Electrical 95 Gt Bad Misfire, Backfire, Runs Ok Spout Removed

Need help. 1995 mustang GT. I have owned the car for 18 years and it is all stock. I have been fighting an intermittent sputter/misfire for the last few years and it has gotten to the point where it is so frequent that it is not safe to drive now . When it acts up it is like its firing on only a few cylinders and there is almost no throttle response. Pressing the gas seems to just make it backfire. I had the car at the local ford dealer for a few months and they actually had the nerve to tell me some cars just can't be fixed. When it is sputtering and barely running, if you pull the spout connector it will run and drive fine (at base timing) plug the spout back in and the car goes back to S#$T. Un-plug it and its fine again. cycling the ignition will make it run ok but the problem comes back within 1 minute or so, but sometimes wont come back. So I think that its something with the computer control for the tfi module. I'm really at a loss. I just pulled the fender off hoping that I would find a mouse chewed all the wires under the passenger fender but there is no obvious damage. I keep getting codes for MAF and Air Bypass and Air Diverter solenoids.



Here is what I have replaced on the car.



tfi module x 2 times , 1 coil, 1 distributor, 1 lkq eecIV (same codes as original computer and when this did not work I put the original back in , coolant temperature sensor (one aftermarket and one at ford oem) x2 times, CCRM, MAF x 4 times (ford warrantied it twice), I have plenty of fuel pressure, replaced plugs and wires (with motorcraft I think more than once).



The ford tech told me that he checked and I have impedance from the MAF sensor to the computer as well as power and ground to it. He said he thought that something was causing the computer not to receive the MAF signal. They said they would have recommended replacing the computer except that i had already done so. I find the odds of having two bad computers with exactly the same symptoms and codes a little hard to believe. He also checked the air bypass and divertor solenoids and said they worked when he put power to them manually.



Any ideas would be greatly appreciated.



Jeff
 
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A few things off the top of my head - fuel filter / fuel pump. Check fuel pressure when it's acting up - your problem might be intermittent. A lean backfire when you hit the gas indicates a possible fuel problem. "Plenty of fuel pressure" doesn't mean the same to you as it does the computer. It needs precisely 39psi with the vacuum line disconnected from the regulator. Check the regulator at the same time (if there's fuel in the hose it's gone bad).

Grounds - make sure all of your grounds (to the block, to the firewall) are in great shape.

Distributor - again. Not uncommon for reman units to be bad out of the box, many rebuilders don't replace the magnetic pickup which causes this issue. Richporters are reported to be decent. I just replaced my own PIP myself - not too hard if you're careful not to mushroom the shaft.

TFI - make sure you have the right part. Some of them don't have dwell control, and some parts manual mess ours up with earlier Foxes.

Timing - check that TDC is where the balancer says it is (I use a piston stop and rotate the engine to hit it both ways - TDC is right in-between). Our balancers sometimes slip / come apart when the rubber deteriorates (if you have rubber sticking out of the balancer that can cause it). You might be too far advanced if pulling the SPOUT makes things better.

Good luck!
 
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What codes are you getting?
Did you get both engine off & engine running codes?
Please provide the numerical value of the codes and not a definition you got from someplace.