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Rough idle, engine miss at medium throttle

Tiny
DESERTDOG8087
  • MEMBER
  • 6 POSTS
What would be the best way to check for leaks around the intake?
I'm not really sure if the PCV valve is working properly.
It was just a thought.
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Monday, June 29th, 2020 AT 7:03 PM (Merged)
Tiny
DEEREDUDE5510
  • MEMBER
  • 3 POSTS
  • 1989 CHEVROLET S-10
Engine: 4.3L
Auto Trans, 2WD, mIleage is about 215,000

This rig has a Goddwrench motor in it, not sure of replacement mileage, bought it used. It was at a very low idle and stalling a lot. GM tech scanned and had no codes. Timing is OK, EGR is new, IAC was replaced last night, it still doesnt run right. Now it seems as if a vaccum leak is the problem, but no ideas. When the heater or vent is on the idle deteriorates, but turning AC on bumps idle up to an acceptible level. My next guess. MAP sensor? Any help would be appreciated. Thank You in advance.
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Monday, June 29th, 2020 AT 7:03 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Could be sticking throttle shaft or binding linkage that the TPS giving the PCM the curve ball of high voltage. Check the TPS voltage should read at close position 1.2volts.

Also check your battery connection fluctuation of voltages will change the position of the IACV.
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Monday, June 29th, 2020 AT 7:03 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,273 POSTS
Many people will spray starting fluid or a carb cleaner around the area. IF there is a leak, the RPM's will increase. My only concern is if you spray an area that is hot enough, the sprays can catch fire. Just be careful and have a fire extinguisher near.

As far as the PCV valve, when you shake it, you should be able to hear a check ball rattle inside. If you do, it's good.
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Monday, June 29th, 2020 AT 7:03 PM (Merged)
Tiny
DEEREDUDE5510
  • MEMBER
  • 3 POSTS
Thank you for the info. I am about to lose my sanity over this thing. I will check on those tomorrow and see if that helps. If not off to the looney bin.
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Monday, June 29th, 2020 AT 7:03 PM (Merged)
Tiny
DEEREDUDE5510
  • MEMBER
  • 3 POSTS
So today I took the throttle body off and the EGR passage was plugged. The gasket was toast and some less than brilliant light buld drilled out the idle plug and messed with it. Soooo.$50.00 and about 6hrs later I think I may have solved the problem. Also, new fuel filter. And then the kicker driving it around the block and asll the "do it yourself" spark plug wired that came with it fell apart. So. I think I fixed it. Time will tell.
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Monday, June 29th, 2020 AT 7:03 PM (Merged)

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