98 Cobra: Random Misfire code. Any suggestions?
09-13-2009, 08:23 PM
#1
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Join Date: Dec 2007
Location: Coral Springs, Florida ~ 33076
Posts: 608
98 Cobra: Random Misfire code. Any suggestions?
It's been a few weeks of pain, to say the least.
I FINALLY thought the car was ready to strap down for a tune, only to have the fan die on the way to the dyno. Long story short, the car overheated and I ended up at the doctor's office with second degree burns on my right arm.
It's amazing what pressurized coolant and a radiator cap that blows off in your hand will do for your day. :shrug:
Anyway, I got the car back and straightened out again (thanks to Jake and the crew at Power by the Hour in Delray Beach,Fl, as well as Nitrostang Racing in Margate) for helping me diagnose and repair this evil machine.
Seriously, it tried to kill me this time. :lol:
Now, the car seems to be running a little rough at idle and when we scanned it, it's showing a random misfire code, as well as a rear 02 sensor error.
The rear 02 sensors are turned off in the tune, so I'm not sure if this is a related issue.
As some of you know, it's a 98 Cobra with a Moduar Powerhouse built short block, Sean Hyland heads that were straightened out by Al Pappito @ Boss330 Racing (valves were 1mm undersized from SHM with 0 miles on them), and stock 98 Cobra cams.
It's also being force fed by a pair of 60MM master power turbos.
So, in an effort to not blow the car up, can anyone give me some ideas as to where I should be looking to figure out the random misfire codes? It felt like it was running fine before, maybe a little rough, but the CEL was on before the cooling fan melt down. (Literally. The connector melted.)
I don't want to blow it up; especially given that the motor's only got like 3000 or 4000 miles on it, all with ZERO boost. The car's only tuned for a break in drive on the street. (new clutch, too)
It's got brand new NGK TR6's gapped at .28, brand new plug wires and brand new OEM Ford coil packs, along with High Impedance 83# injectors.
Thanks in advance guys. I really appreciate the input.
Alan
I FINALLY thought the car was ready to strap down for a tune, only to have the fan die on the way to the dyno. Long story short, the car overheated and I ended up at the doctor's office with second degree burns on my right arm.
It's amazing what pressurized coolant and a radiator cap that blows off in your hand will do for your day. :shrug:
Anyway, I got the car back and straightened out again (thanks to Jake and the crew at Power by the Hour in Delray Beach,Fl, as well as Nitrostang Racing in Margate) for helping me diagnose and repair this evil machine.
Seriously, it tried to kill me this time. :lol:
Now, the car seems to be running a little rough at idle and when we scanned it, it's showing a random misfire code, as well as a rear 02 sensor error.
The rear 02 sensors are turned off in the tune, so I'm not sure if this is a related issue.
As some of you know, it's a 98 Cobra with a Moduar Powerhouse built short block, Sean Hyland heads that were straightened out by Al Pappito @ Boss330 Racing (valves were 1mm undersized from SHM with 0 miles on them), and stock 98 Cobra cams.
It's also being force fed by a pair of 60MM master power turbos.
So, in an effort to not blow the car up, can anyone give me some ideas as to where I should be looking to figure out the random misfire codes? It felt like it was running fine before, maybe a little rough, but the CEL was on before the cooling fan melt down. (Literally. The connector melted.)
I don't want to blow it up; especially given that the motor's only got like 3000 or 4000 miles on it, all with ZERO boost. The car's only tuned for a break in drive on the street. (new clutch, too)
It's got brand new NGK TR6's gapped at .28, brand new plug wires and brand new OEM Ford coil packs, along with High Impedance 83# injectors.
Thanks in advance guys. I really appreciate the input.
Alan
09-14-2009, 02:49 PM
#2
Join Date: Sep 2009
Location: WA
Posts: 21
What I would do is test line pressure and feed pressure to your fuel lines.
Check your fuel injectors with a noid light.
Use an oscilloscope to check the resistance in your firing. (primary and\or secondary)
One cylinder that is misfiring can cause your Primary O2 sensor to act spuratic and not know how to act. If you have a complete misfire your O2 can read that you have a lot of oxyogen and have a high voltage.
If you don't have an oscilloscope try to use a 4-5 gas analyzer. This can tell you a lot!
What did your primary O2 sensor read, rich, lean, or both? Since your motor is new I would suggest some real diagnosis. I'm not an mustang owner but you could test ur distributor.
How bad is your miss fire?
Also don't be afraid to use some brake clean and check for some vacuum leaks (don't spray it on your exhaust
)
One more thing check your timing.
Real diagnosis is going to be in your favor, not a shotgun answer. Hope this helps!
Check your fuel injectors with a noid light.
Use an oscilloscope to check the resistance in your firing. (primary and\or secondary)
One cylinder that is misfiring can cause your Primary O2 sensor to act spuratic and not know how to act. If you have a complete misfire your O2 can read that you have a lot of oxyogen and have a high voltage.
If you don't have an oscilloscope try to use a 4-5 gas analyzer. This can tell you a lot!
What did your primary O2 sensor read, rich, lean, or both? Since your motor is new I would suggest some real diagnosis. I'm not an mustang owner but you could test ur distributor.
How bad is your miss fire?
Also don't be afraid to use some brake clean and check for some vacuum leaks (don't spray it on your exhaust
)One more thing check your timing.
Real diagnosis is going to be in your favor, not a shotgun answer. Hope this helps!
09-15-2009, 11:23 AM
#4
3rd Gear Member
Thread Starter
Join Date: Dec 2007
Location: Coral Springs, Florida ~ 33076
Posts: 608
Thanks for all the info.
The plugs are correct for a turbo application. (TR6 NGKs.)
The odd thing is I'm getting the code, but I don't actually feel a misfire. Generally speaking, it seems to be running fine. A little rough at idle, but it could be my imagination.
The plugs are correct for a turbo application. (TR6 NGKs.)
The odd thing is I'm getting the code, but I don't actually feel a misfire. Generally speaking, it seems to be running fine. A little rough at idle, but it could be my imagination.
09-15-2009, 11:32 AM
#5
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Join Date: Jul 2009
Location: texas
Posts: 311
09-15-2009, 03:23 PM
#6
Join Date: Sep 2009
Location: WA
Posts: 21
Don't be cheap about a turbo'd vehicle. If you cannot afford to do it right you def cannot afford to do it wrong. I learned the hard way when I was much younger.
The Oscilloscope and\or the 4\5 gas will either tell you what is wrong or def point you in the right direction.
09-19-2009, 08:30 AM
#7
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Join Date: Dec 2007
Location: Coral Springs, Florida ~ 33076
Posts: 608
Honestly, I have no idea how to use any of those tools, but I'll see if I can find someone locally who does.
What exactly am I looking for when I use them, i.e.: what results are normal and what results would be out of the ordinary?
What exactly am I looking for when I use them, i.e.: what results are normal and what results would be out of the ordinary?
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