Sudden Miss?
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Instructor
Joined: Apr 2003
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Sudden Miss?
My 88 was running very well, then would not start for some reason, I finally got it started (was running great), and I did an inspection under the hood and found a burnt/ cracked plug wire (must have fell off the loom and touched the manifold?). After replacing the plugwires the thing has a pronounced miss under throttle, it starts up OK, but runs a little rough, all the wires are on the corret cylinder and routed correctly and snapped tight. Cap, rotor, ecm, module etc. are all new, I'm thinking these wires may be bad? anyone got a bad set out of the box?
Thanks.
Thanks.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Yes, I've had a set of new cheap plug wires for a chevy Lumina be bad out of the box.
Some people route thier wires parallel to each other to correct problems similar to what your talking about. Make sure you have no wires crossing at a 90 degree angles to each other. If that shows no results --have you changed the coil or plugs? That might also be a good place to start.
Good Luck!
Some people route thier wires parallel to each other to correct problems similar to what your talking about. Make sure you have no wires crossing at a 90 degree angles to each other. If that shows no results --have you changed the coil or plugs? That might also be a good place to start.
Good Luck!
Thread Starter
Instructor
Joined: Apr 2003
Posts: 149
Likes: 0
Yes, I've had a set of new cheap plug wires for a chevy Lumina be bad out of the box.
Some people route thier wires parallel to each other to correct problems similar to what your talking about. Make sure you have no wires crossing at a 90 degree angles to each other. If that shows no results --have you changed the coil or plugs? That might also be a good place to start.
Good Luck!
Some people route thier wires parallel to each other to correct problems similar to what your talking about. Make sure you have no wires crossing at a 90 degree angles to each other. If that shows no results --have you changed the coil or plugs? That might also be a good place to start.
Good Luck!
Thanks for the reply, plugs and coil are new as well, ECM, MAF , relays etc., everything that goes on these I have replaced. frustrating part is the thing ran great until this wire issue. It will start and idle fine, under throttle it misses badly. The new coil and module in the dist. are aftermarket parts, perhaps they're bad as well, who kows? I'll troubleshoot it a little more, if all fails I'll take it to a shop and have the thing gone through.
Thanks.
Thread Starter
Instructor
Joined: Apr 2003
Posts: 149
Likes: 0
Thanks,
I'll verify that again, I don't have any codes, and the diagnostics are working correctly, it starts up fine as well. It almost drives as the exhuast is plugged, but the problem did not exist until I changed the wires.
Thread Starter
Instructor
Joined: Apr 2003
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Any easy way to check exhuast for resrictions? fuel psi is OK, car is idling fine on all 8 cylinders, no codes, no fouled plugs, new set of plug wires, ICM new, cap and rotor new, coil new, timing OK, new fuel filter. Starts right up, idle somewhat ok, it just acts as if it's running on 6 cylinders. Any other easy stuff I might be missing?
Thanks.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Exaust restrictions usually show up once the engine/exaust is up to temp. You can have somebody rev the engine while you hold your hand infront of the exaust....you should get very positve blows with each engine rev.
If you haven't already check your timing. While you have the gun out strap the pick-up to each of the other 7 plug wires to see if you are firing on all eight.
Check to see that the new rotor is seated correctly and the bolts are tight.....maybe put your "old" ICM back in there if you still have it.....make sure you use dielectric grease or vasoline on the connections brfore you connect them.
Re check to ensure you have not mixed up the wires on the cap......check your firing order.
If you haven't already check your timing. While you have the gun out strap the pick-up to each of the other 7 plug wires to see if you are firing on all eight.
Check to see that the new rotor is seated correctly and the bolts are tight.....maybe put your "old" ICM back in there if you still have it.....make sure you use dielectric grease or vasoline on the connections brfore you connect them.
Re check to ensure you have not mixed up the wires on the cap......check your firing order.
Last edited by engle1147; Aug 26, 2008 at 09:01 PM. Reason: added the dielectric grease thing
Thread Starter
Instructor
Joined: Apr 2003
Posts: 149
Likes: 0
Exaust restrictions usually show up once the engine/exaust is up to temp. You can have somebody rev the engine while you hold your hand infront of the exaust....you should get very positve blows with each engine rev.
If you haven't already check your timing. While you have the gun out strap the pick-up to each of the other 7 plug wires to see if you are firing on all eight.
Check to see that the new rotor is seated correctly and the bolts are tight.....maybe put your "old" ICM back in there if you still have it.....make sure you use dielectric grease or vasoline on the connections brfore you connect them.
Re check to ensure you have not mixed up the wires on the cap......check your firing order.
If you haven't already check your timing. While you have the gun out strap the pick-up to each of the other 7 plug wires to see if you are firing on all eight.
Check to see that the new rotor is seated correctly and the bolts are tight.....maybe put your "old" ICM back in there if you still have it.....make sure you use dielectric grease or vasoline on the connections brfore you connect them.
Re check to ensure you have not mixed up the wires on the cap......check your firing order.
Thanks for the tips, I just went out when it was dark and the passenger side pre-cat is cherry red, I'm almost certain it's that cat, that side of the engine bay is also extremely hot compared to the other one. This is one sick sounding puppy right now. It's the original exhuast system with 60K on it. What tipped me off on this is that the car starts right up and idles just a little shakey. I drove the car more this year than I have in the last 5, and I noticed on the last trip the MPG was only getting 16 on the highway, hopefully this is the cure, I was coming to dead ends on the diagnostics. What you mentioned about restrictions showing up when it gets up to temp is also interesting, the car was always more powerfull when it was cold, it's probably been plugged a while.
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Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Sounds like you've may have found your culprit.....weird that it showed up after a plug wire change though. It's always good idea to always change one component at a time to avoid additional problems but that's kinda tough with a distributor assembly. Way to keep at it! After you remove or replace your "bad" cat/cats check to see what "good" exaust flow from the mufflers feels like.
Good Luck!
Good Luck!
Thread Starter
Instructor
Joined: Apr 2003
Posts: 149
Likes: 0
Sounds like you've may have found your culprit.....weird that it showed up after a plug wire change though. It's always good idea to always change one component at a time to avoid additional problems but that's kinda tough with a distributor assembly. Way to keep at it! After you remove or replace your "bad" cat/cats check to see what "good" exaust flow from the mufflers feels like.
Good Luck!
Good Luck!