When I slow down idle or go speeds 50mph & up the car seems like it resists its almost like it wants to stall

CODYHAZZARD

MEMBER
1998 JEEP GRAND CHEROKEE
V8
4WD
AUTOMATIC
174,562 MILES

I have a 1998 Jeep Grand Cherokee Limited 5.2 V8 4X4.
When I decelerate and have my foot off the brake (10mph or under) and when I idle or go speeds 50mph and up it seems like the car puts and there is a subtle shake that you can feel in the seat and on the floor but not in the steering wheel or brakes. There are no codes, no engine light, and no misfires. I have tried changing the Idle Air Control Valve and it seemed to make it run a little smoother but the problem still persists. I have also done a wiggle test on all the wires on the intake and various other areas around the engine. I have also tried putting gas cleaner in it in case it was just some bad gas but that didnt work either. Any ideas?

I already did OBD2 checks, the only thing that was even close to wrong was the car is running a little rich, nothing out of the ordinary for a car this old. The Catalytic Converter is going bad I think but it has been bad for a while and this problem just started occuring.

2 Replies

CJ MEDEVAC

MECHANIC
11,004 POSTS

The CAT, has like a Honeycomb brittle, sorta ceramic stuff in it (not going into great detail) The exhaust flows thru these honeycomb holes---in fact, they even make the cat bigger, as to have more "Exhaust Holes" in it, TO EQUAL OUT the airspace space ('cause the Ceramic type stuff takes up room, to say it layman like!)

It's kinda like stacking cardboard up, lets say, 30 pieces high, and a foot deep and blowing thru the corrugations!

If the honeycomb stuff gets stopped up---it restricts flow--Many times the Honeycomb stuff will BREAK OFF IN BIG CHUNKS----AND STOP IT UP ALL OF A SUDDEN!The Chunks turn "sideways"---NO MORE GOOD FLOW

The faster your engine turns the more exhaust it must get rid of!

I would check that out 1st!

The Medic