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

gsrboi80 · Jun 8, 2009, 08:00 AM

The car starts running irradically because the code is triggered. Kind of a Limp Mode of sorts. Many have reported the same issue. Lifting off throttle then back on will clear the hesitation.

Try to put in the 0015 rom. PM me if you need a copy I can email it to ya's. If not simply disable the code routine in the ROM.

20gmr · Jun 8, 2009, 08:31 AM

Quote:

Originally Posted by gsrboi80

The car starts running irradically because the code is triggered. Kind of a Limp Mode of sorts. Many have reported the same issue. Lifting off throttle then back on will clear the hesitation.

Try to put in the 0015 rom. PM me if you need a copy I can email it to ya's. If not simply disable the code routine in the ROM.

I agree with your input but i believe that only helps people that get the code without the actual issue. The OP is experiencing a misfire, not phantom knock. The above advice is sound if you get the code without having the issue.

There are tons of reason you can have a misfire but with what the op is describing I believe this case to be an ignition misfire.

does it happen to get worse if it is rainy or humid out? I am almost certain a 30 dollar set of plug wires will completely solve your issue

Gotboost36 · Jun 13, 2009, 06:47 PM

mine does this to but itll do it in any gear... it makes the car vibrate pretty bad and u can see it threw the boost gauge(meaning the needle shakes ALOT) it drives me crazy....

20gmr · Jun 23, 2009, 06:36 AM

Quote:

Originally Posted by Gotboost36

mine does this to but itll do it in any gear... it makes the car vibrate pretty bad and u can see it threw the boost gauge(meaning the needle shakes ALOT) it drives me crazy....

Put a new set of spark plugs in

mad_VIII · Jun 23, 2009, 09:10 AM

Quote:

Originally Posted by dave3kgt

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.

Check all the sockets and pins on your ecu connector... I had this issue on my VIII and cleaning up some of the wiring helped get rid of it. I was never able to figure out exactly what the cause was but I tried everything you could think off (0015 rom, coil packs, plug wires, plugs, cam timing settings, ignition timing, etc etc). Re doing some of the wiring seemed to clear it up. (had various piggy backs installed at various times before going back to stock ecu then to AEM).

One thing I noticed was that if it started acting up, If I stopped, unplugged the ecu from the main harness, plugged it back in, it would fine for a few days before the issue would come back. At that point I started thinking it had to be fuel trim related and would occur right at the transition point from open to closed loop. I was never able to confirm this though, but it may be a good place to start if you have a good logger and can get a log while it is happening.

Getting rid of the fields harness and hard wiring the haltech interceptor (what I was running at the time, but acted the same on ecu+ before the haltech also using the same fields harness) got rid of the problem.

In my case, it always happened at light throttle cruize as you would either start to accelerate just a tiny bit or load would go up a tiny bit as you started going up hill but maintining the same speed. Or from time to time it would do it when I got stuck behind a white hair and was just trying to maintain the same slow speed. Never once did it during WOT, only light load low throttle cruize.

Best bet is to start by getting a log of the event as it occurs. See what your fuel trims looked like just before... if you have a +trim built up just before the event, and then it goes to zero right at the event, Then I would assume it happens as you drop from closed to open loop and have a momentary lean spot as a result of the fuel trims zeroing out on the transition to open loop.

Raceghost · Aug 20, 2009, 02:18 PM

Experiencing the same issue here... What are the tables I need to add to the 94170015.xml to get the CEL codes to show?

Thanks in advance.

*constant_boost · Aug 20, 2009, 02:31 PM

Its your EGR. located under your throttle body theres a valve with 2 limes on it from your intake manifold. Try checking that... Just had 3 evos with this problem fixed...

Raceghost · Aug 20, 2009, 06:19 PM

Quote:

ts your EGR. located under your throttle body theres a valve with 2 limes on it from your intake manifold. Try checking that... Just had 3 evos with this problem fixed...

What specifically? What am i looking for to change or fix? Is it my tables, I noticed that my EGR tables in ECU Flash are not correct. What are the EGR RPM scaling addresses? I also thought with MRFRED's 4 Bar Omni Settings, that the EGR is disabled...

*constant_boost · Aug 20, 2009, 07:51 PM

the EGR will not throw codes, but if the vacuum lines come off of the EGR, your car will misfire as described... i dont have any way to describe it other than reach directly under the throttle body and theres a little gadget like this one posted below with 2 lines on it... check to see if one of them lines came off...

xxblazexx · Aug 20, 2009, 10:14 PM

the egr vacuum lines are what threw my code they would pop off under heavy load ad high boost for some reason.. if you reach under the throttle body and find two vacuum lines connected to each other.. then when you find them try to make sure they both lead to a nipple if one doesnt just look around with your finger and walla

Gotboost36 · Aug 21, 2009, 11:24 PM

ok ill try this in the morning

xspsi4 · Aug 24, 2009, 08:01 PM

Quote:

Originally Posted by *constant_boost

Its your EGR. located under your throttle body theres a valve with 2 limes on it from your intake manifold. Try checking that... Just had 3 evos with this problem fixed...

Ha this worked and fixed my problem so props to you for finding this out.
I am actually on a 2k mile trip and am very happy to have found this.

Easy fix.

RedWing03 · Aug 31, 2009, 04:18 PM

Okay, for the record, I have this same problem...
only on an 8.
But my EGR hoses are all in line, but if that's what's causing the problem, is it possible that the solenoid is just bad?

RedWing03 · Sep 2, 2009, 06:56 PM

Bump

darkside4G63 · Nov 7, 2009, 05:56 PM

i am having the exact same problem as the OP. i have replaced the plugs (several times actually), i got the Spark Tech non cdi COP so my coils are replaced, and i had the 2 vacuum lines pop off the EGR and i put them back on and zip tied them up. i cleared the codes and it stopped for a while (2000 mi.) then it happened again. i checked and the vacuum hoses are still good. i noticed that i was picking up crazy knock when it happens and my wideband bottoms out lean. i dont think it is a fuel issue. im leaning more towards that phantom knock coming from the drivetrain via the input shaft. has anyone had any luck altering the knock filters in ECU Flash in the 3000 rpm, low load area to fix this. if so what direction do you go with the values to de-sensitze the knock sensor? Tephra, do you have any input? any help would be greatly appreceiated as i do not have the funds to rebuild my tranny at this time.