backfire

[planemos]

My car backfires. It always happens in and around the top of 3rd gear and 4th gear. I let off the gas and coast for a while then as soon as my foot get back on the gas it backfires. It seems to happen right after I was in boost I think not certain about that.

 

[Compton74]

Any mods done to the car? Normally when you hit boost the fuel pump obviously delivers more fuel, you let off the gas to shift and the leftover fuel gets dumped into the exhaust and gets ignited thus causing a boom! That is if you have no cat and a full exhaust.

 

[Turbo Habanero]

... Do you have a aftermarket bov while using a AFM ?

 

[planemos]

I have a HKS 3 inch super drager exhaust. Apexi intake. stock bov. I can coast from like 90km/h to 55 in 4th and then hit the gas and it backfires.

 

[Turbo Habanero]

Hmm start looking for leaks... Assuming that you fixed the hg..

 

[IJ.]

Check the TPS adjustment..

 

[AJ'S 88NA]

Check the TPS adjustment..

Then time it .

 

[planemos]

Ok. I did the tps adjustment and then timed it. The timing is lower than 10 when I look at it with a timing light. It seems to jump betweeen 5 and 10 so it's hard to get an exact reading. I did a knock sensor rewire properly and have recently replaced hg with a Toyota one. Thinking maybe I didn't do the tps adjustment exactly right but quite close. I was having issues with the cps. I installed it one time and the timing was way over 10 and I bottomed out the adjustment on the cps and it wouldn't get close enough to 10. I made sure I was at TDC. And so then I took out the CPS and tried re installing it because of the gears on it. I tried taking it out many times and this is a close as I could get. Right now it is bottomed out on the adjustment bolt and ya, like between 5-10 when I check it. It seems better when the car warms up.

 

[kelson]

My car does the exact same thing. I thought it was normal. I have a 1jz with full 3" exhaust, no cat. sometimes when I boost then shift it shoots flame out the back. I'm also running really really rich though.

 

[kelson]

hey I accidentally fixed it! I plugged some vacuum leaks and now it runs smooth all the time. I don't know if this will be the same for you since it's a 7m with a MAF not a MAP, but I would definitely start looking for leaks. I hope that helps

 

[91whitepack]

Did you jump the pins in the diagnostic box when you timed it? The jumping around could be it trying to correct itself. i never would have known that if not for the TSRM.

 

[AJ'S 88NA]

Yeah this^

If not it will jump around for sure.

 

[jetjock]

Are we really talking backfire or is it muffler explosion?

 

[IwantMKIII]

Are we really talking backfire or is it muffler explosion?

Was thinking the same thing. I'm going with a safe bet and saying he meant after-fire.

On another note, YOU CANNOT PROPERLY TIME WITHOUT PUTTING THE CAR IN DIAGNOSTIC MODE. Jump terminals E1 and TE1 (? someone correct me if I'm wrong, I just know it visually at this point) It will be impossible to get accurate.

 

[91whitepack]

Was thinking the same thing. I'm going with a safe bet and saying he meant after-fire.

On another note, YOU CANNOT PROPERLY TIME WITHOUT PUTTING THE CAR IN DIAGNOSTIC MODE. Jump terminals E1 and TE1 (? someone correct me if I'm wrong, I just know it visually at this point) It will be impossible to get accurate.

Thats right. standing on the driverside facing the passenger side, it should be the middle and the bottom right in the cluster of 9.

 

[jetjock]

For timing the engine must be hot, the system in diag mode, and the IDL contact closed. The easiest way to verify the last two things is to check for normal "no code" flashing of the MIL before any timing attempt is made.

 

[Jyrydr]

hey I accidentally fixed it! I plugged some vacuum leaks and now it runs smooth all the time. I don't know if this will be the same for you since it's a 7m with a MAF not a MAP, but I would definitely start looking for leaks. I hope that helps

still relevant. any air leaking out has been accounted for in the system(inc BOV,s that arent plumbed back), when leaked f/a mix ends up rich