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Uneven running at steady speed
Topic Started: Jan 21 2011, 06:01 AM (1,420 Views)
Peaceonearth
New Member
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Greetings fellow Metro lovers,

May I have some advice please?
It began months ago, driving along the highway and once in awhile....a miss. I ignored it.
It has worsened steadily to where I can ignore it no more; it misses constantly - but only at a steady speed. If accelerating or decelerating there is no problem.

I'm suspecting it's the coils and wires, which are original. What do you think?

2000 Metro sedan, 1.3L, 4 cyl. auto, 199,866 miles.

Thanks in advance for your help.
Dave
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944door
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With that many miles its hard to believe that the wires are even in one peice. Is it throwing a check engine light? A scan tool would help you narrow down the "miss" if it was. I would also check compression. Is the car using oil?
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mcmancuso
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Check all the sparkplugs to see if they're tight. Also depending on how old they are, a new set of plugs wouldn't hurt, these are semi-coil on plug design so new coil/wires may not hurt, but the coils are pretty expensive IIRC. I have a metro with this engine and had a sparkplug blow out because it was loose.
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Horn


yea I would recommend the typical tune up. my dads old car would do the same and it was plug wires. but imo a good tune up should do the trick.
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Rang-a-Stang
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Schmuck

200K on original wires?!?! HOLY CRIZAP!!

Tune'r up! :beer
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Horn


holy crap I didn't even see that part.....lol
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Peaceonearth
New Member
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Love this place! I'll drop by more often to help when I can to too - I do know a little.

Should have mentioned; plugs are new, and I torqued them in - I am real sure they are tight but I'll double-check, you never know.
A scan revealed nothing new, just an O2 sensor that I already know about.

I catch the wee hint that coils and wires are due - will do. I'll get back to you next week.

You guys are GREAT, thanks for helping out.
Edited by Peaceonearth, Jan 21 2011, 09:28 PM.
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slander
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Tech Certified

No need to replace the coils unless they go out. New set of plug wires is needed obviously. I'm guilty of not replacing wires soon enough from time to time myself. Matter of fact, just the other day I finally did a complete tune-up on my 88 Chevy K1500 pickup. It was running decent, little rough in wet weather, which is typical with defective ignition hardware. When I pulled the coil wire from the cap, half of the coil plug came with the wire. Pulled right out of the cap. The other half, the button, fell onto the top of the rotor. I couldn't believe the truck had been running this entire time with a cap that was in such bad shape. I had that set of cap, rotor, wires and plugs in that truck for 8 years now, back from when I rebuilt the engine.

Got everything all changed out, and when I checked the timing I noticed my harmonic balancer was wobbling excessively. So, a 45 dollar purchase from RockAuto.com, should be here Monday.
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Jim-Bob
Junkyard Engineer

I would test the primary windings of the coils with a DVOM before shelling out cash for new ones. I don't have the procedure for your car so I won't even try to post it here. However, old plugs and wires CAN blow the coil packs (and possibly even the module!). The reason is because of excessive resistance. It makes the windings run hotter and eventually it kills them. I recently fixed a Grand Am with a similar issue and have seen it on other cars as well. (It was one of those deals where I did the repair for parts cost only just to prove I was right.) Just remember that it is always more expensive to neglect maintenance than to perform it in a timely manner. This also goes for oil leaks, etc. Metros may have been cheap cars to buy when new, but they had quality where it counts. Maintain one and it will reward you with many years of low cost motoring. Neglect it and it will be a throw away car. The choice is yours.
Edited by Jim-Bob, Jan 22 2011, 04:13 AM.
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Car Nut
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slander
Jan 21 2011, 09:41 PM
. I couldn't believe the truck had been running this entire time with a cap that was in such bad shape. I had that set of cap, rotor, wires and plugs in that truck for 8 years now, back from when I rebuilt the engine.

That's a Chevy for you. Takes a licking & still keeps ticking. Now if they could just fix the rusting out issues. That thought reminds me of a 68 mustang I saw with a 350 Chevy & turbo trans behind it. Best of both worlds. lol

I just replaced plug wires & coil on a 94 Ranger 3.0L this week. Had a bad miss under load. Bad wires, #4 was cut & arking, looked like the coil was also arking to it's frame. Pulled the coil wire & it was just like yours. Truck runs great now.
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Woodie
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Remember guys, if he lays all his spark plug wires out, end to end, he's got about four inches there. New ones can't hurt, but that's probably not the problem, coils are definitely not the problem. I think it more likely that it's a wear problem, 200K on an automatic is almost certainly worn out. Do a compression test.
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Bad Bent
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Facetious Educated Donkey

Well, a fun test on these old wires would be the find mist spray of water & a few drops of soap, sprayed on the wires when the engine is running. Garage lights turned out. See if there is any errant arcing. :banana
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CityConnection
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Sir, yes sir!

OK, I feel I should add some clarification here, On the SOHC 16V engines there are only 2 wires (1999+). BUT... That isn't the whole ignition system. Under the coils are replaceable boots. These are never included when you buy a set of wires for this engine. If you need to do all 4 parts of the ignition you will need to order the boots separately. Expect to pay around $12-15 a boot.
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Peaceonearth
New Member
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I don't know whether anyone is yet here to see this, however, if so, please know I appreciate your helpful suggestions and that it is now sorted.
You may not believe this:

Replacing the plug wires definitely helped - about 50%. Thanks!

But here was the main culprit:
Posted Image

The crankshaft sensor connector. About a millimeter down inside of where the wires attach is a partial break that allowed signals to pass intermittently, mimicking a misfiring ignition. This explains why a voltmeter showed good signal from the inserted pins.
I have crimped spade connectors to the harness and securely taped them to the sensor.
Runs like new.
Thanks again!
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