BigBadBandit86

For over a year now, I have been trying to figure out what's wrong with my car. It's misfiring and running like death. I've taken it to 3 different mechanics after getting fed up with it myself. None of them can figure it out.

I've replaced the 02 sensors at least 4 or 5x on both sides, plugs, wires, intake gaskets twice, both knock sensors and pig tail, also tried replacing coils 1 at a time. I've deleted the codes and tried everything I know.

If I allow the car to idle long enough or drive it long enough the computer will compensate for the air/fuel loss and it will seemingly run ok (with the check engine light on). Also, the check engine light will flash at me while it's doing this.

But in the time that it's running rough, it acts as if it's misfiring while I accelerate. If I floor it, it clears up. It also runs hot at higher speeds. I've got a new radiator in it and I got got rid of the power steering cooler by replacing it with just a regular radiator hose.

I've wasted so much money throwing parts at it and going to mechanics that can't fix it. I can't afford to do this anymore.

1slowbusa

iTrader: (8)

Is the car stock? If not, what modifications? What are the actual codes you are getting?

2xLS1

iTrader: (25)

You shouldn't have to ask.

1slowbusa

iTrader: (8)

I know but this is a forum to help people and yes I do have to take a deep breath before replying. I does get frustrating. Maybe the forum should modify the way to create a thread with information boxes to fill out and if they don't, it won't post. This would prevent nuisance requests.

They could modify it like the parts classified section, I know certain fields have to be completed before submitting.

just an idea.

BigBadBandit86

I'm sorry to cause any confusion I just assumed and implied that anyone reading would assume it's not stock.

To clarify, there's no internal engine mods done, just bolt on's. I've got NGK plugs/MSD wires, MSI lid (came with the car) STI STB, RAM slave cylinder, LS7 clutch, Pro 5.0 shift kit, 6' shorty shift ****, Pacesetter LTH w/ORY ceramic coated and 3' Borla adjustable exaust(came off an LT1) CB with no CATS. The car was dyno tuned by Steve Williams (Frost) whom I found from this forum.

BigBadBandit86

The codes vary, I can't remember them off the top of my head. But mostly random misfire codes.

2xLS1

iTrader: (25)

If you want help with codes, remember them. If you can't remember them, write them down. There is only one random misfire code. P0300. Did it run ok after Steve tuned it? Have you asked him to look at it?

gofastwclass

iTrader: (2)

It sounds crazy and I've only heard of a few instances but I actually had a bad PCM in my 02 WS6. I had an intermittent terrible idle and was getting an intermittent cylinder 5 misfire code. I tried all the free stuff and as a last shot since I had several PCM's for other projects I threw one in and flashed it with my current tune - problem solved. I put that PCM in a different car and the intermittent problem followed.

Just an idea if you have the ability to try it.

BigBadBandit86

P0300 is one of the code it threw. When I had it dyno tuned by Steve back in 2007 or 8 it ran like a raped ape (pardon my expressions) for years. I did contact him and asked him about possibly losing it's tune. He swears that was impossible.

Old Geezer

iTrader: (3)

"He swears that was impossible."

He's right.

maf_diver

Indeed.

Something simple and free if you haven't done it already, try disconnecting the maf, disconnecting the battery for a while to reset fuel trims, then taking it for a drive (with maf still disconnected). Hopefully at least one of the mechanics you took it to knew his way around a scan tool and checked out the fuel trims, but you never know. The live data are much more useful than the codes. Fuel pressure check would be a good idea too.

Best would be to get someone with HPTuners/EFILive to look at it, there's no replacement for a good data log.

Slowhawk

iTrader: (12)

You just have to bring it to a decent tuner. They should be able to scan/log the car and tell you exactly whats wrong in 10 minutes.Going by a code you get is not the best way to fix it.

2xLS1

iTrader: (25)

This. Plus knowing what other codes it is setting besides P0300.

BigBadBandit86

Currently, the only 3 codes it's throwing is P0134 and P0155 x2

Stormed_Norm

iTrader: (10)

Not sure why it throws codes for o2 sensors, you have changed them. You have fuel, compression and spark. It should run. Unless there's a mechanical issue. As somebody already posted, pull off a valve cover and see if there's a broken rocker, bent pushrod or a spring busted.

BigBadBandit86

The problem with that is, once it's run long enough it seemingly runs fine. Or when I floor it it seems to run fine as well. The check engine light stays on regardless. It's really acting like it's got a bad misfire, but I can't figure out what's causing it. I've changed everything that would cause a misfire.

2xLS1

iTrader: (25)

You have insufficient activity with the drivers side O2 sensor and heater performance problem with the pass side O2 sensor. Without seeing a data log with the O2 wave forms displayed, it is hard to say what the problem is. What O2 sensors are you using? Brand and application? What is the integrity of the headers and y-pipe connections? Any leaks? What gaskets are between the headers and heads. And you still haven't said what the year and car is.

MUSTANGBRKR02

iTrader: (91)

Most times with LT headers and o2's the wires have burned and are shorting over the header due to improper routing or securing.

BigBadBandit86

The car is a 2001, it has Pacesetter LT headers and ORY both ceramic coated. I've got a Borla exhaust system with no cats. I had to get the front 02 extenders and rears deleted with the tune. I have on at least one side, maybe both, replaced the connecters going to the extensions. That was one of the first things I did when replacing the 02 sensors. The sensors are just stock 02 sensors from Advanced or Auto Zone. I believe they were Delphi.

helga203

When it's running bad turn off engine and pull the spark plugs maybe something will show it's ugly face. I had a miss fire code also p0300 and did this and one of the plugs got wet. Keep cleaning it but proiblem kept coming back. I switch the plug with a cylinder that was working and the problem followed. It ended up being a bad spark plug. I hope this might lean you in a different direction. I feel your furstration. Hope this helps.