of_Tennessee

UPDATE: Just went to back the jeep out of the garage to shut the door due to storm. When I put it in reverse, it immediately sputters and dies. restart, shift to drive, no problem, shift to neutral, no problem, put it in reverse, it dies. What gives????

jordan96xj

Check that the bolts that hold the transmission bell housing to the rear of the engine block are tight. If they are loose, it can cause binding on the torque converter (especially in reverse), which in effect drags your engine rpm down and kills the motor.

Cherokee_of_Tennessee

Ok, all bolts are tight on bell housing. I just changed the distributor cap and rotor button just to eliminate that, and because I have no idea how long they have been on the jeep since I bought it used last January. No change.

Before I did that, I tried to start it up and pull it back in the garage. No start. it would crank and turn over, but no start. I could smell gas, and saw gas vapor?(blue cloud) coming out of the throttle body. Went to Oreilly's and got a set of plugs, wires, ignition coil, cap, and button. I disconnected the battery, changed the cap and button, reconnected the battery, and it started up. Put it in reverse, sputtered and died immediately.

What the hell has reverse got to do with it?????

I put it back in park. Put the fuel pressure gauge on it, with ignition on, I get 42psi. After start, the needle flutters between 50 and 52 psi. One thing to note, after I put it in reverse and it dies, I have a hard time getting it started. Fuel pressure stays at 52psi after it dies. If i turn it off under any other condition, it starts back up fine.

So after several tries, it finally got to where it would stay running in reverse. I took my foot off the brake, and gave it a little gas, and it sputters and dies. Start it back up, put it in drive, no issue, put it in neutral, no issue, put it in park, no issue, put it in reverse, sputters and dies.

I am at a loss here. Somebody throw me a life preserver.

MtnGoat

You pointed out that turning left/right causes the engine to die. So if this little bit of power steering load is killing it, why not the higher reverse gear? Thoughts...

My experience with the 4.0 is limited. I'll try to throw in some basics. Fuel, spark, air.
Fuel seems OK, almost too much. Air filter clean and no blockage? IAC valve clean and functioning? The other item (I loath to change) is the crank position sensor. Could this be causing spark problems?

Maybe one of the regulars here will chime in with more..

Good Luck

nujeepguy

if it runs in neut and "forward" the cps sounds good. the engine runs the same direction in drive and rev.
motor mounts letting it move in rev? causing wire trouble, just guessing...

Cherokee_of_Tennessee

From doing more research last night on naxja and jeepforum, among others, I got a feeling this may be a loose or frayed wire. So you may be right about checking motor mounts and seeing if the motor is moving enough to pinch a wire.
Any body have a suggestion as to where to start looking for a pinched wire that could be getting the insulation worn or frayed?

Cherokee_of_Tennessee

Is it possible that the power steering pump is so bad that it can drag down the engine and make it stall? The reason I say this, the power steering pump has been growling for a while, but not completely failed.

I checked and cleaned all the grounds(again), and the cables running down between the back of the engine the firewall. I could not find anything frayed, worn thru, torn, or loose.

I started the jeep up. Drove just fine for about 9 miles at 55 mph. Was going across a hill in a slight curve and it died. Got it restarted, turned around, started driving back. It started missing a little, but did not die. When I got to my turn, as I was slowing down it died. Everytime I slowed down to turn, it died. I cant be sure if it was turning that caused it to die, or if slowing down made it die. But it drove fine until it got heated up to normal operating temperature.

I don't think reverse had anything to do with it anymore. I think what ever is causing the issue is exacerbated by heavy load, such as low speed and trying to make a turn at low rpm.

One more thing, I have noticed a high pitched whine coming from somewhere around the fuel rail or throttle body. Having a hard time isolating where it is coming from. It sounds just like the whine or whistle from an old CRT television that has a bad flyback transformer. Very high frequency sound.

Still no engine code.

Does anybody have any idea?

MtnGoat

The motor mount on the exhaust manifold side (drivers) will go bad without your noticing.
Get a mirror and take a closer look from ground level

Cherokee_of_Tennessee

Well I think I fixed it. IAC VALVE!!!!!
Believe it or not, it looks like the IAC valve was not just dirty, it was actually bad. Thwre was no change after I cleaned it, so I marked it off the list of suspects. I have a friend that works at Oreillys by night, and does house call mechanical by day. He said it really sounded like idle air control issue to him. So, on his advice, I bought a $60 IAC valve, BWD brand, from Oreillys. No more bucking, sputtering, and the idle has smoothed out a lot as well.