Help!! Pony Stutters when cold start and WOT

SpazLE995 · Aug 8, 2010

When starting car after it has cooled down like over night it has a hard time staying started the first time unless I flick the gas. Then stutter while under hard acceleration until up to operating temp. Note the temp outside is avg 70F to 90F. Also at any time at WOT I need to play with the gas to prevent stuttering.

I this an injector problem? I have used injector cleaner, Lucas fuel additive and only use quality fuel like shell or Mobil.

Car Info:
1996 Mustang GT
32V Motor from '96 Cobra
Kenne Bell 1.7 S/C 5-6psi
Kenne Bell Boost-a-Pump
Kenne Bell PCM Chip
IMRC delete
Ford Racing 9mm Wires
Long tube headers
Cat H-Pipe
SLP Pipes w/glasspacks
Auto meter Fuel pressure gauge
Auto meter boost gauge
Auto meter coolant temp gauge
Auto meter oil pressure gauge
Wiring harness has been corrected for the 32v

Thanks in advance for any help!

trinity_gt · Aug 8, 2010

Considering your S/C'd, be very careful about WOT blasts until you get this sorted. If it is a fuel starvation issue your engine is at risk.

As with most early cars with coil packs and wires (as opposed to COPs) I'd suggest looking into the ignition system first, especially the wires unless they're new.

Is the car throwing any codes? Do you have a fuel pressure gauge?

wmburns · Aug 8, 2010

+1 on the above advice. Don't get into it before the engine is warm.

Having to blip the throttle to start sounds like a bad IAC (not allowng enough air for starting).

Hard restarts could also be low fuel pressure or pressure bleed down. Sources of bleed down could be a leaky fuel injector or bad fuel pump check valve.

Have you done the PPRV delete mod? If so, this could explain the hard cold start.

Try turning the key on/off several times without starting. Does this improve cold start?

Is the MAF clean?

Of course this could be a base tune issue since PCM tune can seriously affect cold start performance. It would be a good idea to monitor the IAT and coolant sensor to be sure they are reasonable (the PCM needs to know the temperature in order to give the best performance).

If you think it is an injector problem, consider using an injector cleaning service such as injectorrx.com.

SpazLE995 · Aug 8, 2010

trinity_gt said:
Considering your S/C'd, be very careful about WOT blasts until you get this sorted. If it is a fuel starvation issue your engine is at risk.

As with most early cars with coil packs and wires (as opposed to COPs) I'd suggest looking into the ignition system first, especially the wires unless they're new.

Is the car throwing any codes? Do you have a fuel pressure gauge?

Wires are new Ford Racing 9mm, No Codes, Do have fuel pressure gauge. When starting I turn key on and off twice to build pressure.

SpazLE995 · Aug 8, 2010

wmburns said:
Having to blip the throttle to start sounds like a bad IAC (not allowng enough air for starting).

Hard restarts could also be low fuel pressure or pressure bleed down. Sources of bleed down could be a leaky fuel injector or bad fuel pump check valve.

Have you done the PPRV delete mod? If so, this could explain the hard cold start.

Try turning the key on/off several times without starting. Does this improve cold start?

Is the MAF clean?

Of course this could be a base tune issue since PCM tune can seriously affect cold start performance. It would be a good idea to monitor the IAT and coolant sensor to be sure they are reasonable (the PCM needs to know the temperature in order to give the best performance).

If you think it is an injector problem, consider using an injector cleaning service such as injectorrx.com.

When starting I turn the key on and off twice to build pressure. Don't see any leaks around injectors. still stutters. well more like it starts then chugs to a stop. start it again and it idles fine but if you give it gas it stutters.

The PCM has the Kenne Bell Tune so not an issue there.

I have monitored the IAT and Coolant temps and they are ok

would the GT tank have the PPRV?

trinity_gt · Aug 8, 2010

SpazLE995 said:
Wires are new Ford Racing 9mm, No Codes, Do have fuel pressure gauge. When starting I turn key on and off twice to build pressure.

Please explain.

When you turn the key the first time, does the fuel pump not start? What does the fuel pressure build to? Why do you need to cycle the key twice?

When you get your foot into it and/or the car is otherwise "stuttering", what has the fuel pressure gauge read?

SpazLE995 · Aug 8, 2010

trinity_gt said:
Please explain.

When you turn the key the first time, does the fuel pump not start? What does the fuel pressure build to? Why do you need to cycle the key twice?

When you get your foot into it and/or the car is otherwise "stuttering", what has the fuel pressure gauge read?

key first time Fuel at 25psi
key second time Fuel at 40psi
"I just went to check it and it only needed one key on this time to get to 40psi, Most of the time I double key it if it has been sitting for a while"

once started idles around 40psi step on gas fuel goes up to 50psi and engine takes a second to catch up kinda like a hiccup or hesitation

SpazLE995 · Aug 8, 2010

the only code I have is for the air injection emissions which I don't have

Cherry99GTvert · Aug 8, 2010

i had the same problem and all it needed was a fuel filter, i bought the car with 135k on it and it had never had a fuel filter change

Cherry99GTvert · Aug 8, 2010

It did the same thing, always took two ignition turns to start so i tried the basics first and havent had a problem since so i would try my 10 dollar advice

Kilgore Trout · Aug 8, 2010

+1 fuel filter

joshjwc9 · Aug 8, 2010

+2. If its not the issue, it won't hurt to replace this.

wmburns · Aug 8, 2010

SpazLE995 said:
When starting I turn the key on and off twice to build pressure. Don't see any leaks around injectors. still stutters. well more like it starts then chugs to a stop. start it again and it idles fine but if you give it gas it stutters.

