1983 Jeep CJ7 Rough Idle

jeep
rough

#1

I have a 1983 Jeep CJ7 with a 6 cylinder 253 engine and 4 speed manual trans. It has 78k original miles. When accelerating, it runs fine, but as soon as you push the clutch in and hit the brakes, the engine acts like it is going to stall. The harder you stop, the worse it seems. When sitting still, the idle is still rough but it does not stall (since most recent work was done).



Several mechanics have tried to fix it including a new fuel pump, new carburator, and machined valves. It is better now than it was, but still not completely fixed.



Does anyone have a clue about this? The rough idle when coming to a stop vs. sitting still may be a clue.


#2

For this problem, the next thing to check is for a vacuum leak somewhere on the engine.

When you’re accelerating, the engine draws less vacuum while at the same time fuel is being added. So this can mask a vacuum leak. When you suddenly let off the accelerator, the engine draws more vacuum. At the same time less fuel is being added. So the engine leans out and starts to run rough.

Tester


#3

Pinch the vacuum hose to the power brake booster and see if that corrects the problem.