Misfiring At Low Revs With High Load

[and3_3]

Yer running 10 psi with standard computer and other supporting mods.

Will misfire in low revs between 2-3k with high load in 4th/5th at say 70-90. Problem is worse when it is cold too...

I'm thinking coilpacks on the way out but wouldnt that mean it would miss up high not down low?

Please any similiar experiences?

[Moodles2]

Before going with into coilpacks, worth checking the usual, gap the plugs to 0.8mm, problem persists go with a new set of copper plugs and gap them down to 0.8mm, check existing coilpacks for cracks etc

[geraus]

BCPR6ES 0.8

[benro2]

You are possibly experiencing what I am? See point 4 in the first post in this link:

http://www.skylinesaustralia.com/forums/Se...em-t296541.html

Is it actually misfiring or does it sort of feel like R&R?

A summary of the stuff to check, which I got from my thread linked above are:

- coolant temp sensor

- incorrect plug heat range - use heat range 5, gap to 1.0mm. As you can see in my thread, I'm currently using 7 w/ 1.1mm gapping and it doesn't like it!

- use correct oil viscosity - if you have any problems with the hydraulic lifters (do you hear a tapping noise sometimes?) then possibly oil that is too thick will prevent some of the lifters working properly - although that's just my logic that could be totally incorrect However under cold start conditions it could definitely have an effect.

- ignition timing

- fuel pump (not sure about this but can't hurt to check! Mine also failed recently even though it's a totally unboosted car... as in, *less* than stock boost, long story )

- ignitor pack

- crank angle sensor

- I admittedly did have Splitfire coilpacks, but even when I switched back to stockers, I noticed no difference under high load situations, only idle. I think for a stock(ish) car, the stockers should be fine!

[and3_3]

Yer have plugs gapped to 0.8 mm problem improved but still there.

I use motul turbolight 10w40 never had this problem before after years of using it so can rule that out.

Could be R&R but isnt that high in the rev range not low?

Unlikely fuel pump as only around 2-3k not up high when fuel pressure is highest.

Going to try a mates gtr coilpacks that apparently work, got another mate who has a stagea so might swap coils and see if that rectifies problem.

[benro2]

Could be R&R but isnt that high in the rev range not low?

Going to try a mates gtr coilpacks that apparently work, got another mate who has a stagea so might swap coils and see if that rectifies problem.

I was getting R&R ages ago when I was running 10 psi without the fuel adjuster to lean out the mixture. I noticed it would R&R at around 4000rpm and would come back into power again at about 5500rpm. It just felt like the car lost a heap of power and was spluttering a lot out of the exhaust. I think you could also see a pile of black smoke coming out.

However if you have a few mods that is allowing more air than the ECU is expecting at those rpm (which sounds likely since you're only seeing it in a high gear/high load), then that would definitely be R&R.

I don't think R&R is limited to high rpm, I think it can just happen whenever the ECU is running outside its safety parameters. AFAIK, you have to use some sort of AFR adjustment when you're running much over 8 psi??

As for whether it's R&R or misfiring... you should be able to tell the diff between the two fairly easily. Misfiring is sort of random and is more sudden than R&R. You'll feel little bursts of power (or really, pockets of reduced power) a few times every second, whereas R&R is more like you've just turned the boost waaaaay down while you're in a certain rev range. Once you get out of that range it'll just take off again. Also, misfiring would most likely happen all of the time, no matter what rpm, although having said that, when my coilpacks were on the way out it tended to be from 5500 rpm onwards, but I knew it was misfiring because of the way it was behaving at idle (random power cutouts).

Hope this helps!

Edited December 7, 2009 by benro2