Searched, Need Help P0301

**Smokeybrnout** · 09-08-2008, 10:11 PM

I've been working on this problem for 3 months, so here's the list. Any help or recommendations are appreciated.

P0301, barely noticeble miss at idle (sounds a little like a bass hit). Throws the code about every 500 miles. The problem first surfaced in June on the Power Tour, had just finished gears, transmission, clutch, and master cylinder.

Replaced plugs/Wires (taylor spiro pros and NGK TR6. Switched from Granatelli and TR5); new MAP Sensor, Pulled intake, cleaned injectors (ultra sonic cleaning and flow benched). New fuel filter, pump has 15Kmiles, fuel pressure shows 60 PSI idle to Redline. Cleaned MAF (it is less than a year old), new O2 sensors (NTK). Switched back to a rubber tranny mount (noticeable improvement in MPG, by the way, I was getting KR in 5th and 6th). Compression test revealed a low pressure of 169 and high pressure of 175. The car runs rich (11.5:1 on the dyno). Leaned it out a bit with tuner. Better MPG, but no significant change. No sign of a vacumn leak.

My next theory is that because the car runs so rich I have carbon build up in the chamber/valve/piston head. Any thoughts? Is there an effective way to clean without pulling the heads?

I have ruled out mechanical issues due to no issues showing on the compression test; I assume that a bent pushrod or broken valve spring (I lift and shift at 5800) would effect that test?

Thanks in advance for your assistance.

**JoshieDoom** · 09-09-2008, 02:31 AM

I believe thats a cylinder 1 misfire. Check the coil? Spark plug gap on that plug?

**0rion** · 09-09-2008, 03:38 PM

if you suspect carbon build up you could try to seafoam it and see if that helped. It's cheap. Like JD said, it's cylinder 1 that's giving you the problem so just go over everything with a fine tooth comb. Try swapping the coil with another cylinder and see if the code follows it and things like that until you nail it down.

**blue02Z** · 09-09-2008, 03:56 PM

boom Orion hit it! if the code follows the cylinder you swapped the coil with its the coil. if not, could be the plug, wire, fuel injector... your wire prolly fell off, happened on my brothers 02 but on #7 cylinder

**Sarge** · 09-09-2008, 04:00 PM

Originally Posted by Smokeybrnout

I've been working on this problem for 3 months, so here's the list. Any help or recommendations are appreciated.

P0301, barely noticeble miss at idle (sounds a little like a bass hit). Throws the code about every 500 miles. The problem first surfaced in June on the Power Tour, had just finished gears, transmission, clutch, and master cylinder.

Replaced plugs/Wires (taylor spiro pros and NGK TR6. Switched from Granatelli and TR5); new MAP Sensor, Pulled intake, cleaned injectors (ultra sonic cleaning and flow benched). New fuel filter, pump has 15Kmiles, fuel pressure shows 60 PSI idle to Redline. Cleaned MAF (it is less than a year old), new O2 sensors (NTK). Switched back to a rubber tranny mount (noticeable improvement in MPG, by the way, I was getting KR in 5th and 6th). Compression test revealed a low pressure of 169 and high pressure of 175. The car runs rich (11.5:1 on the dyno). Leaned it out a bit with tuner. Better MPG, but no significant change. No sign of a vacumn leak.

My next theory is that because the car runs so rich I have carbon build up in the chamber/valve/piston head. Any thoughts? Is there an effective way to clean without pulling the heads?

I have ruled out mechanical issues due to no issues showing on the compression test; I assume that a bent pushrod or broken valve spring (I lift and shift at 5800) would effect that test?

Thanks in advance for your assistance.

Couple of questions before I say anything....
What compression ratio are you running? What brand of gas/octane do you usually get? Stock ECM? Any fuel or oil additives utilized? What do you have your plugs gapped at? Do you have an smaller "performance" underdrive pulley by any chance?

**Smokeybrnout** · 09-09-2008, 09:30 PM

Originally Posted by Sarge

Couple of questions before I say anything....
What compression ratio are you running? What brand of gas/octane do you usually get? Stock ECM? Any fuel or oil additives utilized? What do you have your plugs gapped at? Do you have an smaller "performance" underdrive pulley by any chance?

Stock compression (9.5 :1 ?) , engine has roughly 70K. I use Sunoco 94 Octane, if not available, Amaco 93. ECM is stock, with a Davinci Tuner with their standard program, however, I pulled 10% on fuel. No additives. I have moved plugs and wires from cylinder to cylinder, the code doesn't follow. Plugs are TR6's at .055. No underdrive pulleys. Stock long block, just LT headers, catback, free mods, etc.

I checked the coil pack with a test plug and saw nothing to indicate an issue, just a consistent spark. Is there another method? I will try swapping it with #3. The injectors flowed within 1% of each other before and after cleaning, plugs/wires did not effect it. PLugs all look the same after 600 miles, too.

Thanks for everyones input, I will try the Seafoam (snake oil?) and swapping coils around. After 3 months of this, I will try some VooDoo dancing as well.

Oddly, the highest pressure on the compression test was cyl 1 (175 PSI).

**JoshieDoom** · 09-09-2008, 10:07 PM

Seafoam definately isnt snake oil. I would leave the switched coilpack on the car for a while and see if it does move. IF it stays with number 1 then you most likely have a mechanical issue.

**0rion** · 09-10-2008, 02:56 AM

it sounds like you've covered most of your bases really. Swap that coil pack and see if it follows but I'm betting it stays put. Check the harness' going to the coil pack and injector for cylinder 1. It's a matter of narrowing it down. If you're getting consistent spark and fuel then it almost certainly has to be mechanical. I would think a pushrod or valvespring issue should've shown up on your compression test but stranger things have happened.
Is there anyone up there local that can log the car with autotap or something similar to that?

**Smokeybrnout** · 09-10-2008, 07:42 AM

Is there anyone up there local that can log the car with autotap or something similar to that?[/QUOTE]

Thanks for the feedback. No one here locally that I am aware of; there doesn't seem to be a lot of LS1 guys in this area. A lot of SRT4's and Mustangs. Anyone know of a tuner in NW Ohio?

Thanks, I will update this thread as I progress for anyone else having similar issues.

**Smokeybrnout** · 09-10-2008, 09:11 PM

I tried the sea foam treatment today, and switch the #1 coil pack with #3. Misfire is still there on #1. My next action will be to pop the valve covers and look for a bent pushrod or broken valve spring. Still open to suggestions. Thanks again for everyone's help. I am considering using this damn thing for a boat anchor and buying a horse.