Still Having Idle And Drivability Issues

[aah86mustang]

I recently converted over to mass air flow on my 86 gt and since then I've had a horrible idle and it's pops real bad from exhaust when I'm downshifting and the motors revving down. I've replaced everything I could possibly think about including every thing that was throwing codes. It was also hesitating and running very poorly down the road and I changed out the ecm after I had already changed out many parts and it fixed that. But I still have the horrible idle and it still backfires when downshifting. One thing I wanna add though is that is has 24# injectors but there thr ev6 style with matching maf. But a friend of mine said somethin about these injectors not workin right on older cars because of the spray pattern and that there a "high impedance" injector? Any help right now would be greatly appreciated because I'm lost on what else to do.

 

[2000xp8]

When swapping to mass air IMO, you always swap in 19's and a stock meter, get the car running right then go from there.

Not sure what mods you have, but 24's are way too much for a stock engine.

 

[aah86mustang]

I understand what your sayin but I already had the 24# injectors before I swapped it over. But it can't be runnin like this cause of the injector size. If it was it would be running rich and it's not its runnin a little bit on the lean side right now.

 

[jrichker]

When swapping to mass air IMO, you always swap in 19's and a stock meter, get the car running right then go from there.

Not sure what mods you have, but 24's are way too much for a stock engine.

You just got some very good advice, I would advise you to take it.

Start with stock, get it running good and them make changes. Make a change without having a good baseline configuration and you never know what caused the problem. There could be a whole bunch of things wrong and you will not know where to start.


You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 159,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

 

[2000xp8]

I understand what your sayin but I already had the 24# injectors before I swapped it over. But it can't be runnin like this cause of the injector size. If it was it would be running rich and it's not its runnin a little bit on the lean side right now.

You had 24lb injectors on the car before you swapped to mass air and the car ran fine?
Foxes have high impedance injectors stock, so impedance isn't the issue.

What is done to the car?
Having the correct meter and injectors for you setup is very important, 24's on a stock engine even with the right meter is not going to run right. How do I know? I've done it.

Regardless, i'd still suggest getting a stock meter and injectors (should be dirt cheap or even free), they will support around 275rwhp. It will rule out those 2 things as the problem.

 

[Mustang5L5]

Measure the resistance of one of the injectors. Should be around 14.4 ohms.

 

[aah86mustang]

Yeah it ran fine when it was still speed density. I have the correct maf for the injectors on the car now too. I tried puttin a friend of mines maf calibrated for 24# on there and no change. So the ev6 with its different spray pattern will work on my car? I'm gonna try to find a set of 19# and stock maf and try that but I'm just wondering if I bought a set of the older style ev1 injectors 24# if it wouldn't fix my problem? And I'm guessin you check the resistance with car running right?

 

[Mustang5L5]

Negative. Just unplug any injector and wity a multimeter set to resistance, touch the two electrical prongs on the injector. Should get around 12-16ohms of resistance