Stutter at full boost....

I originally posted this about 3 months ago where i was only seeing a slight stutter at high speeds when flooring it.It was also only intermittent.

Now this stutter is alot more pronounced and i am seeing it from speeds of 60mph +. Up until this speed i get full boost and the car accelerates as it always has(gives me hope the turbos arent knackered:blink:).

Basically i get surge,cut,surge,cut and so on.

If i gently apply the pedal and not all the way to the floor all is fine and it accelerates ok.

So am i looking at a dodgy FCD? or problems with second turbo? or what?. I have checked all fluid levels and have always had them regularly changed.They are all ok. The only one i dont know how to check is for the diff but this was not done that long ago(about a year). I have tried to visually check for split hoses etc but all seem ok.

My technical knowledge is about the same as your average saxo driver so please try & give a very basic guide as how to diagnose this.

Thanks

Mark

Spark plugs maybe, by stutter do you mean hesitation?

http://www.mkivsupra.net/vbb/showthread.php?t=35931&highlight=hesitation

Thanks for that but i do have colder plugs fitted (denso IK24's).

However from reading that i would say this is the most accurate desc of my symptoms...

3c - massive overfuelling - you will get a drop in power harsher than 3b but less harsh than 2a. The engine pretty much won't get past the load site, it will just keep cutting out, so acceleration is lost. If you have a BOV, it will fire rapidly as power comes on and off.

But still with a big lacking in technical knowledge i dont know. Could my walbro pump be knackered?

Ah the spluttering gremlin.

Do an error code check first mate if your FCD is dodgy you will probs get a code 31 which is map sensor. if its all clear I would check or change your plugs and go from there mate.

Good luck

Did you Check for codes?

what boost are you running, and at what boost is the problem occouring?

Could be the coil packs breaking down under load, bad coil pack connectors, bad plugs as it sounds like an ignition problem under load, i.e. if you ease the car on to boost the problem dos'nt occur.

Ah the spluttering gremlin.

I take it this one is not uncommon or you have had it before lol.

Thanks for your help.

Did you Check for codes?

what boost are you running, and at what boost is the problem occouring?

Could be the coil packs breaking down under load, bad coil pack connectors, bad plugs as it sounds like an ignition problem under load, i.e. if you ease the car on to boost the problem dos'nt occur.

Am only running stock boost and only ever have.

Will check for codes now but what you are saying on coil packs makes sense so thanks.

I know you say you changed the plugs but did you gap them correctly? How recent were they done? If its not plugs then check ignition coil pack clips, could also be your coilpacks. Does it do it only on boost, past a certain pressure...ie in the high load points. Or would it do it above 60mph say at cruise?

I doubt its mass overfuelling, expecially on the stock ecu (you are using the stock ecu?). Also, your would see nice clouds of sooty black smoke out the back if it was!

I know you say you changed the plugs but did you gap them correctly? How recent were they done? If its not plugs then check ignition coil pack clips, could also be your coilpacks. Does it do it only on boost, past a certain pressure...ie in the high load points. Or would it do it above 60mph say at cruise?

 

I doubt its mass overfuelling, expecially on the stock ecu (you are using the stock ecu?). Also, your would see nice clouds of sooty black smoke out the back if it was!

Plugs were done about 10k ago iirc and fitted by interpro and it was fine for 9 months or so.

Only does it at high boost above 60mph its fine at cruise. Its only on stock ecu and no smoke so overfuelling is hopefully fine.

Ik24's are probably overkill for a stock boosted supra.

How much fuel is in the car ? I used to get a missfire when i accidently went below empty, due to picking up the dregs at the bottom of the tank.

Usual culprits are either plugs or broken connectors to the coil packs.

Usual culprits are either plugs or broken connectors to the coil packs.

I did an error code check and its not showing any.

I will have the plugs swopped and then look to swop the coil pack connectors. How much are the connectors and how many do i need?

Thanks

Are you running an aftermarket gauge to prove what boost you're running? Could cold weather not be contributing to you "just" seeing fuel cut?

PS when I say "just" I'm not be-littling the problem , I mean you're seeing just enough boost for fuel cut to register

PPS the only reason I ask is that it sounds sooo much like fuel cut, and you garage says BPU (does that mean you've been decatted???)

Are you running an aftermarket gauge to prove what boost you're running? Could cold weather not be contributing to you "just" seeing fuel cut?

I have been running the same mods since i bought the car nearly two years ago and have only seen this problem recently. It does have an FCD fitted.

I dont have a boost guage fitted so probably need to do this to gain more understanding as to whats happening.

IMHO you need to know what boost you're running, you could spend a lot of time & money tracking this problem through the ignition system. If I were tracking this I'd want to know exactly what boost the car is running & what level the FCD is set at. I'm not saying it's the problem but there are some basics you need to eliminate first IMHO.

IMHO you need to know what boost you're running, you could spend a lot of time & money tracking this problem through the ignition system. If I were tracking this I'd want to know exactly what boost the car is running & what level the FCD is set at. I'm not saying it's the problem but there are some basics you need to eliminate first IMHO.

Agreed & Thanks:)

The odd thing is it flies to 60ish but a month or 2 back that was 90ish before i saw the same symptoms.

Does sound a bit like fuel cut, but the gradual breakdown says no. Personally this points straight at coilpacks as once they start to go they get progressively worse quite quickly. Change the clips 1st though as you may be lucky!