Jeep Enthusiast Forums banner

Stalling and driving me crazy!

811 views 9 replies 4 participants last post by  Desertdweller87 
#1 ·
2010 wrangler unlimited 125k miles. Stalls at lower RPMs and when sitting at stop lights but only after driving for an hour or more. It will start right back up again. Originally thought I had a run or PCM relay getting weak/hot, changed them and made no difference. Then thought it might be the PCM but that doesn't add up to what the engine is doing. There is no MIL check engine light. Here lately it has been acting up sooner but then some days it takes quite a while before it dies Just before it dies the engine RPMs start to stumble acting like a vacuum leak and the RPMs stumble more when there is a load at idle like the AC running or having it in gear. I've replaced the PCV, battery has been replaced ALL power and ground connections under the hood have been wire brushed, cleaned and tightened. Throttle body has been inspected and cleaned. Have used carb cleaner to check for any vacuum leaks. Any thoughts? What's really throwing me is it will start right back up and run till it goes back to idle or the RPMs drop below a 1000. Any ideas would be appreciated.
 
#2 ·
Does it pop in the intake when you try to accelerate?- if so it is usually a sign of low fuel pressure. Nonetheless it can still be low fuel pressure. - eventually it should code (ie: fuel trim lean ). If it drives fine at higher RPMs even at near WOT then it likely isn't fuel related.

Now If I had to give my first gut feeling I would guess/look at a bad EGR valve. Your symtomes are typical of a bad EGR except for the "no check engine".
it is at the rear right (passenger side) behind the head and it's "exhaust" tube goes up to the top of the intake
Do you have access to a scanner?.... as a few data readings such as a high MAP- manifold absolute pressure reading...may indicate such leakage.
there may still be a history code (pending) even if it didn't light up the MIL.
Some codes require a couple of failures to light it.
 
#4 ·
No it doesn't pop, yes I have a scanner. No codes and map pressure stays relatively steady till it starts to stumble. Then as the RPMs drop the MAP pressure will increase as it trys to compensate for the drop in RPMs. It actually did it last night sitting in my garage so I was able to monitor it while it was acting up. Also didnt see any change in the EGR position when it happened. Changed the crank position sensor and it didn't make any difference. I also originally thought it was fuel related but the fuel pump doesn't care whether the engine is at idle or higher RPM. I've looked for a port to check fuel pressure on this 3.8 but don't see any port for checking pressure. Anyone know where to check fuel pressure on a 3.8 liter?
 
#5 ·
Is your jeep an auto or manual transmission?
 
#7 · (Edited)
If possible, I would like you to monitor the short term fuel trim data and the pos1 o2 sensor readings (both banks) while it stumbles- or rather just before it starts to stumble.
It will tell a lot about what is happening as far as combustion. Don't rule out that maybe there is a bad o2 sensor (ie shorts to power or ground )and that will cause a leaning out/or enrichment of a bank to the point of stumble.

If you see one bank go bananas first- unplug him (o2 on that bank) and run like that (it will default the fuel trim to it's own default mapping for that bank ) .... that will confirm or rule out if it is the O2 or another problem.
 
#9 ·
It ran for three days with no problems. Started acting up on the fourth day coming home from work at about the third stop light. Had the scanner with me. Pulled over and monitored STFT and O2 for both banks. When it started to stumble both fuel trims became eratic as well as both O2 readings. Like it's running out of fuel but when it dies it will start right back up without cycling the key. Also makes no sense that it runs fine at highway speeds but stumbles and dies at stop lights. The fuel pump doesn't care whether the engine is at 2000 RPMs or at idle. It's not a PWM pump so it's delivering a constant pressure. It doesn't make sense but the problem is definitely fuel related
 
#8 ·
The last issue I had with stalling and chugging randomly was a torque converter not fully disengaging, after a fluid and filter swap it was a little more than a quart low. Refilled and problem went away.
 
#10 ·
Uodate, it died on the way home yesterday. Idle became eratic sitting at a stop light, it stumbled and died and would not restart. Once I got it pushed off the road, with the help from another jeep enthusiast. Hooked up the scanner and had two pending codes for fuel system trim lean, both banks. Used a jumper to power the fuel pump relay fuse and could hear the pump running, but it wouldn't start. Got it home dropped the fuel tank and replaced the fuel pump. The filter on the bottom of the pump was plugged with debris which I believe starved the pump and eventually took the pump out. Drove it extensively last night and this morning. So far looks like problem found and fixed. I attached a pic of the pump and filter.
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top