Jeep Strokers

ok right now My jeep when puttin around in the trails in 4wd it loads up real bad and won't run I have to go down the road and open it up to clean it out.. Itll run fine driving around but as soon as i start trail riding slow its terrible

Its a 94 YJ 4.7 stroker with 258 crank and rods .030 over pistons, .0040 head gasket, comp cam, banks exhaust torque tube back no converter, stock injectors.

I have about 1000 miles on the motor when i first built it i tried the 24lb injectors it ran way to rich and sucked to much gas. so i went back to stock injectors and it ran fine for the longest time now this just started a little bit ago

Things I tried
new oxygen sensor
new plugs and wires
new map sensor
new temp sensor
compression is all around 190
fuel pressure is 31 and 39
so those all seemed good


I will try anything just little confused right now don't know what else to try any help would be appreciated

I bet a dollar its a vacuum leak going to the MAP, causing the ECU to dump a WOT load of fuel into an idling engine.

I doubt its a vac leak. He would have noticed it at idle. Sounds like he has issues at lower RPMs. When at lower RPMs the PCM will favor the O2 sensor data and do anything to maintain that 14.7:1 AFR. Possibly O2 sensors? Describe exactly what happens at these conditions: cold start, driving around town, no heavy throttle, and under heavy throttle.

I'll bet a $2 towards an O2 sensor.

its at low rpms when im crawling around there is a brand new o2 sensor in there about 2 weeks ago thats the first thing i did


i checked for all vacuum leaks with a hose to my ear none

What type of O2 sensor did you use? snap in or the splice in?

Being that its at low RPM its not the injectors unless they are clogged and causing poor atomization.

Try checking for vacuum leaks using an unlit propane torch or some brake cleaner... if you find a leak the idle will change.
Have you tested the TPS or the temp sensor? Which temp sensor did you replace?

As a followup on the leak idea.
An exhaust leak before the O2 sensor will read lean and ECU will add fuel (unless over 80% throttle)
An intake leak will do similar.

check your intake/exhaust manifold bolts.

I did a click in 02 sensor
i did the temp sensor in the front of the motor
and no exhaust leaks
i did a vaccuum check with starter fluid no raise in idle

Check you COIL FOR CRACKS lately. They often crack and lose power and can cause rich running from weak spark. Mine was cracked on the inside near block where you couldn't see them without removing the two small bolts holding it to the ground bracket. Changing the coil did help mine, but a gremlin a bit like yours still exists within the heart of my I6 XJ.

Don Jr

On YOUR LIST, I didn't see the TPS. It can easily be checked with voltmeter by back probing a wire or two and seeing if it moves evenly to open throttle up to 4.8volts or so from just under 1 volt.

It reports to the MAP sensor, correct me if I'm wrong.

Jr

Don H Jr wrote: It reports to the MAP sensor, correct me if I'm wrong.

Jr

How so?

I'll have to dig around and check, but I think I remember reading that the info from TPS went to MAP sensor. I'll go out and check the wiring from TPS again to make sure, If I can get myself out there to look, lol! I just came back from oral surgery session and it hasn't all hit yet but it is starting to...ouchy!
Jr

Well i think I found the problem I changed my MAT sensor and wheeled last night for a couple hrs and no issues. I hope this solved the problem. I aprreciate all the lead I did check everything that you guys said Thanks

The air temp sensor?

MAT, I was wondering too, Silver. I know when I changed my MAT sensor made a huge difference; with it malfunctioning, I had black soot in my plugs and tailpipe for years. Also Silver, I think I misspoke on the TPS signal going to the MAP.

Don Jr

the book calls it a manifold air tempature sensor located right on the top back corner of the intake