Bad stumbling at speed, better at high RPM's

I put new Ford injectors in about 3 weeks ago and the 89 jeep ran great. It was like I gave it a tune up!
Then a week ago, I notice a slight stumbling during acceleration at the bottom end of the RMP range in 1st gear.
Then. last night while getting on the freeway it started stumbling and bucking really bad in all gears unless I had it wound up. I had to drive home in 4th to keep the RPM's up @ 65mph.

It seems to run fine as long as the RMP's are at the top range of each gear but internmittently stumbles and bucks at lower RPM's. I don't have a tach so I don't know the exact RPM's ...

It has a new 5K miles new fuel pump/filter, EGR, injectors, distributor cap/rotor, plugs & wires, no vacuum leaks, new clutch/flywheel/slave...

It does have pretty bad oil leaks (valve cover & rear main I'm pretty sure) which I am fixing next weekened but I can't figure out why it runs well at high RPM's and not low.

Any ideas?

Sounds like an EGR problem. It occurrs while cruising in the 1200-2400 RPM range?

What part(s) of the EGR system is new?

Double check the bell housing bolts. We just saw a similar symptom on a rig and the bellhousing was loose and moving.

--------------------------------------------------------------------------------

Double check the bell housing bolts. We just saw a similar symptom on a rig and the bellhousing was loose and moving.

This would cause my symptoms? It doesn't FEEL like a tranny/clutch problem..
Feels more like it missing on mutliple cylinders but only and the low end of each gear.

-------------------------------------------------------------------------
Sounds like an EGR problem. It occurrs while cruising in the 1200-2400 RPM range?
What part(s) of the EGR system is new -

I replaced the EGR valve about 6 months ago.
-------------------------------------------------------------------------

Like I said, it seems to be almost OK if I am at the high end of the RMP range in a given gear. I say "almost" because it'll go but I can still feel a slight stumble or stutter and it still has a loss of power it's just negligable..

It's seems to only do this under load at low RPMS. It's OK just before you would shift.

It idles fine for a 149K 89 jeep.

Does a '91 have a egr ??

I dont know about yours, but we have been fighting a similar situation in my 87 XJ for about 3 years off and on now.

A few weeks ago after i "Thought" my jeep was FINALLY fixed, it left me stranded.

I have replaced every sensor...the list goes on...

Well, being the impatient person that i am i decided to do some spaz tests while waiting for the towtruck...

So, while talking to a friend on the phone i decided to lift my toes up a bit and wiggle all the mess under the dash above the gas and break pedal while cranking. THE DAMN THING STARTED!!

So, the next morning i get in, NO START is back again...so i do the wiggle method, lightly of course, and VIOLA! it fires again.

So i get out on the interstate and cant get above 55, the usual stumble, buck, and jump speed and of course normal bumps in the road would cause it also.

So i pull over on the side of I-80 and start playing with wires under the steering column while cranking, finally it fires. So i got the pair of shoes out of the back, pulled a string off one, and tied the harness off on one end and the other end tied to the 4wd shifter...

VIOLA!! it is fixed. I cruised in the 80's all the way down the interstate, havent had a buck, jump, stumble, no start since!! But i cant find the short, so its back to the mechanic again.

Just a thought.

Cory

titan4u2c said:

Does a '91 have a egr ??

Click to expand...

No. Only the Renix setups had an EGR system.