Backfire and power loss at high RPM's

[Tsmith]

I have read both of these posts:

http://www.dsmtuners.com/forums/newbie-forum/97442-backfire-redline-high-rpms.html

http://www.dsmtuners.com/forums/new...isfire-bucking-almost-backfire-high-rpms.html

Neither of them actually state what fixed the issue so I wanted to start my own thread.

Same issues with high rpm (above 5k usually) and cold weather. Sounds like a backfire and the car bucks for a second under WOT. If I am not at WOT this doesn't happen at all. Also I didnt have this issue three days ago and it was the day my CEL came on throwing a P1500 and P0505 code again. Now I do want to add I live in Colorado and this also all happened the same day the weather dropped to around 38 degrees. I do want to add I have had the CEL codes for about 2 months on and off and this problem isnt always tied to the CEL coming on. Every so often I clear the codes when the light starts bugging me and it will stay out for about 2-3 weeks.

Any help is appreciated!!

 

[n0de]

P0505 which is an Idle System Malfunction

Try testing your IAC or just replace it entirely.

P1500 Alternator FR Terminal circuit

Test or replace your alternator. Your alternator could not be failing and unable to supply enough voltage to the fuel on WOT pulls.

 

[talon314]

You Are running extremely rich at that point and that is what causes the backfire, Get a wideband and do a realy good tune and it will fix it

 

[Riceburning101]

BLT that mofo. idk what mods you have but the cold air could be making the intercooler pipes shrink etc. or worn tbody gaskets, shaft seals shrink and cause a boost leak which would cause the car to run rich

 

[n0de]

This Post
Like i said. Get the alternator and battery tested. Seeing as how the car was something that happened out of nowhere I believe this to be the likely cause of failure.

This post
Even this person simply replaced the battery and saw better performance at WOT. I'm fairly certain they changed their alternator too seeing as they checked the voltage and it was low.

Another link

Although BLT wouldn't hurt but I don't think that is your main issue, especially since you are throwing a code related to the alternator.

 

[Tsmith]

I did want to add that I have a ebay 16g, FMIC, and Greddy BOV as my only mods. BLT has been done as I just found out that my cat was plugged about 2 weeks ago causing a no boost problem. Before that I BLT the car like 4 times and replaced all of the rubber connectors thinking the same thing. I do not have a way to tune the car since I do not have Eprom installed nor do I have DSMLink even if I installed my eprom I have laying in the trunk right now.

There is a wire hanging from the alternator that I will take a picture of tomorrow and post it. I thought maybe it was causing a low voltage but my Turbo Timer shows almost 13 volts while the car is running and just over 11.5 when it is not running. I will try replacing the IAC since I know it needs to be replaced anyways.

 

[Ozyeclipse]

EBay 16g isn't much of an upgrade you would be better off with a 14b faster spooling and last longer than that knockoff 16g it would last a month before it starts spitting your engine oil out the exhaust if your Lucky
Do the basics first test the idle control, you know boost leaks are almost always a culprit rubber acts different in cold and hot environments , also proper plugs etc do some test runs and tell us the results. Hope it helps

 

[n0de]

I did want to add that I have a ebay 16g, FMIC, and Greddy BOV as my only mods. BLT has been done as I just found out that my cat was plugged about 2 weeks ago causing a no boost problem. Before that I BLT the car like 4 times and replaced all of the rubber connectors thinking the same thing. I do not have a way to tune the car since I do not have Eprom installed nor do I have DSMLink even if I installed my eprom I have laying in the trunk right now.

There is a wire hanging from the alternator that I will take a picture of tomorrow and post it. I thought maybe it was causing a low voltage but my Turbo Timer shows almost 13 volts while the car is running and just over 11.5 when it is not running. I will try replacing the IAC since I know it needs to be replaced anyways.

And what about the battery, can you test that too. Also your altenator reading is kind of low. Try running your engine at 3k rpm, if you can get over 13v then the alternator might be ok.

Use a multimeter (you can borrow one at pepboys), Ive heard of people getting readings that were 1v + off on using the apexi turbotimer (so i just dont trust any turbo timer). I believe pepboys will even test your battery for free as well.

 

[kenamond]

Please update your car profile.

If you're running an evo316g and boosting on the threshold of too high, you'll be effectively boosting even higher at colder temperatures (colder temps, especially with a FMIC, will give you better efficiency than at warmer temps). But for this to be the problem, you'd have to be hitting fuel cut, which I doubt. What does your boost peak out at when it stutters/cuts?

