qwiketz

Hi guys. My car was working fine a few years ago. The car sat for an extended period of time because I burned up the transmission. Anyhow, once the trans was repaired, the car would die when I let off gas while driving.

A year later, I'm trying to get the car running. Just driving around the neighborhood, it dies everytime I let off the gas and don't shift into neutral and rev it.

The tune is the same except I added a new fuel pump. The car is running rich, but I'm thinking that the iac may not be working. Should I pull the throttle body and clean it and the iac?

Also, where is the best spot to pickup a throttle body gasket and the iac gasket? I went to the dealer today and they are out of stock and discontinued.

Thanks!

toptechx6

Is the speedometer working after the transmission replacement? The speed sensor is one of the inputs used by the PCM to set IAC and prevent a stall when coming to a stop. I would pull the codes and make sure the PCM is seeing that signal before doing anything else.

qwiketz

Well, I'm back from vacation and took the car around the block again today.

The car started pretty easily, idled for a about 15 seconds at a decent rpm and then the rpms started to drop to about 550 or so. 550 with the tune in the car is low as it always idled at about 650-700 once running and I never had a problem with the car stalling after being started; at least for the first 6 or 7 years I have had the car. It has been getting progressively a little more "finneky" as of recently (the past 2 years of mostly sitting).

I hooked up datamaster to see what was going on with the IAC. It pretty much said 160 and didn't change. From checking my old data logs, it would be in the 80's and 90's under throttle and in the 60's and low 70's while decelerating. It would be in the high 50's upon stopping completely.

I tried to record the datalog, but it stopped recording when it stalled out and I had to restart the car. It's been a while since I've used this program, so I'm not the quickest on the fly.

Also, of note, the car was running rich as my wideband told me previously; the 02's were in the mid 500's at idle and part throttle.

Datamaster did indicate that the speedo was working; I got the car up to about 5 mph while just driving at near idle around the neighborhood. It also showed 1mph as I was backing out of the driveway.

When driving, if I don't very, very gradually get off the gas and then go to coasting, the car dies. The car has quite a bit of trouble recovering, even if I put it into neutral and give it a slight amount of gas. I stalled about 3 times going about 150 yards each way down my street.

With the iac reading 160 and not moving, should I just replace it or are there any other things that I need to look for or test on it?

Thanks!

65Z01

If manifold vacuum holds well the IAC would be my next choice for service.

What kind of BLM & INT values are you seeing now?

I'd always gotten the FelPro top end gasket set from AutoZone for the TB and other such gaskets, though I'd not found a new IAC gasket source.

To cleak the IAC bore I used a tightly would cottom swab & TB cleaner, being careful to not leave any threads inside the bore.

ToniJ1960

Maybe try the foam swabs? They were great for cleaning vcr heads.

qwiketz

Hi guys. Thanks for the input. I pulled the throttle body this morning and am in the process of replacing the part.

I thought it would be a 1 day deal, but it's going to take a bit longer. At autozone, I bought:

http://www.autozone.com/autozone/par...mString=search

but I really need this:

http://www.autozone.com/autozone/acc...er=168206_0_0_

or this:

http://www.autozone.com/autozone/acc...uestid=1169296

I basically need the one with the flange. What I've learned as the flangeless is on the 93 f body and the flanged is on the 94-97 from what the internet images show. The plug is different also.

qwiketz

I also bought the stock throttle body gasket but I have an Arizona speed and marine one that is larger than stock.

One thing I did notice is that my intake's runners are completely cnc ported all the way to the plenum.

qwiketz

Anyone have any preference on what unit to pickup as a replacement? Being that I have to order one, I can order from wherever. I'll also need to hunt down the gasket as well. I went to the az speed website and it looks like I have a dual 58mm.

qwiketz

ordered the replacement parts from summit today. Hopefully I'll have this back together Wednesday night!

Cliff Harris

If your IAC is really at 160 and you're running rich, I'd guess that your fuel pressure regulator diaphragm has ruptured and fuel is being drawn into the plenum through the vacuum line.

To find out: pull the vacuum line off the FPR. Turn on the ignition. Check for fuel coming out of the vacuum port on the FPR.

qwiketz

Hey Cliff, that's a pretty simple and interesting thing to try. I swapped in a bigger fuel pump and I was worried that it was going to give my regulator fits.

I'm going to button everything back up tomorrow and I'll try it. Stock replacement regulators are only about $40 if I have to fix it or I can go up to the aeromotive for about $169.

qwiketz

okay... I had a little time to work on the car today. I installed the new iac, new throttle body gasket and buttoned it back up.

afr is still 12.4 or around there. It's rich.
the iac is still maxed at 160
my boost/vacuum gauge appears to be reading normally
the car is having trouble idling. The idle is lower than usual.
no fuel out of the vaccum line to the intake manifold from the fuel pressure regulator

Any other ideas on this one?

hooked073

I would start with a base idle procedure. I would also do a TPS setting. If a load is placed on the engine like turning the ac on or anything where the idle would drop do the rpm up Im just wondering if given a need for the rpms to rise do they? My thinking is maybe you are not getting what is need for the IAC to function broken wire connection ect.

qwiketz

I know in datamaster, when the temp gauges aren't working or hooked up it says something like -40* or something like that. Being that mine is just saying 160 all the time, is that the same as it grounding out? Anyone have a schematic or know where or what to check/test?

qwiketz

Well, I idled and rev'ed the car while datalogging in datamaster today. I can email the .uni file that it recorded if anyone has datamaster. Or, I can list off some of the values that I saw if there are any particular ones of concern... The car idled okay today; it didn't sound perfect but it didn't stall out either once running.

I'm still figuring out embedding youtube links... but here is the link:

Cliff Harris

Your long term fuel trim is showing that you're running lean. That would happen if your IAC counts really are 160 (lots of air). I believe the IAC is limited to a maximum count of 160.

I also see you are getting a lot of knock counts and the spark is being retarded. That's not good (there's a reason it shows red). Running lean can cause that.

The ECM tests the ESC system by advancing the timing during startup and looking for knock counts. That will typically set a few counts (less than 10). You should not have any more knock counts while running. If you do that's a problem.

qwiketz

cool. thanks for the input Cliff. I'll reinspect the car. Perhaps I have left a line disconnected causing a major vacuum leak or something.

qwiketz

update...

So I tried the water method to try to find the vacuum leak with no luck. I tried making a homemade smoke generator but I didn't really see anything either.

I found a local shop about 1/2 mile from my house that I'm going to drop the car off at tomorrow. They're going to hook it up to the smoke machine and try to find the leak. Hopefully it works!

qwiketz

dropped the car off at the shop today to be smoke tested. They should have it done tomorrow morning.

I also replaced the header collector gaskets as the old ones were shot. The o2's were literally 4" from the collector so I hoped that it would have made a difference but it didn't. Little by little all the small things are getting replaced...

C409

..... I see that you are boosted ... have you looked at the FMU ? it might be thinking that there is boost at idle .... 160 IAC counts indicates that its full open trying to lean out the mixture ... you have extra fuel coming in , not extra air ..........