Odd gas issue
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2nd Gear
Joined: Feb 2026
Posts: 2
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Odd gas issue
I just got my truck back from the mechanic. Fixed some vacuum leaks. Ran great the first day but now (and again) when I start it it just barely idles until it I run for awhile. But now when driving if I let off the gas its like the gas just cuts out till I press the pedal then it cluncks the Trans like I just dropped it in gear. Cant afford another mechanic fix.
Fleet Mechanic
Joined: Jun 2023
Posts: 1,394
Likes: 384
From: WA
What is it? Year, model, engine, transmission (manual or auto).
Why was it at the mechanic's shop? Original problem.
How long have you had it, and has it ever worked correctly for you?
I assume that when you say "odd gas issue" you mean gas pedal behavior. ?
Good luck.
Why was it at the mechanic's shop? Original problem.
How long have you had it, and has it ever worked correctly for you?
I assume that when you say "odd gas issue" you mean gas pedal behavior. ?
Good luck.
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2nd Gear
Joined: Feb 2026
Posts: 2
Likes: 0
Its a 2000 screw 5.4. 2wd auto. I had it at the mechanics for idle issues. Had a few vacuum leaks and new ball joints. Id compare it to a "Jake break" when I let off the gas. It'll go fine a few seconds then its like it just cuts the gas off.
It did it before when I was working on my stereo and again when I put a new battery in,but I was told the computer had to "relearn" how to drive? Took a few cycles and it ran just fine.
It did it before when I was working on my stereo and again when I put a new battery in,but I was told the computer had to "relearn" how to drive? Took a few cycles and it ran just fine.
Mountain Pass
Joined: Dec 2025
Posts: 117
Likes: 52
You need to look at your long and short term fuel trims.. They should be close to zero. If not and they get better at higher rpms then you still have a vacuum leak. If all that checks out your IAC could be an issue.. Let the truck idle for a few min. Then, unplug the IAC. IF the truck shuts off, its working as it should. If it keeps running it means you either have a large vacuum leak or the IAC is sticking open.
Fleet Mechanic
Joined: Jun 2023
Posts: 1,394
Likes: 384
From: WA
LEEDSnDEED has good advice on the IAC valve. That's what lets air past the throttle when you take your foot off the gas so you don't get the jake brake action. And when you do a cold start to keep idle speed up. Your symptoms sound like a bad or unpowered IAC valve. I left mine unplugged once and it would barely stay running when cold.
Looks like this, on top of the front of the engine. The guy might have left it unplugged or didn't push the connector on all the way.
https://www.rockauto.com/en/moreinfo...t=6072&jsn=689
Looks like this, on top of the front of the engine. The guy might have left it unplugged or didn't push the connector on all the way.
https://www.rockauto.com/en/moreinfo...t=6072&jsn=689
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