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miss at idle and cruise...


importwarrior
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i have been chasing a miss for a few weeks now.

it all started with changing the plug wires and rotor and cap.

the plugs , rotor and cap fixed my miss when under boost at WOT.

 

but now i have a miss at idle and cruise.

 

after 2 weekends of messing around and checking all that i can.

including every ground i can find. i think i have it half way resolved.

 

i replaced all the vac line from the T where the cruise control is to the t-body.

 

i noticed the White Check Valves near the wiper motor do not seem to move smoothly

or freely. thet seem to take A LOT of effort to get them to move. once they are blocking the

vacuum it takes a ton to get them to open again.

 

shouldn't they move easily with no force?. I tested them out off the

car with clean hose and the suck test.

 

on a side note i believe the GM MAF is also causing some issues.

i need to get another one to test with.

 

i will be doing the TPS reset tomorrow. too dark out.

i did test the TPS with an analog meter and it sweeps just fine.

i tested the ISC per MIKE C instructions and it seems to be functioning properly.

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got the check valves working good.

 

 

Still missing at cruise and idle.

 

TPS

tested TPS sweeps fine no issues

set tps properly to .50 volts

 

ISC

ISC tested fine per Mike C write up

tested fine.

 

MAFT and GM MAF sensor

MAF tested fine and swapped it out with a brand new MAF sensor with the same results.

 

changed spark plugs cap and rotor

still miss while at idle and cruise.

 

injectors are not dripping when the fuel pressure is up and solid 41 PSI

 

when i turn the car off it holds pressure but eventually drops off in 10 minutes or less.

 

Running out of ideas.

 

don't know what else to check.

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  • 3 months later...
  • 4 weeks later...
any update on your issue.... you get it fixed?
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yes it all checked out ok.

 

the problem was basically the cap on the distributor was the problem.

 

when looking in to the center of the cap where the brush touches the

rotor was stuck in flush. the spark was arcing inside the cap to the rotor

and not making a solid contact to the rotor.

 

the other problem was i used too much dielectric grease on the spark

plug wire ends.

 

so far so good. pushing 20 PSi.

 

OH! and gaped the plugs down to .028 fixed my hiccup when the car was

floored and accelerating at mid range RPM.

 

Thought that was caused by the MAF-T. the MAF-T had nothing to do

with it. The spark was getting blown out.

Edited by importwarrior
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good information, thanks!
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