Intermittent high idle fixed; was corrosion in EEC relay

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PA Brian

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 Ive'  been chasing this high idle problem for a long time. Rebuilt engine 30,000 miles ago , changed all sensors and IAC. Did'nt  find any vac leaks. Checked all grounds. Pulled computer and checked connecters, no problems. Finally found the problem! Found corrosion at EEC relay at left fenderwell. Now idles at 600 rpm in drive. Latest sympton was when i tryed to pull codes reader would not connnect. Then when i turned ignition on i lost CEL untill i disconnected battery. Now everything is good. Hope this helps someone!

 

Pamm

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Ive' been chasing this high idle problem for a long time. Rebuilt engine 30,000 miles ago , changed all sensors and IAC. Did'nt find any vac leaks. Checked all grounds. Pulled computer and checked connecters, no problems. Finally found the problem! Found corrosion at EEC relay at left fenderwell. Now idles at 600 rpm in drive. Latest sympton was when i tryed to pull codes reader would not connnect. Then when i turned ignition on i lost CEL untill i disconnected battery. Now everything is good. Hope this helps someone!
What does the EEC relay look like so I can check mine?
 

Tiha

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Should be right next to the fuel pump relay on driver's fenderwell.
 

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Jimbo26

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+1 on the detective work there.
Have been slowly going thru my rig with the connectors, each one that gets disconnected gets slopped with the dielectric grease before put back together.
Come motor-job time, the entire batch of them on that LH fender well will get the treatment. That will take care of Everything as such under the hood. 🤞
 

johnnyreb

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Ive' been chasing this high idle problem for a long time. Rebuilt engine 30,000 miles ago , changed all sensors and IAC. Did'nt find any vac leaks. Checked all grounds. Pulled computer and checked connecters, no problems. Finally found the problem! Found corrosion at EEC relay at left fenderwell. Now idles at 600 rpm in drive. Latest sympton was when i tryed to pull codes reader would not connnect. Then when i turned ignition on i lost CEL untill i disconnected battery. Now everything is good. Hope this helps someone!
Thank you for coming back and giving the good news and solution.
 
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Does this idle look right after new plugs and wires? It was already hitting 1200 at start and dropping to 800 after initial warm up like this before the ne.wplugs and wires .. but now it's also running rough in low gears and low speeds...
 

miesk5

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Yo 91
EFI High Idle Tips by Mikey 350:
"Take off the air intake hoses so you can access the throttle bores. Start the engine and place a piece of stiff cardboard over the throttle bores. That should NOT change a correctly configured engine, as the idle air is only from the opening of the IAC, and nothing through the throttle bores.
If that make a difference, then the throttle plates are slightly open due to the removal of the Teflon coating, or the linkage/return spring/throttle stop is screwed up.
If the engine still runs too fast with the throttle opening blocked, try taking off the IAC and blocking those openings.
What you have done is (supposedly) removed all the "normal" air intakes, and if the engine still runs, you have a vacuum leak.
You could then try leaving the air intakes (throttle and IAC) blocked and cap off the vacuum lines coming off the vacuum tree. (except the MAP line) If one of those makes a difference, investigate the leak.
Check the vacuum line from the vapor canister (on the left side of the throttle, when facing the throttle assembly) (cap it, on the outside chance that the solenoid has failed open) (if equipped)
Pull the EGR connection to the intake and plug or cover it. (if you have wide duct tape, use that to cover the hole)
If it still is running with the throttle blocked and the IAC and the lines from the vacuum tree capped, then you have a manifold or PCV line leaking. Plug the PCV line to the intake, then the vacuum line to the brake booster (if it has it's own fitting on the manifold)
Something is causing that high idle, and 95% of the time it is a vacuum leak."
...
 

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