help with a rough idle on a 98 cobra

[BigChiefSVT]

Ever since the first day i got my cobra it had the check engine light on, the dealership that had it didnt have clue what was wrong and took a huge chunk off the asking price(worked for me). It seemed to run good for the first few days i had it then i started noticing a rough idle every once in awhile while sitting at stop lights and would sometimes have to fight to keep it running. My best guess was that the o2 sensors were acting up since it has an aftermarket exhaust and cats. I just got a bama tuner hoping it would fix the problem and get rid of the check engine light. First off i plugged it in and set it to the street tune(87-89 octane), it loaded up everything alright. Next i started up the car and it did the rough idle thing it likes to do and died. I started it back up again and revved it a little, it did seem more responsive and had the check engine light off though. Any suggestions on the dying issue? maybe tune the fuel/air mixture?

 

[01yellercobra]

First thing I would do is make sure there are no vacuum leaks. If that checks out you're going to have to do some datalogging to see what's going on. What mods does the car have?

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[2002BLGT]

probably should look for a local SCT dealer to take the car to for a once over by an experienced tuner that might be able to spot something wrong or mismatched parts.

 

[BigChiefSVT]

First thing I would do is make sure there are no vacuum leaks. If that checks out you're going to have to do some datalogging to see what's going on. What mods does the car have?

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All the mods i have are listed in my signature thingy. The weird thing about the rough idle issue is that it will do it randomly sometimes. Half the time ill come up to a light and it will sit at 700 rpm and idle all day perfectly fine, the other times ill be at a light and the rpms will start bouncing all over the place between about a grand and then down to zero where it dies. The vaccuum leak might be it but im still thinking its an ecu issue. Another weird thing is when im coasting in neutral right after being in gear, it likes to stick at 1500 rpm till i give it a rev and it comes back down to normal which is around 1000

 

[01yellercobra]

All the mods i have are listed in my signature thingy. The weird thing about the rough idle issue is that it will do it randomly sometimes. Half the time ill come up to a light and it will sit at 700 rpm and idle all day perfectly fine, the other times ill be at a light and the rpms will start bouncing all over the place between about a grand and then down to zero where it dies. The vaccuum leak might be it but im still thinking its an ecu issue. Another weird thing is when im coasting in neutral right after being in gear, it likes to stick at 1500 rpm till i give it a rev and it comes back down to normal which is around 1000

Ok. I couldn't see your sig because I was tapatalk before. That sounds like an IAC issue to me. Since it's not constant. Did you tell Bama you have long tubes? Adjustments need to be made for the O2 sensors to work correctly.

 

[BigChiefSVT]

Ok. I couldn't see your sig because I was tapatalk before. That sounds like an IAC issue to me. Since it's not constant. Did you tell Bama you have long tubes? Adjustments need to be made for the O2 sensors to work correctly.

Since you mentioned the IAC I decided to take it out and clean the heck out of it today with throttle body cleaner, boy it was dirty on the inside. I started it up and its still doing the rough idle. It was frustrating. I did let Bama know i have long tubes when i ordered the tuner. At least now I know its not the IAC, the vacuum leak will be the next issue im gonna check i think that might be the issue to solve all issues

 

[2002BLGT]

you may want to go ahead and pull the intake off of it completely and check the IMRC plates

 

[encasedmetal]

you may want to go ahead and pull the intake off of it completely and check the IMRC plates

they have dick to do with idle. I have noticed lately alot of BAMA cars doing this. OP- you need to datalog using livelink and a laptop.
IDLE problems:
To work on fixing this you need to datalog “Spark Source” and see if it returns a value of 8, this means that it is on the minimum spark clip and not controlling idle. A returned value of 9 means it is in control. If it is not 9, you need to lower idle spark. If still having problems with idle, -with the engine running unplug the IAC valve, if it stalls the engine restart with IAC unplugged. Adjust using the throttle stop screw to find desired idle speed. Turn engine off and disconnect the negative battery cable, press the brake pedal 3-4 times. Reconnect the battery cable, plug in the IAC valve and the car should idle better. Try to make sure that TP absolute is close to 200. Vacuum at idle on a stock cammed car should be 18-22. ISC duty cycle at idle needs to be 35-50%, and if using a EEC V, the idle speed integrator should be close to zero. If you get anything below 15% duty cycle the ISC valve is closed and not controlling anything.
here is what to choose once getting livelink set up:

