Cobra 96 engine troubles...

[Bullitt66]

Hi again, haven't been here because I just stored the Cobra since I got this problem, I want to fix it now! THe car came with a diablochip, had a supercharger and I took it out, The problem came before that, then I tuned it with a Sniper Delta force, turned off egr, rear o2, turned the fans earlier because it overheats, I hope it's the condenser, but that´s just another problem, The real problem is the car doesn't run good at wot, no check engine light, good fuel pressure, changed fuel filter, bought another maf and ran the same, if I took the air filter it runs better, but the revs still climb slow, then I disconnected the maf and the car ran great at wot, just like before, I did put a t56 before I took out the diablo chip and haven't hooked the speed sensor (need speed cal ER) could that be a problem?

Scanned it with an innova 3160, only o2 sensor not reading voltage is B1S2, that wouldn´t make that problem at wot if Im not wrong, The car also dies if I let off the pedal at speed, bad iac, no codes, so Why if I disconect the maf, the car runs great at wot? what parameters does the ecm ignores if I do that?

Please help, my Cobra needs love :bored:

 

[White96svt]

Have you checked the voltage, grounds and signal circuits for the MAF? Generally when unplugging the MAF like that, the computer reverts back to stored default values. That's why it will run smooth. With the scanner that you have, can your read live sensor data? If so, see what the MAF sensor is doing when its plugged in while doing a slow accel from idle to WOT. It sounds to me like there is a problem with the MAF readings but its not the sensor itself. I don't have a schematic in front of me and aren't the most 100% familiar with these systems as I was always a GM tech. Should be relatively the same principle. If I'm incorrect someone will hopefully chime in and lead you better. Good luck.

 

[Bullitt66]

Thanks, maf readings in live data goes from 0.500-.600 from idle to as much as 17.000 at wot (lb/min)

 

[White96svt]

Thanks, maf readings in live data goes from 0.500-.600 from idle to as much as 17.000 at wot (lb/min)

17 lb/min seems awful low for WOT. A rough rule of thumb is 10 rwhp per lb/min. Are you able to read the data as voltage or just lb/min? MAF sensors use a 5 volt reference that varies up to 5 volts as air flow increases. Now you said you removed the supercharger, is everything back to stock? Whats on the car? I just noticed that you said it dies when letting out of the throttle, I didn't see that before. That may be a sign that there is a problem with the 5 volt reference circuit. I'm not 100% sure on mustangs but I know on GMs they share the same voltage circuit. With your MAF reading that low of voltage that kinda indicates that you either have something reducing flow or a wiring problem with the MAF circuit. I'm leaning towards a wiring problem since you swapped MAF sensors and that didn't seem to fix it. Since it runs fine with the MAF unplugged I would eliminate the possibility of a restriction.

 

[Tyler72]

This may sound dumb, but what about the injectors? Is it possible that the previous owner put in bigger ones for the blower? If you didn't switch them back to stock, that may be your issue.

 

[White96svt]

This may sound dumb, but what about the injectors? Is it possible that the previous owner put in bigger ones for the blower? If you didn't switch them back to stock, that may be your issue.

I don't see how injectors is going to cause his MAF to read low air flow. He said he took the blower off the car but I assuming he is still running the same MAF and injectors that were with the blower. If so, the injectors would be calibrated to the MAF already. If the injectors were the issue, then I would think that unplugging the MAF wouldn't resolve anything. Maybe I'm wrong with my theory but I believe its a wiring issue. Bullet66 make sure you update us with what you find.

 

[Bullitt66]

17 lb/min seems awful low for WOT. A rough rule of thumb is 10 rwhp per lb/min. Are you able to read the data as voltage or just lb/min? MAF sensors use a 5 volt reference that varies up to 5 volts as air flow increases. Now you said you removed the supercharger, is everything back to stock? Whats on the car? I just noticed that you said it dies when letting out of the throttle, I didn't see that before. That may be a sign that there is a problem with the 5 volt reference circuit. I'm not 100% sure on mustangs but I know on GMs they share the same voltage circuit. With your MAF reading that low of voltage that kinda indicates that you either have something reducing flow or a wiring problem with the MAF circuit. I'm leaning towards a wiring problem since you swapped MAF sensors and that didn't seem to fix it. Since it runs fine with the MAF unplugged I would eliminate the possibility of a restriction.

The 17lb min was at idle, voltage never sees more than 5v, i bought the car without the supercharger and ran great, the car still has 24lb/hr i do get code for iac, i just ordered it, fuel pressure is 38psi without vaccum

 

[Bullitt66]

I don't see how injectors is going to cause his MAF to read low air flow. He said he took the blower off the car but I assuming he is still running the same MAF and injectors that were with the blower. If so, the injectors would be calibrated to the MAF already. If the injectors were the issue, then I would think that unplugging the MAF wouldn't resolve anything. Maybe I'm wrong with my theory but I believe its a wiring issue. Bullet66 make sure you update us with what you find.

