1997 Jeep Cherokee, no previous issues or CELs.

Installed APN exhaust manifold and '99 XJ intake manifold last Saturday. Two days later after a bit of driving...Now have P0301 cylinder 1 misfire...XJ has stalled once at a stoplight then after giving it a little throttle it fired back up to get home. Checked all connections, thought it might have been a loose connection so cleared CEL and everything seemed fine. After a day of driving and things seeming fine fired the XJ up tonight to have it just not sounding right at idle and the CEL coming back on...

Pretty obvious to me it has something to do with the install...

Any thoughts? Need help!

 

Vacuum leak can cause lean misfire. Spray around the injector and manifold with carb cleaner while listening for change in idle speed.

 

Did you torque the manifold bolts down properly and use a good gasket and make sure you have it sealed good on there? Did you clean any tar or gunk out of the intake at all?

Same thing happened to me after doing my freeze plugs. it was running like crap after I got it back together and throwing codes for multiple misfires. But, I had cleaned some gunk out of the intake best I could, and knew that a little piece fell onto one of the injectors. I cleaned it out but who knows if something might have been stuck. I pulled the battery cable to reset the computer and double-checked my vacuum lines and injector connections, and it's been running great since.

 

I plan on trying this today when I get home.

Used the gasket that came with the APN exhaust manifold with high temp copper spray. Other guy torqued it and pretty confident he did it right but will check the torque.

Ok, I will start by doing the same before I start spraying around with the carb cleaner.

 

When I did mine I had to retorque the bolts after driving for for the first day or so. Go through and make sure all the bolts are properly torqued. Especially that bastard bolt that's right behind one of the tubes.

 

Good to know. Didn't get to it tonight, too tired so ride to work for me tomorrow. Gonna pull the negative, check the injector connections, check the torque on the bolts and if that don't work move onto carb cleaner. Hoping one of the first two will work but I have a feeling its the o-ring on the injector for cylinder 1 so carb cleaner should confirm then all new o-rings.

 

The second time I put my injectors and manifolds back together, injector 2 and 3 were leaking. I learned from that experience to use dielectric grease on the O-rings so they dont need to be forced in.

 

Dielectric grease, got it at the house and will use it. Thanks.

Hopefully find the issue tonight after work and be able to fix tonight as well.

 

Pulled negative, disconnected injector connector for cylinder #1 cleaned out some dirt...tightened front exhast manifold bolt and first two intake manifold bolts...sounds like the XJ is running better, been driving it around and so far no CEL. Fingers crossed problem solved.

 

Cleaning out dirt is always a good thing! Mine kinda sounds like it has an exhaust leak up there somewhere since I put the manifolds back together. I need to retorque my bolts as well....but I think I didn't tighten the exhaust flange enough.

Glad you're runnin good so far.

 

Ive read on a post that the APN gasket was not up to snuff. I ordered a Fel Pro for when I do the job.

Side by side, the Fel Pro is of better quality.

Hope your problem is fixed.

 

I got a Felpro from autozone for around 12 bucks I think it was. Stood up to removing the damn things at least 2 times. mines running good but there's a slight ticking from the drivers side that most certainly is an exhaust leak somewhere

 

Still running good with no CEL. Gonna change the valve cover gasket this weekend due to mine is leaking so while under the hood gonna check the torque on the bolts again.

Idle isn't too smooth but found out the distributor cap and rotor are shot thus need changing along with the distributor itself has some movement...changing the distributor, cap, rotor and wires soon (parts sitting on tool box).

 

I did all that too. Last weekend I discovered the source of my exhaust leak, I had a hunch it was the exhaust flange because I rushed through getting it back together after the 3rd time tearing it down because I was...exhausted! badump-ch!

Anyway, I discovered that my laziness in tightening those two rusty bolts resulted in one falling out while I was driving at some point. I replaced the bolt and made damn sure I tightened them down and it's running like a top now. Still a little rough starting sometimes, but always fires up and runs good once it is. Quite an interesting experience getting to know the 4.0. Put a few hundred miles on her since, no CEL.