car misses at low rpm

[evil347]

I've checked timing, plugs, replaced pick-up in dist., tfi module, car seems to run better above 3,000 rpm anybody ever ran across this. It is a 347 stroker fuel injected, car ran fine parked it for a week and now i have a miss can't figure it out, any insight would be greatly app. thanks:
:confused:

[redfirepearlgt]

Had the same problem on a modular 02. The car rans smooth above 3000 RPM (open loop). Had it to 2 different tuners and they could not get rid of it. Changed O2 sensors, IAC, throttle body, spark plugs, fuel injectors, COP's, and still had the problem. Was worst at 2000 RPM. Got rid of the car finally. Ran good like yours at 3000 or above. The miss was light but even under load you could feel it lightly undernormal drive conditions. My next move would have been either the MAF or a kitchen sink. Also, all vacuum testing I did checked good. Also verified that the Fuel rail sensor (feedback for closed loop fuel system) was working properly. Did the same wit stock tune, MD tune, or PAE tune. Good luck. I know how you feel, it is very annoying.

[evil347]

will a broken valve spring cause this or would it miss all the time

[TurboNG]

Valve spring would cause it to run like crap all the time. But you would notice it more at low RPM. Do a leak down test. Tool is cheap at Harbor Freight Tools.
Do you know it has a broken spring or is this Speculation? Have you pulled the valve covers off?
Does it do it under exceleration at low RPM or just at idle.? Check your TPS out put if it is at idle with no throttle. Check wiring, grounds ect. Mice might have got to it.

[highball69]

i would try a compression check not sure but a burnt valve or broke ring at low idle compression could cause it to leak off faster

[evil347]

motor only has 2200 miles on it, broken valve spring is a speculation, i am stilll running the stock tune , but it also ran fine on stock tune too, im worndering if i got a bad tfi module, ill pull compression test first and check voltage @ the tps anymore insight would be greatly app.

[TurboNG]

You can do the paper test on the oil fill, start the car and remove the oil fill cap, place an 3x5 index card on the hole. The index card should remain on the hole at idle with out you holding it. If it don't then you have to much crank case pressure. Could then be a bad ring seal or not enough engine vacume.
Check out your Vaccume lines