Weird Misfire-- Can't figure it out!

[BooostedAWD]

Hello everybody!

I'm not new to DSMs. Hell, usually, I'm the one with all the answers. This time, I'm stumped and needed to ask for help. I've been searching for a couple days now, and I can't seem to figure out this misfire that developed about 2 months ago. I noticed this problem began when my turbo gaskets blew out and was force to drive with no gaskets for a while due to lack of cash (They did not happen at the same time, so I don't know if they are directly related).

I have a looot of mods.
The most important ones:
Complete 6-bolt in a 2G, (ross pistons, eagle rods w/ a fully built head)
Bullseye 60-1,
Stainless steel charge piping,
Buschur FPR,
Walbro 255,
PTE 880cc injectors,
DSMLink,
NGK Plug wires..

The engine only has 14,000 miles on it. When I built it, I replaced the fuel filter.

On to the problem...
Whether the engine has load or not, when revved to anywhere from 5500 - 6500,
It will start misfiring. It sounds like it's running on 2 cylinders.
If I try to rev again or shift gears, the misfire will still remain. Pretty much like if the intercooler piping popped off, except it goes away.
It takes about 10-20 seconds of throttle usage to work the misfire out of the system.
After it's "worked out," it drives normal again. Pulls pretty hard and drives like it should.

I was reading another post where someone told another user to gap the plugs smaller and see if it makes any kind of difference. I went from .029 on NGK BPR7ES plugs to .025
and it seemed to "push back" the RPMs where it misfired. For example, it was misfiring at 6300 and now it's more like 6800 RPMs.

Things I have tried:
EDIT: -Replaced plugs. (NGK BPR7ES)
-Replaced the CAS from a 1G black-top to a 1G green-top.
-Replaced my coil-pack and wires
-Replaced the power transistor
-Gapping the plugs from .029 to .025
-Boost leak test
-Rewiring my Fuel Pump

Things I think I should try:
-New ECU
-New Front O2 sensor
-New MAF
-Opening up the valve cover to see if any of the rockers popped off

I've taken a couple logs.. and nothing really seems to be out of the ordinary.
My TPS voltage looks good.

Gah, I'm hoping it's not a prelude to something more serious.
I don't know what it is.
Although the Fuel Pump rewire makes perfect sense (or at least to me).
I'm going to rewire it today or tomorrow, whenever I get the chance.

EDIT: It seems to be worse when it's warmed up. When the engine is semi cold, the misfire is more like a stumble and goes away instantly.

Any insight would be awesome.
Thanks so much in advance!


-Josh

 

[turbobird14]

If you have all of that going on mod wise.. i think the rewire would be a good start... especially on a dsm.. have you done a grounding mod or grounding kit yet?

 

[BooostedAWD]

If you have all of that going on mod wise.. i think the rewire would be a good start... especially on a dsm.. have you done a grounding mod or grounding kit yet?

I agree about the rewire kit.. I should have done it when I put the engine in. I'll be doing it when I'm done with my final exams either today or tomorrow.
The battery is relocated to the rear of the car. I have assembled numerous grounds to the battery in the trunk.. And a few more in the engine bay..
It wouldn't hurt to check on those grounds though.

My buddy was thinking it may be power issue also.

What will really tell me if it's the fuel pump or not: I just got new gauges and haven't had the chance to run the wires for my fuel pressure gauge. Along with the rewire kit for the Walbro, it will be installed either today or tomorrow..

Thanks for the reply, BTW.

 

[jcurcillo]

From what you say, you have not replaced the plugs only gapped them. I recommend replacing them. I had a plug with cracked porcelain and it would misfire once the engine warmed up. It would run fine while cold, but once the engine warmed up it would misfire.

 

[BooostedAWD]

From what you say, you have not replaced the plugs only gapped them. I recommend replacing them. I had a plug with cracked porcelain and it would misfire once the engine warmed up. It would run fine while cold, but once the engine warmed up it would misfire.

Sorry, I didn't state it before.. But yes, I have replaced my plugs and the misfire is still there.
It was actually the first thing I thought of.

 

[BooostedAWD]

UPDATE:

I rewired my walbro255 and it still misfires.
I wired in my fuel pressure gauge and the pressure stays constant (no drops in pressure or anything out of the ordinary).

In about a week or so, my friend is going to let me use his Eprom ECU to see if the ECU is the problem..

Any other ideas?

Thank you very much!

 

[Project2G]

I had a similar problem and I found out the ground wire on my MAF was not grounding.

 

[BooostedAWD]

I had a similar problem and I found out the ground wire on my MAF was not grounding.

Thank you very much. I'll check that out!

EDIT: Just curious, Project2G, did it throw a CEL for the MAF?
I have no CELs.

 

[Project2G]

Thank you very much. I'll check that out!

EDIT: Just curious, Project2G, did it throw a CEL for the MAF?
I have no CELs.

Yeah my car would start just I couldn't drive it because it idled like crap and smoked. I checked the CEL and I think the code was P0300 or something around there. I used the voltmeter to determine which wire on the MAF was bad and found out the ground was not grounding.

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[Defiant]

Replace the spark plug wires.

 

[BooostedAWD]

Replace the spark plug wires.

Already did that.. I said that in the first post.
Thanks for the reply though.

 

[Defiant]

Has the miss come on since the current set of wires were installed? Pop the hood in the dark and look for spark leakage.

 

[BooostedAWD]

Has the miss come on since the current set of wires were installed? Pop the hood in the dark and look for spark leakage.

Yes, and already looked for spark leakage.
I've replaced the coil pack and the wires.. And a combination of the old wires, the new coil, and the old coil and the new wires.
I've even included a third coil pack into the equation.. one that I know for a fact works. Same problem.

Same exact problem.. Same exact RPMs. Which is starting to lead me to believe it's not an ignition problem.
On the first post, look and see all of the things I've tried and have not tried. The problem still persists, so that means it didn't work.

The things I think I should try as soon as I can:
-borrow my friend's Eprom ECU
-borrow my friend's MAF
-Check under the valve cover for popped off rocker/broken springs
-New O2 sensor
-While I'm at it, I'm going to check my knock sensor to see if any goo is oozing out.
-Perform another boost leak test and this time, see if I can't check for a broken intake manifold gasket by holding open the TB valve.. all the air is going to leak right out the valves. I'm going to try to spray the intake manifold down with some glass cleaner so when the air rushes out, it will cause it to bubble.

 

[BooostedAWD]

I figured it out..
Ripped off the valve cover and found that
one of the outer valve springs on cylinder #3 had broken right in half!

When the I moved the cam gears with two 17mm wrenches, and the lobe wasn't touching the rocker, I could spin the spring with my finger!

thanks to everybody who replied.
Now, it's time to find a new set of dual springs for cheap.


Thanks again!