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Timing/RPM issue
Topic Started: Dec 9 2016, 09:07 PM (364 Views)
Fastlane1221
WolfBearMoon
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Hello, I have a 1996 Geo Metro LSI. While going about checking the current timing on my car I saw that the RPM was jumping all over the place from 600 to 1,200 at idle. and my timing was jumping from about 8 to 6 or so it seemed. I did bridge the connectors and I also set my TPS using this link: http://geometroforum.com/topic/1341780/6/#post666068

My idle has seemed smooth from the moment I start my car but as I start putting a load on my engine for a good 10 to 20 minutes of driving without many electrical systems being in use except running lights and my heater fan which I keep on low, my cooling fan for my radiator kicks on and the idle gets rough. At a dead stop my car will shake a little. Which has been going on from day one.

I have replaced my fuel filter, trans fluid and filter, air filter, seafoamed my engine top to bottom as well as my vacuum system and fuel system, used fuel injector cleaner, replaced spark plugs twice and the wires for those plugs once, I have flushed my heater core twice and burped my coolant system that many times if not more. I am beating my head against a wall trying to figure this problem out. :banghead I have checked vacuum lines and wires. I have even checked my coolant sensor and it is working fine, my TPS is working fine, and I just replaced my catalytic converter about 3 weeks ago. I plan on checking compression next week when I get my tester. The only thing I think might be the issue is the Idle control valve. However my engine in the morning has piston slap due to the cold but it goes away once the engine has warmed up and there are no extra sounds like spark knock or any sticky lifter noises that I can tell.

Let me know what you think.
Edited by Fastlane1221, Dec 9 2016, 09:15 PM.
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myredvert
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myredvert

Quote:
 
I also set my TPS using this link:
One very critical step in the factory procedure for checking/setting the TPS is to make sure the idle Speed Control (ISC) motor is not touching the throttle screw.
Factory Service Manual
 
1. Insert a 3.5 mm (0.14-inch) feeler gage between the throttle stop screw and the throttle lever.
2. Inspect the Idle Speed Control (ISC) motor plunger. If the ISC motor plunger is contacting the throttle lever screw, then the engine must be brought to operating temperature.
If the ISC plunger was in contact with the throttle lever screw, the TPS will be mis-set.

I wouldn't worry about the exact timing until you get the variable idle condition sorted out first. The timing will change with that large of an rpm variation, and your timing is somewhere in the ballpark which should be fine for now.
Quote:
 
The only thing I think might be the issue is the Idle control valve
You have an Idle Speed Control (ISC) motor. No air valve. Besides making sure your TPS is set correctly in accordance with the factory instructions, you can observe the ISC plunger and see if it seems to be causing the idle variation, or if it's retracted when the engine is at operating temperature and the idle swings are still happening on their own.

Piston slap on start up is already one big clue as to the condition of your engine. I think you're probably going to get some more valuable information from your compression test.

As far as vacuum leaks go, with a car that old it's a good (and inexpensive) idea to replace the vacuum lines and verify they are route correctly in order to eliminate that possibility as well.
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Fastlane1221
WolfBearMoon
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I made sure to use a feeler gauge when setting the TPS as they show in the link I provided. Also the engine was at operating temperature.

I only get piston slap in the cold. When the outside temperature is warm it almost never happens.

If I have time later today, I will check the ISC plunger.
Edited by Fastlane1221, Dec 10 2016, 04:54 AM.
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Fastlane1221
WolfBearMoon
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I did compression check and from cylinder 1 to 4 dry I read 140, 150, 120, and 155. So now I know my engine needs help, what should I do to go about this? Will my engine be good as long as I take care of it?

I was thinking if my engine will last long enough, I would like to buy another engine to rebuild (because my car is my daily) and drop it in, and then rebuild my current engine. This could take up to two years. I love my car so any feedback would be appreciated.
Edited by Fastlane1221, Dec 10 2016, 08:53 PM.
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freegeo
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Fastlane1221
Dec 10 2016, 08:51 PM
I did compression check and from cylinder 1 to 4 dry I read 140, 150, 120, and 155. So now I know my engine needs help, what should I do to go about this? Will my engine be good as long as I take care of it?

I was thinking if my engine will last long enough, I would like to buy another engine to rebuild (because my car is my daily) and drop it in, and then rebuild my current engine. This could take up to two years. I love my car so any feedback would be appreciated.
Quote:
 
Will my engine be good as long as I take care of it?


Any engine can be good as long as you maintain it properly.

Quote:
 
I was thinking if my engine will last long enough, I would like to buy another engine to rebuild


For a 96 4 cylinder there is only 3 years you can get an engine from that is the same. 95, 96 and 97. 95 has differences and would have to have some things taken off your 96 to make it run right.
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Fastlane1221
WolfBearMoon
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Alright sounds good, that is exactly what I wanted to hear. I think around tax time I might buy a truck to lessen the wear on my Metros engine and also I think it would be a good idea to have a back-up vehicle for any possible failures. Maybe I will also get one of those trailers that you can tow a car with just in case.
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