Datalog these PIDs for idle values:
Fuel source- when in closed loop, this will read 0.00

Idle air integrator-should be fairly close to zero. If it’s negative then you need to take air out of the ISC tables, if it’s positive then you need to add air into the tables. It’ll never be exactly zero. Allow the car to be at operating temp and idling for a few minutes before making a decision on this.


Idle speed valve duty cycle- aka-ISC duty cycle- log this at idle, it should read between 35-45%.

Desired idle rpm- desired idle is what you have it set for, being in drive or any adders such as AC will affect this.

Rpm- actual rpm at idle, in comparison to desired idle rpm, these should be extremely close.

Battery voltage- Another issue in getting the A/F may be the “Injector comp battery volt”, try adding 0.2 or 0.4 to the voltage area where you are idling (if that doesn’t work, try subtracting that much). You may be overcompensating for pulsewidth based on battery voltage.

Spark source- if it returns a value of 8, this means that it is on the minimum spark clip and not controlling idle. A returned value of 9 means it is in control. If it is not 9, you need to lower idle spark.

Spark- * timing at idle.

TP absolute- should be close to 200, and can be adjusted to desired by adjusting TPS sensor location

 

[AMWill]

I have noticed lately alot of BAMA cars doing this.

The OP is saying that he had an idle issue before installing the tune. He installed the Bama tune hoping that it would fix his idle issues. It's mechanical.

Ever since the first day i got my cobra it had the check engine light on, the dealership that had it didnt have clue what was wrong and took a huge chunk off the asking price(worked for me). It seemed to run good for the first few days i had it then i started noticing a rough idle every once in awhile while sitting at stop lights and would sometimes have to fight to keep it running. My best guess was that the o2 sensors were acting up since it has an aftermarket exhaust and cats. I just got a bama tuner hoping it would fix the problem and get rid of the check engine light. First off i plugged it in and set it to the street tune(87-89 octane), it loaded up everything alright. Next i started up the car and it did the rough idle thing it likes to do and died. I started it back up again and revved it a little, it did seem more responsive and had the check engine light off though. Any suggestions on the dying issue? maybe tune the fuel/air mixture?

BigChiefSVT,

My advice is do a complete tune up on the car. Check for vacuum leaks, change the fuel filter, spark plugs, clean your MAF and air filter, etc. See if this makes a difference. If you're still having issues after that, you can take a few datalogs to send into Bama and we'll be able to tell you how all of your sensors are working (especially o2 sensors) and see if we can find the problem that way.

Also, you can pull codes with your Bama tuner as well. Have you tried this at all?

Shane

 

[encasedmetal]

can I ask why BAMA would sell a tuner to someone that has a car that is running like poop? sounds like a communication breakdown somewhere there. regardless- and not bashing- I was making an observation based on the 96-98 cobras lately. OP- datalog and return with results please.

 

[AMWill]

can I ask why BAMA would sell a tuner to someone that has a car that is running like poop? sounds like a communication breakdown somewhere there. regardless- and not bashing- I was making an observation based on the 96-98 cobras lately. OP- datalog and return with results please.

It's possible that the OP ordered the Tuner online and filled out the tuning info form via email without talking to anyone from Bama initially. Our Bama Specialists wouldn't have told him a Tune would fix a problem like this. If they did, then that's something I will personally get straightened out with them.

Since the OP already purchased the Tuner with us. Bama will work with him and try new adjustments to see if they can help find a solution!

