car studdering

[v8etr]

I have a very modded 87tr and it has a bad studder when it hits 15lbs of boost. And if you get on it and let off it dies every time
Thanks

[HairDrier]

The car dying when you let off the gas could be due to a misadjusted or malfunctioning IAC motor. What is it set at?

The breakup at 15psi is either fuel or ignition. What is your fuel pressure, what chip are you using, does the fuel pressure rise with boost, is your fuel pump new and hotwired, etc

[v8etr]

I have a double pumper and it is hot wired. I have a jay carter chip, I will check the fuel pressure again .
Thanks alot

[Mistascott]

Check your vac lines. If they're old, replace them.

[HairDrier]

How fast is your car? Unless it runs 10's a double pumper is just another thing that can go wrong. Make sure the second pump isnt coming on and flooding your engine with fuel.

You can try swapping coil packs if you have access to one that works for sure

[Chuck]

I have a very modded 87tr and it has a bad studder when it hits 15lbs of boost. And if you get on it and let off it dies every time
Thanks

If the car has a smaller converter in it, it may need some tweaks to the chip. The lighter converter has reduced the inertia of the rotating mass, and the engine rpms will sag too fast to allow the IAC to keep up.
As for the "Stutter". Look at the MAF and see if it's going thru a dropout...
Also check all the other suggestions.. adding in a check of the batt cables....

[tweaked]

QUESTIONS & comments .....

Is the 15# of boost on the stock gage or aftermarket?

If stock gage - check boost lines on turbo boost control for integrity. Possible overboost.

What do the spark plugs look like? If suspect - change them.

What kind of plug wires? Make sure they are good RFI resistance type.

Try the MAF test - @ Hi-idle - rap it with a scrwedriver handle - If the rpm changes - it is bad.

Does it studder with hi octane? If not check the timing in the chip.

What is alternator voltage? I like 13.8 - 14.5V.

When it studders - do you get a check engine code? Does it set a code?
- If yes and no - check the positive battery cable - make sure that it is not touching the exhaust manifold under boost.

Borrow someones Coilpack and wires - see if it continues.
Borrow someones computer and chip - see if it continues.

Measure resistance from block to firewall - I like < 1 ohm.

With HI-OCTANE FUEL and GOOD Boost Gage .....
- Raise FP - Does it get better or worse?
- If worse - Lower FP.
- If better - Continue to raise FP.
- disconnect the knock sensor. Does it still studder? If not - replace sensor.
- disconnect the cam sensor [you will get ck engine light and car will not restart until re-connected] - does it shudder - if not - advance cam sensor setting.
- disconnect injector wiring harness - spray both connectors "liberally" with WD-40.
- disconnect computer connectors - spray liberally with WD-40.

If this fails feel free to contact me after 5:00PM CTS.

Good luck, keep us appraised and have a nice day.

LC
281-540-FAST