Help, 94 Cobra problems

[fastimes69]

Hey guy's, my buddies got a 94 Cobra with some mods. S-trim,30 lb inj,MSD 6al,BTM,255lph pump,all the exhaust is BBK,75mm mass air, 70mm throttle body,etc..The car was running fine until a week ago. It starts up fine,then after about 10 seconds the idle drops, it backfires, sputters.It feels like it loads up on fuel. I checked the ignition,fuel pressure, compression test,replaced plugs, checked for codes, check engine light does not come on even though it runs horrible.Everything so far has checked out ok. If I shut it off and turn it on again it idles and drives right for a few seconds then starts to stumble again.I have no idea what it could be, any ideas are appreciated..thanks...

 

[Chythar]

Hey guy's, my buddies got a 94 Cobra with some mods. S-trim,30 lb inj,MSD 6al,BTM,255lph pump,all the exhaust is BBK,75mm mass air, 70mm throttle body,etc..The car was running fine until a week ago. It starts up fine,then after about 10 seconds the idle drops, it backfires, sputters.It feels like it loads up on fuel. I checked the ignition,fuel pressure, compression test,replaced plugs, checked for codes, check engine light does not come on even though it runs horrible.Everything so far has checked out ok. If I shut it off and turn it on again it idles and drives right for a few seconds then starts to stumble again.I have no idea what it could be, any ideas are appreciated..thanks...

Check the MAF and ACT sensors. The MAF tells the computer how much air is flowing into the engine; it's on the Mass Air Meter. Clean the MAF first. Use a q-tip with rubbing alcohol or electrical cleaner and GENTLY clean the MAF wires. It's really easy to break one, so be careful.

If the trouble is still there, check the ACT. The ACT tells the computer the temperature of the air; the conputer will make additional adjustments based on the temperature. It's in the inlet hose between the Mass Air Meter and the Throttle Body. Clean it as well, and make sure the sensor is clocked right so it gets the most air flow over the sensor.

If you're still having problems after cleaning the sensors, come on back.

 

[94Blue302GT]

You can take it to a dyno with a wideband O2 and then you get an exact readout of when it's dying out. It may be that your ignition isn't retarding when it's supposed to be.

 

[fastimes69]

Thanks for the response guys. Well the air meter along with injectors were installed about 2 weeks ago so I doubt thats the problem since they are fairly new.If the ACT sensor was bad wouldn't it thow a code or check engine light come on ?Any other ideas. No one in my area can dyno-tune correctly so for now that's out of the question.

 

[fordtech28]

Thanks for the response guys. Well the air meter along with injectors were installed about 2 weeks ago so I doubt thats the problem since they are fairly new.If the ACT sensor was bad wouldn't it thow a code or check engine light come on ?Any other ideas. No one in my area can dyno-tune correctly so for now that's out of the question.

Just because the parts are new doesn't mean they are good I had a brand new distributor go bad on me after 3 hours on the car I was super pissed because it left me stranded at the store so you might try a different air meter just to rule it out maybe it wasnt calibrated correctly it happens.

 

[SVTCobra306]

Yeah, it really sounds like a MAF issue to me. The car runs fine open loop, and when it goes closed it turns to crap. Could also be O2's as mentioned above.

You said it has an S trim... How is it tuned? could be an issue with that too..

 

[fastimes69]

Yeah, it really sounds like a MAF issue to me. The car runs fine open loop, and when it goes closed it turns to crap. Could also be O2's as mentioned above.

You said it has an S trim... How is it tuned? could be an issue with that too..

Well if the O2's were bad, the check engine light would come on.I checked for codes and everything was ok.I highly doubt it's the air meter though,but it's a possibility.I'll try another one of my friends air meter and see what it does. I'll get back to ya.Later

 

[Chythar]

Thanks for the response guys. Well the air meter along with injectors were installed about 2 weeks ago so I doubt thats the problem since they are fairly new.If the ACT sensor was bad wouldn't it thow a code or check engine light come on ?Any other ideas. No one in my area can dyno-tune correctly so for now that's out of the question.

If the sensor is dirty or bad, it still might not throw a code. See, one issue with Ford sensors is, they can give off bad readings while staying within the proper range. For example, let's say the MAF sensor is supposed to return a value between 0.1 and 1.0. At idle, say the MAF should read 0.2. But if the sensor is dirty, it might return 0.5. So the sensor appears to be working properly, but it's returning a bad value.

The MAF sensor in our experience is the primary cause of what you're describing. Most times this issue happens on new MAFs when you've got a K&N or other oilable filter, and happens right after you oil the filter. Excess oil streams off the filter and oils up the sensor. Or the sensor could have gone bad right away. If an electrical part fails, it's usually real quick or not at all.

I don't think it's the O2 sensors, personally. Don't they just get used at part-throttle? They aren't used at WOT (wide open throttle), but are they used at idle?

 

[fastimes69]

Well it was the sensor that was bad.We replaced it and the car ran fine.My buddy took it for a spin and spun for 1st through 3rd.He turns around and on the way back he nails it again and a beautiful white cloud of smoke follows him back.Damn, all that time troubleshooting and figuring out the problem and now blown headgaskets .Oh well back to the drwaing board LOL himself