Erratic engine pulse width at idle

[XjJeepacorn]

Hey guys so I've been trying to figure this crap out for ever and after putting on a new Cps, tips, map sensor and a damn aic my jeep is still running like crap periodically so me and a friend just put a good code reader on it and when it starts doing the funky chicken the pulse with was going from normal it's seemed around 4.5 ish then it would jump to like 5. Something then up to like 9. Something 6 back down to for the. To 9 all crazy like, going to do some research but I was just wondering if any of you have run into this before and if you could give me any ideas on how to diagnose the problem thanks :)

[4.3LXJ]

Not sure what you mean. Pulse width on what?

[XjJeepacorn]

Fuel injectors sorry thought you guys could read my mind lol

[4.3LXJ]

Replace the O2 sensor?

[XjJeepacorn]

It's throwing that code too but The parts store is closed I'm going to get a new one. It was a high voltage code

[XjJeepacorn]

Un plugged it and it didn't make a difference in the idol

[4.3LXJ]

It wouldn't until the engine is warm. Then it will rely on it for information for the mixture which determine the pulse width. If it thinks it is shot or gone, the computer will be in limp mode.

[XjJeepacorn]

It's an intermittent problem thought because it'll run ok and then it acts up, so yes it's getting replaced but I think something else is there

[4.3LXJ]

Take care of the known problem, then go from there

[XjJeepacorn]

Yep, we'll see tomorrow

[XjJeepacorn]

I've been searching and the ironic thing is I found Simone with a similar problem and before he found out what was wrong the engine blew up and he put a new one in lol and then one other one person who described the same problem on a 4L and there are no replies to the post lol! Figures! Any way like ya said Steve lol maybe I go to bed and stop over thinking!

[Dredwolf]

Take care of the known problem, then go from there

Steve's advice is spot-on....I was dealing with my XJ literally cutting off and dying 15-20 minutes from the house, and refusing to crank until it had set for the night.

I pulled the codes, and was trying to fix everything else that was "known to be a problem" instead of the simple things first...

Turned out, my issue was the coolant temp sensor....the FIRST code the scanner found, but I ignored.

it was tricking the computer into thinking the engine was cold, and dumping too much fuel, the engine would choke, and shut off, and was literally flooding when I tried to restart it.

The computers are a pain, but computer sensors are simply switches...deal with the known first.

[gary63]

we had something like that around here two jeeps had a pulsing one would stop pulsing after it got warmed up good the other was just off and on. What we ended up finding was the motor was sucking alittle bit of coolent into the cyl. and the one when it got hot it closed the leak the other sometimes the leak was pugged and sometimes it was unpugged. The coolent was so little it took a mounth of watch it and other things to figer it out.

[XjJeepacorn]

Thanks for the tip! I'm working now but I'll let yas know what happens when the new sensors go on, until then my jeep is still being a bitch lol

[XJ Wheeler]

A bad head gasket/cracked head can cause an erratic idle. Hope its not that but may be a good idea to do a compression test if the sensors check out.

Sent via messenger pigeon - i talk, he types.

[XjJeepacorn]

Thanks, don't think it is the fuel pressure is different, that's why I didn't bother doing a pressure test. This is an electrical signal issue as far as I can tell.

[XjJeepacorn]

I replaced the o2 sensor and it runs fine now lol talk about freak out for nothing!

[4.3LXJ]

Glad it is running well now.