New Mods Causing Car To Miss, Backfire, And Surge?

[Peter]

Hey everyone,

I’m a bit perplexed….

Have had the Skyline (Series 1 R33 GTS 25t) for about six years now…came with a 3inch cat back exhaust system….was running well….in the last six months I have done the following….

Full 3 inch exhaust system

Greddy V-Spec FMIC

Apexi Pod Filter

Apexi Mechanical Boost Gauge

Turbotech Manual Boost Controller (the eBay one).

After I installed the exhaust, intercooler, and pod, I noticed that when flat out accelerating, in 3gear, a slight hesitation (miss??) around 5000rpm would occur – boost was at 7lbs (0.4Bar). This would happen intermittently, in cold and warm weather.

Just recently installed the Turbotech Manual Boost Controller and increased the boost to 10lbs (0.7 Bar) and this hesitation (miss(?) with a backfire) was more pronounced at the same RPM – around 5000.

Took the car out today on the highway and gave it flat to the floor acceleration from a standing start in 1, 2, 3, 4 gear, and it seemed to backfire when it reached the higher revs (above 4000rpm), making popping noises out of the exhaust, and surging forwards – it would lose power with every pop, then pick up again….so I stopped this very quickly, and drove it home, off boost, and it ran fine. It also runs fine when accelerating hard at low rpm, but as soon as it gets to around 4000 - 5000rpm+ it seems to miss and backfire – can’t hear any pinging though?

I have read on these forums that re-gapping the spark plugs to .8mm may help when turning up the boost (as they are 1.1mm stock I think), so I’ll probably buy some new plugs with the smaller gap, but was wondering if it could be anything else?

Any suggestions would be appreciated.

Pete

PS: I reset the ECU after every modification as suggested in other threads.

[axe s]

by the sounds of it, it's your plugs... i had the same problem... gapped mine to 0.7 and it went perfect

[tridentt150v]

so I’ll probably buy some new plugs with the smaller gap, but was wondering if it could be anything else?

You don't buy plugs with a smaller gap!!! You buy plugs and then use feeler gauges and set the gap by knocking the tang on the plug in or bending it out a bit. Or you could just do it to the plugs you already have in it. A set of feeler gauges will set you back like sub $5 [you can get a bigger set for $30 approx.]

[race_snooze]

did you bother getting it re tuned, or even using a SAFC

[Peter]

Thanks axe s and tridentt150v...I'll regap the plugs using feeler gauges to .8mm or .7mm and see if it makes a difference....

race snooze I didn't get the car retuned, nor am I using a SAFC, I only reset the ECU - should I be considering these options for such low level mods??

Thanks,

Pete

[VB-]

plugs, if that dont work, coil packs, but my guess would be plugs at this point

[evil_weevil]

Fuel pump may be dying.

Increased power, increased boost - standard fuel pump in an older car wont last too long.

I did similar mods ages ago, and same thing happened.

I replaced fuel pump and also got a powerFC. Best mods ever.

Yourself now, I'd be looking at some sort of engine management also.

[SevenAngryPenguins]

spark plugs and yes you can buy 0.8mm gapped plugs NGK coppers bcrp6es cost you f**k all and isn't dodgey

coil packs have probably had it as well,

stock ecu runs the engine pretty average at that boost pressure (very rich),

I also get flat spots (not missfire) up around the 5k mark with stock ecu & 10 psi,

I threw my un-tuned PFC in it and it ran perfect to the redline out of the box (tune coming soon)

Edited January 29, 2008 by SevenAngryPenguins

[Peter]

Ok, cool...thanks for the additional info VB, sevenangry, and evil weevil....I'll definately look at the plugs as numer one priority (hope that's all it is!)..(BTW thanks for the reference number for the plugs sevenangry).

Hopefully this wont lead me down the path of replacing coil packs or the fuel pump....so I'll sort the plugs out first and see what happens...

I'll definately consider an aftermarket engine management in the future as well, evil weevil and sevenangry - once funds permit....

Pete

[Dale FZ1]

Took the car out today on the highway and gave it flat to the floor acceleration from a standing start in 1, 2, 3, 4 gear, and it seemed to backfire when it reached the higher revs (above 4000rpm), making popping noises out of the exhaust, and surging forwards – it would lose power with every pop, then pick up again….so I stopped this very quickly, and drove it home, off boost, and it ran fine. It also runs fine when accelerating hard at low rpm, but as soon as it gets to around 4000 - 5000rpm+ it seems to miss and backfire – can’t hear any pinging though?

PS: I reset the ECU after every modification as suggested in other threads.

