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misfire\sputter at high rpm, rough idle after

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lars y

15+ Year Contributor
141
1
Oct 11, 2007
Halden, Europe
Hi,
I was turning up the boost today and mistakenly turned ip up a bit too high (somewhere over 35psi) and in 2nd gear at over 5k rpms the car really sputtered\misfired, it lost power and made bov kinda sounds while i was on the throttle.

The engine felt hesitant right after and as i pulled over it almost died and the idle was really low and sounded like it was going to die then it stopped, i started it up a couple minutes later after having a look in the engine bay and it was still doing the rough almost dieing idle.

I let it cool while looking for faults, then started it up about 30 minutes later and then it ran fine, took it home and looked over things.

I turned the boost way down to 13psi and did some test runs and everything works and sounds fine.

My wideband is showing good numbers. My plugs, injectors, fuelfilter and fuelpump is new (less than 100 miles on them)

Does anyone have any idea what happened?
Some loose wire or faulty sensor maby? Coilpack?

Thank you
 
High RPM cutouts/misfires like that are usually ignition related. Did you lean out hard when this happened?

You could have damaged a plug during a lean condition. (If so, let's hope it was the only thing damaged during the lean condition)

I would go into detail further about ignition related misfires at high rpm, but let's clear up the question about your AFR's first.
 
I wasnt logging when it happened, but ive never had problems with not enough fuel. I was carefully looking at the guage afterwards and it was good. It happened again today and it sounds like its only firing on 2 cylinders.

Thanks
 
Sounds like you started pre-detonating like crazy and pressure was being pushed back out the the intake.

Time for a compression test to make sure you didn't damage rings or valve seals.
 
Damn.
When it happens the rpm needle shows about 400 but my turbo timer is showing 2k rpm.

Rpm needle is true output.

Depending upon your pickup the turbo tine probably picks up spark signal to determine rpm.

I.e. , not a healthy engine. I would do a compression check before anything else... I think you are in store for an engine rebuild.
 
I think i found out what was the problem now, two of the cylinders aren`t getting any spark, the coil must have intermittenly stopped working yesterday, and today one half of it stopped working completely.

Its probably the reason for the misfire at high rpm and then just making the engine run on two cylinders.

I`ll find out how to check the coil pack to determine if its the problem or any wires that went bad.
Could there be any other reason for the coil not to give any spark on one half of the pack? Like cam or crank sensor or the ecu?

This can`t be a blown engine right? I`ll get the equipment to do a compression test just to make sure anyway.

The oil filler cap is leaking a bit and the coilpack sits right behind there so there were some oil steam deposits on the coilpack.

Thanks for all the answers.
 
Test/Replace your coil pack and get spark on all 4. And do a compression and/or leakdown (preferably leakdown) test for peace of mind.

Don't jump to conclusions until you get some hard data.
 
have not yet got the equipment for either a compression or leakdown, but i`m optimistic that it`s just the sensor.
I will get back to you.
 
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