WTF!?! Random misfire happening around 3k RPMs at 71-74 MPH in 5th gear only.

dave3kgt · Apr 9, 2009, 12:22 AM

Okay, so the majority of my problem is listed in the title. Here is whats not. This happens randomly. It only happens at 71-73 MPH in 5th gear only. Here is the real kicker, I have had this problem before and I have since installed a new engine and the misfiring just started again today. I was not boosting at all, but it has happened under boost as well. Parts that I have checked are the coil packs, and spark plugs (ie: gapping, fouled) and everything looks to be ok. Does anyone have any idea what is wrong with my car, and how or why it followed after the engine swap? Fuel related? ECU related? Vacuum? Need some help here guys. Thanks in advance.

Dave

dave3kgt · Apr 9, 2009, 01:29 AM

Bump!

nval001 · Apr 9, 2009, 01:45 AM

how about cam position sensor?

evosoh · Apr 9, 2009, 01:46 AM

Immediately after misfire, try to check the spark plugs and see if you can spot the difference.
Is your ecu tuned or standard?
Have your tried changing the cam sensor?
Each time it misfires, how long does it last?

dave3kgt · Apr 9, 2009, 06:06 AM

Quote:

Originally Posted by evosoh

Immediately after misfire, try to check the spark plugs and see if you can spot the difference.
Is your ecu tuned or standard?
Have your tried changing the cam sensor?
Each time it misfires, how long does it last?

I will pull the plugs tomorrow when I wake up. As for the ECU, it is very mildly tuned. (Email flash) I will say that I had the problem with the OEM tune as well. As I stated before, the problem followed with my engine swap. The new engine had a new cam sensor on it, but I will test it out. When the misfire occurs, it usually only lasts for the duration of the drive when it starts to misfire. I can also get it to stop misfiring by letting off the throttle and then gettting back into it. Here is the catch with that. If I accelerate back to 3K RPMs, it will immediately start to misfire again. If I accelerate past 3K it will run perfect. After being turned off for a while (12 hrs. +) the check engine light will automatically reset and everything goes back to normal.

*constant_boost · Apr 9, 2009, 06:42 AM

^

who did you email flash through?

evosoh · Apr 9, 2009, 07:57 AM

Since your check engine light comes on, there must be engine check codes. Get the engine check codes.

dave3kgt · Apr 9, 2009, 03:21 PM

Noelsevo is the guy that tuned my ECU. The only code it throws is P0300 Random Misfire.

dave3kgt · Apr 9, 2009, 06:14 PM

Back to the top!

evosoh · Apr 10, 2009, 11:56 AM

Check out this link
P0300 code on IX...anyone else have it?
See Post #19, I think it will help somewhat

dave3kgt · Apr 10, 2009, 06:16 PM

Here is my only problem with that thread, they are talking about getting the p0300 with no real reason. With me, my car is misfiring badly and it basically sounds like a sick Subaru when this is happening. I do not think that the tranny would actually cause it to misfire rather than the stated "trick the ECU into thinking it is misfiring and pop the code" .

awdrivin · Apr 10, 2009, 10:59 PM

this is off the wall, but i had a misfire because i had an issue with fueling.

check injectors/fuel pump/etc...

dave3kgt · Apr 11, 2009, 11:34 AM

Quote:

Originally Posted by awdrivin

this is off the wall, but i had a misfire because i had an issue with fueling.

check injectors/fuel pump/etc...

Noted ^^ I am working on getting a multimeter to test the injectors among other things.

dave3kgt · Apr 11, 2009, 08:51 PM

Bump!

dsm25psi · Apr 12, 2009, 09:33 PM

Quote:

Originally Posted by dave3kgt

Here is my only problem with that thread, they are talking about getting the p0300 with no real reason. With me, my car is misfiring badly and it basically sounds like a sick Subaru when this is happening. I do not think that the tranny would actually cause it to misfire rather than the stated "trick the ECU into thinking it is misfiring and pop the code" .

when i had misfire like that it was my coil