Ws6 Randomly Misfires

[JeepJake]

Hey guys, I have been watching my sisters Trans Am WS6 while she is away for school. She told me that it had a few random issues and asked me if I could take a look at them while she was gone. I've been driving it around for a little while and I've noticed that when it warms up and is sitting still, it will have what feels like an inconstant misfire. I also noticed that when I turn on the A/C that the problem gets worse and it misfires more consistently. When cruising, I don't really notice the problem unless I have to accelerate significantly. (it will hesitate and studder before it takes off). I took it into the local autoparts store to get the codes read and the only two things that came up were a bad EGR valve and some kind of EVAP leak (maybe just a bad gas cap?). I hooked the car up to my fuel pressure gauge and it read a consistent 60lbs.

Any help or opinions would be appreciated! I consider myself a decent mechanic but I'm used to working on Jeeps, not sports cars.

Thanks,
Jake

[98TransAmWs-6]

Hey guys, I have been watching my sisters Trans Am WS6 while she is away for school. She told me that it had a few random issues and asked me if I could take a look at them while she was gone. I've been driving it around for a little while and I've noticed that when it warms up and is sitting still, it will have what feels like an inconstant misfire. I also noticed that when I turn on the A/C that the problem gets worse and it misfires more consistently. When cruising, I don't really notice the problem unless I have to accelerate significantly. (it will hesitate and studder before it takes off). I took it into the local autoparts store to get the codes read and the only two things that came up were a bad EGR valve and some kind of EVAP leak (maybe just a bad gas cap?). I hooked the car up to my fuel pressure gauge and it read a consistent 60lbs.

Any help or opinions would be appreciated! I consider myself a decent mechanic but I'm used to working on Jeeps, not sports cars.

Thanks,
Jake

Well if there is an evap leak it is most likely the evap solenoid tube or canister. The tube is attched to the driver's side of the intake and the other end is attached to the canister. Check the tube out to make sure it isn't damaged and the same with the canister. I would run the car at night with the hood up for the random misfires, to see if it is arcing or spark jumping at all.

[JeepJake]

Well if there is an evap leak it is most likely the evap solenoid tube or canister. The tube is attched to the driver's side of the intake and the other end is attached to the canister. Check the tube out to make sure it isn't damaged and the same with the canister. I would run the car at night with the hood up for the random misfires, to see if it is arcing or spark jumping at all.

I forgot to mention, we did run the car with the hood up at night and didnt see anything arcing. Also, we checked for leaks in the lines and couldnt find anything. Maybe I'll try again tonight.

[98TransAmWs-6]

Well if there is an evap leak it is most likely the evap solenoid tube or canister. The tube is attched to the driver's side of the intake and the other end is attached to the canister. Check the tube out to make sure it isn't damaged and the same with the canister. I would run the car at night with the hood up for the random misfires, to see if it is arcing or spark jumping at all.

I forgot to mention, we did run the car with the hood up at night and didnt see anything arcing. Also, we checked for leaks in the lines and couldnt find anything. Maybe I'll try again tonight.

Do you remember what codes came up? Does the car have any valve cover breathers? Leaks in the evap can be darn near impossible to see unless they are really large.

[SMWS6TA]

Good call on the evap tubing and gas cap.

I had same code pop up and I replaced the cap and it is gone. Car is 14 yrs old that rubber o ring on the cap will go bad. I got mine for $13 at Advance. Tried to find a locking cap and couldn't find anything that would fit.


Codes -
You can disconnect the battery for 25-30 mins to clear all codes out. Reconnect and take it for a drive. If code pops up, get the code read and post here. It will let us know what is going on.


Other items that could cause misfires:

Do you have a K&N air filter? If so when's the last time the MAF was cleaned? Parts stores sell the cleaner for about $6-7.
If it's been a while or never go ahead and clean the MAF, just be careful to not touch the wire, break it and you are looking for a new MAF ($$$$$$)


How long has the misfire been going on? Did it start after a fill up? Bad gas can cause misfires too. I use HEET for these issues.


