awdsully

I know there are many different threads with discussion on this problem, but nothing has really been helpful to my particular case so I have to ask for some helpful advice!

Specifics:
1994 Cherokee Country 4.0HO ODO shows 218k but previous owner claims motor was rebuilt.
Anyway, car started having a rough idle by dropping to about 500rpm and acting like it wanted to stall and occasionally would, especially when throttle was applied.

When throttle is applied from idle, it stumbles and eventually climbs to rpm. Leaving a really rich smell. After about 1500rpm it runs perfect.
To start I did a simple tune up with plugs, plug wires, dist cap, rotor, and a fuel filter. Also ran BG44k through her. Helped a little but still horrible gas mileage and rough idle running rich.

More recently I have done Throttle Position Sensor, MAP sensor, cleaned all around the throttle body and IAC. Also replaced O2 sensor, compression tested and all around 140lbs, and lowest being 130lbs. Fuel pressures came back fine, and there seem to be no vacuum leaks.

Ive currently got the injectors sitting in B12 injector cleaner, and after playing with a meter they all read about the same voltage.

I'm out of ideas! Please help!!
Thank you!

OleBlue

Unplug your new 02 sensor and drive it, see if the problem went away, if it did, your 02 sensor was a dud.

Also may need to reset your computer if u replaced the bad sensor and dont know it. Try the o2 sensor trick first. The upstream sensor.

awdsully

Update: injectors are cleaned with new o rings and it didnt seem to fix the issue. I tried OleBlue's advice and it didn't change the troubles. I am going to look at the coil and the two lines on the top of the valve cover and see if that changes anything.

There isn't much of any soot in the tailpipe, and the spark plugs look almost new.

1976Mustang

Did you try resetting the computer?

awdsully

The only way I knew how to try to reset everything was to unplug the negative terminal on the battery. I did that for about 10-12 minutes and then put it back together. If there is another way to reset I will definitely give it a try.

Thank you for help everyone!

Mendax13

Have you considered a vacuum leak?

awdsully

The HEEP is still running really rich, backfiring a lot more, and breaking up/ falling on its face in low rpm in gear. Any other thoughts? The exhaust is leaking, I just do not know if it is bad enough to cause this problem.
I am going to check timing and see if it helps anything.
Thanks!

jeepthings1995

if the leak is big enough and is before the o2 sensor yes it will cause drive ability issues b/c it will pull air into the exhaust stream so the sensor misreads and the computer richens the mix due to a lean reading by the o2.

JeepsAreForSpeed

try changing your map sensor vacuum line? That little inline check valve was messing mine up I just took it out fixed the problem. I think mine was right where it went into the intake manifold.

The Rooster

Your condition point to a possible map sensor problem... Have you check your jeep for codes? You have a 94 which has a obd1 system in it... It's easy to do just check it with the key trick

awdsully

From what I can tell, the exhaust leak is further back around the cat, but I have not really checked, so that could potentially be the issue.
I replaced the MAP sensor, but not the vacuum line so I will look at that as well thank you for all the help!!

I am not familiar with the key trick, I have had the codes read a couple times recently, and they came back with a faulty O2 sensor, so I replaced it. That was all they found in the stored codes though.

Thanks again for all of the insight! I appreciate the help!