jkshavoc

Hi guys im in need of some assistance, for a couple weeks now the rpm gauge on my 89 has been acting crazy and my truck has been stalling and sputtering. Heres what happens: when i turn it on, the rpm will start jumping all over the place like from 700 rpm up to 2000 and the back down again and the jeep will either sputter really bad or it will stall, it happens whether im driving in the street, at a stop sign and at highway speeds. I thought it was the egr valve so i purchased another one and it seemed to help for a couple days but now the problem is back again. I checked spark plugs, wires and for any vacuum leaks. Any suggestions or ideas are greatly appreciated.

cruiser54

Click on the link in my signature and do #1, and 3 for sure.

Your TPS may be bad.

But, I'm concerned about wires that are okay and I'm wondering if you pulled the distributor cap and inspected it. All those components are due to be replaced every 30,000 miles.

jkshavoc

I bought a new tps sensor today and still have the same issue When idling it seems to get worst as i step on the brake. You have any idea why that would be?

jkshavoc

As i step on the brake the rpm goes up and then it stars jumping all over the place.

cruiser54

Your brake booster could be leaking internally. How do your brakes feel? Different than before?

jkshavoc

They feel the same. But it has an effect on the rpm, if i pump the brake the rpm will rise

cruiser54

Put some vice grips on the hose to the booster and see what happens to your idle, especially when pressing the brake.

jkshavoc

ok, i will try this right now. Thanks for the help

cruiser54

I'm going to bed. I get up at 4 am.

jkshavoc

i just tried it and the rpm stayed steady at about 600 rpm, as soon as i took the vice grips off the rpm climbed to about 1000rpm and as i pumped the brake it kept climbing.

Turbo X_J

Is the one way (check) valve still in place and functioning in the vacuum line leading to the brake booster?

Radi

Brake booster has a vacuum leak. Replace it. The check valve is there to hold vacuum in the booster as reserve during times of no engine vacuum- like when you accelerate- but does nothing to stop a ruptured booster diaphragm from creating a monster vacuum leak. It allows engine vacuum through to the diaphragm, it blocks stored booster vacuum from flowing back into the intake.

jkshavoc

Do i replace just the valve or do i need to replace the whole brake booster?

Radi

Have to replace the booster. Not the master cylinder and all, just the booster portion. You can do it without opening any of the hydraulic system.
The check valve is only there so you don't lose power assist during times of low engine vacuum.

jkshavoc

Is it difficult to replace the booster? Thanks for the replies