Jeep Strokers

Hey guys, a friend and I are putting together a decent 4.0L build and have run into issues with upgrading the cam. What we have done so far:

1989 Renix Cherokee 4x4
AX15 transmission
4.0L engine out of a 1991 Cherokee (HO?)
Megasquirt 3X with coil on plug ignition and sequential injection
1999 Intake manifold and throttle body
Comp Cams lifters
Comp Cams 68-232-4
Springs that fit and could handle the lift (spec'ed by machine shop since comp cams springs do not work)
Comp Cams timing chain set 3219

The above specs worked out great and we had it all running on the Megasquirt, nice and smooth. That setup also included the older intake and throttle body. What we decided was to go with a bigger cam and change out the intake manifold along with the throttle body to open the top end up a bit. We swapped over the intakes and also went ahead and installed a Comp cams 68-239-4 cam. It all cranks up no problem, but there is a loud clapping noise for a few seconds with cylinder 5, which can be removed if we unplug the coil to it. We are guessing that something is wrong with one of the lifters on that cylinder. But that's not the worst of our problems. As soon as you crank it up, the IATs just start climbing. The IATs get to 200 degrees pretty fast from that point.

Any clue on what could be the cause of the IATs? Is there some goofy timing setup that we need that is different between the less aggressive cam above? Was the cam possibly cut/degreed wrong? What are we missing?

That sounds like the intake/exhaust manifold gasket is broken or seated incorrectly around those cylinders.

Alexia, the gasket is new and we had no problems installing. We will look at it again though, thanks for the suggestion.

Sounds like your engine could either be running lean or the ignition timing could be off.
Which injectors are you using?
You might also want to check the intake manifold vacuum and see if there are any leaks.

Currently we are using 30lb Volvo 850 injectors at 58psi and the wideband is reading around 12-13:1 AFR. Rich, yes, but definitely not lean nor a misfire condition.

As for timing, is there something goofy that needs to be set/adjusted when going to a cam like this? We aren't using the distributor, though the distributor is still running the cam sensor for cam sync (which is adjustable). We have that setup exactly like stock and it does crank over fine. We started with fixed timing of 10 degrees, noticed 3 degrees off on the timing marks, and accounted for those 3, so mechanical timing should be dead on. I've tuned other engines and have never experienced anything like this before.

Anyone ever see this before?

How was it running with the 232 cam?

Are those injectors in the order they came out of the engine?

You are definitely running rich for some reason. Those appear to be quite large injectors. However, if it was an injector issue you think it would apply to all the cylinders, not just a few. Possibly a gasket issue.

SilverXJ wrote:Those appear to be quite large injectors. However, if it was an injector issue you think it would apply to all the cylinders, not just a few.

If they were used injectors to begin with, it's quite possible that at least two are sticking open for too long. It would be worth swapping injectors around to see if the corresponding plugs look black again.

Your IAT appears to go up because you are pumping hot cyl compression out back into the intake. Your plugs are fouled because if you pump out some of the air with the same fuel squirt as the others cyls...too rich. Do a compression test..its probably a lot lower on the fouled cyls. You might have to go in to the head to make sure the intake valves are ok

like wood jeep said check compression...i doesn't sound good tho

You ever take her apart yet? What did you find