The PCM has the Kenne Bell Tune so not an issue there.

I have monitored the IAT and Coolant temps and they are ok

would the GT tank have the PPRV?

From your reply, I get the sense that you do not understand what it means to have a "leaky fuel injector" and what effect it will have.

The injectors do not leak EXTERNAL to the engine. The leak is from the tip. The fact that you DO have a leak somewhere is confirmed because the fuel pressures is not 40 PSI before cranking.

A properly working fuel system should maintain full fuel pressure whenever the car is turned off. In this way, the fuel pressure builds to the full 40 PSI immediately.

Turning the key on/off several times improves starting because the PCM runs the fuel pump for only a few seconds with each cycle. The multiple key on/off's allows the fuel pressure to build to correct levels.

For further proof of the leak, leave the external fuel pressure guage attached while the motor is off. Monitor the fuel pressure say over 15 minute intervals. How long does it take to bleed down?

The leak is either at one (or more) fuel injectors or at the fuel pump check valve. Since you do not know what the PPRV delete mod is, I am going to assume that you have NOT removed the fuel pump check valve.

Consider using an injector cleaning/flow test service such as injectorrx.com. For a price much less than new injectors, they will clean and flow test all 8 injectors. Once tested, the injectors are as good as new. More importantly, will be flow balanced and confirmed leak free.

After building fuel pressure, perform a basic IAC test. Hold the throttle half way open. Does this improve starting?

I get the impression that the car runs fine once full operatng temp is reached. Is this true? Because if it is, this means that the fuel system is basically sound. However, it is NEVER a bad idea to have a known good fuel filter in your car as this could save a lot a headachs.

OBTW, the 96 GT does not have an air injection system. It does not make sense to me that the KB tune would consider it "OK" to have a check engine light on even on a perfectly working car. It might be helpful to post the full DTC as it may provide an additional clue.

SpazLE995 · Aug 8, 2010

wmburns said:
OBTW, the 96 GT does not have an air injection system. It does not make sense to me that the KB tune would consider it "OK" to have a check engine light on even on a perfectly working car. It might be helpful to post the full DTC as it may provide an additional clue.

Well It is well known that it is NOT a GT Engine, Cobra's had 32V and an Air injection system which is what is in the car.

Kilgore Trout · Aug 8, 2010

wmburns takes the time to provide all that info and you choose to correct him on a detail?

SpazLE995 · Aug 9, 2010

Kilgore Trout said:
wmburns takes the time to provide all that info and you choose to correct him on a detail?

I'm not trying to insult him I'm making sure everyone knows what app I have so that it wont get off topic like it has when I tried getting this problem solved prior times.

I hope he did not take offense to this and If so I do apologize.

joshjwc9 · Aug 9, 2010

Kilgore Trout said:
wmburns takes the time to provide all that info and you choose to correct him on a detail?

The OP has a '96 Cobra Motor in the car that is having this issue. So, KT there might be another way to ascertain the problem that is causing the poor fuel pressure and etc...

wmburns · Aug 9, 2010

Question, would the IMRC delete affect the part throttle esp when cold? How about if the PCM hasn't been re-tuned for the IMRC delete?

The OP's description of "sputtering" kind of sounds like an ignition problem. But one would expect that an ignition problem would not be affected by engine temperature.

Sorry about asking about air injection. I assumed that the PCM came from a GT. I couldn't understand how a GT's PCM would have any codes about air injection. Perhaps I also assumed the OP might have meant something else. In any case, the actual DTC would clear up the confusion. Consider the issue dropped.

SpazLE995 · Aug 9, 2010

Thanks for all the help guys, I am going to take a look at the fuel pump and see about deleting the PPRV, yes I will change the fuel filter at the same time and yes I do change it regularly. I will also Clean the IAC to see if that helps.

Is there any difference in the fuel system between the '96 GT and Cobra?

Would it be beneficial to change the pump at this time? More flow?

SpazLE995 · Aug 12, 2010

So I changed the spark plugs to the e3 plugs, old ones had some carbon build up.
cleaned the IAC, MAF, and Throttle Body.

She Seems to be running smoother and starting better.

She still has a problem at WOT at High RPMs
I talked to Kenne Bell and they say it would still be running rich.

It runs good when I hold the throttle at about 98% but when it is at 100% the RPMs stay about the same, Fuel pressure spikes up to 50psi rather than 45psi.

could there be a problem with the TPS?
MAF?

Help!! Pony Stutters when cold start and WOT

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