EFI question regarding idle

[BNC04]

Hi All,,
One of the bronco's that I have on my list of possibles has had a efi conversion done. In emails with the owner, he stated that It has an odd idle issue, where if you are rolling at speed and take it out of gear it doesn't drop all the way to idle like it would if you were sitting still, but it like sits on high idle, only when you are rolling, as you stop it drops to regular idle.

5.0 EFI motor from a 1988 Mustang with Mass Air..

Any thoughts on what could cause this? VSS not hooked up correctly perhaps? Maybe using a computer for an Auto in a manual bronco? I'm just looking for a feel as to what it could be and how much work it would be to diagnose and repair it.

Thanks
Brett

[ZOSO]

From all my EFI tuning experience that is completely normal. It has to do with emissions and helping make sure the rpm doesnt drop so fast it stalls. Now I pretty sure this does look at the vss and Im sure thats not hooked up. At least thats wht I know.

[BNC04]

Thanks for the reply Zoso. I would have never guessed that it was normal. Though I have not seen nor driven it to be sure that the owner is describing it accurately.



Brett

[ZOSO]

Im not a 100% sure for the year but from what I know with dealing with the newer stuff it's normal.

[Viperwolf1]

That's somewhat normal for an auto EEC. Could be something else too, but wouldn't be hard to troubleshoot
/fix.

[Jesus_man]

I wouldn't be concerned with it. My guess is they idle high until you stop because most likely the '88 mustang had vacuum boost brakes, which work better with the more vacuum produced at a higher rpm. Also, power steering works better too. Again, that's my guess, but it does make sense.

J.D.