Stock R33 Series 2 Gtst Flat Spots On Boost

[donnaile]

Hi All

My name is Ed. I am new to Skyline ownership. I have been looking over this forum the past 4-6 months before buying a car, its a great source of information so thanks to everyone. I ended up getting a series 2 r33 gtst. I'm loving it so far but have one nagging issue...flat spots on boost.

I have been researching forums on the issue I'v been having with my gtst but can't find anyone with the same issue. Its completely standard, no exhaust, no pod etc.Everyone with flat spots seemed to develop after mods were added.

I have two flat spots when on boost. Between 4000rpm - 4500rpm & 5000rpm - 5100rpm. It feels like the car is hesitating when it hits these spots and mostly noticeable at full throttle.

Reading the forums I can see its common to have a flat spot between 4000rpm - 4500rpm when you upgrade parts on standard ECU but in my case the car is standard. Before I bought it however I believe it had an exhaust, fmic and pod. The previous owner removed these, serviced and replaced timing belt.

What I have done so far:

Cleaned the AFM
Reset the ECU (disconnect battery/brake pedal)
Replaced plugs

I am running shell vpower. My guess is timing but I don't have the tools/knowledge to check this. I have put around 600km on it since I bought it. Its running sweet besides the flat spot issue. If anyone can point me in the right direction that would be great.

Thanks
Ed

[KiwiRS4T]

Depends what you call a flat spot. There is normally a dip on the RB25 as the VCT changes over. Did you gap the plugs down to 0.8mm? Give the coils a good clean? Put your location up on your profile so maybe somebody close by can take a drive to compare or point you to a good RB workshop if there is really a major fault.

[donnaile]

Depends what you call a flat spot. There is normally a dip on the RB25 as the VCT changes over. Did you gap the plugs down to 0.8mm? Give the coils a good clean? Put your location up on your profile so maybe somebody close by can take a drive to compare or point you to a good RB workshop if there is really a major fault.

Thanks KiwiRS4T.

Just updated my location. Have not checked the gap on the plugs yet. Will check it out this weekend. How should I go about cleaning the coils?

Not sure how to describe the flat spot. It feels like the car is holding back from its full potential just after it gets on boost, then boosts hard, then slight flat spot again. Its not as evident on half throttle. Happens in 1st, 2nd & 3rd. Have not had the opportunity to test out 4th or 5th.

Edited February 22, 2016 by donnaile

[RB25PWR]

Made sure the plugs are gapped correctly, I had this exact problem and gapping the plugs correctly fixed it. Inspect the coil packs (mine were fine) also.

[GTSBoy]

. How should I go about cleaning the coils?

Youtube

[89CAL]

What boost is it running? I get the impression its stockish now but had some parts on it that have since been removed. If its running any more than 7 psi then you may run into issues with R&R

Keep in mind the stock gauge is in mmHg not PSI

May not be relevant but there was no mention of a boost figure so thought i would throw that in there.

The other suggestions so far are probably on the money if boost is indeed stock

[hy_rpm]

Try driving it with the o2 sensor dissconeccted

If it fixes it the o2 sensor is cactus

[89CAL]

It won't be the O2 sensor

[hy_rpm]

Its worth a shot free and my r33 developed the same symptoms as that and it was the o2

Sometimes floor it nothing othertimes it goes ok but power isnt smooth or linear

Got a few basic mods but still a r33s2 there getting old 97 model going on almost 20years old

[Antek]

I am too having this issue since upgrading my turbo last week ( yet to be tuned), I opened it up on the freeway the other day, all was going well until i got a pop of air from the engine bay and lost boost, all pipes have been checked and only found one lose which did not fix the problem. I have been told the intake manifold gaskets are known for giving in and have been recommended to replace the gasket with silicon??

[donburtron]

I had a very similar problem just after rebuilding my engine and turns out it was the TPS not set properly.

If you only use the first inch or so of your throttle does the problem still persist?

With mine i was able to use about a inch or so of throttle and it was like i was using full throttle but anything past that inch or so it would feel underpowered and completely drop boost for a second around that 5k rpm..

You will need a multimeter to set the TPS but its pretty easy once you find a manual off google on how to set it..

Its abit fidly but i used a small screw driver to tap the sencor once i backed off the screws a quarter turn

[Antek]

No so, I can gradualy accelerate and its fine all the way up so long as its not under complete pressure. When i apply full throttle it is fine until boost starts to come on at around 4.5-5+rpm it just seems to almost starve it self self all the way up witch is were i littler cannot take it to.

As i mentioned before in my previous post when it first occurred it did seem like something popped, what it is and were it was is a mystery for the moment, but the noise that occurred defiantly contributed to the problem.

Edited March 28, 2016 by Antek

[donburtron]

Have you checked your piping from the turbo to airbox etc.. i know they can make a popping sound under pressure or even slipt into 2 from crappy clamps done up to tight..

Edit.. also could be a turbo exhaust wheel.. happened to a mates rx7 and he said it made a popping sound.. when he replaced it there was only 2/3rds of the turbine barely holding on

Edited March 28, 2016 by donburtron

[Antek]

I have, though i will do a through check tomorrow, I did find one lose pipe.. I replaced the clamp.

What do you mean by "slipping into 2"

[donburtron]

I have, though i will do a through check tomorrow, I did find one lose pipe.. I replaced the clamp.

What do you mean by "slipping into 2"

By splitting into 2 i mean splitting in half and if your on boost at the time it can make a pretty load pop when it lets go..

[Antek]

right-o well.. cheers for the input fellas once again, I been out in the shed looking over all the pipe work on the induction side, yet they came across tight as i wiggled every one of the with some decent force though, it wasn't until i came across a section that was tucked away were i noticed a seep of oil that seemed to spread it self.. long story, lose clamp..

[donburtron]

right-o well.. cheers for the input fellas once again, I been out in the shed looking over all the pipe work on the induction side, yet they came across tight as i wiggled every one of the with some decent force though, it wasn't until i came across a section that was tucked away were i noticed a seep of oil that seemed to spread it self.. long story, lose clamp..

Awesome.. has it fixed the problem?

[Antek]

Yep, the problem has now been fixed.

[donburtron]

Yep, the problem has now been fixed.

Good news mate

[75coupe]

I am too having this issue since upgrading my turbo last week ( yet to be tuned), I opened it up on the freeway the other day, all was going well until i got a pop of air from the engine bay and lost boost, all pipes have been checked and only found one lose which did not fix the problem. I have been told the intake manifold gaskets are known for giving in and have been recommended to replace the gasket with silicon??

Yet to be tuned with an upgraded turbo, but opened it up on freeway.

Nah i cant see any problem there