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4.3 High idle, then popping and surging.

2K views 7 replies 5 participants last post by  maximus7001 
#1 ·
So I've only had my van for about a week and a half. When I bought it, it would Idle high then slowly drop down. So, like if I came to a stop light it would take like 5-6 seconds before the idle would drop. I even put it a stronger throttle return spring thinking the throttle body wasnt getting closed all the way. That didnt solve it. Well now another problem arises. It just started doing this today, but if I get on the gas quick or have a decent load on it, it surges really bad and backfires and damn near kills itself. I have to just baby the throttle or accelerate really slowly for it to not do it. GOing through the log book the PO had, it says it recently got new cap, rotor, plugs, wires, fuel pump, air filter, etc. I didnt notice a fuel filter in the log so Im gonna replace that first thing in the morning. If that doesnt solve it what should I look at? I was thinking maybe TPS, but not sure. @ $80 I didnt wanna just throw a new one at it until I got some opinions. Thanks for any help you guys might have.
 
#2 ·
Backfiring sounds like a timing/spark issue to me.
Check your cap and rotor, even though they are relatively new. Aftermarket caps and rotors have a tendency to burn fast on these 4.3's.

The idle could be a number of things. Vacuum leaks are very common. Thin plastic vacuum lines get dry and crack or if they are by a leak of some type, the petroleum turns them into mush. How many miles and what year?
PCV valve might be choked on carbon build-up. Pull it, clean and replace the non-screened gasket with a gasket with a screen to catch the carbon pieces.
Idle Air Control valve might be stuck also. I dont think these "clean", at least it didnt work for me. And again.... stay away from aftermarket parts, youll be back in there again replacing it. When mine went out it did the same high idle then dropping down to a semi normal idle after a second or so.
 
#5 ·
I've gone over the ignition and timing. Its solid. The weirdest thing about the popping and surging is it just started all of a sudden, no build up to it, just BAM started doing it. It reall feels like a fuel issues but according to the log the fuel pump was replaced 10k miles ago. I better go out and do some diagnosing. The high idle doesnt bother me near as much as the popping and surging. Oh and BTW, the popping seems to be out the exhaust some times and out the the throttle body at other times.
 
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