924Board.org

[j. johnson]

performing intensive tune-up/restoration on 1980 924 turbo and in process of street testing. we notice that the engine hesitates and sputters at every other stop sign. one time it will accelerate hard with no hesitations, next time it won't?

why?

[fiat22turbo]

I would start by looking at fuel delivery, specifically ensure the fuel filter and injectors are clean and flowing properly and the fuel lines are in good shape.

Check for vacuum leaks, there are a number of rubber elbows for the turbo charger plumbing that tend to begin leaking overtime and aren't usually replaced since some require pulling the timing belt to reach. While the engine is idling after a run, carefully spray some water with a spray bottle on the vacuum lines, intake hoses and injector seals. If the engine stumbles then you have a leak.

Finally, check your plugs for lean/rich that may indicate a fuel issue or you may have weak spark. You may need to change heat range depending on what you find (turbo cars typically like "colder" spark plug ranges since the combustion temps are usually higher) when you check the fuel system and spray pattern you can then focus on ignition if needed.

A wideband oxygen sensor with datalogging can help you determine your mixture as well and whether you might need to make some adjustments based on back to back runs or tests on a dyno.

Retest after every major change and try to only make one major change at a time, that way you don't compound issues or lose track of what actually fixed the issue.

Good luck!
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Smoothie]

+1^ with emphasis on vacuum leaks.
Check all the charge tube plumbing from turbo to throttle body, rubber boot from air meterer to turbo, replace all rubber vacuum elbows and lines..
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[bear924]

Check that your spark plug leads aren't breaking down. I had one lead that would sometimes open circuit which presented symptoms simliar to yours. I would suggest a close visual inspection, you could also use a multimeter to check resistance while moving the lead around.