I didn't think that had any impact, though?
P0303
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
Likes: 0
From: Palmdale California
P0303
Ok, so I had a P0420 and a faulty Oil Pressure sender. I took it to a local mechanic I know, he replaced my 02 sensor and Oil Pressure sender. He also told me that I had a bad exhaust leak and needed to take it to a muffler shop to re-do the welds. Once I took the car home it was fine, but within an hour or so I noticed the car started to hesitate at around 60-70 MPH, I was concerned.
I figured it might have been due to my exhaust leak and my CEL popped back on generating the P0420 again. Re-enforcing my initial thoughts. It was later so I waited for another day to take it to the muffler shop. The next day my CEL began to flash, I had my code reader so I plugged it in and it had P0303 then P0420. I took it to a muffler shop and they welded the exhaust leaks and gave the exhaust a good look through and it was good.
Unfortunately the car still hesitates, no CEL, yet...I was wondering if perhaps the misfire/hesitation can be from the intake manifold not being re-installed correctly. Please help!
I figured it might have been due to my exhaust leak and my CEL popped back on generating the P0420 again. Re-enforcing my initial thoughts. It was later so I waited for another day to take it to the muffler shop. The next day my CEL began to flash, I had my code reader so I plugged it in and it had P0303 then P0420. I took it to a muffler shop and they welded the exhaust leaks and gave the exhaust a good look through and it was good.
Unfortunately the car still hesitates, no CEL, yet...I was wondering if perhaps the misfire/hesitation can be from the intake manifold not being re-installed correctly. Please help!
Tech Contributor
Joined: Jan 2007
Posts: 19,245
Likes: 1,092
From: Dyer, IN
Ok, so I had a P0420 and a faulty Oil Pressure sender. I took it to a local mechanic I know, he replaced my 02 sensor and Oil Pressure sender. He also told me that I had a bad exhaust leak and needed to take it to a muffler shop to re-do the welds. Once I took the car home it was fine, but within an hour or so I noticed the car started to hesitate at around 60-70 MPH, I was concerned.
I figured it might have been due to my exhaust leak and my CEL popped back on generating the P0420 again. Re-enforcing my initial thoughts. It was later so I waited for another day to take it to the muffler shop. The next day my CEL began to flash, I had my code reader so I plugged it in and it had P0303 then P0420. I took it to a muffler shop and they welded the exhaust leaks and gave the exhaust a good look through and it was good.
Unfortunately the car still hesitates, no CEL, yet...I was wondering if perhaps the misfire/hesitation can be from the intake manifold not being re-installed correctly. Please help!
I figured it might have been due to my exhaust leak and my CEL popped back on generating the P0420 again. Re-enforcing my initial thoughts. It was later so I waited for another day to take it to the muffler shop. The next day my CEL began to flash, I had my code reader so I plugged it in and it had P0303 then P0420. I took it to a muffler shop and they welded the exhaust leaks and gave the exhaust a good look through and it was good.
Unfortunately the car still hesitates, no CEL, yet...I was wondering if perhaps the misfire/hesitation can be from the intake manifold not being re-installed correctly. Please help!
Melting Slicks
Joined: Feb 2007
Posts: 3,266
Likes: 8
From: Indian Rocks Beach FL
St. Jude Donor '08-'09-'10
If the AC and heat worked before the intake was removed there is an excellent chance the vacuum hose at the back of the intake is off.
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
Likes: 0
From: Palmdale California
Well I took it down to A&A Corvette and they changed my cats out, but found my drive shaft was done for, so they fixxed that. changed my spark plugs and checked my wires and the car was fine, so when I took it to get smogged today the guy was warming my car up and about 2min in it started misfiring now it's shooting out the P0300 code I'm so frustrated it was fine at Andy's and now it's acting up again! The guy said that it looked like the intake had not been removed at all when he did the oil pressure switch that sits behind the intake.
Last edited by Fujikura; Apr 17, 2010 at 12:32 PM.
Tech Contributor
Joined: Jan 2007
Posts: 19,245
Likes: 1,092
From: Dyer, IN
Well I took it down to A&A Corvette and they changed my cats out, but found my drive shaft was done for, so they fixxed that. changed my spark plugs and checked my wires and the car was fine, so when I took it to get smogged today the guy was warming my car up and about 2min in it started misfiring now it's shooting out the P0300 code I'm so frustrated it was fine at
Who is "the guy"? How would one determine if the intake had been removed or not? The sign of a good mechanic, is to leave no signs that the car has ever been apart......yet all repairs are done.
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
Likes: 0
From: Palmdale California
I forget the tech's name at A&A Corvette and he said the spark plugs all looked ok, but a little white. Not sure what he meant, but he checked the connectors, then tested the car and it was fine but acted up again when I was about 1/2 way home. Has new plugs now.
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Tech Contributor
Joined: Jan 2007
Posts: 19,245
Likes: 1,092
From: Dyer, IN
Yeah that sucks, as luck would have it, the car was on it's best behavior while at the shop... I guess you'll have to take it back to Andy, if you don't intend on doing anything yourself.
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
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From: Palmdale California
I was thinking of replacing the coil packs and wires myself that seems, easy just remove some bolts and wires, etc..? right?? Would uprading to MSD's help? Also would I need to replace those wires? (not sure what they're called) Also the injectors could be a cause, should I put injector cleaners in or replace/upgrade them as well?? When it comes to vacuum leaks I'm a bit at a loss for that...
Tech Contributor
Joined: Jan 2007
Posts: 19,245
Likes: 1,092
From: Dyer, IN
I was thinking of replacing the coil packs and wires myself that seems, easy just remove some bolts and wires, etc..? right?? Would uprading to MSD's help? Also would I need to replace those wires? (not sure what they're called) Also the injectors could be a cause, should I put injector cleaners in or replace/upgrade them as well?? When it comes to vacuum leaks I'm a bit at a loss for that...
Factory parts are all you need where wires and coils are concerned....no need for MSD's. Injector is a possibility, or associated wiring.
12495519 – GMPP red spark plug wire set
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
Likes: 0
From: Palmdale California
I have gotten a flashing CEL before, not lately. P0303 isn't on now, it was when I gothome, but I reset it and the p0300 is now I havent driven it, really all day, been a bit slumped
Tech Contributor
Joined: Jan 2007
Posts: 19,245
Likes: 1,092
From: Dyer, IN
1) Swap the #3 plug wire with another cylinder, and see if the code changes. Personally, I'd just change out the wires, since you did the plugs.....that's just me.
2) If the above does not yield any result, you can swap the #3 injector to a different position (provided you are confident the wiring is all good).
3) If neither of the above yield any result, you can swap coil packs with another cylinder.
Thread Starter
Intermediate
Joined: May 2005
Posts: 43
Likes: 0
From: Palmdale California
It looks like I have a bad intake manifold, trying to find one now, my code reader read a
P0303, but the actual code was a P0300, cylinder misfires in 3,5, and 7 the manifold is not sealing correctly due to a crack...
P0303, but the actual code was a P0300, cylinder misfires in 3,5, and 7 the manifold is not sealing correctly due to a crack...
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
P0300 is the only misfire code that will ever display in the DIC. It is a catch-all code for any/all misfires detected, all that is needed for OBDII purposes.
The last digit (P0303) further identifies the specific cylinder that's misfiring, but that can only be read with external scan tools.
The last digit (P0303) further identifies the specific cylinder that's misfiring, but that can only be read with external scan tools.
