wjamyers

I swapped a broken full blown 70mm TB for the Mil.Spec 65mm ported unit back in the fall of last year, did not update tune i had from CBRD.

I also switched:

• Stock route ETS UICP to a CBRD short route
• 3.5" ETS ic to a 3.8" Garrett core
• Stock intake pipe to a Perrin Intake

Everything was fine until the weather got warm a few weeks back and my idle now drops to 500 rpm and i got the code:
----------------------------------------------
P0506 Idle Air Control system RPM lower than expected

I read that a TB cleaning and ECU reset is in order but maybe it really needs a retune to account for the new throttle body maybe it's running too rich getting dirty? I also have an old filthy Amsoil air filter waiting to be replaced which could be an issue.


Questions:

• Do I have to remove the TB to clean it?
• Should I use standard CRC brand TB cleaner or would you recommend I just put some seafoam in there?
• Do I have to be careful to not scrub off the sealant layer on the Mil.Spec 65mm ThrottleBody as I would on the stock unit?
• Is this something I should [have] tune[d] for right away?

Please help!

Boost Demon

iTrader: (22)

Check your IAC valve:

wjamyers

Thanks, will do. Running a cheap ebay IAC at the moment. Voltage never tested right (with multimeter) and it idled a little bit high occasionally with the AC compressor on, but for the most part was fine. the housing seems like cheaper material than the stock unit. it is on my list to check.

wjamyers

BTW, yes I did search for "P0506" here and there were only three threads containing only one claim of success, not even from the OP, the resolution being clean TB and reset "battery" (ECU, i guess).

I also searched for Mil.Spec-specific instructions for cleaning the TB, I just want to make sure that if they exist I follow them.

And I will not leave this thread dead after I resolve this issue as the others did.

Aby@MIL.SPEC

iTrader: (161)

check your iac = borrow 1 from a friend. honestly a 5 minute swap over. Generally, when the iac fails, it doesnt close; or so what i have seen, then the thing will idle high.

if you were to unplug your iac & start it up, the engine should rev to ~2300/2600 rpm. if you unplug it, make sure the engine is warmed up first.

can you verify that the tps is fine as well, with regards to idle voltage & WOT?

im 99% confident it doesnt have anything to do with the tb, as there isnt a whole lot that will make your car suddenly idle at 500 rpm.

how does the car drive otherwise?

wjamyers

I don't know how to verify the tps, I'll look into ... I don't think this is a problem with the TB either, but perhaps the tune?

The car was completely fine for many months and now, when you're on the throttle and it climbs past 1000 RPMs, it seems more or less normal.

But I did want you guys to confirm the Mil.Spec TB cleaning procedure before I started... remove it? Use CRC? Avoid scrubbing the inside? Hoping to hear it from the horses mouth.

Aby@MIL.SPEC

iTrader: (161)

how many months is "many"?

there shouldn't be a reason to clean the tb, even after a few years.

what is getting on the tb?

do you have evoscan or know someone who does?

have you tried unplugging the iac yet? no tools required & takes less than 5 seconds to disconnect.

wjamyers

I guess 18 months or so, you know you're getting old when 18 months feels like 6.


I'll take your word that it's not likely it needs cleaning. I do have evoscan and it worked to pull the code so I expect it's fully functional. I haven't had time to do the IAC check, had class after work tonight. Maybe tomorrow night. Will let you know. Thanks very much for your help.

wjamyers

As soon as I started looking at the IAC the problem was obvious... the damn screws were loose!

Tightened them back up and reset the battery and went for a drive... vroom!

Sorry to waste people's time, but at least anyone who searches re: P0506 can find out to make sure their IAC is tightened up.

Does anyone know the torque spec? I tend to break stuff so I have to be really careful not to over torque things (especially tiny little screws going into aluminum) and then this type of dumb crap happens. I have a little HF 1/4" torque wrench that measures in/lbs.

wjamyers

Never mind:

Erik@MIL.SPEC

iTrader: (94)

Glad you solved the issue

Now go enjoy the heck out of that MIL.SPEC TB

wjamyers

silkey smooth...

wjamyers

the low idle came back pretty much immediately.

When I finally took the car to Moore Automotive, they said my spark plugs were badly fouled causing the low idle causing the CEL. I guess going from a 70mm to a 65mm TB without tuning resulted in running too rich which is why it took months to finally cause problems with fouling.

just posting an update for everyone else to learn from my mistakes. changing throttle bodies? tune your car!

wjamyers

It was more complicated than that, even.

The first hot day I was driving around the exact same thing happened. I drove it home and immediately switched back to my original OEM IAC and ... problem solved. Again. For now.

So, looks like a compound problem, exacerbated by my originally just chucking parts at it.

FYI