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Rebuilt 4.7...Will not idle

10K views 23 replies 9 participants last post by  Turbozcs2003 
#1 ·
Hey guys. First time posting here but have been coming here awhile, really good site. I have recently purchased a '99 grand cherokee limited with the 4.7. It had a spun bearing so I pulled it out and replaced the crank, main and rod bearings, number 8 rod and piston and some timing components that had worn out. Got every thing back together and now I'm having a idle problem. When I first go to start it it will fire right up and attempt to idle for 5-10 sec or so then die. If you go to restart it you have to apply throttle to get it going and you have to keep it above 1000rpm's or it will die. Also the plugs on the passenger side bank are completely covered in soot while the drivers side look brand new. I'm assuming this is a sensor problem but I am out of ideas. So far I have replaced all the spark plugs, the iac, and the crankshaft position sensor. Oh and compression is good, timing is good and fuel pressure seems to check out. So dose anybody have advice, I could really use some help, thanks.
 
#5 ·
That was on the list of sensors to replace, just hated buying a bunch of sensors without knowing exactly what is going on but what can you do I guess. Earlier though I was out looking at somethings when I noticed I had left my o2 sensor disconnected (after that cat), would that have anything to do with my rich condition?
 
#7 · (Edited)
It really sounds like you may be off a tooth on your timing. I would pop your valve covers off and verify.

Ultimately a sensor failure should throw a code if you have run it for 30 seconds give or take, and a sensor that is killing the engine should throw a code if its so out of whack the motor cannot keep running.
 
#10 · (Edited)
Just last week we had an other member with the same problem, he also checked the valve timing 3 times and thought is was ok, but then lateron he discovered that he had used the wrong procedure. (seems that he didn't knew about the markings on the timing chain and only looked at the V8 mark on the sprockets)
http://www.jeepgarage.org/showthread.php?t=28449
 
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#11 ·
Well I think you guys are right about the timing. I'm pretty sure I did the same thing the guy in the link did. I reused my old chains and couldn't see any marks so I just put them on assuming as long as the v8 marks were lined up I would be fine. So time to tear it back apart.
 
#14 ·
Here attached the procedure for the timing chain adjustment, if you don´t have it. It seems that the colormarks on the chains only line up when first installing them.
 

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#15 ·
Well I finally had time to replace the timing components. Everything was lined up perfectly this time around. Get everything back together, go to start it and guess what. No change. Still idles like complete shit, have go give it gas or it will just die. Haven't checked the plugs yet but I don't know. I'm feeling pretty rough right now, I was really hoping this would do it.
 
#17 ·
Depending on how far of the timing was, there is a possibility that a piston(s) has hit a valve(s). It seems that intake valves can easily be hit by the respective pistons, when valve timing is incorrect. Did you do a compression check on all cylinders already?
 
#18 ·
No, I have not checked compression yet. My tester decided to stop working so I need to pick up a new one. The first time putting it back together I made sure there was no piston/valve contact, everything was smooth. I am thinking it's something valve related. Is checking the cam followers fairly straightforward, I've not messed with head's yet.
 
#24 ·
11 yr old thread my friend, hopefully they corrected the problem.
 
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