Problems! Rough idle, Gas Smell, No Power, Ect..

Hey Guys, Ive got a problem.
I was driving home the other day and the jeep ran fine. Parked it for around 30 minutes and went to move it and it had hell starting. It turned over fine just wouldnt fire. I got it to fire and drove it about 2 miles. Idle shuttered, no power, engine stumbled, and a strange odor could be smelled inside. The further I drove the more it lost power, especially from a stop. I started it up today and there was a strong fuel smell comming from the tail pipe. I did a complete tune up 2 months ago.(plugs, wires, fuel filter, ford 5.0 injectors, cleaned throttle body) 2 weeks ago I flushed the cooling system, replaced the thermostat and radiator cap. I bought the jeep back in January so im not sure of the service history. It has always idled a little rough, just thought it was the IAC valve.
I am looking for any ideas on where i should start to diagnose this. This is my daily driver so I am needing some help.

BDenglund
1991 Cherokee Laredo
147,000 miles
AW4
4.0

First guess would be the CPS. The CPS doesn't have to be all or nothing, it can just be failing and make the motor run like crap.

I'm not sure whether you can read the stored on board computer trouble codes or not in the 91. Worth a shot, along with a CPS ohm test. A CPS may ohm test good and still be bad.

The wires going to the CPS may be bad, especially if it has been replaced before and the mechanic neglected to get the wires back into the tie down clamp.

There are other possibliliteis but the CPS is the place to start in my experience.

I checked the codes using the ignition key process and all I get is the "55" code. So it's not throwing a code.

Check your fuel pressure.

Hey guys, I finally got around to checking the fuel pressure and with the ignition "ON" I get a reading of 5psi. After I start the engine the pressure is 35psi, and after I kill the engine it immediately drops back to around 5psi. It is still hard to start and stumbles. Thanks for the replys

Bdenglund

I also did a test on the CPS sensor and the AB terminals read 195 and the BC terminals read 1 (OPEN). This was all done on a cold engine.
Thanks guys

Stuck injector possibly. Since it does it cold it's probably dripping fuel in your cylinders over night. You can test it by pulling the inj rail and place a paper towel under it over night. By morning the paper towel (white) should be stained.

Talyn said:

Check your fuel pressure.

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Did the fuel pressure go to 49 psi in 1991, or 1996?

Might be a bad fuel pressure regulator (FPR), or an injector stuck a little open.

OP, if there is an FPR on the front of the fuel rail, check the vacuum nipple for a gas leak, if it is leaking the FPR is bad.

I've had the same problems as the original poster for almost a week. Just picked up an '87 XJ, 4.0L Renix. Ran horrible, no power, seemed like no throttle response (RPM wouldn't go past 25K without cutting out.

Checked compression 140-150PSI on all cylinders. 160,000 miles so not high mileage. I changed all plugs, cleaned throttle body, disconnected and reconnected TPS and IAC. Checked TPS sensor (working fine-readings didn't jump around as I moved the throttle. Fiddled with vacuum connectors. Yesterday, it ran great as far as power but the idle was still little rough and my neighbor yelled over that 1 spark plug must be bad. By process of elimination, number 1 cylinder was affected. If I removed the wire from #1 , no change in idle but any other plug wire removed and it ran worse so that means we have either no spark or no fuel at #1. Changed spark plugs on number 1 three times and wire as well so I believe it has spark.

I'm thinking clogged fuel injector but is there any way to test if the injector is getting the signal to squirt? I hate to remove the injector from the rail as I read somewhere that you have to replace the o-rings if you do and I don't have any supply. I'm going to measure the fuel pressure on the weekend. Any thoughts? Is it possible to swap out injectors to see if problem follows the injector?

Thanks!

You need a noid light to see if they're getting signal. If you dont have a mechanic's stethoscope take a long screw driver put one end to the inj body and the other to your ear (handle end). You can hear it ticking. Or unplug the injector

EFR98XJ said:

You need a noid light to see if they're getting signal. If you dont have a mechanic's stethoscope take a long screw driver put one end to the inj body and the other to your ear (handle end). You can hear it ticking. Or unplug the injector

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Thanks-That's a good low-tech method. I'll try it.

Ok just pulled the fuel rail with the injectors and turned on the ignition. Found the leaking injector. I put a paper towel under each one and #5 left a ring of fuel on the towel. I have emailed Precision about a replacement. Hope this fixes the problem!

Bdenglund

Keep us posted

I will. Just waiting to hear reply from the injector people. Want to say thank you again for the help. Much obliged

How long did you let the injectors sit?

They didnt set long, maybe 45 minutes. The jeep was a daily driver.

Anyone ever have hell getting Precision Injectors to respond to a problem?

Brett

Thank you to everyone for their advice!
Well I finally got the injectors from precision auto and installed them today. Seems to run as well as it was before the problems began. So I would say the leaky injector was the problem. I put the gauge on the fuel rail and it's holding pressure fine. The idle seems to be a little rough still, but not at all like is was when the injector was stuck. Anymore ideas to cure the rough idle.

Bdenglund

Did you reset the PCM? What size are those injectors?

I did reset the PCM. The injector size I am not sure though.