How to "read" spark plugs?
Thread Starter
Drifting
Joined: Feb 2000
Posts: 1,591
Likes: 53
From: Central MN
How to "read" spark plugs?
Anybody know of a web site with pictures on how to read spark plugs?
After 28K miles on the stock plugs, I changed out the ACs and went with a set of NGK TR55s. Of the stock plugs, #4 & #5 were missing the pucks. The gap on #4 & #5 was at .67 all the others were at .60. All the plugs were a rust brown color. This is normal. Right?
After 28K miles on the stock plugs, I changed out the ACs and went with a set of NGK TR55s. Of the stock plugs, #4 & #5 were missing the pucks. The gap on #4 & #5 was at .67 all the others were at .60. All the plugs were a rust brown color. This is normal. Right?
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: How to "read" spark plugs? (NewVetteLover)
When I pulled my stocker 41-906's three weeks ago at 28,000 miles ('95 LT1), all the pucks were there, but each plug had black residue everywhere except around the pucks where the spark occurs. The residue was not set-- some of it would wipe off with my fingertip. Not really specks, but an even coating of dry black residue. I also seem to get some black carbon residue on the back bumber/fascia area higher up than just around the LT1 muffler tips, some of which takes some work to remove (like little black greasy specks you have to rub awhile to fade out and it's not tar).
I always run 93 octane, pcm tuning is stock, only mod on the engine is a aFe filter (K&N clone) and opened up (louvers, baffle cut out) lid.
Good news is GM Major Guard is in force for another year and a half if this is something expensive to fix.
Car seems to run good though, although idle is sometimes rough and there's some moderate stumble from about 1000rpm - 1400rpm on the tach.
I know this is the C5 zone, but read the thread and thought I'd post my symptoms in hope of advice :D
[Modified by 95_C4_convertible, 10:41 PM 3/24/2002]
[Modified by 95_C4_convertible, 10:43 PM 3/24/2002]
I always run 93 octane, pcm tuning is stock, only mod on the engine is a aFe filter (K&N clone) and opened up (louvers, baffle cut out) lid.
Good news is GM Major Guard is in force for another year and a half if this is something expensive to fix.
Car seems to run good though, although idle is sometimes rough and there's some moderate stumble from about 1000rpm - 1400rpm on the tach.
I know this is the C5 zone, but read the thread and thought I'd post my symptoms in hope of advice :D
[Modified by 95_C4_convertible, 10:41 PM 3/24/2002]
[Modified by 95_C4_convertible, 10:43 PM 3/24/2002]
Thread Starter
Drifting
Joined: Feb 2000
Posts: 1,591
Likes: 53
From: Central MN
Re: How to "read" spark plugs? (123vette456)
123vette456...........What happens to the missing pucks? Hopefully, they just blow out the exhaust. I think that is what happend to mine, anyway. Fortunately, I do not have any oil consumption problems.
GM claims that the stock plug is good for 100K miles. Well, to that I say :bs .
GM claims that the stock plug is good for 100K miles. Well, to that I say :bs .
Melting Slicks
Joined: Aug 2000
Posts: 2,248
Likes: 1
From: Newland US
Re: How to "read" spark plugs? (95_C4_convertible)
95_C4_convertible,
It sounds like your running a little rich or possibly have weak ignition.
You may want to hook up a spark checker and note the condition of the spark. Should be a good strong blue or bluish-white color.
The OptiSpark distributors were subject to water damage....at least that was the case on the LT1 Z-28's. 28K miles sounds like way too soon for failure of the Opti.
Do you drive a lot in rainy conditions? Do you wash down the engine compartment frequently? Have you had a water pump go out and leak coolant on the Opti? Trying to establish if the distributor has been subjected to any moisture.
A check of the coil would be what I would check first if the spark check indicates a weak ignition. Examine the coil to distributor secondary wire. They were noted for loosening and arcing and burning badly....in some cases if the arcing was occuring at the distributor end, sometimes the plastic connector on the Opti would suffer damage.
Start her up at night and look under the hood while it is running; see if you notice any arcing....especially around the coil and distributor.
The above suggestions are based on owning a 96 Z-28.
Good luck.
Mark
It sounds like your running a little rich or possibly have weak ignition.
You may want to hook up a spark checker and note the condition of the spark. Should be a good strong blue or bluish-white color.
The OptiSpark distributors were subject to water damage....at least that was the case on the LT1 Z-28's. 28K miles sounds like way too soon for failure of the Opti.
Do you drive a lot in rainy conditions? Do you wash down the engine compartment frequently? Have you had a water pump go out and leak coolant on the Opti? Trying to establish if the distributor has been subjected to any moisture.
A check of the coil would be what I would check first if the spark check indicates a weak ignition. Examine the coil to distributor secondary wire. They were noted for loosening and arcing and burning badly....in some cases if the arcing was occuring at the distributor end, sometimes the plastic connector on the Opti would suffer damage.
Start her up at night and look under the hood while it is running; see if you notice any arcing....especially around the coil and distributor.
The above suggestions are based on owning a 96 Z-28.
Good luck.
Mark
Melting Slicks
Joined: Jan 2002
Posts: 2,192
Likes: 0
Re: How to "read" spark plugs? (MDT)
centuryperformance.com/spark.htm :cheers:
most complete site I've seen! :cheers:
[Modified by aces, 11:10 PM 3/24/2002]
most complete site I've seen! :cheers:
[Modified by aces, 11:10 PM 3/24/2002]
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Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: How to "read" spark plugs? (MDT)
I got the car last month, so can't comment on before that but I've not put water on the engine, haven't even had it in rain yet.
I set an appt for Wednesday to drop it off at a dealership service dept. and have it diagnosed. The LT1/LS1/L98 mechanic at this dealer has got a good repr for being sharp and doing good work.
I agree with you that it may be running rich, possibly the O2 sensor(s). Might be why Hypertech Power programmer 3 actually seemed to make it run worse than stock, since Hypertech richens the mixture slightly and if it was already a little rich... :nonod: I've been running it stock ecm programming though, only tried the hypertech for one afternoon and didn't like it, put it back to stock program. Hoping they come back saying it's only the O2's, but either way opti or O2's the ext warranty should cover it :D
I set an appt for Wednesday to drop it off at a dealership service dept. and have it diagnosed. The LT1/LS1/L98 mechanic at this dealer has got a good repr for being sharp and doing good work.
I agree with you that it may be running rich, possibly the O2 sensor(s). Might be why Hypertech Power programmer 3 actually seemed to make it run worse than stock, since Hypertech richens the mixture slightly and if it was already a little rich... :nonod: I've been running it stock ecm programming though, only tried the hypertech for one afternoon and didn't like it, put it back to stock program. Hoping they come back saying it's only the O2's, but either way opti or O2's the ext warranty should cover it :D
