Jump to content
SAU Community

Recommended Posts

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.

Link to comment
https://www.sau.com.au/forums/topic/1096-car-missing-at-around-5500rpm/
Share on other sites

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

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.

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.

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.

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

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

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...

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.

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???

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...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • As discussed in the previous post, the bushes in the 110 needed replacing. I took this opportunity to replace the castor bushes, the front lower control arm, lower the car and get the alignment dialled in with new tyres. I took it down to Alignment Motorsports on the GC to get this work done and also get more out of the Shockworks as I felt like I wasn't getting the full use out of them.  To cut a very long story short, it ended up being the case the passenger side castor arm wouldn't accept the brand new bush as the sleeve had worn badly enough to the point you could push the new bush in by hand and completely through. Trying a pair of TRD bushes didn't fix the issue either (I had originally gone with Hardrace bushes). We needed to urgently source another castor arm, and thankfully this was sourced and the guys at the shop worked on my car until 7pm on a Saturday to get everything done. The car rides a lot nicer now with the suspension dialled in properly. Lowered the car a little as well to suit the lower profile front tyres, and just bring the car down generally. Eternally thankful for the guys down at the shop to get the car sorted, we both pulled big favours from our contacts to get it done on the Saturday.  Also plugged in the new Stedi foglights into the S15, and even from a quick test in the garage I'm keen to see how they look out on the road. I had some concerns about the length of the LED body and whether it'd fit in the foglight housing but it's fine.  I've got a small window coming up next month where I'll likely get a little paint work done on the 110 to remove the rear wing, add a boot wing and roof wing, get the side skirt fixed up and colour match the little panel on the tail lights so that I can install some badges that I've kept in storage. I'm also tempted to put in a new pair of headlights on the 110.  Until then, here's some more pictures from Easter this year. 
    • I would put a fuel pressure gauge between the filter and the fuel rail, see if it's maintaining good fuel pressure at idle going up to the point when it stalls. Do you see any strange behavior in commanded fuel leading up to the point when it stalls? You might have to start going through the service manual and doing a long list of sensor tests if it's not the fuel system for whatever reason.
    • Hi,  Just joined the forum so I could share my "fix" of this problem. Might be of use to someone. Had the same hunting at idle issue on my V36 with VQ35HR engine after swapping the engine because the original one got overheated.  While changing the engine I made the mistake of cleaning the throttle bodies and tried all the tricks i could find to do a throttle relearn with no luck. Gave in and took it to a shop and they couldn't sort it. Then took it to my local Nissan dealership and they couldn't get it to idle properly. They said I'd need to replace the throttle bodies and the ecu probably costing more than the car is worth. So I had the idea of replacing the carbon I cleaned out with a thin layer of super glue and it's back to normal idle now. Bit rough but saved the car from the wreckers 🤣
    • After my last update, I went ahead with cleaning and restoring the entire fuel system. This included removing the tank and cleaning it with the Beyond Balistics solution, power washing it multiple times, drying it thoroughly, rinsing with IPA, drying again with heat gun and compressed air. Also, cleaning out the lines, fuel rail, and replacing the fuel pump with an OEM-style one. During the cleaning process, I replaced several hoses - including the breather hose on the fuel tank, which turned out to be the cause of the earlier fuel leak. This is what the old fuel filter looked like: Fuel tank before cleaning: Dirty Fuel Tank.mp4   Fuel tank after cleaning (some staining remains): Clean Fuel Tank.mp4 Both the OEM 270cc and new DeatschWerks 550cc injectors were cleaned professionally by a shop. Before reassembling everything, I tested the fuel flow by running the pump output into a container at the fuel filter location - flow looked good. I then fitted the new fuel filter and reassembled the rest of the system. Fuel Flow Test.mp4 Test 1 - 550cc injectors Ran the new fuel pump with its supplied diagonal strainer (different from OEM’s flat strainer) and my 550cc injectors using the same resized-injector map I had successfully used before. At first, it idled roughly and stalled when I applied throttle. Checked the spark plugs and found that they were fouled with carbon (likely from the earlier overly rich running when the injectors were clogged). After cleaning the plugs, the car started fine. However, it would only idle for 30–60 seconds before stalling, and while driving it would feel like a “fuel cut” after a few seconds - though it wouldn’t fully stall. Test 2 – Strainer swap Suspecting the diagonal strainer might not be reaching the tank bottom, I swapped it for the original flat strainer and filled the tank with ~45L of fuel. The issue persisted exactly the same. Test 3 – OEM injectors To eliminate tuning variables, I reinstalled the OEM 270cc injectors and reverted to the original map. Cleaned the spark plugs again just in-case. The stalling and “fuel cut” still remained.   At this stage, I suspect an intermittent power or connection fault at the fuel pump hanger, caused during the cleaning process. This has led me to look into getting Frenchy’s fuel hanger and replacing the unit entirely. TL;DR: Cleaned and restored the fuel system (tank, lines, rail, pump). Tested 550cc injectors with the same resized-injector map as before, but the car stalls at idle and experiences what feels like “fuel cut” after a few seconds of driving. Swapped back to OEM injectors with original map to rule out tuning, but the issue persists. Now suspecting an intermittent power or connection fault at the fuel pump hanger, possibly cause by the cleaning process.  
×
×
  • Create New...