LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Odd problem, car randomly runs on four cylinders

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Old Feb 28, 2010 | 11:29 PM
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Default Odd problem, car randomly runs on four cylinders

I know how that sounds but thats what happens. I'll be driving along and out of nowhere it just starts running on what I'm guessing is four cylinders. Although I can't be sure but thats what it sounds like. It does not sound anything like a misfire. I have no idea where to begin looking for the issue. Car has 145000 miles on it. New opti, plugs, wires, coil, injectors.
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Old Feb 28, 2010 | 11:40 PM
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Have you checked fuel pressure? A dying fuel pump will act like that.
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Old Mar 1, 2010 | 12:09 AM
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Displacement on Demand?
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Old Mar 1, 2010 | 12:39 AM
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Originally Posted by the_merv
Displacement on Demand?
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Old Mar 1, 2010 | 01:19 AM
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put vtec decals and you'll fly yo!jk but have you diagnosed it might be a bad pcm or the wires didn't click on the opti?
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Old Mar 2, 2010 | 01:01 AM
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Originally Posted by maybl8r09
Have you checked fuel pressure? A dying fuel pump will act like that.
Forgot to say the pump has about 40,000 on it. I'll give it a test and see. Also it goes away if I turn the car off and right back on.
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Old Mar 2, 2010 | 01:02 AM
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Originally Posted by raging fury
put vtec decals and you'll fly yo!jk but have you diagnosed it might be a bad pcm or the wires didn't click on the opti?
Checked all the wires.
How do you check the PCM
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Old Mar 2, 2010 | 10:06 AM
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It runs on 4 cylinders or you just guessing it does
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Old Mar 2, 2010 | 12:18 PM
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Originally Posted by nomoneyz
Forgot to say the pump has about 40,000 on it. I'll give it a test and see. Also it goes away if I turn the car off and right back on.
That's not how you test your fuel pump. You need to get a fuel pressure gauge that you can buy from any parts store, put it on your Schrader valve, take the vacuum line off the fuel pressure regulator, place the gauge to where you can see it while driving and take a trip around the block. Give the throttle a few quick blips and see what the gauge reads. It should read a consistent 43 to 45psi (factory is 43.5). If the pressure goes below these readings then most likely it is going bad.
Does this happen only when you accelerate? Did this start happening after you worked on it? It could also be plug wires. Do you have headers? Check them carefully to see if any of them are burnt or damaged.
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Old Mar 2, 2010 | 12:25 PM
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check your fuses, each bank has a fuse
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Old Mar 2, 2010 | 08:14 PM
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Originally Posted by pillarpod
It runs on 4 cylinders or you just guessing it does
Just guessing it does by the way it sounds. I have had misfires and it sounds nothing like this. When it happens it reminds me of a four cylinder with a loud exhaust.

Originally Posted by SS RRR
That's not how you test your fuel pump. You need to get a fuel pressure gauge that you can buy from any parts store, put it on your Schrader valve, take the vacuum line off the fuel pressure regulator, place the gauge to where you can see it while driving and take a trip around the block. Give the throttle a few quick blips and see what the gauge reads. It should read a consistent 43 to 45psi (factory is 43.5). If the pressure goes below these readings then most likely it is going bad.
Does this happen only when you accelerate? Did this start happening after you worked on it? It could also be plug wires. Do you have headers? Check them carefully to see if any of them are burnt or damaged.
I know thats not how, I was just stating that when I turn the car off and back on it goes away. It happens just whenever. Sometimes when cruising, sometimes when cold, sometimes when hot, it has never happened when I'm gettin on it. I'll go grab a fuel pressure guage and see what happens. This has been going on for a while just starting doing it more often lately. I have LT headers, I'll give the wires another good look. Thanks alot.
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Old Mar 2, 2010 | 09:49 PM
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Any codes? Not all codes will light the SES.

Scan it and take it from there.
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Old Mar 2, 2010 | 10:55 PM
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Originally Posted by Paul Bell
Any codes? Not all codes will light the SES.

Scan it and take it from there.
I'll grab a scanner from work and see if I could do it tomorrow.
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