Hi Peter

you are most likely experiencing the rich/retard syndrome. It is a failsafe threshold in the factory ECU, designed to not let you exceed a certain power limit. Search "rich + retard" and you'll come up with plenty of reading on the topic.

By installing the less restrictive FMIC and pod, you are effectively allowing the engine to swallow a larger MASS of air at the same boost pressure. Then when you increased the boost, well it is just trying to exceed that boundary by a larger amount. The ECU responds as it is programmed to do, and your car stutters and stammers as described.

There are ways around it, either by fooling the factory ECU (use a piggyback interceptor), or using a different ECU.

With the mods you are running, there is no sound reason to be running smaller plug gaps IMO.

cheers

[MotoMan]

i would put money on the fact that it missfires at 4500rpm.. SPOT ON 4500RPM..

Gapping the plugs isnt the answer.. I did that and it fixed my missfires.. but also induced pinging..

now i could be wrong here (i often am) but wouldnt putting a smaller gapped plug in, slightly advance the timing (therefor inducing pinging..) Spark doesnt have as far to travel.. so it sparks slightly earlier?

based on coilpack design which work on resistance?

Im having the exact same issue.. but im getting a SAFC2 installed and tuned withing the next 2 weeks.. so ill let you know the outcome

EDIT* just noticed Dale FZ1 has the same idea i do.. I believe it is rich/retard.. simply as it missfires DEAD ON 4500rpm everytime.*

so hopefully the SAFC2 will fix the issue

Edited January 29, 2008 by MotoMan

[eddieeeee-ro]

sounds like he just needs a safc/pfc or any aftermarket ecu and tune the air/fuel ratios.

do it, the car will go harder aswell

[SevenAngryPenguins]

oops got the code a bit wrong its bcpr6es

smaller gap wont increase timing!, its done to because when you increase the boost pressure it can effectively blow the spark out so closer gap makes it easy for the spark to jump across. If your coils are a bit tired the smaller gap helps also.

I doubt its R&R you really know when you hit that and it happens up about the 12psi mark

wont hurt to check your new cooler piping too if it leaks under boost the car will run really bad

+eleventy billion for safc or something

Edited January 29, 2008 by SevenAngryPenguins

[buggor34]

sounds like the very common problem- coil packs arching out. Series 1 very common for it.

[Dale FZ1]

I doubt its R&R you really know when you hit that and it happens up about the 12psi mark

Sorry, mine did hit R&R with exactly the same mods as Peter described, and running stock boost. There was absolutely no doubt that I had hit it either.

And it is a Series 1 R33 also...

As an aside, the coils in a vehicle that age would be getting a tad tired.

[SevenAngryPenguins]

Sorry, mine did hit R&R with exactly the same mods as Peter described, and running stock boost. There was absolutely no doubt that I had hit it either.

fair enough.

stange how each car can be so different, I have same mods also minus the turbo tech, I cranked my boost up and up till i hit the R&R just to see what it felt like (not cool)

I find it hard to believe that you hit it with stock boost though but I have been proven wrong many many times before

Edited January 29, 2008 by SevenAngryPenguins

[aaron_25t]

The other thing it might be is a vacuum leak?

I had a very annoying misfire/cutting out issue and I tried all the above (SAFC II retune, changed AFM, Splitfire coils, new 0.8mm plugs) with no luck, turned out to be a really small cut in one of my joiners. With your new intercooler, and other bits teeing off boost lines. I figured there might be a small chance this is it.

More likely to be one of the other solutions in other posts but still worth checking I guess.

Sorry, mine did hit R&R with exactly the same mods as Peter described, and running stock boost. There was absolutely no doubt that I had hit it either.

And it is a Series 1 R33 also...

As an aside, the coils in a vehicle that age would be getting a tad tired.

Edited January 29, 2008 by aaron_25t

[Jmaac]

Definately a tuning problem, youve increased the airflow/density accross the board

Yes the stock ECU has room to move; adding a pod or slightly bigger FMIC is ok, but the combination of the two coupled with higher boost pressures is just crazy- especially if you expect it to work hunky dory

Get a SAFC2, PFC, or EMU

Edited January 30, 2008 by Jmaac

[RaZ_TuRbO]

Before trying anything just try gap the spark plugs down...its free and easy to do and youve got nothing to loose really. safc blah blah all cost money. I have had the spark blow out before sounds like the same story here, but cars are funny things..

[33drifta]

hey mate i have just been through the same shit, you do need to gap down the plugs. but your ECU wont like the new mods at all. in the end i had to get...

PFC

z32

bigger fuel pump

highflow injectors

and of corse a tune

and im still having boost problems.

the morel of the story is, if you mod 1 thing you need to mod the rest!!!