misfire on cylinder 5/7
09-24-2006, 01:55 PM
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misfire on cylinder 5/7 Thurs night about a mile from my house, I noticed a change of pitch in my exhaust and the car started to feel a bit sluggish. Friday morning, I am leaving for work and the car has no power whatsoever - when pressing the gas pedal it takes a second for it to start moving. It does this the way to work and the way home. (only work 5 mi away).
Saturday, I hook up HPTuners and run a misfire count on all 8 cylinders. When the car is at idle, it showed nothing, but it was clearly not running on all 8 cylinders. When I would rev it up to about 1.5k, the counts on cylinders 5 and 7 would climb like crazy - both at the same time.
This morning I replaced the spark plugs to both cylinders and 'checked' the plug wires (disconnecting from the plug and watching for an arc) Both were recieving spark fine so I hooked everything up but it makes no difference.
Anything else I could check or any ideas on what else it could be?
Saturday, I hook up HPTuners and run a misfire count on all 8 cylinders. When the car is at idle, it showed nothing, but it was clearly not running on all 8 cylinders. When I would rev it up to about 1.5k, the counts on cylinders 5 and 7 would climb like crazy - both at the same time.
This morning I replaced the spark plugs to both cylinders and 'checked' the plug wires (disconnecting from the plug and watching for an arc) Both were recieving spark fine so I hooked everything up but it makes no difference.
Anything else I could check or any ideas on what else it could be?
10-02-2006, 12:35 AM
#4
well now that uve checked one of the 3 dependants....check your fuel and your air going into those cylinders....i know you can do it with efi live...blur i believe hptuners has both a edit and scan suite that on the scan mode can run a missfire count....ive never used it but i have heard of other people getting the same info....hpedit however cant do that
01-03-2008, 12:37 AM
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I wanted to revive this thread from the dead and find out if any of you out there have any updated suggestions.
I know its been over a year. In that time, I ended up paying off the car so its been sitting in my garage as a project. I had been checking things from time to time. since then I had done the following:
1. replaced plugs
2. replaced wires
3. swapped coil packs from working cylinders (problem never moved)
4. perfomed compression check (150psi on 5 and 145 on 7)
5. Took it to an aquaintance's newly aquired shop for eval as a trade of services (my networking ability for his mechanics). Let me say this was an lube/oil place he had invested in and planned on turning it into a performance shop. I lost faith quickly in these guys as they would call to tell me i just needed a tune up and new coil packs (even though i had already done that). I had my car towed home when the shop owner left town for a few weeks and had some concerns with it staying there. When i went to make arrangements the mechanic said he stopped looking when he found a yellow residue in the oil fill cap attributing the problems to a blown head gasket or something wrong with the block.
6. tore down drivers side to replace head gasket. I followed the guide on ls1howto.com and reused the original bolts. after reassembling the car, it feels it runs just the same. I am unable to connect to the PCM to rescan the trouble codes for some reason (probably laptop related).
7. thinking that the head could be warped (since I had regular overheating problems during the summer). I went ahead and am picking up a pair of PRC stg2.5 5.3L heads from a member here. I will be installing these along with another set of stock gaskets and head studs.
I have been in high hopes until my stepdad made the comment about how it would suck to spend all this money and not have it correct the issue.
My question to all of you is this:
Is there anything i overlooked while trying to track down the source?
is there anything in particular I should look for while replacing the heads?
BTW - the car has between 80k-90k miles on it.
I know its been over a year. In that time, I ended up paying off the car so its been sitting in my garage as a project. I had been checking things from time to time. since then I had done the following:
1. replaced plugs
2. replaced wires
3. swapped coil packs from working cylinders (problem never moved)
4. perfomed compression check (150psi on 5 and 145 on 7)
5. Took it to an aquaintance's newly aquired shop for eval as a trade of services (my networking ability for his mechanics). Let me say this was an lube/oil place he had invested in and planned on turning it into a performance shop. I lost faith quickly in these guys as they would call to tell me i just needed a tune up and new coil packs (even though i had already done that). I had my car towed home when the shop owner left town for a few weeks and had some concerns with it staying there. When i went to make arrangements the mechanic said he stopped looking when he found a yellow residue in the oil fill cap attributing the problems to a blown head gasket or something wrong with the block.
6. tore down drivers side to replace head gasket. I followed the guide on ls1howto.com and reused the original bolts. after reassembling the car, it feels it runs just the same. I am unable to connect to the PCM to rescan the trouble codes for some reason (probably laptop related).
7. thinking that the head could be warped (since I had regular overheating problems during the summer). I went ahead and am picking up a pair of PRC stg2.5 5.3L heads from a member here. I will be installing these along with another set of stock gaskets and head studs.
I have been in high hopes until my stepdad made the comment about how it would suck to spend all this money and not have it correct the issue.
My question to all of you is this:
Is there anything i overlooked while trying to track down the source?
is there anything in particular I should look for while replacing the heads?
BTW - the car has between 80k-90k miles on it.
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01-04-2008, 01:34 AM
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making sure they are all within a cetain amount I think its like 8% or 10% but if your at 145 and 150 on 5 and 7 and 190 everywhere else then something messed up
01-04-2008, 11:20 PM
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i know on lt1's which have about a half a point higher compression usually see ratings over 180 psi so i would certainly check into that and you stating you have had over heating issues in the past certainly raises some eyebrows as to what is wrong
01-04-2008, 11:23 PM
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Thurs night about a mile from my house, I noticed a change of pitch in my exhaust and the car started to feel a bit sluggish. Friday morning, I am leaving for work and the car has no power whatsoever - when pressing the gas pedal it takes a second for it to start moving. It does this the way to work and the way home. (only work 5 mi away).
Saturday, I hook up HPTuners and run a misfire count on all 8 cylinders. When the car is at idle, it showed nothing, but it was clearly not running on all 8 cylinders. When I would rev it up to about 1.5k, the counts on cylinders 5 and 7 would climb like crazy - both at the same time.
This morning I replaced the spark plugs to both cylinders and 'checked' the plug wires (disconnecting from the plug and watching for an arc) Both were recieving spark fine so I hooked everything up but it makes no difference.
Anything else I could check or any ideas on what else it could be?
Saturday, I hook up HPTuners and run a misfire count on all 8 cylinders. When the car is at idle, it showed nothing, but it was clearly not running on all 8 cylinders. When I would rev it up to about 1.5k, the counts on cylinders 5 and 7 would climb like crazy - both at the same time.
This morning I replaced the spark plugs to both cylinders and 'checked' the plug wires (disconnecting from the plug and watching for an arc) Both were recieving spark fine so I hooked everything up but it makes no difference.
Anything else I could check or any ideas on what else it could be?
try compression test
01-05-2008, 01:56 PM
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Have you swapped injectors to see if perhaps the injectors are failing on 5 and 7?
BTW - I know most people dislike linking articles, but sometimes bench mechanic 101 can save you a ton a $ - so here ya' go. This saved a couple of my Mustang buddies lots of $ by narrowing their misfire before trying everything off the shelf and then some.
http://www.aa1car.com/library/misfire.htm
Good luck. Single and adjacent misfires are a bitch!
But, I agree with your stepdad on this one.
BTW - I know most people dislike linking articles, but sometimes bench mechanic 101 can save you a ton a $ - so here ya' go. This saved a couple of my Mustang buddies lots of $ by narrowing their misfire before trying everything off the shelf and then some.
http://www.aa1car.com/library/misfire.htm
Good luck. Single and adjacent misfires are a bitch!
But, I agree with your stepdad on this one. 