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d1rtyj4k3
03-31-2010, 02:40 PM
i have been searching around reading as much as possible cant really come up with anything helpful
my sr20 notch top is sputtering/missing/backfiring around 4-4500 rpm when under boost, i was having a boost fluctuation problem but i found out that was the boost controller, its now back to stock bypassing the boost controller, if i allow revs to build without giving it much throttle(making no boost) the car revs normal and doesnt begin to missfire. im running very rich but the car has been like that since i got it, i am going to check out the fuel pressure here in the next day or so.
anyone have any clues of what to check? thanks

shagspeed
03-31-2010, 03:43 PM
i have been searching around reading as much as possible cant really come up with anything helpful

my sr20 notch top is sputtering/missing/backfiring around 4-4500 rpm when under boost, i was having a boost fluctuation problem but i found out that was the boost controller, its now back to stock bypassing the boost controller, if i allow revs to build without giving it much throttle(making no boost) the car revs normal and doesnt begin to missfire. im running very rich but the car has been like that since i got it, i am going to check out the fuel pressure here in the next day or so.

anyone have any clues of what to check? thanks

check your plug gap... check wiring to maf as well.. make sure its got good solid ground.... i had heavy miss fire over 20psi before my msd 7al2 gaping plugs down helped.. ohh also with coil packs make sure they have clean power and good grounds...

d1rtyj4k3
03-31-2010, 04:00 PM
ok will check grounds,
just put new plugs in recently and gapped them to .028 i believe cant remember

teamsprock
03-31-2010, 04:29 PM
Sounds to me like a boost leak, pressure check the system. The reason it wouldn't do it under low throttle is the boost is not present causing a coupler or something to allow a leak. I'd be willing to bet a lot that you will find either a cracked/lose coupler or hose. Some sort of boost leak I'd be 99% sure.

shagspeed
03-31-2010, 04:33 PM
Sounds to me like a boost leak, pressure check the system. The reason it wouldn't do it under low throttle is the boost is not present causing a coupler or something to allow a leak. I'd be willing to bet a lot that you will find either a cracked/lose coupler or hose. Some sort of boost leak I'd be 99% sure.

Well under higher cylinder pressures "Boost" If ignition is weak it will blow out the spark... Boost leaks are usually really noticeable by there sound.. ;) Also does it miss from say 5800-6800 RPM @ WOT?

teamsprock
03-31-2010, 05:08 PM
I agree ignition problems can be as you describe but that shouldn't be the case unless he is running a big turbo. I ran the stock gap at 400+ hp for 5 years with no problems.

Also I beg to differ on the noise of a boost leak. I had 7 pin hole sized leaks from a beat up Greddy intercooler, and later had a cracked coupler and you could never hear them. Some bigger leaks would sometimes make some noise but most in my experience do not. Even when you know you have a leak its not always easy to find, thats why I would pressure test the system. Its easy to do and I again would be willing to bet unless the poster has a big turbo running 20+ psi that its probably not ignition related. I could be wrong but I've dealt with a lot of SR's in the last 10 years and would nearly stake my name that will end up being his issue. I've seen too many people buy ignition stuff they don't need when usually it all comes down to the simple things like leaks and timing. I've ran 26 psi on my Gt30r with stock ignition with no problems.

shagspeed
03-31-2010, 05:42 PM
I agree ignition problems can be as you describe but that shouldn't be the case unless he is running a big turbo. I ran the stock gap at 400+ hp for 5 years with no problems.

Also I beg to differ on the noise of a boost leak. I had 7 pin hole sized leaks from a beat up Greddy intercooler, and later had a cracked coupler and you could never hear them. Some bigger leaks would sometimes make some noise but most in my experience do not. Even when you know you have a leak its not always easy to find, thats why I would pressure test the system. Its easy to do and I again would be willing to bet unless the poster has a big turbo running 20+ psi that its probably not ignition related. I could be wrong but I've dealt with a lot of SR's in the last 10 years and would nearly stake my name that will end up being his issue. I've seen too many people buy ignition stuff they don't need when usually it all comes down to the simple things like leaks and timing. I've ran 26 psi on my Gt30r with stock ignition with no problems.

Yes... at 16PSI I was making 406WHP on pump gas and this was back in 2000 on a SR20DET 54C Engine with forged internals. the 54C does not have a coil for ea Cyl.. Also 7 pinhole size holes will not create enough of a leak to make a misfire IMO.. Any thing worth a misfire due to leak I would think you would easily hear and the miss would not really be from Cyl pressures but a super rich condition...

Though back to misfire at hand.. I have seen lots of swaps where wiring has poor power or bad grounds... Though everyones input should get him giong..

buentellomma
04-01-2010, 12:08 PM
check your mafs, mine had one of the wires bent and did the same thing.

d1rtyj4k3
04-01-2010, 03:02 PM
its a gt35 but only running 16 psi illl see if i can find any boost leaks, but i do think the most likely cause is over fueling causing the miss im going to get a fuel pressure guage on it this weekend its got some junk pressure regulator on it im betting on that is the problem,
thanks for all the ideas guys this will atleast give me a starting point

doomviillain
04-01-2010, 04:44 PM
my friend had the same problem wit his s13 SR blacktop. It would sputter at 4000rpm, he adjusted the tps sensor and it was back to normal. Try adjusting the tps sensor and see what happens

steve shadows
04-02-2010, 08:24 PM
What ecu are you using?

If it's aftermarket send me a pm

d1rtyj4k3
04-08-2010, 03:24 PM
sent pm


found out that i only have 38-40psi fuel pressure, seems mighty low to me

steve shadows
04-08-2010, 04:45 PM
That's pretty much standard fuel pressure

Sounds like vacuum leak possibly