I have a '96 A4 with Vortex Ram Air, K&N, Granatelli MAF, and BBK 52 Throttle Body. The previous owner installed them. I keep getting a P507 Code... Idle System High. The RPMs are at about 650-700 on the RPM gage on the console, with a smooth idle and running engine. Do I need to knock down the RPM through the PCM? If so, does Tuner Cat, or any other PCM programs allow you to do this? What do you recommend?

 

Your above specs; ie, the IAC isn't able to control idle within 50 +/- of targeted RPM. Check for air/vacuum leaks. These type of problems aren't something you want to tune out.

 

OK, I'll start with that, but the hoses do look good. Only 48K miles on the vehicle. Thanks.

 

Also verify that the cable is allowing the throttle to return against the stop. Since you didn't install it, the previous owner may have installed it wrong - particularly if you bought the car and it had the problem. The minimum air flow usually needs to be adjusted on new throttle bodys - it should at least be checked - after installation. I don't have the specs for yours, but most injected GM's (port, sequential and even throttle body apps) seem to have a spec somewhere between 400 and 450 rpms. Mininum air is simply a slight amount of air flowing through the butterfly with the throttle closed and the IAC fully extended into it's bore. On every OB2 vehicle I've worked on, you use a bi-directional scanner to fully extend the IAC and once extended, you turn the screw until you achieve the specified RPMS. Assuming the previous owner didn't do this - or worse yet just cranked up or down on the screw - you can get the high idle code. If you need help, seek out an independent shop, as a Dealer is going to tell you that the throttle body is crap and that you need an OEM.

Other considerations might be that the throttle body is the wrong application so you can probably get a # off of it and call the Manufacturer. They should be able to verify it's the right one. It might also have the wrong IAC in it - pintle is too small for the bore and air is getting in around it. It could also have the wrong gasket or the pintle may just be hanging up in the bore and a good cleaning will get it working again (so if you see a bunch of gunk inside of it, at least shoot it with some throttle body cleaner).

Hope this helps.

 

Good stuff, thanks SunCr. I removed the IAC and TB. The IAC had a lot of build up on the pintle. I cleaned it off as well as the inside of the TB where the pintle extends. I also cleaned the TB, but it was relatively clean.

Anyway, put it all back together (along with a new thermostat seal which was leaking) and it ran the same. The car runs great, just the high idle remains. On the gage it's around 600-700 rpm at idle.

"On every OB2 vehicle I've worked on, you use a bi-directional scanner to fully extend the IAC and once extended, you turn the screw until you achieve the specified RPMS. Assuming the previous owner didn't do this - or worse yet just cranked up or down on the screw - you can get the high idle code." The throttle cable does allow the throttle to go to the stop. I think it may lie in what you said here. Maybe time to take it to someone?

 

Trust the pintle fit squarely (roundly?) in the bore? Unless you can borrow a bi-directional scanner from someone, you're probably going to have to take it to a shop to reset minimum idle speed or to troubleshoot it further. The only other possibility is to take a guess at it by turning the adjustment screw counterclockwise, maybe no more than one complete turn and hope that if it doesn't fix it or if it creates other driveability issues, turning it back will at least get you to where it was.

 

I'll give the adjustment screw technique a shot. ...more later.

 

It worked! Approximately one turn of the stop screw with a 3mm allen wrench lowered the idle to approximately 500-550 rpm, warmed up, stopped, in drive. After 8 or 9 driving cycles over the past few days, no SES High Idle RPM light. Your da man, SunCr. Thanks.

 

Glad it worked - though my guess is that it's about 50 rpms too low. Hopefully, that won't generate a 506 (opposite of the 507). If it does, a half turn the other way should fix it.

 

I'll definitely keep an eye on it. ...should it not begin snowing here and prevent the machine from leaving the garage. But for now, it's great.

 

Neato - a White Xmas - we should see mid 70's maybe 80 by the 25th - still had to mow the lawn today!