WOT Detonation? Not sure

[Bluefire16]

Hey guys, so i tuffed it out, and and installed my fmic in 20-30 degree weather here in michigan. So we have had dried roads the last couple of days and i decided to do a couple pulls, soon as i step on it and go WOT i get a jerk. I believe its detonation, but not sure, it only does it when WOT. So im gonna switch to a colder burning plug, im running bpr6es right now with a 14b at 15psi. Im also ordering new Thundersport wires...

 

[kenamond]

Did you boost leak test after the install? If you have a leak in the charge piping, it might be fuel cut, not detonation. Or it could just be running pig rich from a boost leak which can cause bogging.

I didn't check your profile, but if you don't have a logger, you should get one.

I'd also check the plug gap. If it's too large and you're cramming more air into the motor, it might be missing (not sparking across the denser fuel-air charge in the cylinders). I wouldn't think you'd need 7ES plugs at 15psi.

If you're running the same boost as before the FMIC install and you're all of the sudden hitting this problem, I'd suspect a boost leak.

Good luck!

 

[Bluefire16]

Yea ive checked, i have the day off tomorrow (well besides hangin out wit the girl) but im gonna try to check again...there is one spot i believe could be leaking. But my last set of 6's were burnt up pretty good, and when these new ones went in i set the gap at .028. Now recently ive read to go to .026.... But tomorrow i will pull the plugs and check and do another blt. Any other ideas? ### i have had boost leaks before and this is nothing like it...its a BIG harsh Jerk.

 

[kenamond]

I've never personally experienced fuel cut, but everyone says it's like your motor stops firing completely for a short period, and since it usually occurs at WOT, it is quite abrupt.

When you say you've tested, you've actually pulled the intake pipe off of a warmed-up motor, put the boost leak tester on the compressor inlet, appled 20psi to the tester from a compressed air source and monitored how slowly the pressure leaks down? If not, that's what you need to do. My car will leak down about 1psi every 4 seconds from 20psi initial pressure on a warmed-up motor.

A bad boost leak will cause fuel cut. A less-bad boost leak will cause fuel cut on a cold day but not on a warm day due to the increased density of the colder air. If the ECU measures too much airflow at the MAS (which is pre-turbo), it will cut fuel and spark to the motor as a safety precaution.

Until you get to around 17psi boost, you should be good with BPR6ES plugs gapped to 0.028".

 

[Bluefire16]

Hmm ok well ill still get some new ones i think.... im sure they shot neways. But yes tomorrow i will be getting out the air compressor and all haha

 

[MaNGiNa24]

Hmm ok well ill still get some new ones i think.... im sure they shot neways. But yes tomorrow i will be getting out the air compressor and all haha

They are probably shot from running too rich because you have a boost leak

If you just installed a FMIC and are retaining the same boost settings you definitely shouldn't be experiencing knock. In fact you should be getting less knock due to the cooler air.

 

[nkosi]

Hey that use to happen to me too ...i live in quebec canada and when it gets cold i would hit fuel cut when i was running stock...get ## self a data logger kit and then u can see if its knock ## getting.

 

[Bluefire16]

Ill see if i can borrow a friends, but just an update. NEW PLUGS gapped at .028 and BLT. Found 2 SMALL leaks but nothing serious enough to cause this. So if i stay on the gas it will just keep jerking, ANYONE with any other suggestions? Im thinking bad gas or crank sensor could be shot?

 

[->PrOjEcTGS<-]

A video would help but I'm guessing fuel cut also. Did you remember to plug your MAS back in?

 

[carfan2000]

Ill see if i can borrow a friends, but just an update. NEW PLUGS gapped at .028 and BLT. Found 2 SMALL leaks but nothing serious enough to cause this. So if i stay on the gas it will just keep jerking, ANYONE with any other suggestions? Im thinking bad gas or crank sensor could be shot?

If you have aftermarket plug wires... try replacing them. That is, try putting your stock wires back in, or borrow someone's wires. Bad wires can cause heavy hesitation under WOT (it will feel like it is cutting out). The link below provides more info. Good luck.


Magnecor Race Wires: Mitsubishi twin cam technical bulletin

 

[Bluefire16]

I have your regular Autozone Replacement wires. AC Delcos i think...they were in the car oringally. But hmm fuel cut at 14/15 psi? Ill reduce the boost and see if that helps. I will post a video asap

 

[Bluefire16]

Also i am not recirculating my BOV at the moment, due to the fmic pipe set up...im getting some new flex tube.

 

[Bluefire16]

So i believe the Canadian was right, i believe i was hitting fuel cut due to the cold weather. I turn the boost down to 12 psi from 15psi and guess what. NO BUCKING or JERKING!

 

[nkosi]

So i believe the Canadian was right, i believe i was hitting fuel cut due to the cold weather. I turn the boost down to 12 psi from 15psi and guess what. NO BUCKING or JERKING!

Im glad i could help ...i got a dsmchips from jeff and got rid of that fuel cut ...thats the best way and a data logger.

 

[nkosi]

Im glad i could help ...i got a dsmchips from jeff and got rid of that fuel cut ...thats the best way and a data logger.

sorry thats a dsmchips stage 3 ecu with a chip burned to my specs with the help of jeff of course...good guy i recommend him.

 

[Bluefire16]

You reprogrammed your ECU? Is that what your saying you did? ### i just plan on putting a bigger fuel pump (a 190). Then eventually injectors and whole new FPR setup.