Intense vibration at idle after header install
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Joined: Nov 2020
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Intense vibration at idle after header install
What I have:
91 RS 3.1L auto.
Exhaust mods in case it helps:
Magnaflow muffler
Magnaflow cat
Pacesetter headers (removed AIR pump but kept the pulley and using shorter oil filter)
IROC snorkel + ram air setup
The Problem:
After putting in the pacesetter headers mentioned a lot around here I have an intense vibration at idle. The vibration is like a pulsing through the whole car, the best example I can give is when I turn the idle screw down too low on my bike and it bogs out but this is a pulsing that starts then stops every 30 seconds or so. It happens in drive, neutral, and park exactly the same and the tach shows that the RPMs are dropping very very slightly while it's happening.
While it's doing this if I let off the brake and start rolling forward hitting the gas hard causes it to hesitate and buck really noticeably, if I give it some gas slowly and consistently it'll hesitate for a split second then accelerate like normal. The best example I can give for this is also from my bike, it's like letting off the clutch but not giving it enough gas so it bogs down and hesitates a bit.
When it happens and what I've tried fixing:
This only happens after the car heats up but it happens consistently every single time I get off the highway and sit at a light after a quick 10-15min drive to work. This started only after the headers were put in, I had the muffler and cat in for months with no problems and I'm completely stumped... Its a problem at idle so I checked the plugs, they were kinda sooty and about a year old so I changed them, then I tried cleaning out the IAC valve but both of these only made the vibration very slightly less intense.
I couldn't find anything like this around the forums, anyone got any ideas? Fuel delivery? Bad cat? Vacuum leak? I'm no mechanic but I got a lot done on this car learning as I go so I'm not the best at identifying problems.
91 RS 3.1L auto.
Exhaust mods in case it helps:
Magnaflow muffler
Magnaflow cat
Pacesetter headers (removed AIR pump but kept the pulley and using shorter oil filter)
IROC snorkel + ram air setup
The Problem:
After putting in the pacesetter headers mentioned a lot around here I have an intense vibration at idle. The vibration is like a pulsing through the whole car, the best example I can give is when I turn the idle screw down too low on my bike and it bogs out but this is a pulsing that starts then stops every 30 seconds or so. It happens in drive, neutral, and park exactly the same and the tach shows that the RPMs are dropping very very slightly while it's happening.
While it's doing this if I let off the brake and start rolling forward hitting the gas hard causes it to hesitate and buck really noticeably, if I give it some gas slowly and consistently it'll hesitate for a split second then accelerate like normal. The best example I can give for this is also from my bike, it's like letting off the clutch but not giving it enough gas so it bogs down and hesitates a bit.
When it happens and what I've tried fixing:
This only happens after the car heats up but it happens consistently every single time I get off the highway and sit at a light after a quick 10-15min drive to work. This started only after the headers were put in, I had the muffler and cat in for months with no problems and I'm completely stumped... Its a problem at idle so I checked the plugs, they were kinda sooty and about a year old so I changed them, then I tried cleaning out the IAC valve but both of these only made the vibration very slightly less intense.
I couldn't find anything like this around the forums, anyone got any ideas? Fuel delivery? Bad cat? Vacuum leak? I'm no mechanic but I got a lot done on this car learning as I go so I'm not the best at identifying problems.
Joined: Oct 2013
Posts: 2,610
Likes: 156
From: Louisville, KY
Car: 1983 Z28
Engine: 385 Fastburn
Transmission: T-5
Axle/Gears: BorgWarner 9-bolt posi, 3.27 gears
Re: Intense vibration at idle after header install
Do the headers or y-pipe touch any part of the body? That’s my first guess.
Supreme Member
Joined: Feb 2005
Posts: 2,508
Likes: 201
From: Hawaii
Car: 89' Firebird / 87' Formula
Engine: 3.4 / 5.0
Transmission: 700-R4
Axle/Gears: 3.42 / 3.42
Re: Intense vibration at idle after header install
Its possible you popped off or broke a vacuum line when installing them.
try check all your vacuum hoses and the fittings they connect to,
try check all your vacuum hoses and the fittings they connect to,
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