Thread: 02 GTP w/Misfire, No Boost on Gage and Rocks at Idle

Hi,

I'm new here and have a very clean 02 GTP that I love but can't figure out my misfire. It's been to my buddy's garage who's a Master Tech and he's done everything. Code is P0303 Cylinder 3 misfire. It runs down the highway smoothly but at idle it really rocks at times and doesn't seem to have the gitty up it should. Wires and plugs were changed by the owner. The check engine light wasn't on when I bought it. I also think the boost gage quit working when the check engine light came on. I replaced the coils. It looks like it has a new intake gasket and head gasket. My buddy says that #3 cylinder has 100% leakdown. I'm dying to get this check engine light off and get this thing running like it should. Also, checked the valve springs, they were fine and he soaked the valves w/Seafoam thinking that carbon build up may be possible... still having a problem. I thought 3800's were almost bullet proof. Any ideas? It has 91K miles. Any help or ideas will be appreciated. Thanks.

Mark

Don't recall what brand the plugs are but I'll check that and the gap. What plugs are recommended? Thank you.

Sorry but what is the BBV? I know it's been checked for vac leaks. I'm not sure if the injector pulse width has been checked. I'll ask. Thank you.

Dumb question, but you are running at least 91+ octane in it, right? Must use premium fuel in it.

BBV= Boost Bypass Valve.

On the plugs, see below:

Spark Plugs - Change out those stock spark plugs with new ones to restore any lost power. Brands that most tend to go with are either Copper Core Autolites or NGK Spark Plugs. Get these at your local auto parts store also. They range as follows in order from hottest to coldest plugs...remember...you want the hottest spark possible...so running a super cold plug on a larger pulley to combat knock isn't the best plan...ACD's, AL606's, and AL605's are basically for stock cars or very small bolt ons still running the stock S/C Pulley or modded N/A guys...you want to keep a hot spark. NGKTR55/AL104's for your 3.4" Setup, TR6's are a tad cooler...best used around the 3.25" pulley area, and AL103's...are for the extreme supercharged application...3.0" pulley or lower. Here is a picture to reference the firing order and the correct coil number if yours aren't numbered or you just need a quick reference picture: http://i33.photobucket.com/albums/d6.../plugwires.jpg

Originally Posted by FordMan77

Dumb question, but you are running at least 91+ octane in it, right? Must use premium fuel in it.

BBV= Boost Bypass Valve.

On the plugs, see below:

Spark Plugs - Change out those stock spark plugs with new ones to restore any lost power. Brands that most tend to go with are either Copper Core Autolites or NGK Spark Plugs. Get these at your local auto parts store also. They range as follows in order from hottest to coldest plugs...remember...you want the hottest spark possible...so running a super cold plug on a larger pulley to combat knock isn't the best plan...ACD's, AL606's, and AL605's are basically for stock cars or very small bolt ons still running the stock S/C Pulley or modded N/A guys...you want to keep a hot spark. NGKTR55/AL104's for your 3.4" Setup, TR6's are a tad cooler...best used around the 3.25" pulley area, and AL103's...are for the extreme supercharged application...3.0" pulley or lower. Here is a picture to reference the firing order and the correct coil number if yours aren't numbered or you just need a quick reference picture: http://i33.photobucket.com/albums/d6.../plugwires.jpg

BBV. Thank you. Yes, I run 93 in the car. I'm going to try and check the plugs tonight. Thanks again.

Mark

Originally Posted by BillBoost37

Wires and plugs were changed by the owner.
Aren't you the owner? I see it was the previous owner from other posts. Just goofing around

I also think the boost gage quit working when the check engine light came on.
The gauge and light are not connected. Check that the MAP sensor is connected to both it's plug and vacuum line. It is possible that the misfire/knock is bad enough that the pcm is not allowing boost.

My buddy says that #3 cylinder has 100% leakdown.
Meaning .. it will not hold compression? If so, you have a problem in #3 that might look like the below pics. Might have a chipped piston.
No compression


And.. missing piston

I'll check the vac and connector to the MAP. I have about 70 compression on cylinder 3 and 120 on the other 5 cylinders. 70 is on the line of acceptable. The leakdown on cylinder 3 is 100 meaning that I've got a valve or something that's causing the problem. Could a valve seal or heavy carbon on a valve in cylinder 3 be causing the problem? Next I think is a carbon clean to see if carbon build up is the problem. I just want to eliminate everything possible before removing the head.