Engine cutting out when throttle cracked

[marcos5192]

I have a turbo busa sand rail. The engine starts up and idles great. I can throttle it up when it's in neutral. As soon as I put it in gear and crack the throttle the engine starts to cut out. The engine runs great when I get into it. I ran it like that for a few hours and it ran great. Any help would be appreciated. Thanks in advance. Marcos

 

[Red05]

Does it run good in gear with the clutch disengaged?

 

[Kiwi Rider]

I have a turbo busa sand rail. The engine starts up and idles great. I can throttle it up when it's in neutral. As soon as I put it in gear and crack the throttle the engine starts to cut out. The engine runs great when I get into it. I ran it like that for a few hours and it ran great. Any help would be appreciated. Thanks in advance. Marcos

Does the engine run good with it in gear and under load? Is that what you meant by “when I get into it”?

 

[Mr Brown]

I think he's saying that the part throttle fueling is off.

 

[marcos5192]

Does it run good in gear with the clutch disengaged?

Yes I have disengaged the clutch and it revs up no problem

Does the engine run good with it in gear and under load? Is that what you meant by “when I get into it”?

 

[marcos5192]

It does run good with the clutch disengaged. It also runs good with it in gear under load.

 

[Kiwi Rider]

It does run good with the clutch disengaged. It also runs good with it in gear under load.

By the way you have described the symptons, it appears to be a fueling/tuning issue.
You really need to get it on a Dyno with a reputable tuner IMHO.
With it being a turboed engine, the fueling is critical to prevent leaning out air/fuel ratio which in turn creates detonation, so let's not take any chances here.
Oh, one thing to check would be the throttle position sensor at idle, closed throttle. Search the oRg for more info or refer to the service manual on this.

 

[Kiwi Rider]

One thing I've just thought of . . .
I have a power commander on my NA stock Gen 1, I had it dyno tuned and a map made for my PC3 by the tuner.
It went fine, and then a year later I fitted some new stage 1 Yoshi grind camshafts.
Then it had a hesitation, a 'miss' like the engine cutting out momentarily as I put it in 1st and released the clutch to move off.
This happened frequently, almost every time I released the clutch in 1st with revs just above idle.
I disconnected the PC3 to see if the fuel map in it was out of tune for the new cam timing and sure enough . . that was the issue.
It never hesitated or mis-fired again as I took off slowly in 1st.
I'm not suggesting you unplug your Power Commander, your turbo set up is going to be tuned by it, BUT I am saying maybe it's not correctly fueling at the point where it 'cuts out' as you put it.
Just something to chew over really.
I hope this is helpful.

 

[Mr Brown]

As I understand it, part throttle (less than wide open) is the most difficult part of a turbo tune to get right. @Boosted Cycle Perf can explain it better, and correct me if I'm wrong.

 

[BlackHammer]

Get that thing tuned up before riding again.

 

[marcos5192]

One thing I've just thought of . . .
I have a power commander on my NA stock Gen 1, I had it dyno tuned and a map made for my PC3 by the tuner.
It went fine, and then a year later I fitted some new stage 1 Yoshi grind camshafts.
Then it had a hesitation, a 'miss' like the engine cutting out momentarily as I put it in 1st and released the clutch to move off.
This happened frequently, almost every time I released the clutch in 1st with revs just above idle.
I disconnected the PC3 to see if the fuel map in it was out of tune for the new cam timing and sure enough . . that was the issue.
It never hesitated or mis-fired again as I took off slowly in 1st.
I'm not suggesting you unplug your Power Commander, your turbo set up is going to be tuned by it, BUT I am saying maybe it's not correctly fueling at the point where it 'cuts out' as you put it.
Just something to chew over really.
I hope this is helpful.

I am leaning toward the TPS having a bad spot in it. I have not had the time to troubleshoot it. Is it a 0-5V signal? Do you know the resistance of the TPS. I do not run a power commander. It is stock expect of course for the turbo. As I understand from the builder, as the manifold pressure goes up it delivers more fuel pressure (adjustable fuel pressure regulator). This is a 2007 car, it came with a turbo and never had this problem. Thanks

 

[Mr Brown]

I am leaning toward the TPS having a bad spot in it. I have not had the time to troubleshoot it. Is it a 0-5V signal? Do you know the resistance of the TPS. I do not run a power commander. It is stock expect of course for the turbo. As I understand from the builder, as the manifold pressure goes up it delivers more fuel pressure (adjustable fuel pressure regulator). This is a 2007 car, it came with a turbo and never had this problem. Thanks

You have to have a way of controlling the fueling, i.e. power commander or other piggy back, or tuned through the ECU. You can't simply add a turbo and fmu, it still needed to be tuned. The tps is unlikely to have a "bad spot" in it, when they fail, they tend to fail completely.
Are you saying that since you've owned it the car never had this problem, and it developed out of nowhere?

 

[marcos5192]

You have to have a way of controlling the fueling, i.e. power commander or other piggy back, or tuned through the ECU. You can't simply add a turbo and fmu, it still needed to be tuned. The tps is unlikely to have a "bad spot" in it, when they fail, they tend to fail completely.
Are you saying that since you've owned it the car never had this problem, and it developed out of nowhere?

Yes never had this problem. I have ran this car with this set up for 10 years.

 

[Mr Brown]

Yes never had this problem. I have ran this car with this set up for 10 years.

Dude, getting information from you is like pulling teeth!
Did you change anything before it started acting up? Anything at all? Even if you don't think it's related?
Have you checked your plugs?

 

[marcos5192]

Dude, getting information from you is like pulling teeth!
Did you change anything before it started acting up? Anything at all? Even if you don't think it's related?
Have you checked your plugs?

LOL I think I have heard that before. I changed the plugs and fuel filter. Other than that nothing has been changed or messed with. Thanks for the help

 

[Mr Brown]

Was the filter a stock item? Have you made sure the coils are pushed down on to the plugs until they click?

 

[marcos5192]

Was the filter a stock item? Have you made sure the coils are pushed down on to the plugs until they click?

Stock filter. The fuel pressure is good. Yes I checked the coils. I am going to check my vacuum lines.

 

[Mr Brown]

Stock filter. The fuel pressure is good. Yes I checked the coils. I am going to check my vacuum lines.

Always good to check those.

 

[marcos5192]

Always good to check those.

Finally got time to work on my car. Turns out that the throttle position sensor had a bad spot in it. The resistance would open when the throttle was about 10%. Thanks for all the help.

 

[Mr Brown]

Finally got time to work on my car. Turns out that the throttle position sensor had a bad spot in it. The resistance would open when the throttle was about 10%. Thanks for all the help.

Thanks for checking back in with news. What do you mean by bad spot in the tps?