geo metro, cylinder not firing, tried everything

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  #1  
Old 01-24-04, 03:53 PM
extremesanity
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geo metro, cylinder not firing, tried everything

I have 92 geo metro 3 cylinder/1.0L/tbi. 85,000 miles.

When initially started and cold the engine sounds like it is firing all 3 cylinders when idling and when I press on the gas in neutral. When put in drive for the first few minutes it is fine and then while driving it loses power and runs erratically. If I put it in park the idle will be very erratic and will sometimes smooth back out to running on all 3 again.

I pull off the #3 cylinder wire and the sound and rpm does not change. Pulling of the #1 or #2 wires makes the engine die. I have done this test multiple times while trying to fix it and it has done the same thing everytime.

Started a couple of weeks ago, only used to do it when the engine was cold, now lately its been doing it when the engine is cold or hot. It tends to come and go for no apparent reason.

What I have tried
Air
- Compression test was perfect - almost exactly 160 psi on all 3 cylinders

Spark
- Spark plug wires resistance checked with multimeter, checked for cracks on wire - fine
- Spark plugs looked fine and were already replaced about 2K miles ago. Replaced #3 spark plug anyways, no change.
- Checked for spark on #3 wire - very strong, hopped an inch out of the boot with no trouble, sequence of fire was fine.
- Not sure when wires/rotor/cap were replaced, but the cap/rotor looked in very good shape

Fuel
- TBI setup uses one fuel injector for all 3 cylinders like a carb. If 2 cylinders are working fine, 3rd should be also.


I don't know what the heck to try next. The problem seems to come and go, lately its been worse. It does not seem to come or go based on rpm, speed, temperature, or moisture. Would a worn spark plug wire/cap/rotor cause an intermittant problem while still providing a strong spark at idle?
 
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  #2  
Old 01-24-04, 04:16 PM
billys68ss's Avatar
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Since you dont know the age of the wires, cap and rotor I would start with that. I had a 92 Geo Prizm (4 cylinder) in the shop today with the same problem. It was misfiring on number 2. The plugs and wires didnt look bad, and the compression was 175 psi. I replaced plugs, wires, cap and rotor and it ran great after. Sometimes its the simplest things.
Hope this is helpful to ya,
Billy
 
  #3  
Old 01-24-04, 05:14 PM
darrell McCoy
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Have seen plug wires check OK, but under a load, they misfire.
 
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Old 01-25-04, 02:50 PM
extremesanity
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Replaced wires, cap, and rotor. No change, same symptoms.
 
  #5  
Old 01-25-04, 03:58 PM
Desi501's Avatar
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A dead miss should not be that difficult to find. What does the plug look like? Is it staying real white of is it getting yellow or brown? You could have a serious vacuum leak near that cylinder preventing fuel from being drawn in. Is the fuel injector spraying a good pattern. You can check that with a timing light. Have you taken the valve cover off and looked at the cam for a bad rocker or worn lobe? It has to be something like that.
 
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