blober54

So I picked up this jeep last month and been getting it up and running but theirs one issue I can not figure out. Driving me and my buddy nuts.

When we drive the jeep she wont rev past 3500rpms, and after driving for awhile it gets worse and worse down to 1500rpms.

We have checked ECM/ECU (works fine in buddies jeep) CPS, TPS, fuel pressure, air intake sensor, compression is 125-130 all across, new plugs, new cap, new rotor, their is no cat to get plugged (replaced exhaust with cat free since we have no emissions here)

Not sure what else it could be lol. I have done alot of reading and research from others and tried everything I could see was issues with others, but no luck so far.

With it changing after driving is odd, but hopefully that helps narrow it down?

Any help would be awesome.

Thanks

Bustedback

Check the fuel pressure and put the catalytic converter back on.

blober54

already checked fuel pressure, its perfect, and the cat was in good condition when pulled and had the issue before being removed. That's not the issue.

Bustedback

I know the lack of the cat is not the problem, but it's a federal law that it is there. Any codes? Have you checked the function of the CTS with a scan tool?

modded96xj

Its not a law for the cat. Its a regulation. Two completly different things

blober54

we ran a snap on scanner and the cps checked out working like it should, went through and tested every sensor and what not the tool could and everything checked out good.

:-(

Bustedback

Not the CPS, the CTS (coolant temp sensor).

blober54

thats what I meant sorry... slip of the finger lol... the temp sensor checked out fine.

Bustedback

You haven't screwed with the distributor or anything, have you?

blober54

We replaced the cap and rotor, checked the bottom half of the dizzy and the little magnet part in their, was alittle dirty so we cleaned it up and didn't hurt or help the jeep running.

Is their another part to check or test in their?

blober54

if timing works out, I should be going over to my buddies after work and pulling his dizzy and trying it in mine, to mark off another thing on the list... since it works perfect in his zj

I just wanna get her figured out... as soon as we get her running right, planning on building the lift... she wont do too well with bigger tires then stock lol

blober54

ok, went over to buddies, swapped over his magnet part under the rotor, same thing... swapped his coil pack over... no difference.

:-( haha, its got to be something stupid lol... what is it!!! I dont know lol

Bustedback

I'm at a loss, sorry.

drhoward1988

Does it idle/accelerate up to those RPM's correctly or is it rough? And dont always trust a hand scanner. Those are notorious for not giving you correct info. My wifes car had a check engine light on and wouldnt throw a code with a handheld. Seems to me it could be a vacuum issue somwhere with it heating up and getting worse.

blober54

it idles great and drives good too, just if you put her in nuetral it acts like the revbox is at 3500 or 1500... and when driving she wont go past it like its the rev box.

I'm going to test out the vacuum leak tomorrow... my dad had the same idea/suggestion alittle earlier. I will report back with what happens.... fingers crossed lol