HELP! I'm at wits end with a misfire.

[Guest]

My Legnum is misfiring at low to mid range revs @ light throttle applications. Needless to say this is a bastard for daily driving.

The miss is violent, more like cuts in power, in and out. At WOT its fine and doesnt seem to be any slower than it ever was.

So far I have checked intercooler piping best I could, changed the plugs, plug leads, tested the BOV for leaks by removing and test driving.

I just cant seem to get rid of it!!!!!

Any ideas for me???

Cheers, Bart.

 

[bradc]

Do you get any smoke coming out? Have you reset the ecu, and did that make a difference?

 

[Guest]

no smoke that ive noticed, ecu reset = no difference.

 

[dimi_108]

Bart, how much boost are you running? Also, what kind of boost controller are you using? Manual or electronic?

Also, have you had your injectors ulstrasonically cleaned yet?

 

[Guest]

Stocko rocko boost.

Not had the injectors cleaned.

Interestingly, I just didn another ECU reset and it seemed to help for the first 2 mins, until it relearnt a few things. But why would it learn in a miss? Mis-calibrated sensor somewhere??

Cheers, Bart.

 

[bradc]

Hmm, my car did something similar for a bit. It would run fine for 15 min to a few weeks, then start misfiring and stuttering like mad, blowing tons of white smoke out of the exhaust. Flooring it would fix things for me, and resetting the ecu would fix it again. I didn't really get around to fixing the issue, I installed the Autronic SM4 and never got around to fixing it. I'm guessing the fault was with the MAF or O2 sensor.

 

[Guest]

bugger, lol.

Doing a manual conversion soon, so the ecu will be replaced, but only with a factory manual one. Any way of reliably checking the functionality of the O2 sensor and MAF?

Cheers, Bart.

 

[bradc]

With the O2 sensor you can check it in EVOScan and see if it oscillates between 0 and 1v at idle. The MAF will report a frequency in EVOScan related to how much air is flowing through the engine. Flooring the car at high rpm will obviously increase the value by a lot.

 

[Guest]

Righteo, i'll hook up the laptop tomorrow. Lol the saga continues.

 

[Guest]

Hooked up evoscan this evening, the O2 sensor seems to be functioning just fine, but laptop battery died b4 i could look at the AFM output

 

[gorgath]

Hooked up evoscan this evening, the O2 sensor seems to be functioning just fine, but laptop battery died b4 i could look at the AFM output

There's the problem!!! LOL

 

[Guest]

Amen! The problem is fixed!

Ran evoscan on the way to uni this morning, logging the TPS, and by the end of my street it was obvious that it was not logging anything at light throttle applications. Pulled over, lifted the bonnet and now knowing where I should be looking the TPS was wound round to its limit, not in line with the nice japanese white out where it had previously been.

So i pulled it back round, tightened it up, went through a few cycles of full throtte while driving so it could get its limits again and is now running perfectly! Also gearbox warning light is gone!

Lol happy morning with the VR4. Bring on the manual box.

Cheers, Bart.

 

[SiliconAngel]

Great to hear Bart, fantastic news! Good work on the trouble-shooting

 

[Scubasteve]

Amen! The problem is fixed!

Ran evoscan on the way to uni this morning, logging the TPS, and by the end of my street it was obvious that it was not logging anything at light throttle applications. Pulled over, lifted the bonnet and now knowing where I should be looking the TPS was wound round to its limit, not in line with the nice japanese white out where it had previously been.

So i pulled it back round, tightened it up, went through a few cycles of full throtte while driving so it could get its limits again and is now running perfectly! Also gearbox warning light is gone!

Lol happy morning with the VR4. Bring on the manual box.

Cheers, Bart.

Whewre and what is the tps?

 

[Macca]

Its a little black box on the side of the throttle body and it’s the throttle position sensor, it tells the computer what position the throttle is at.