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Car Missing at around 5500rpm

paulgts-t

By paulgts-t,
in Engines & Forced Induction

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paulgts-t Apprentice

paulgts-t

Posted
Posted

I have an R33 GTS-T that has just developed a mis occuring at around the 5500rpm mark. It is not constant in every gear but is a common enough problem to cause concern.

I have changed the plugs and re-gapped them to no avail.

I am thinking it may be the fuel pump starting to die on me? How do I test it?

The car has a full 3 inch exhaust, aftermarket BOV, K&N Pod filter, FMIC. It is running standard boost at the moment, when I crank it the mis is more noticable.

Please help.

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https://www.sau.com.au/forums/topic/1096-car-missing-at-around-5500rpm/
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Zahos Mentor

Zahos

Posted
Posted

I had the exact same problem, and managed to get rid of it. Only problem is that I dont know exactly what it was that i did to get rid of it, but i have an idea. I will run through my problem first to see how closely it matches yours.

- at stock boost all fine, except a mis sometimes between 4500 - 5500 rpm. (only in 2nd and third gear)

- once boost is raised, problem is more evident at 4500 - 5500 rpm. happens sometimes in 1st, but almost always in 2nd and 3rd. After 5500 rpm, all is smooth until 7000 rpm.

What I did

- Regap spark plugs. The spark plugs i had put in, were NGK BCPR7ES. Now I read that since they are copper plugs, the gap needs to be smaller so the 0.8mm gap i thought would be fine. EEERRRRR WRONG. Well not really wrong, but 0.8mm was not small enough. See the 7 means that the plugs are also a colder rating which means that it will be even harder for the spark to jump (due to heat rating AND that fact that they are copper as opposed to the recomended platinum).

Solution: regap to 0.7mm.

- Next, as I was putting the spark plugs back, I noticed that there was quite a bit of dirt around some of the plug holes. This is due to the fact that the previous owner must have had sh*t for brains and hosed the crap out of the engine b/f selling to make it look much cleaner, and the fact that plugs it came with were not screwed in very well, meant that a lot of dirt and crap got stuck in there.

SO, with a screwdriver wrapped in rag, soaked in petrol, i cleaned around the rim before i slid my long hard shaf... wait, sorry... been watching too many porno movies. Where was I, oh.. yeah, once clean, put a little oil on the washer of the plug before screwing (hehe) back in. Do them tight, but not too tight as not to break them. ALSO: before putting all the plugs back in, crank it over a few times to expell any dust in your cylinder chambers.

- Then: I put it all back to gether and took it for a 5-10 min drive (without re-setting the computer) to warm it up a little. When u get home, reset the computer, redo the timing maybe 2 degrees faster than normal, and take the bitch for a good beating for about 5 - 10 mins.

This is what I did to rectify the problem. I have just recently installed a boost guage and noticed why the problem was occuring. The factory boost guage tells lies!!!! It shows no spikes, but my aftermarket shows a spike at about 5000 rpm. So at this point, all the excess boost is making it hard for your car to spark.

My solution: wind down the boost (just a little) and plumb the factory boost solenoid back in (as well as my preasure regulator and preasure relief valves). Now I get a very tiny spike or about 0.05 bar at 5000 rpm, where the bosst drops that small amount for a microsecond, and then raises a little again thanks to the factory boost solenoid.

One other thing to look for which i did a while ago, is the resistance accross your coils. I forgot what is should read, but do a search on SDU and you should find it.

Happy trouble shooting

Zahos

paulgts-t Apprentice

paulgts-t

Posted
  • Author
Posted

Thanks for your help.

I have re-gapped the plugs to .7 but it did not make a difference. I will clean the plug housing and see what that does.

I have not measured the air/fuel, but I am keen to do that next. Looking at the plug condition I am concerned that the car is leaning out when it misses?

The problem that your car was having is exactly the same as mine.

I will keep trialing and hopefully find an answer.

Zahos Mentor

Zahos

Posted
Posted

what boost r u running?

