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Idle problem; slow at start up high at warm up
Topic Started: Jan 23 2010, 08:49 PM (2,859 Views)
magboy
New Member
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I was wondering if there is a sollution to my high idle. I have a 1998 Chevy Metro with a 3 cly 5 speed tranny. When I start it it runs slow idle and ruff, unless I give it a little gas to bring up the idle. But when it's all warmed up it has a high idle and won't go down. Is there a adjustment I can do for this, or do I need a complete Throttle body. I bought a used one and really don't want to replace the one on the car. I haven't ever done that. And how hard is it to do so. I can't find any photos anywhere to show me how. Ant help would be appriciated.
Thanks
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Bad Bent
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Facetious Educated Donkey

Take a look at High Idle before you change Throttle Bodies (TB). It's a solvable problem, it may be a vacuum leak and the next solution may be clogged coolant hose on the TB. You can check those by simply feeling if they are hot when the engine is warmed up.

You would need to unhook all the cables, hoses and air cleaner on the TB and it has two ground wires. Unbolt and remove it. Use a new gasket when reassembling. ;)
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Johnny Mullet
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Fear the Mullet

I suspect a vacuum leak.
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geonewbie
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BB,

i have seen your comments before about the TB ground wires, and the way and places to improve the level and effect of ground to the systems. i believe they are valid and accurate.

but.........having been all over and around the TB and everything around it constantly for the last couple months / 3,000 mls. i have not found or seen a wire disconnected and/or hanging in the area. nor do i see the cut off ends of any wires sticking out the the rest of the harness.

where should i look for the signs of where they would have terminated at the grounding point ?

thanks,
steve
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rmcelwee
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I have the same problem but have been too busy to take a look at it (so I am glad you posted your question). I don't think you would be able to see a bad ground. You will need to pull off the grounds, scrub them up a bit, and reconnect so you know you are getting a better connection.

BTW, my idle is only low for the first 15 seconds of driving and my high idle is only around 1500 with no pulsing. I'll work on it soon and let you know what I find. I'm pretty sure at least part of my problem is a bad/out of adjustment TPS since my car never sees a TPS closed condition (based on my MPGuino).

Edited by rmcelwee, Jan 24 2010, 04:54 PM.
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magboy
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adjusting the TPS, what's the TPS and where is it?
I took off my 1996 TB and was looking it over and where the Throttle cable attaches to the lever that is spring loaded there is a black round knob with a screw end. what is that for? Is it something that will help in the adjusting it? Could someone tell me more about that?
Thanks
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rmcelwee
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That is the idle adjustment. Everyone says not to touch it (I did on my convertible though). If you decrease it for your high idle it might make it so that your car will die on cold idle. If you wanted to play with it, I would screw it completely in and count the number of turns so you can always put it back where it was. If you look on the opposite side of it you will find your TPS (sticks out the other end of the throttle body). I think it has 4 wires on it. I fixed my gas leak today and will probably work on my idle tomorrow if I get a chance. If I fix it you will be the second person to know...
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Bad Bent
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Facetious Educated Donkey

I would caution against seating anything, like the idle screw, to tight, it could damage the seat, or spring.
It is best to get a service (shop) manual for your car. The '96 is a green 2 volume set; ebay.com/1996+geo+metro+manual.
You can take a look at TPS Report and the three pages to see if you can apply the test to your car. :hmm as I did to the Wife's '96.

For giggles check out How to pull a G10 by starscream5000 and #27. Disconnect ECU Grounding Wires (Another underneath-the-car task). This is a ground on his '96. It would be good to clean and tighten this ground. B-)
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rmcelwee
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We might be talking about two different things. I am talking about adjusting the TB stop (just an external nut and screw with nothing seating inside the TB). Hmmm, maybe I have been taking the warnings about adjusting a screw to mean something that it never meant.
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Bad Bent
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Facetious Educated Donkey

I have found it to be a "round robin" affair. Without consulting a manual (a bad thing) and knowing that the settings had been tampered with I had to make changes on my '91s high idle. Throttle stuck so #1 was to adjust the cable tension. Still sticks... so I burped it by hand and saw the butterfly was sticking. Made several small adjustments to the set screw until it stopped. Small Allen wrench and comb. wrench handy.
Idle went up. I adjusted the idle set screw until it lowered but these changes threw my TPS out and it had to be adjusted to the new settings. Finally got my idle down to the proper 800 rpm by balancing the settings. B-)
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magboy
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Now I put on another TB and the idle is a little low when warm, not bad. And a good idle at start up. I ran it for about 20 miles then the engine service soon lite came on. What would of caused that. I did replace the front small vacumme line as it had a small crack in the hose. I cleaned the TB prior. It was in a 96 geo and the lite was not on. Thanks for your help.
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Bad Bent
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Facetious Educated Donkey

1996, it has the OBDII diagnostic system like the Wife's '96 then it would be good to get a scan tool. eBay $36, buy now incl. shipping

Double and triple check your connections, maybe the MAP or IAT sensor was left disconnected, the ground wires, EGR vacuum hose or something disconnected is my speculation, without the ODB code. :dunno

Note: Some parts stores will read the codes for you and clear them(?). A scan tool is a good tool to have if you drive a lot. It allows you to know what's wrong and if you take it to a mechanic to read the codes you'll know if they are telling the truth. ^o)
Edited by Bad Bent, Feb 8 2010, 12:16 AM.
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Dugger
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If you have a spare TBI for your 98 try swapping out the ISC box. It's the large plastic housing screwed to the back of the TBI. It uses a plunger to control the idle and may be defective.

GL :cheers
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