Condition of plugs and wires? Even if you can't see spark arcing you could still have bad plugs and wires.


How old are they?

[98TransAmWs-6]

Also another thing that can cause a misfire, I know it's weird but th pcv hose in the back of the intake. I would check if it is broken. Clogged injectors can cause misfires also.

An easier way that doesn't take that much time is pulling out the pcm and battery fuses for 5 minutes.

[JeepJake]

Thanks for the replies guys. Like i said, this isnt my car so im not 100% sure but i did ask about the plugs and wires and from what i understand, the plugs and wires are fairly new. I will disconnect the battery and see if the codes pop back up and get them read again.

This problem has been going on since before i got it and ive been through almost 3 tanks of fuel now. So i dont think its bad gas but i will probably clean the MAF sensor and injectors and see how everything goes from there.

Once i get the codes read i will post them up here.

[cpop98ws6]

Seeing that you had an EGR code I would look into that. If you EGR valve is bad that can very well cause a random misfire. If there is carbon build up under the EGR valve it will cause a vaccum leak.

[az gt eater]

Another thing to try, is disconnect and reconnect the coil pack wire harness. I had the same problem, and this fixed it for me. And, it threw codes, that is how I knew to look.

[SMWS6TA]

You should hear 2 clicks for the coil pack and one for the plugs......or was that vice verse?

[pajeff02]

^^ You are correct.

[az gt eater]

You should hear 2 clicks for the coil pack and one for the plugs......or was that vice verse?

No,I meant the wiring harness that clips into the coil packs. They have the safety lock out thing on them.

[SMWS6TA]

This has had me thinking about all day... Make sure they put the plugs wires to the right pkug, hell they could have half ass it and not connect all the harness. I'd look at everything just to make sure.

[pajeff02]

Other considerations: Is it setting off the SES? If so, get the codes read and post them, please. Plugs could simply be worn out and in need of replacement. Could have a cracked plug. Headers? If so equipped a plug wire (or wires) could be cooked. You can check for arcing by opening the hood at night and looking things over with the engine running.

[98TransAmWs-6]

Any updates?

[JeepJake]

Sorry guys, ive been busy the last few days. I have been taking all of your comments into consideration and im going to be working on it this week. I will let you all know how it goes.

[20ws6speed01]

Start with that EGR code..A bad EGR will let in too much exhaust gas back in the intake so what happens is there is no air in the cylinders to properly fire the cylinder causing a Misfire...

[JeepJake]

Ok guys I finally had time to start working on the car again today. I cleaned the MAF sensor and there didnt seem to be any difference. I disconnected it with the car running to see if anything happened and it just idled down a little bit. It didnt seem like it was causing the misfire so I plugged it back in. I went to get the codes read again and this is what came up:

EGR valve
P1404 EGR stuck open (appeared twice)
P0405 EGR circuit sensor low
P0404 Exhaust Gas Recirculation Circuit Range/Performance

MAF
P0103 Mass Air Flow (MAF) Circuit High Input
P0102 Mass Air Flow (MAF) Circuit Low Input

I think that the MAF codes came up just because i unplugged the sensor and plugged it back in while the car was running. To me it seems that it is misfiring bc the EGR is stuck open thus letting too much exhaust gas back into the cylinders during idle and causing the miss. The EVAP code that showed up lastime I had the codes read wasnt there anymore. Im guessing the computer saves the codes and never clears them itself??

Let me know what you guys think.

Here are some articles i found on the codes:
Pontiac Grand Am: DTC code P1404 - Car Forums - Edmunds
P0405 Exhaust Gas Recirculation Sensor A Circuit Low
P0404 Exhaust Gas Recirculation Circuit Range/Performance - DTC Code
OBD-II Trouble Code: P0102 Mass Air Flow (MAF) Circuit Low Input
OBD-II Trouble Code: P0103 Mass Air Flow (MAF) Circuit High Input

[pajeff02]

Sounds like the EGR is leaking. I agree that unplugging the MAF is probably what threw those codes.

[20ws6speed01]

I would replace the EGR valve...Don't think too much into it ..u could make a big deal out of nothing