I know u said stock, but the factory guage is that bad, using that will give you no propper indication. Going by that guage i thought i was running 7psi when in fact i was running over 10! Every time i cranked it up (to what i thought was 10) i was boosting to about 14. Lucky i only did this twice.

So r u unsing the factory guage or an aftermarket? Overboosting can cause this exact same problem as most pnuematic boost controllers spike at about that point.

blind_elk Grand Master

blind_elk

Posted
Posted

Go and get Zoom! #51, and go to page 60. Can't gaurantee it will solve your problem, but it shows you the progression of checks.

I'm sure I read somewhere recently that the boost controller will often get a spike and throw the ECU into over-boost protection mode.

Cubes Grand Master

Cubes

Posted
Posted

Check the spark plugs for any cracks in the ceramic..

Have a really good look as mine looked like a hair.. hence hair line fracture.

Anyway mine began by starting to miss on idle..

then i pulled the plugs out re gapped then then it started to miss on boost then it would smooth out towards 6000rpm - 7000rpm..

THEN... I pulled them out again and checked everything.. coils etc..

THEN... put them back in and it would not just miss but make a huge backfire.. I put the old plugs in pulled the new ones out and it ran fine..

Then i had a good look at the sparky and there now was a big crack which must have got worse as i pulled them in out in out in out...

Thats my experience.. :D

U WERE MINE Veteran

U WERE MINE

Posted
Posted

guys i have the same problem.. :( except mine does it around 3000rpm..

I HAVE NO IDEA WHAT TO.. i have changed it all.. afm, plugs, all coil packs,tps,cheaked for boost leaks, had car on dyno cheked all sensors with diagnostic computer,changed timing..changed fuel filter, checked fuel pressure, restet ecu..

now what have i got left... chenge the ecu with another one?... check injectors for cracks/leaks.. and anymore than that.. ? i honestly dont know guys... hope u solve it... ive been liek this for 3 months

Cubes Grand Master

Cubes

Posted
Posted

Dodgy Earth some where?

What else is there... You've basically checked every thing..

It could even possibly be a cracked/brittle wire that runs to the coil packs from the igniter.

I remember when I was checking mine over to try to fix the miss I noticed that the wires had seemed to go quite hard.

  • 1 year later...
Anquetil Mentor

Anquetil

Posted
Posted

Mine misses in first at high rpm. I put my platinums down to .75 from 1.1 on the weekend but is made no difference.

I checked the coil packs but dont really know what im looking for, they looked in good nick to me? So I just swapped around the coil packs into a different posi. Still does it.

ylwgtr2 Grand Master

ylwgtr2

Posted
Posted
what boost r u running?

I know u said stock, but the factory guage is that bad, using that will give you no propper indication. Going by that guage i thought i was running 7psi when in fact i was running over 10! Every time i cranked it up (to what i thought was 10) i was boosting to about 14. Lucky i only did this twice.

So r u unsing the factory guage or an aftermarket? Overboosting can cause this exact same problem as most pnuematic boost controllers spike at about that point.

Is this because the factory guage is in bar not psi???

Cecam Enthusiast

Cecam

Posted
Posted

My GTS25t is completely 100% stock and I had this misfire but I had hesitation at about 4500rpm and then surging or misfire at 5500 (and audiable detonation twice).

I changed the fuel pump and gave it a general service with all new filters (inc fuel, not that the plugs showed signs of leaning out but I had the pump so..) Also rebuilt the AFM and adjusted all the sensors (TPS etc) while I was at it to make sure everything was 100%. Still misfired. Retarded/Advanced timing to no effect. This is at 7psi btw on aftermarket gauge, and yes the factory one is very slow to react in comparson...

Put in new (platium) plugs to replace the current coppers and the hesitation went away but not the misfire. Using another set of platiums I had to wind the gap down to 0.6mm before it went away...

0h yeah, removing the cover so the coils get some air and are alot cooler has helped slightly too... yet the coils appear to check out fine...

Will wind some boost into it later when the exhaust etc is done and see if the problem returns again. I suspect it will...

Btw, I don't think it misfired when I unplugged VCT once...

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