'88 Chevy Nova misfire when cold & fully warm

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  #1  
Old 01-23-15, 09:45 PM
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'88 Chevy Nova misfire when cold & fully warm

Have an interesting problem with a Chevy Nova econobox my friend just (unfortunately) purchased.

With engine cold, there is a miss on the leftmost cylinder. When it warms up slightly, the miss goes away and engine runs fine. When the engine reaches full operating temp, the miss returns and continues from then on out. This sequence happens like clockwork every time.

I checked compression and spark when engine was both stone cold and fully warmed and found both to be good. The spark plug in the offending cylinder was changed but problem continues. I checked the plug after the engine idled for a while and found it to be a bit carboned, but that could be cuz the car has been idling and not driven. Nonetheless, I wire brushed the plug and popped it back in but problem remained.

Not sure if I have a lean/rich problem or if something is up with the valves/lifter for that cylinder.

Any ideas as to what's going on? It's been a real head scratcher for me so far. This is a SOHC carbed engine, btw. Oil level is fine and was just changed.
 
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Old 01-24-15, 03:15 AM
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Welcome to the forums! You say "plug".....only one? Change them all, and change the wires while you are at it. So many things to go wrong on an older engine. Points, dwell angle, coil. It will be a matter of elimination. Valve lash is another critical point, too.

Just be thankful it isn't a '66 Nova with a V8. To change #8 plug, the engine mounts have to be loosened and the engine raised 6" to access it. A good case for engineers being tunnel visioned during the design process. "Hey, the hole is big enough, put a V8 in there".
 
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Old 01-24-15, 05:44 AM
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Make sure that the carb hold down nuts or bolts are tight. GM is noted for them vibrating loose. Normally, I do what you did & that's check the spark first but since it runs well part of the time, there is something else contributing to the problem.

BTW, there are no points on an 88.
 
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Old 01-24-15, 06:10 AM
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Was thinking that after I posted it. So many changes over the years, I forgot when the inductive pick up went viral. Forgot, too, this was a Chevy II, not a REAL Nova of earlier years.
 
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Old 01-24-15, 06:30 AM
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Is the miss there at idle or all the way through the power band?
Wire brushing a plug is virtually useless in trouble-shooting a fault. Change the plugs.

This car is a Toyota Corolla and you'll likely find folks at toyotanation that can help you.

Good luck.
 
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Old 01-24-15, 07:05 AM
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2granddaughters, I was about to ask why did you mention Toyota but then I remembered that a Toyota engine & parts were used in them.

The OP mentioned that the miss is when it's cold & fully warm but not in between.
 
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Old 01-24-15, 11:49 AM
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Thank you all for the very quick replies, and thanks also for the welcome!

To address some of your questions/comments: all plugs (and wires) were changed, actually. I ended up replacing that plug I wire brushed just to make sure, and no change. I will check the carb bolts to make sure they're tight. Pulpo is correct, this is a Toyota engine. Cylinder miss is constant throughout rev range. Points aren't used on this distributor. .

Cap and rotor will be changed when parts arrive, but I don't think that will help since spark at that cylinder is strong and consistent.

I think this engine uses hydraulic lifters. Would setting valve lash be necessary in that case?

Thanks for mentioning toyotanation. I will give them a try.
 
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Old 01-24-15, 03:31 PM
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What lifters? Didn't you say that it was an overhead cam engine?
 
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Old 01-24-15, 03:52 PM
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Ooops. Forgot about that.........................................
 
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