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vacuum leak, can't find it! idle wanders; idle wanders, lopes under some conditions
Topic Started: Aug 17 2011, 06:37 PM (1,830 Views)
eric7blu
Fresh Fish
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I've been fighting this one for quite a while now and no mechanics around here are any help. Diags have indicated it's a vacuum leak somewhere, which would be consistent with a wandering idle. It's a '97 Geo metro 3 cyl 1 liter, 5 speed manual transmission.

If I turn on the blower fan it will start to lope, like I'm repeatedly punching the throttle every half second or so. Doesn't matter if it's
set to heat or blow cool air. Now, here's the interesting part: if I turn on the running lights/headlights or even just the lower power
headlights with the parking brake off then it will stop loping. Presumably this is because the PCM bumps up the idle a bit when the lights
are on to compensate for the increased load.

I've changed, I think, all the vacuum hoses. The entire throttle body has been changed out with one I got on ebay and while it helped
with some other problems it hasn't affected this one. I've had the EGR valve replaced with a brand new one. I've replaced the vacuum modulator with one I got on ebay, all no help for this problem. I've had the intake manifold gasket replaced, and of course the EFE
heater gaskets when the throttle body was replaced.

When the blower motor is off and whether lights are on or not, the idle wanders around. Not a huge amount but it is noticeable.

Please, please, anyone have any suggestions? I'm in the Clifton Park, NY area and I'd love to find a Geo mechanic somewhere around
here. I noticed mwebb in south duchess county, I'd be willing to drive several hours to a mechanic.

I love my Geo, it's an incredible car.

Best Regards,
eric7blu

(and it's blue too!)
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96Geoman


I would suggest you do a compression check. The directions are on this forum.

You may have a burnt exhaust valve. Put a vacuum gauge on the engine, if the gauge flutters, it could indicate a bad valve.
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91 ragtop
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I don't know how much difference there is in the 97 vs 91-92 models but I have had the same problem on several of the older ones after pressure washing the engines. It would also have a dead spot in the throttle that felt like the gas would shut off at a certain rpm. I've had to replace the tps after thy got wet with a known good one and the idle searching went away.
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Damneck
Advanced Member
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Check your map sensor on the 96 it is on the firewall left of the throttle body. It has a filter right below it . Just unplug the Map wires and if the idle smooths out its the MAP sensor.
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Damneck
Advanced Member
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oh yea, if its the MAP sensor, after its fixed, disconnect the battery for awhile and then the PCM will reconfig after a cupple of cycles
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mwebb
Member Avatar
FOG


assuming the locals have tested your car with a smoke generator ? as this will pinpoint vacuum leaks quickly ....?
you could find a friend that smokes... blow smoke into brake vacuum booster line and watch to see where it comes out , rag to seal off throttle body .... brake vacuum booster could also be leaking ....
====================
check the closed throttle switch
if it does not close
the system will never know it should Idle

or
look at the IAC , the spring / contact inside breaks and when it does the systems will be in decel fuel cutoff and
lope ...

never mind
you are in decel fuel cut off as proved by the "lope" , your IAC is broken ,internal search this forum for a how to on the repair

the correct term for the "lope" is "surge"

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clarkdw


If he has an EFE heater as indicated, he does not have an IAC solenoid valve. He has an ISC motor.

Adjusting the TPS may help or as another member pointed out it could well be the MAP sensor.
Edited by clarkdw, Apr 29 2012, 05:38 PM.
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