Cracked manifold?

Could a cracked manifold cause the motor to stumble at higher RPMS? I have been having a problem for a bit now and it caused my jeep to die on me the other day. I will be driving and when it gets to about 3800 RPMs it will do a fast pop pop pop and sound like it is mis firing or hitting a rev limiter. I was messing with the TPS adjusting it and it got worse a little bit and it would do a little pop at 2500 RPMs but then go all the way to 3800 and then do the same thing. I tried new injectors and nothing changed. When it died on me it sputtered and then died like it wasnt getting gas and then i had no fuel pressure. I could hear the pump kick on but wasnt getting any fuel. I took my lines off and blew them out with compressed air. After that i got good pressure again. But still no change. Now when i drive it i will get a sputter a little after i take off from a stop at about 2000 RPMs and it will ocasionally die. I have been trying to figure this out the entire week and nothing has helped.

I've never seen a cracked exhaust manifold cause that (I guess anything's possible, but not likely)

I'd get a pressure gauge and install it so you can see it when driving-- duct tape on the windshield works. Look for fuel pressure drop-off at higher RPM.

Try an analog volt meter and make sure you don't have a "dead spot" in the TPS around where you would have your foot at 3000 RPM also.

AJTorris said:

I was messing with the TPS adjusting it

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I'm curious, how can you do this? I just replaced it on my '96, and didn't notice any means of adjustment. I'd like to know, because I've noticed that the engine doesn't settle right down after letting up on the gas, the revs will stay up about 3 or 4 seconds, then come down.

I had a dead spot on my TPS for a few years, alternator went and the battery got disconnected for a whole day which reset the ECU, new alt and battery reconnect back up and running, no longer that dead spot in the throttle.

well i got a gasket today and went to take the manifolds off and come to find out that there was about 4 of the bolts were finger tight if that and one was almost all the way out.... Just starting to finish bolting it up and then gotta hook it all back up and see what happens! Wish me luck LMAO

So I know the loose bolts would cause a major exhaust leak but could that cause it where it would sputter at higher RPMs?

Exhaust leak can cause the 02 sensor to misread and keep the mixture too rich. Could that cause a high RPM sputter? Seems like it could.

ok so it is still doing it after replacing the gasket and torquing all the bolts to spec. I though maybe it was a cloged cat and nope with it off it still does it. Im stumped at this point.

Whenever chasing engine problems, it is a good idea to cover the basic question of having adequate compression. Do a compression test before spending time or money on other possibilities.

i have and it was 145. I adjusted my TPS but not sure if i got it right but it helped majorly. But now i just heard a clunk and the engine died and now cylinder 3 is not firing.

So i retested the compression and i have 30 on cylinder 3. Time for a new motor im thinking.

My 1988 would do the exact popping your talking about when my exhaust manifold had cracks in it. I have replaced mine twice in 255k miles. Both times I would get those symptoms under high load or rpm's. Pop Pop Pop...

ya will i fixed all that and got it where it wasnt doing it and then i heard a clunk and now no compression on cylinder 3

:gee: Time for a craigslist or JY replacement. Good luck.

eh im getting a 92 stocker tomorrow so i will be swapping motor,trans, tcase into mine depending on the tcase that is. along with the wiring harness. Or swap my sister in law the 92 for her 87 and just swap motors.