The car has stock maf and injectors, the car came with a diablo chip, ran great at the track, high 13' on a not prepped track, slow times but that's Nother story, stock ls1 runs low 14 here, the problem didn't originated because of the removal of the supercharger, then i removed the diablo chip and still no power at wot, put a new tune with sniper, still no power at wot, now itnhas a stock tune, the fuel pump does sound too much for a stock one, could it be posible i have pressure but not volume? And the fuel pump is going bad? I just ordered a walbro 255 too anyways

 

[White96svt]

Thanks, maf readings in live data goes from 0.500-.600 from idle to as much as 17.000 at wot (lb/min)

The 17lb min was at idle, voltage never sees more than 5v, i bought the car without the supercharger and ran great, the car still has 24lb/hr i do get code for iac, i just ordered it, fuel pressure is 38psi without vaccum

Okay, I'm a little confused here. What was the lb/min during WOT? First you said it was 17 now your saying that 17 was at idle? With the MAF hooked up, try watching the scanner to see what the lb/min and voltage are while raising the rpms from idle to WOT. What do you see, whats the min at idle and max at WOT?

 

[Bullitt66]

You mean from idle to redline in wot always?

 

[White96svt]

You mean from idle to redline in wot always?

I'm saying to slowly raise the rpms from idle to WOT and see what the values are. If your only showing 17 lb/min through the MAF at WOT, something is wrong!

 

[F8L BYT]

Sounds like a bad MAF

 

[Bullitt66]

I'm saying to slowly raise the rpms from idle to WOT and see what the values are. If your only showing 17 lb/min through the MAF at WOT, something is wrong!

Sorry, just read my post, at idle is 0.500-0.600lb/hr and in wot almost at readline is reads about 15.00-17.000, gona try the other stock maf i have here and post the readings...

 

[Bullitt66]

Put the 2nd maf i already tested and now the car runs ok, reads 25.000+/- at wot, that's without air filter, if i put the air fiter it won't idle and runs rough, it has this adapter

Its definetly a restriction but the car ran great when i bought it, what would cause that?

 

[White96svt]

Put the 2nd maf i already tested and now the car runs ok, reads 25.000+/- at wot, that's without air filter, if i put the air fiter it won't idle and runs rough, it has this adapter

Its definetly a restriction but the car ran great when i bought it, what would cause that?

I thought your original post said removing the filter didn't seem to change it and only unplugging the MAF did? Well 25 lb/min is a bit more reasonable for WOT on a N/A stock motor. Now your saying that you put on a different MAF and it runs fine with out the air filter but like crap with the air filter? What about with the other MAF? Same thing? That air filter does have some damage to it. That could cause a loss in air flow. The filter maybe be dirty as well which could be clogging it. That appears to be a K&N or other brand which are cleanable style filters. Maybe try cleaning and recharging it and go from there. Maybe we are heading in the right direction now. Let me know what you find.

 

[Bullitt66]

With the stOck maf it runs bad at wot without air filter, 2nd maf runs good without air filter, both mafs wont idle with the air filter on, i cleaned the air filter (k&n) before storing the car, i looks good, you can see light through it haha, maybe i should try another one?

 

[White96svt]

With the stOck maf it runs bad at wot without air filter, 2nd maf runs good without air filter, both mafs wont idle with the air filter on, i cleaned the air filter (k&n) before storing the car, i looks good, you can see light through it haha, maybe i should try another one?

Okay, so it sounds like the 1st MAF is bad. The 2nd seems like it eliminates your WOT problem. I know you said at one point the you had a code for the IAC motor, try looking into fixing that first. That is prob contributing to the idle issue. If your having trouble with it running now with the air filter on, then try a new filter. Like I said, the pic you posted did show some damage to it.

 

[Bullitt66]

Ill wait for the iac to come along with a walbro I ordered an post back, the speedo doesn't work, does the ecm uses mph for something?

 

[PSUCOBRA96]

you said you tuned it? As in you tuned it yourself or uploaded someones tune you purchased? have you ever tuned a car before, what parameters did you mess with

 

[Bullitt66]

you said you tuned it? As in you tuned it yourself or uploaded someones tune you purchased? have you ever tuned a car before, what parameters did you mess with

I tuned it myself, not that you have too much parameters to play with, since I used Sniper Delta Force, used it for turning off EGR, rear o2, and turning the fan earlier, didn't play with ignition or fuel, I have tuned different kinds of cars, not too much, but the results have been great! The worst I got was blowing one headgasket on my '90 Turbomustang lol