I agree with all the other recommendations. It could be several things, but if you get the CEL to stay off, that's a lot fewer potential things to investigate.

Finally, repeat the BLT after the cold snap. You're a pro at BLT now, so you know how easy they are. Who knows...something might have let go recently.

Good luck! Pray for snow! I'll be up your way (Wolf Creek and/or Summit County) if it does! One benefit of cold.

 

[Tsmith]

Just wanted to say that today I went to get my alternator tested and noticed that my positive battery clamp was too big for the post so it was a little loose. I bought a shim for it and when I got everything all put back together they tested the battery and alt and everything was good. Also since I pulled that pos cable it reset the CEL. Anyways on the ride home didnt get any issues with backfire at all. Maybe this will fix it but I will update after a couple days of driving.

 

[n0de]

Just wanted to say that today I went to get my alternator tested and noticed that my positive battery clamp was too big for the post so it was a little loose. I bought a shim for it and when I got everything all put back together they tested the battery and alt and everything was good. Also since I pulled that pos cable it reset the CEL. Anyways on the ride home didnt get any issues with backfire at all. Maybe this will fix it but I will update after a couple days of driving.

Good news, I've heard of people having issues because of loose clamps around their battery terminals, so this very well may have been the issue.

Let us know in a few days.

 

[Tsmith]

EBay 16g isn't much of an upgrade you would be better off with a 14b faster spooling and last longer than that knockoff 16g it would last a month before it starts spitting your engine oil out the exhaust if your Lucky
Do the basics first test the idle control, you know boost leaks are almost always a culprit rubber acts different in cold and hot environments , also proper plugs etc do some test runs and tell us the results. Hope it helps

Let me just say that I have owned this car for a year now and I am very happy with the Ebay 16g. Only issue I have is that the spool up is rediculous. I dont feel any boost until about 4500 rpms. As for reliability I cant say anything bad about it. Even with driving the car with a plugged cat (which I assume puts more pressure on the turbo seals since it cant escape out the tailpipe) I dont have any issues right now.

 

[laserspeeddemon]

The spool you are experiencing is indicative of a boost leak. Did you also check your TB shaft, ERG and valve seals?

 

[CrashGNX]

Upgrade your exhaust to 2.5 inch all the way from turbo to end, get the plugged cat out og the system and youll see a real improvement in the turbo spool, also the shorter and least restrictive you can make your intake and IC the the better for spool. FMICs cause a large pressure drop from turbo to intake and cause bad spool lag.

Ive seen my DSMs do really odd things like that due to bad grounds or bad connections at the battery or anywhere else. They are seriously prone to electrical issues if everything isnt 100%. I've even had my alternator diodes go out and charge at 20-24 volts, car ran like a raped ape but the stereo just turned off above 20 and the battery didnt appreciate it much .

also check your plugs and maybe test or change your coil pack, usually issues with misses or backfires in the 5k range (if no boost leaks or obvious reasons are found) are either spark being blown out by too much boost or the gap is too wide on the plugs causing a weak spark in the first place, or the coil is just old and dying putting out a weak spark. gap should be .26-.30 depending on what your motor likes on copper plugs.

 

[Tsmith]

The spool you are experiencing is indicative of a boost leak. Did you also check your TB shaft, ERG and valve seals?

I might have misstated what I mean. I see about 3-8 psi at about 2k rpms but really dont feel the car start to push until about 4500 rpms where I start to boost at 12-18 psi.

Upgrade your exhaust to 2.5 inch all the way from turbo to end, get the plugged cat out og the system and youll see a real improvement in the turbo spool, also the shorter and least restrictive you can make your intake and IC the the better for spool. FMICs cause a large pressure drop from turbo to intake and cause bad spool lag.

Ive seen my DSMs do really odd things like that due to bad grounds or bad connections at the battery or anywhere else. They are seriously prone to electrical issues if everything isnt 100%. I've even had my alternator diodes go out and charge at 20-24 volts, car ran like a raped ape but the stereo just turned off above 20 and the battery didnt appreciate it much .

also check your plugs and maybe test or change your coil pack, usually issues with misses or backfires in the 5k range (if no boost leaks or obvious reasons are found) are either spark being blown out by too much boost or the gap is too wide on the plugs causing a weak spark in the first place, or the coil is just old and dying putting out a weak spark. gap should be .26-.30 depending on what your motor likes on copper plugs.

