turbo stang dies after spinning tires

0G2T · Sep 24, 2010

hey guys, every time i burn through first and second gear my car hesitates and shakes after i let off the throttle. It did it tonight and when i went to go shift third while buring through second gear the car totaly lost all power when i mashed on it in third. The car doesnt die out under hard accleration when the tires arent spinning. my set up is a mmr900 short block pi heads and a 60mm turbonetics turbo running 15-16 psi. also i will occationally get a flashing ses light under hard acceleration. not sure if thats related though.

trinity_gt · Sep 24, 2010

The flashing MIL is indicating a misfire.

What coils are you running? What plugs? What gap are the plugs set at?

As for falling on its face, first question: Do you have a fuel pressure gauge?

Second question: Is the traction control actually turned off?

wmburns · Sep 24, 2010

My vote is that you are over spinning the alternator and the brushes are bouncing. This is causing the alternator output to drop. Without the correct voltage, the PCM flakes out.

Monitor the voltage during a run. Does it drop? Consider getting a larger alternator pulley or don't rev quit so high.

The flashing check engine light means that a misfire is occuring.

0G2T · Sep 25, 2010

hey guys thanks for the prompt response. i am running ngk tr6 plugs at a .30 gap. stock coils. i do not have a fuel pressure gauge. traction control is deff off. as for spinning the alternator too fast, that makes sense because its close to redline in this situation. why do i keep getting misfires? the car has been professionally tuned. so i am confused as to why this is happening. would a boost a spark help my situation out?

wmburns · Sep 25, 2010

0G2T said:
hey guys thanks for the prompt response. i am running ngk tr6 plugs at a .30 gap. stock coils. i do not have a fuel pressure gauge. traction control is deff off. as for spinning the alternator too fast, that makes sense because its close to redline in this situation. why do i keep getting misfires? the car has been professionally tuned. so i am confused as to why this is happening. would a boost a spark help my situation out?

With regards to misfires, two reasons quickly come to mind. Not enough voltage to power the ignition (see alternator brush bounce).

Or the cylinder pressure is just plain too high for the spark to over come the gap (see #1).

Kilgore Trout · Sep 25, 2010

That gap is too large I think the problem is spark blowout. Get new ngk tr7ix and gap them at .021-.023

Kilgore Trout · Sep 25, 2010

Also consider upgraded coils like WeaponX or MSD.

Edit: re-reading how you describe the problem it almost sounds like you are hitting the rev limiter?

trinity_gt · Sep 25, 2010

Re misfires: You might also consider a Kenne Bell boost a spark (BAS) to increase coil output.

Kenne Bell Boost-A-Spark

trombonedemon · Sep 25, 2010

trinity_gt said:
Re misfires: You might also consider a Kenne Bell boost a spark (BAS) to increase coil output.

Kenne Bell Boost-A-Spark

So thats what those things are for, like the MSD Coil what'cha ma' call' its. I wanted to try that ignition control module out but never really knew what the thing was for. Guess I don't need one.
This is gonna be an interesting thread.

Ateup · Sep 25, 2010

LOL, I was gonna suggest maybe not tearing through first and second gears anymore? But I guess that's out of the question.

0G2T · Sep 26, 2010

Kilgore Trout said:
Also consider upgraded coils like WeaponX or MSD.

Edit: re-reading how you describe the problem it almost sounds like you are hitting the rev limiter?

deffinetly not rev limiter. because it happens after i let off. from what everyone is saying i can think it is probably i spark issue. i will have to order up the boost a spark and change the plugs and see what happens. as for not tearing through the gears, yes that is out of the question.

Don 95Vert · Sep 27, 2010

If you are running a draw through MAF setup, your problem is the turbos are still spinning down and creating more airflow when you let off the throttle causing MAF backwash and usually creating a momentary very rich condition that kills the motor. This is something that usually cannot be tuned around. Fixes include lengthening the inlet pipe so the MAF is further from the turbo creating more air volume to act as a buffer or the best option of going to a blow through setup.

We have helped one major turbo kit manufacturer improve their kits where this had been been a problem by prototyping a new design inlet pipe to help alleviate this.

Seen this on many turbo cars.

If it is already in blow through, then I'd look at the air intake for loose couplings.

Spark blow out usually happens at much higher loads than you are seeing when cylinder pressure is highest - which means at the top of 'high' gear near the end of the track above like 3500-4000 RPMs.

Hope this helps.

Don

0G2T · Sep 27, 2010

thanks don,
i am running a blow through set up. is it possible that my bov could be leaking due insuficient spring pressure? all of my connectors seem to be air tight.

bhuff30 · Sep 27, 2010

It is very possible for a leaking BOV to be causing the problem. A wideband would be a tremendous help in diagnosing the problem. The engine only needs 3 basic things to run: spark, air and fuel, all in the correct amounts and at the right time. I'm guessing this one is fuel related due to air escaping or entering the system after the MAF.

0G2T · Sep 27, 2010

is it possible that my knock protection kicked in? i didnt hear any detonation but that would take all the power away correct?

Don 95Vert · Sep 27, 2010

If it's an 02 GT, it HAS no knock sensors - If it is draw through, I think my reply answered your inquiry - we had the exact same thing on our turbo Mustang and turbo Lightning many years ago and came up with fixes as I described. Since then we have tuned hundreds of turbo cars and see this exact same problem on some, but not all of the turbo vehicles with draw through MAFs. Unfortunately there is no easy fix for it other than what I described - you might be able to add an additional 'damper' pipe to the inlet, i.e. a smaller diameter pipe that is connected to and runs parallel to the inlet as some OEMs do this, but we have never tried it.

Kilgore Trout · Sep 27, 2010

Yes it does have knock sensors, ALL 99-04 GTs have knock sensors.

Kilgore Trout · Sep 27, 2010

Oh and for **** sake check the plugs and close the gap before you start re-engineering the whole ****ing car.

Don 95Vert · Sep 28, 2010

Wow, such misinformation - the internet is really good in a lot of cases but not so good in this case. Sorry, you are wrong, do some checking before posting please because other people will read this and take it as gospel. The DOHC motors had knock sensors, except for the 03-04 Cobras, the SOHC 2vs on Mustang GT motors did not. 05 and up 3vs do have them as does the 2011. My reference is the SCT Dealer's Tuning Manual and the SCT Pro Racer Manual (both of which I wrote). What is yours?

I'm taking the time out of my busy day to help this person out with the turbo based on my experiences seeing this exact issue many times, if someone thinks it's wrong - fine. In fact it may NOT be it, but in my opinion, that's the best bet.

Kilgore Trout · Sep 28, 2010

Before he gets all fancy and starts taking your pro mechanic advice he should look at the plugs. He is running copper plugs which wear quickly and the gap was already too big the day they were installed.

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