need help with high speed miss..
Thread Starter
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
need help with high speed miss..
I'm getting a high speed miss on acceleration 4500-5800+
I had a problem where the engine wouldbreak up after being in stop and go traffic for about 20 min. I replaced the plug wires and the coil wire and still had the problem.. I checked fuel pressure according to the helms manual and all was ok.. I tested the injectors and all read within 1 ohm of each other.. Fuel filter is less than 5k miles old.. I thought it was the opti-crap.. and I took that off and saw the bearing was shot.. so I replaced the opti-spark with a new sealed unit GM part right from the dealer.. I also changed the water pump while i was in there.. went for a ride and it felt great.. then I hit it and it rev'ed up fast but broke up around 5200 rpm in first gear.. i left of the gas it switched to second and I hit it again and around 4200 or so it began to have a slight miss.. the miss stated there all the way up until I got off of it..
I also noticed the rear speaker in the car is making a funny static type sound that is loud and stays consistant volume no matter what the volume of the radio is..although the volume of the song changes,,,
wife is not happy with me.. please help!
I had a problem where the engine wouldbreak up after being in stop and go traffic for about 20 min. I replaced the plug wires and the coil wire and still had the problem.. I checked fuel pressure according to the helms manual and all was ok.. I tested the injectors and all read within 1 ohm of each other.. Fuel filter is less than 5k miles old.. I thought it was the opti-crap.. and I took that off and saw the bearing was shot.. so I replaced the opti-spark with a new sealed unit GM part right from the dealer.. I also changed the water pump while i was in there.. went for a ride and it felt great.. then I hit it and it rev'ed up fast but broke up around 5200 rpm in first gear.. i left of the gas it switched to second and I hit it again and around 4200 or so it began to have a slight miss.. the miss stated there all the way up until I got off of it..
I also noticed the rear speaker in the car is making a funny static type sound that is loud and stays consistant volume no matter what the volume of the radio is..although the volume of the song changes,,,
wife is not happy with me.. please help!
Thread Starter
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
The helms manual test for the coil was pretty simple.. hook up a spark plug tester and see if it lights.. it did.. I understood that to mean the coil is cool.. now how to check the coil driver... I have no idea
8th Gear
Joined: Sep 2004
Posts: 8
Likes: 0
I have the same problem. I've resolved to believing that it is the ecm sitting in the engine compartment about the battery. the miss is directly related to underhood temps and it INDEPENDENT of coolant and oil temp.
another member suggested on the forum that you might test this by using a hairdrier to heat the ecu to make it malfunction.
another member suggested on the forum that you might test this by using a hairdrier to heat the ecu to make it malfunction.
Last edited by carbonLT1; Nov 19, 2004 at 08:55 PM.
Le Mans Master
Joined: Feb 2002
Posts: 5,970
Likes: 20
From: San Marcos Texas
What plug gap are you running? Did you try replacing all the plugs. Could be a bad one, wrong gap, fouled plug(wrong heat range).
Start with a new coil and plugs. The coil could check out OK at idle but could be weak at the higher rpm range. I have seen this before with the coil being strong enough to pass the sparkplug tester but weak enough to have a high speed miss.
Start with a new coil and plugs. The coil could check out OK at idle but could be weak at the higher rpm range. I have seen this before with the coil being strong enough to pass the sparkplug tester but weak enough to have a high speed miss.
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Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Originally Posted by 383_BluByU
plugs look good... is there a test procedure for the coil besides jsut replacing it?? what about for the coil driver?
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Originally Posted by 383_BluByU
The helms manual test for the coil was pretty simple.. hook up a spark plug tester and see if it lights.. it did.. I understood that to mean the coil is cool.. now how to check the coil driver... I have no idea
Thread Starter
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
email sent.. I didnt set the gap on the tester (i didnt even know it had a setting). The plug have less than 5k miles on them.. they are the ac delco platnium plugs as specified for the LT1 (gap and all).
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
To check your coil driver , there is a procedure in book #2 page 6E3-A-75. If you don't have a Helms, I'll send you an IM with my # as there is to much to type. ....if your stillwanting to test the driver.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
It's very possible that the platinum pucks have come off of your AC Delco plugs and you're trying to jump a much bigger gap than you need. IMHO platinum plugs are a complete waste of money. Go spend $11 on a set of Delco R44LTS plugs and you'll be set for another 30k miles.
Race Director
Joined: Aug 2000
Posts: 11,506
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From: Vancouver,Wa.
Originally Posted by bogus
stupid question... fuel filter or pump? The speaker static makes me think the fuel pump could be to blame...
