**UPDATE - Fix the problem! Passenger catalytic converter was plugged. Runs good now! See my last post**

OK, I am trying one more time for some solid advice on what could possibly be wrong with my engine. Here's the history:

1. original engine had an MTI Stealth II cam and Comp Cams 918 springs. Valve spring broke, blew engine.
2. Bought 2004 GTO block, HKE machined block for 3.905" Mahle pistons, 4" SCAT crank, line honed, clearanced for stroker. Bought Comp Cams 224/228, .610/.605 lift, 114LSA. .020 milled LS6 heads, LS6 intake.
3. Assembled and started. Noticed low on power, which progressed into a SES code P0300 (multiple misfire). Thought just the tune was off. G-Force loaded a 383 tune, no change.

So, here I am. The car still has serious misfires, which appear to be isolated to the passenger bank. Passenger bank plugs are showing rich, while driver's bank show normal burn. This is a list of what I've tried:

1. Different plugs and wires. Started on NGK TR55's and new MSD wires. Tried another set of TR55's with the stock wires. Got TR6 plugs, some improvement, but still misfires. Even tried Autolite platinums, but no change.

2. Tried a different passenger side coil pack from a running car. No change.

3. Replaced passenger side O2 sensor. No change.

4. Replaced crank position sensor and had G-Force run a crank relearn. No change.

5. Pulled injectors and fuel rail to see if plugged. Nothing obvious. Might try having the injectors cleaned and balanced at the local NAPA.

6. Pulled intake maifold to inspect rear wires, inspect intake gaskets, etc. re-installed. No change.

7. Did a compression check. Cylinders 2 & 4 - 200 pounds, #6 - 195 pounds, #8 - 185 pounds.

8. Did a leak down test. Cylinder 2 - 17%, 4 & 6 - 15%, 8 - 25%. Now, this was on a cold engine (intake was off at the time).


I'm left with bad computer, bad cam position sensor, or sticking injectors.

What do you think? What else can I test?

 

Cam pos sensor or it's wiring? Got all the ground wires to the block hooked up?

Dumb question, but your tune has the random misfire tables maxed out, right?

 

Ground wires all hooked-up. Double checked when the intake was off. Cam position sensor - wouldn't it throw a code if faulty?

Brian

 

Have you pulled the valve cover?

I just had a misfire issue and turned out to be a broken rocker...

Just a thought man... I hate that you're having so much trouble and I wish you good luck soon...

 

Yes, inspected all the rocker arms and springs. No problems. Springs are new, rockers perfect.

 

This will likely sound wierd... but I had a very similar problem with my 04 gto swap into my jeep. The problem turned out to be a bad altenator. seems that there is a lead wire coming off the altenator that got pinched and grounded out . after we replaced the altenator and fixed the wire.... the damn thing ran great! ....that is until the # 7 rod broke with only 134 original miles anyway, sound like you've checked or replaced everything else!? couldn't hurt?

 

Are you still running cats? If so check backpressure on it.

 

Also check your coolant level... if it's going down then it may be leaking into combustion chamber(s) and causing misfire(s).

 

Did a leak down test. I don't think this is the problem.

 

Still having the problem. Got sidetracked by the hurricane and traveling on business. Here's a quick summary:

2001 Trans Am - 383, LS6 heads, decked .020", LS6 block, decked .008", Comp Cam 224/230 - 610/605 114LSA.

Passenger bank does not want to fire consistently. I can pull the passenger bank injector fuse and the engine idle hardly changes at all. Pull the driver's fuse and the engine dies immediately.

1. Bought a noid light kit. All injectors are receiving an injector pulse.

2. Tested each coil - all cylinders getting spark.

3. Did a compression check - 200, 200, 195, 185 on the passenger bank.

4. Did a leakdown test - nothing bad.

5. Tried shorter pushrods on the passenger bank - no changes.


Could lifters effect the firing on just one bank?

Cam position sensor?

Cam not ground properly?

Any advice is greatly appreciated!!

Brian

 

Does the problem go away and then come back after you've disconnected the battery for a while and then reconnected?


Bird

 

nope - constant problem.

 

Any data logging - fuel trims, spark, etc?

 

No - I don't have any tools for that.

 

Reluctor Wheel?

I hate those "ghost" issues. But a live dataloging software could help isolate this more with data feedback analysis.

Also coolant on O2 connectors can do similar issues (yes it can be as simple as that). Might want to clean that bank's O2 connector.

 

Well, I replaced the O2 on that side, no change. I even tried running it without the O2 hooked-up. No change, either.

What about the reluctor wheel?

 

Bad reluctor wheel could cause similar symptoms that you have.
Did you try cleaning the O2 connector. If it got soaked with coolant and coolant dried in there, it could cause missfires. (I know you changed that O2, but the connection, is it clean)

 

I had the same problem on bank 2 and my car threw that code it was misfiring real bad.It turned out to be a vacume leak.I changed plugs ,wires ,coil packs ,gas filter ,checked fuel pump and brought a new 02 senser and nothing worked.I tighted up all of the bolts on the intake manifold and it was fixed,so check all of your vacume lines and tighten up the intake start in the middle and work your way out.

 

You say you swapped the coil pack and I assume you tried wires also.

You can check for an intake manifold leak by waving an unlit propane torch around the junctions and see if the idle changes.

 

I had already pulled the intake manifold off to inspect the gaskets. Reinstalled with no problem, so I don't think it's the intake manifold leaking vacuum. But I'll certainly give it a try.