EFI Help Missing and Surging

[EFI Guy]

I would look in to using a MAF Viper suggested.

If your MAF curve is different it will cause surging idle. The PCM expects to see a certain voltage coming through the MAF at a given RPM, if it's incorrect the PCM will try to compensate for the incorrect MAF and you get the surging.

I have no idea what MAFs will interchange properly since I always tune the PCM for the MAF I'm using, but I trust Vipers tech knowledge on the issue. The other option would be to tune the PCM for the MAF you have.

 

[Eads74bronco]

I would look in to using a MAF Viper suggested.

If your MAF curve is different it will cause surging idle. The PCM expects to see a certain voltage coming through the MAF at a given RPM, if it's incorrect the PCM will try to compensate for the incorrect MAF and you get the surging.

I have no idea what MAFs will interchange properly since I always tune the PCM for the MAF I'm using, but I trust Vipers tech knowledge on the issue. The other option would be to tune the PCM for the MAF you have.

I'm running the stock mustang MAF. Well as far as I know, it came out of the donor car with the motor.

 

[EFI Guy]

Oh, sorry, I guess I got confused with 2 posters and similar issues. That would apply to Tito's situation, not yours.

Do you still get code 18 after replacing the TFI?

 

[Viperwolf1]

I'm running the stock mustang MAF. Well as far as I know, it came out of the donor car with the motor.

Might want to post a pic of the sensor and housing. Might be a good idea to give a good cleaning too.

 

[Eads74bronco]

Oh, sorry, I guess I got confused with 2 posters and similar issues. That would apply to Tito's situation, not yours.

Do you still get code 18 after replacing the TFI?

Haven't had a chance to run the codes again. I have a 94 5.0 mustang stick computer, can it be swapped out with the 89 5.0 stick computer?

 

[EFI Guy]

Haven't had a chance to run the codes again. I have a 94 5.0 mustang stick computer, can it be swapped out with the 89 5.0 stick computer?

Can it be done? Probably. There are a lot of differences with the harness and would require a lot of re-pinning. I know of a few people that have ran 94-95 PCMs on a Fox harness with some modifications.

Should it be done? No. It would probably be quite a bit of work to do for zero gain. The 94-95 PCM is better than a Fox PCM anyway, it's just not as popular.

 

[Tito]

Well got mine sorted today. Checked my tps and it was out of range, adjusted it and the surging went away but still ran like a beat dog. Went through And found a couple exhaust leaks causing a rich driver side, replaced donuts and manifold gaskets, found a couple fouled plugs, replaced them all and new wires, cap and rotor and runs like a champ now. Very excited to be back to life with it. Was driving me crazy but got back to the basics and got it fixed.