Lt1 Misfire and running very poorly - Page 2 - Chevy Impala SS Forum
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post #11 of 23 (permalink) Old 08-11-2019, 11:26 AM
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What year is your car? A good scanner may be as easy as a $10 cable and a download for scanning and programming or a $30 cable for scanning and a $300 cable for programming.


-Brian

'95 B4U LT1/T56 in Purple Pearl. 24x 355 with I believe most of the bolt-ons.
'63 C10 LT1/4L60E from B-Body. Rides like a Cadillac thanks to air bags.
'06 GTO LS2/T56 Torrid Red with CAI and Borla Cat-back thanks to the lady who rear ended me.
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post #12 of 23 (permalink) Old 08-11-2019, 01:43 PM Thread Starter
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What year is your car? A good scanner may be as easy as a $10 cable and a download for scanning and programming or a $30 cable for scanning and a $300 cable for programming.


-Brian
Sorry I forgot to mention its a 1994, OBD1. Today the car was mostly running good. CEL did the same thing today as last night, but this time it ran good longer after the light went off.

$300 just for a cable? Seems ridiculous, is it made from gold?
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post #13 of 23 (permalink) Old 08-12-2019, 08:53 AM
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There is a whole section on pcm programming, the sticky should tell you how to check things out for as cheap as possible.
Good Luck.

https://www.impalassforum.com/vBulle...ing-cheap.html


-ALF out...
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post #14 of 23 (permalink) Old 08-12-2019, 09:33 AM
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I've mentioned this before, but the old Snap-On MT2500's can be had for $100-$200 with troubleshooters which walk you through some pretty detailed troubleshooting steps and do much more than just read a code. They even had a graphing one for a while, though those might be just a bit more $$.

https://www.google.com/search?q=Snap...hrome&ie=UTF-8
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post #15 of 23 (permalink) Old 08-13-2019, 05:59 PM
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Never ever you those plugs, Bosch platinum plugs are known for going bad i would definitely say that's your issue and if you want some good advice stay with O.E. parts if you can. I now buy all my o.e. parts from these two websites mostly because their real parts and much cheaper then the dealers and they have Discontinued parts that gm dealers can't order anymore.
check these links out,

https://www.gmpartsprime.com/oem/gm-...odel=&Filter=()

https://www.gmpartsgiant.com/parts-l...9bede51e1649ff

Almost the same price but 6 bucks each. better than the dealer's 11 bucks

Best of luck but get those plugs out regardless.
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post #16 of 23 (permalink) Old 08-13-2019, 11:26 PM
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Had a very similar issue with my 96 although that's OBDII and the scanner showed which cylinder was misfiring. You would notice it once it warmed up. Ended up being one plug wire with the plug heat shield contributing. Even after swapping the one plug wire the misfire would continue with the heat shield on. I replaced the heat shield with spark plug insulation boots (or whatever they are called) and that solved it.

This all occurred after I changed the plugs and wires with AC delco parts... one bad wire/plug shield.

At first I thought it was the ICM since it seemed most noticeable after it warmed up and you were stopped (slight rumble)

Not sure what OBDI supports with respect to misfires but thought I would post my experience for you.
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post #17 of 23 (permalink) Old 08-15-2019, 02:16 PM Thread Starter
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Quote:
Originally Posted by angelo View Post
There is a whole section on pcm programming, the sticky should tell you how to check things out for as cheap as possible.
Good Luck.

https://www.impalassforum.com/vBulle...ing-cheap.html


-ALF out...
This is wonderful! Except in struggling to find the "$4 cable" all the ones I'm seeing are around $100. Probably worth it but I'm shopping around. Still need to read that whole thread too it's quite long but is excellent so far. Thank you!

Quote:
Originally Posted by Fix Until Broke View Post
I've mentioned this before, but the old Snap-On MT2500's can be had for $100-$200 with troubleshooters which walk you through some pretty detailed troubleshooting steps and do much more than just read a code. They even had a graphing one for a while, though those might be just a bit more $$.

https://www.google.com/search?q=Snap...hrome&ie=UTF-8
This sounds like a good option although I'm leaning towards the option Alf pointed to. I will need to learn tuning anyways and that seems like a great option but I like the idea of troubleshooting steps laid out for me too.

Quote:
Originally Posted by Impalapro View Post
Never ever you those plugs, Bosch platinum plugs are known for going bad i would definitely say that's your issue and if you want some good advice stay with O.E. parts if you can. I now buy all my o.e. parts from these two websites mostly because their real parts and much cheaper then the dealers and they have Discontinued parts that gm dealers can't order anymore.
check these links out,

https://www.gmpartsprime.com/oem/gm-...odel=&Filter=()

https://www.gmpartsgiant.com/parts-l...9bede51e1649ff

Almost the same price but 6 bucks each. better than the dealer's 11 bucks

Best of luck but get those plugs out regardless.
Wouldn't this affect the engine at all temps if it were the plugs? Also it seems to be a multicylinder misfire on the driver side bank, based on my test I did with disconnecting the plug wires. Hard to believe 4 plugs would go bad at once. Also been running then for about 500 miles with no issues previously. I haven't had the issue in the past two days I've driven it. Today I've been driving around quite a bit without a misfire so far.

Quote:
Originally Posted by vegas_ss View Post
Had a very similar issue with my 96 although that's OBDII and the scanner showed which cylinder was misfiring. You would notice it once it warmed up. Ended up being one plug wire with the plug heat shield contributing. Even after swapping the one plug wire the misfire would continue with the heat shield on. I replaced the heat shield with spark plug insulation boots (or whatever they are called) and that solved it.

This all occurred after I changed the plugs and wires with AC delco parts... one bad wire/plug shield.

At first I thought it was the ICM since it seemed most noticeable after it warmed up and you were stopped (slight rumble)

Not sure what OBDI supports with respect to misfires but thought I would post my experience for you.
I did the ICM mod a while ago to pull it away from the head so I dont think it's my ICM either. So far it's been running well for the past few days without any misfires.

I think it was residual oil from my air filter at this point. Why it only effected the driver side bank is beyond me though.

Thank you everyone for a your input and help! I will report back if the misfires start up again but so far it's been running well the past few times I've driven it.
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post #18 of 23 (permalink) Old 08-29-2019, 03:09 PM Thread Starter
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Just wanted to follow up and let everyone know that a few hundred miles later the car is still fine. So apparently too much air filter oil seems to be able to cause misfires isolated to one bank, strange but that's what the data says.

My other thought, and justification to be conservative with air filter oil is that excess oil can get into the opti from the vacuum line on the intake. For this reason i am going to add a separate filter for the opti and plug the hole in the intake. Still wired to cause a miss on just one back but I guess its possible?

Anyways this is my experience so far
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post #19 of 23 (permalink) Old 08-29-2019, 07:16 PM
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Glad to help. It's always good when it is something simple.
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post #20 of 23 (permalink) Old 08-30-2019, 10:49 AM
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If using oiled filter and you clean & re-oil it...let it sit for a day so the fluid absorbs into the filter AND oil it VERY sparingly. To much oil and it gets sucked onto MAF wires causing all kinds of drivability issues

Have had K&N filters for decades on a few cars, including the SS, without issue.

With that said cleaning MAF, carefully, for maintenance regardless of what filter is used is SOP.

\'96 BBB 383/T-56
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