post #1 of Old 04-11-2011, 03:29 PM Thread Starter
IBIUIRIKIE
Registered User
1993 ZJ 
 
Join Date: Mar 2011
Location: Davison
Posts: 16
Need Help! Stumped.

I have a 93 jeep grand cherokee with the 4.0. The jeep for the most part drives great when it is running. I have noticed it does have a rough idle when stopped and transmission is in drive. If the jeep is put in park or is in motion their seems to be no problem.

But if i leave the jeep parked overnight with out driving it for 5 or more hours it will run very rough, spit sputter, and seems to be a backfire in exhaust if i try to give it gas. I have to wait till the jeep is at operating temp. so it can be drivin. I can then usually drive the jeep all day with no problems. I'm hopeing somone may have had this problem and knows how to fix it.

I HAVE CHANGED the fallowing: Fuel pump, Fuel filter, Idle air control valve, MAP sensor, Air/Temp flow sensor, coolant temp sensor, oxygen sensor, Plugs twice ( they seem to run a little hot), plug wires, cap, rotor, igniton coil. brand new battery. All the vacuum lines look good, canister not cracked.

I thought to change the TPS but i get NO codes at all, and the sensor tests good with the volt meter, with throttle shut and open.

Its not a security issue, the alarm is disarmed. Also the PCM has been changed before i owned the jeep, its not a factory PCM which leads me to think thet the previous owner has changed it.

What would make the jeep spit and and almost die out after sitting overnight? could mostiure be getting somwhere? i have no idea what to check next. it seems to me if it was anything electrical i would be getting a code. And i am not getting any codes what so ever. Please help if any ides.

if it is a fuel presure regulator, wouldnt the jeep run bad the whole time?

IBIUIRIKIE is offline  
post #2 of Old 04-11-2011, 03:35 PM Thread Starter
IBIUIRIKIE
Registered User
1993 ZJ 
 
Join Date: Mar 2011
Location: Davison
Posts: 16
Ive also put a crank shaft postion sensor, still no fix. Still runs bad in morn ing until jeep is at operating temp. Then i can dive the jeep all day unless it sits for more than 5 hours then i have to wait till it is operating temp.
IBIUIRIKIE is offline  
post #3 of Old 04-11-2011, 05:00 PM
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Posts: 8,550
Try taking all the relays that are in the PDC that will interchange and swapping them around. Clean the legs.
ZeeJay1997 is offline  
post #4 of Old 04-11-2011, 05:09 PM
ZJBEN
Registered User
1997 ZJ 
 
Join Date: Mar 2011
Location: San Antonio
Posts: 9
Have you tried any injector cleaners? Thats about the only thing not mentioned on your list that I can think of. I would think it would run bad all the time if an injector was clogged. I don't know.
ZJBEN is offline  
post #5 of Old 04-12-2011, 01:10 AM
93zjbums
Registered User
1993 ZJ 
 
Join Date: Feb 2011
Location: kalamazoo
Posts: 288
i was looking on another thread on older fuel pumps the check valve starts to wear out and it loses fuel pressure when it sits for too long and takes time to get back to full pressure, maybe check fuel pressure after it sits for a while should be at 35-39psi im told

93 zj laredo 4.0 with k & n intake 2 inch bb skyjacker shocks and 31 bfg at
92 chevy cheyenne 4x4 w/t with 32in procomps "The Beast" 184k
92 honda accord ex
92 xj stock 358k miles wifes
93zjbums is offline  
post #6 of Old 04-12-2011, 04:03 AM
a70eliminator
Registered User
1998 ZJ 
 
Join Date: Dec 2004
Location: Kent Ohio
Posts: 957
Had similar issues with my work van, not a jeep but neverthless, there was an ambient air temp sensor behind the grill somewhere that was reporting -30F engine world run extremely rich and load up at idle. Circuit was not open or shorted so no codes were generated, a mechanic and alot of head scratching but eventually fixed it, -30 outside air! This just happened last week, we've had some wild temp swings here in ohio, 80 one day 35 the next and thats what we think finally did it in.
a70eliminator is offline  
post #7 of Old 04-12-2011, 09:05 AM Thread Starter
IBIUIRIKIE
Registered User
1993 ZJ 
 
Join Date: Mar 2011
Location: Davison
Posts: 16
I have tried seafoam to try to clean injectors, but i believe if i had a leaking injector the problem would clear up in 2 min or so. Im not to sure about the ambient air temp sensor, i will have to look into that. And also i will check the check valve. Thanks guys i will let you know what i find.
IBIUIRIKIE is offline  
post #8 of Old 04-12-2011, 09:14 AM
Foundrydude
Registered User
1995 ZJ 
 
Join Date: Jan 2011
Location: Flatsville
Posts: 2,690
What's going on with the egr valve? What's intake vacuum reading when running rough?
Foundrydude is offline  
post #9 of Old 04-13-2011, 11:29 AM Thread Starter
IBIUIRIKIE
Registered User
1993 ZJ 
 
Join Date: Mar 2011
Location: Davison
Posts: 16
there is no EGR valve, in 93 i guess its all ran with vacum. The jeep has a vent tube that runs from fuel tank, to canister, and vacum off the to manifold and such. All the lines look good, and so does the canister.
IBIUIRIKIE is offline  
Reply

Tags
backfire , fuel , rough idle


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
stumped on what to do ABerry ZJ Grand Cherokee Forum 9 11-12-2008 03:48 PM
Okay, I'm stumped RyanZJ ZJ Grand Cherokee Forum 12 11-30-2007 11:39 AM
Ok Now I am stumped I have never seen something like this before! 99cherokee ZJ Grand Cherokee Forum 1 09-21-2006 12:13 PM
Stumped nekked_frogg_52 ZJ Grand Cherokee Forum 10 07-17-2006 11:26 PM
This has me stumped jeep946 ZJ Grand Cherokee Forum 22 06-24-2006 04:31 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome