jolly green giant

Hi all i got i intermittent fault which causes the engine to lose power slowing idle to almost a stall then every 2 or so seconds engine revs to just over 1000rpm then back to near stall .Any thoughts ?

fb97xj1

Clogged cat perhaps. Fuel pressure. Could be anything. What year, what model, and what engine?

jolly green giant

its 1997 or 8 not got log book yet engine straight 6 4lt

fb97xj1

Trouble codes? Even if the CEL is not on, i always check. Also, when was its last tuneup? Ever clean the IAC or throttle body? Look for any vacuum leaks. This includes the rubber elbows, etc. Dont forget the one under the MAP sensor. And refresh your engine grounds. Like said in my last post, fuel pressure. A clogged cat can cause an engine to stall. You can test the cat by removing it and roadtest.

Geek

Try cleaning the IAC, it is just throttle body cleaner and an easy one to do. Then move on from there if it is just an idle problem.

tjwalker

Agree with others.

1. Post all codes (full code not a description) here for comment.

2. Test fuel pressure. Has to be done with a gauge. For that vintage, it should be 49 psi, (consistently) plus or minus 5 psi.

There are so many possibilities, but I would start with above for sure.

RocketMouse

not to jack..but doesn't need a whole new thread.... What is the most common stalling issue (doesn't actually shut off).. but after warmed up to op. temp, a few miles down the road, will just lose power for several seconds. Just enough to have to pull over let it idle for several seconds, then she seems fine to go again. Has happened twice so far.
99, 4.0, auto,
Starts and idles just fine this is only after I've been driving down the road for several minutes first. Any ideas?

jolly green giant

thanks for your thoughts will do sum investigating