CPLSeraphim

I have a 2002 Jeep Grand Cherokee Laredo 4.0 that I bought. Blown engine and I broke the bell housing.
I replaced the engine, transmission, fuel tank, pump and filter. Did a tune up, replaced all brakes and rotors, electric fan, headlamp housing and light whole front grill assembly, and rear bumper assembly, exhaust and that's what I remember. Everything seems to be doing great, except:


starting is a pain, and idling is horrible. Straight up sounds like it is going to die, misfiring, shaking. the works. as soon as you give it gas, it seems to do great. The only part that wasn't straight from the new engine was the cast air intake. I broke the third mount for the power steering, so I cleaned and used the air intake off the old engine. That throttle body was shot, so I used the new engine throttle body and put a new(I think it was new, may have been from other engine) black box with torx screws on the side of the throttle body (brain fart on what that is). The new one was a different style, but seemed to work as is should without vehicle running.


Everything is ready to pass inspection, except that you can barely get the thing to move. I put some super in it tonight, along with some seafoam, for whatever water fuel may still be in the lines, and it was running for over an hour. at first it would snuff itself out (There was bad gas used, until the premium fuel got mixed with it). After it was running half decent (not dying) I moved it into the garage. I was surprised it didn't sound bad when I went from drive to reverse, Then drive again. Once in the garage, where it ran for most of its hour, it would idle then smooth out for a few seconds then rough idle again, misfiring and just running crappy. give it fuel, and she runs beautifully. I have read of a few issues including that part I replaced whose name eludes me and the moment (Idle air control valve?) If I can get this idle issue taken care of it has already passed the rest of inspection, and I can really give this thing a road test. If anyone has any ideas, please reply.


I am not sure if it is just a normal rough idle issue or has something to do with 75% of this thing being new parts on it together. I think it will be something simple, but please give it your best shot. I really appreciate any help and hope I was descriptive enough. BTW, it is not reading a single code whatsoever.

dave1123

There are only 2 things that grab me. Try a new good quality IAC ( preferably Mopar) and you might have damaged the CPS when you had the trans and engine separated. That sensor mounts less than 1/8" from the flexplate.

CPLSeraphim

Yeah, that is where I am at with it. Last night while I was thinking about it, I am pretty sure the IAC wasn't new. The Crankshaft position sensor is acuall where I broke the old bell housing. but that is brand new. My research also said something with a camshaft position sensor. I didn't look to far into that until I check out the IAC.


Basically, I wasn't sure if this issue was a normal issue, or a rebuild issue, but everything I have read points to IAC. I will replace that when done camping and see if that fixes the issue.


Any other thoughts are welcome, the weirdest part is its not popping a single code.

ZombiePopper

Agree 100% with Dave.
Typical IAC Valve symptoms.
Been there several times.
You might try cleaning it first, if it's really carbon-ed up...
As Dave said,
Get a GOOD quality unit, don't skimp, avoid the BWD brand (Borg-Warner). I went thru 2 of them in about 2 weeks.

CPLSeraphim

Thanks for your input as well, Zombie. I got a new one, and as soon as I get her in, I will update. I may be getting the same model jeep for myself. On vacation, I realized my blazers' frame isn't exactly in the best condition. but anyhow, I will update.

MNOE

Id like to know the resolve of this thread since im still having a similar problem. Mine starts and runs decent, but has a misfire that shakes the jeep at idle, especially reverse. But as soon as you hit the gas it goes away. Also seems to get worse once it warms up to op temp.

ZombiePopper

MNOE,
I went thru the same exact symptoms you're describing and it turned out to be my EGR valve.
I'd pull it, clean it and reinstall to see if there's a change.
Also while you're back there pull your dizzy cap and check its condition (make sure your cap/rotor isn't worn/corroded.). What plugs are you running?

dave1123

Forget it! This is a WJ we're talking about. No EGR or dizzy cap. We don't know what MNOE has.

ZombiePopper

Good catch Dave I missed that!
My above post was meant for MNOE only though, but you're right we don't know what vehicle he/she has.
MNOE whatcha got?

CPLSeraphim

heading over now to try the IACV. I'll post tonight. Hopefully we drive her home tonight.


Update: So I replaced the IACV... notta. I turned the key to see if the check engine light came on at all. notta. So I scanned it. 7 codes. most were o2 sensor and running lean. the one that jumped out was the camshaft position sensor. bought one and replaced it. New things coming up. PITA to start. We got it started using starting fluid. so we have spark. it ended up running pretty good on its own gas pick-up, at 3000 rpms, but idling was crappy and it took forever to get it running. she ran a hile, tried idling her, and she shut off. everything was hot, exaust (the air, not the tailpipe) was hot enough to singe the hair on my fingers just by passing it by the exhaust.


We are going to try fuel injectors tomorrow. maybe there is crap in there since there was crap in the old fuel tank and the water in the gas. After this, it is literally just throwing money into parts. whats worse? The other IACV was new. I couldn't remember. lol

MNOE

WJ, Its an 03 GC Laredo. I've already changed plugs, coil pack 2x. cleaned throttle body. Cleaned IAC. And its throwing multiple misfire code and misfire on cylinders 3 an 5 I think?

dave1123

What did the spark plug insulator boots look like? They can get hard and start to carbon-track. Some times you don't get them when you buy a coil pack.

I just had a brain fart. There are 3 coil circuits in the coil pack and 6 plugs. Do they fire the plugs on the exhaust stroke as well? Chrysler did that with the Crossfire to try for cleaner emissions. With a 6 cylinder, it's difficult to tell where #2 is when #1 fires. I'm thinking #3 and #5 are on different coils so the misfire must be injectors and not ignition. JMHO however.

MNOE

Yea it came with all new boots, as far as the misfire, ill have to doublecheck which cylinders were indicated when my wife gets home later. And I have no idea about the exhaust circuits firing. Beyond my knowledge.

dave1123

Yeah, when I first heard about exhaust stroke firing, I though why do that? Then I stopped and realized most all small utility engines do that because their ignition points are on the crankshaft and open every revolution, not every other.

CPLSeraphim

I did not replace the coil packs on my jeep. It seems to run fine once she is up and running and accelerated. I wonder if me and MNOE are having the same issue. I thought initially mine was because of an engine from one, and tranny from another, neither from my jeep. I notice she tried to start in N, which isn't a biggie, I have the new NSS sitting at the house. That thing is a Pain to reach though. Anyhow, MNOE, keep us posted as well. Hopefully between the 2 of us, and everyone here, we can get our jeeps up and running. Have you looked into redoing your injectors?