Shane

 

[encasedmetal]

It's possible that the OP ordered the Tuner online and filled out the tuning info form via email without talking to anyone from Bama initially. Our Bama Specialists wouldn't have told him a Tune would fix a problem like this. If they did, then that's something I will personally get straightened out with them.

Since the OP already purchased the Tuner with us. Bama will work with him and try new adjustments to see if they can help find a solution!

Shane

excellent! for some reason I thought that it was required that purchasers of BAMA stuff had to talk to someone in order to buy. my bad.

 

[BigChiefSVT]

ya i bought the tuner online without talking to anyone from bama like an idiot. a couple of my friends who had tuners and aftermarket exhausts convinced me to get it, i would have bought it either way even if i didnt have the bad idle. yes i have done a diagnostics check with the tuner and gotten a reading of bank 2 sensor 1 lean. i also took it to autozone to try their code reader and it said the same thing and then listed out possible causes including possible vacuum leak, fuel pressure high or low. i have a printed receipt of the code reader check that says the problems. i did check for vacuum leaks and found nothing, then i noticed that whoever had the car before me had put on an aeromotive fuel regulator. ive been looking all over online how to mess with the thing and have been making some progress by making very minor tweaks with it, it doesnt have a gauge on it though which is a must! im gonna get the gauge and get the pressure to where it needs to be and see what happens from there.

 

[AMWill]

ya i bought the tuner online without talking to anyone from bama like an idiot. a couple of my friends who had tuners and aftermarket exhausts convinced me to get it, i would have bought it either way even if i didnt have the bad idle. yes i have done a diagnostics check with the tuner and gotten a reading of bank 2 sensor 1 lean. i also took it to autozone to try their code reader and it said the same thing and then listed out possible causes including possible vacuum leak, fuel pressure high or low. i have a printed receipt of the code reader check that says the problems. i did check for vacuum leaks and found nothing, then i noticed that whoever had the car before me had put on an aeromotive fuel regulator. ive been looking all over online how to mess with the thing and have been making some progress by making very minor tweaks with it, it doesnt have a gauge on it though which is a must! im gonna get the gauge and get the pressure to where it needs to be and see what happens from there.

Sounds like you're on to something! Your fuel pressure should be around 29-33psi with the vacuum hose still connected. When you get a psi gauge, post back and let us know where you're at. Hopefully it's really low and you found the lean issue!

Good luck!

Shane

 

[encasedmetal]

Sounds like you're on to something! Your fuel pressure should be around 29-33psi with the vacuum hose still connected. When you get a psi gauge, post back and let us know where you're at. Hopefully it's really low and you found the lean issue!

Good luck!

Shane

Fuel pressure should be 39 psi with hose disconnected.

 

[AMWill]

Fuel pressure should be 39 psi with hose disconnected.

That's correct, we typically see 38-40psi with the vacuum line disconnected and 29-33psi connected, like mentioned above.

BigCheifSVT,

Did you get a chance to install a fuel psi gauge over the weekend? I'm anxious to see the results!

Shane

 

[prostkr]

Your lean bank code can also be from an exhaust leak close to the o2 sensor its self. He did mention he has long tubes. Can the sensor be swapped form side to side to see if the code follows?

 

[filebug]

i also have a bama tune and decided to swap to amazon tuning cause of the addition of a supercharger and them saying they won't do my lifetime tune revision with that addition. My car didn't really run better with the bama tunes (still had issues with cold start and it ran real rich and by rich i mean getting high in the carport rich) but i do hear positive things about them. i can tell you one thing i would trust anything encasedmetal says cause he pretty much is a expert on these cars.

 

[perry2k12]

I had the EXACT same symptoms, and same code (both sides were lean though), and I turned out to have a terrible vacuum leak. I know they're different cars but it has to be something... Fixed a severe leak, and a minor one and now my car runs better than ever.