Engine "skips" while turbo boosting

[skeens43]

Freind just bought a 1987 Daytona Shelby Z - all stock with low miles. Car runs great under normal driving, however if you get on the throttle and begin to wind the turbo up the engine "skips" and jolts like the spark is being interupted or something. There's a "whistle", almost like a leaking vacum line you can hear when your foot is on the gas. Anybody know what the causes for any of this is and how to repair it?

[InfinityShelbyZ]

Someone can offer a better explanation, but the sake of offering advice quickly its probably a vacuum leak allowing the turbo to overboost and cutoff the engine. Whats the boost reading when it does it? Most likely thats the problem. Hopefully someone could better elaborate which lines are most susceptible to this.

[Turbo-Baron]

^+1
Watch your boost gauge when you get on it.If your going past 14.7psi then your hitting overboost.

[roachjuice]

or the vacuum line going to the map sensor can have a vacuum leak.

[skeens43]

Thanks guys for all the helpful info - I'll start checking things out.

[william]

Just to be different, I will guess the two conditions you describe are unrelated. For the miss I would check secondary ignition components (wires especially, but rotor, and possibly coil), as the energy needed to fire a plug increases greatly under higher cylinder pressures (boost). If the wires are bad, the cylinders will misfire.

[BobsBlackACR]

I would also check your spark plug gap too as that will have an impact. Maybe go down to .035-.032"

although the whistling you describe in this combination leads me to believe that you are possible inducing compressor surge.... at what rpm does this all happen and does it continue to redline?

[crazymadbastard]

My guess is gas starvation, change your fuel filter and look for leaks on the gas line.

[RGHoskins]

Quote:

Originally Posted by william Just to be different, I will guess the two conditions you describe are unrelated. For the miss I would check secondary ignition components (wires especially, but rotor, and possibly coil), as the energy needed to fire a plug increases greatly under higher cylinder pressures (boost). If the wires are bad, the cylinders will misfire.

+1. My C/S did the cutout thing and it turned out I had a spark plug loose. Check your ignition components. The whistle is probably an unrelated vacuum leak.

[chilort]

I would say it also depends on the sound of the whistle...

Suck through designs do "whistle" because the turbo runs such a higher rpm than a blow through. Though looking for vacuum leaks is never a bad idea.