I have a 3 inch from the O2 sensor back and have already fixed the plugged cat. Just bought new plugs yesterday and went with NGK BP7ES plugs that I am going to put in today. I have a leaking VC gasket which I will be replacing this week. Hopefully this will help the spark a little. I will also be replacing the IAC in about 2 weeks.

The battery post didn't completely fix the issue. Still getting the backfiring last night while cruising, funny thing is it never happens in first gear only in 2nd or higher at about 5k rpms. Still had a great night for the first night out in nearly 9 months (I just got back from Afghanistan).

 

[n0de]

I might have misstated what I mean. I see about 3-8 psi at about 2k rpms but really dont feel the car start to push until about 4500 rpms where I start to boost at 12-18 psi.



I have a 3 inch from the O2 sensor back and have already fixed the plugged cat. Just bought new plugs yesterday and went with NGK BP7ES plugs that I am going to put in today. I have a leaking VC gasket which I will be replacing this week. Hopefully this will help the spark a little. I will also be replacing the IAC in about 2 weeks.

The battery post didn't completely fix the issue. Still getting the backfiring last night while cruising, funny thing is it never happens in first gear only in 2nd or higher at about 5k rpms. Still had a great night for the first night out in nearly 9 months (I just got back from Afghanistan).

You should have full boost on a 16g well before 4k rpms. You should probably be seeing full boost by around 3500rpm or maybe even sooner. There are people with stock block that are running HTA86 turbo that see full boost around 4500rpm. A 16g Should be fully spooled to X amount of boost well before that.

Actually, since you're in Colorado I think the altitude makes a big difference in when you'll see boost, so everything might be accurate as you're stating.

 

[boostednate]

I would check your spark plugs for gap size, and probably wouldn't hurt to change them anyway ($8 for all of them). Also check your coils. I had the same problem and turned out that my plugs had way too wide of a gap

 

[Tsmith]

Changed plugs to NGK BP7ES and gapped .028, also new plug wires. CEL is no longer on after installing a new battery and there are no more codes. Still getting a misfire or backfire at high rpms. Its much worse in 2nd gear or higher. I dont remember if I mentioned that it is an auto or not.

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Either way as soon as I get into boost you can see that the A/F goes straight to rich.

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Sorry the videos are so bad but hopefully it gets the point across. Thanks for looking.

 

[CrashGNX]

Dude, its fuel cut. only real way around it is to re-program the ECU, go with ECMLink would be most cost effective. test it by turning your boost down to about 12lbs and see if it does it still. The stock ECU cuts the fuel pump or shuts off the injectors above a certain amount of air intake measured at the MAF.

Man thats so much less violent in a auto! in a manual with good mounts it literally feels like you hit a brick wall.

 

[Tsmith]

Yea thats what I heard about fuel cut and is why I ruled it out. I thought it was just a tuning problem.

 

[CrashGNX]

Slip of the torque converter and trans takes alot of the shock out of yours but its definitely fuel cut. Mine did the same thing when I went to a 16g.

 

[EclipticalGS]

Sounds like fuel cut.

You may have;

Boost Leak
Front O2 not cycling (usually throws bank 1 fuel code as well)
Huge exhaust leak pre front 02 showing your ecu a lean mix, in turn you get additional fuel
Your boosting your car to 18psi like you mentioned with a slight boost leak and your stock injectors are not capable of handling 18psi plus a leak.
Your downpipe is too large letting your boost creep to the point of fuel cut on stock injectors

Do a BLT, check exhaust for leaks, ensure your not getting boost creep

 

[Tsmith]

so is link the only way to get rid of fuel cut properly? Or can I go with manual injectors since they are 450's and my auto ones are 390?

 

[ktime]

Sounds like fuel cut.

You may have;

Boost Leak
Front O2 not cycling (usually throws bank 1 fuel code as well)
Huge exhaust leak pre front 02 showing your ecu a lean mix, in turn you get additional fuel
Your boosting your car to 18psi like you mentioned with a slight boost leak and your stock injectors are not capable of handling 18psi plus a leak.
Your downpipe is too large letting your boost creep to the point of fuel cut on stock injectors

Do a BLT, check exhaust for leaks, ensure your not getting boost creep

x2 that's what I was thinking

 

[Funfettie]

a tuning system is the only way to get rid of it (at least that i know of) DSMlink is by far the best, and will give you TONS of room to grow.