With the IAC closed and disconnected the car runs good under throttle, but idles poorly. With the IAC connected, the idle is worse, and the car reeks of gas like its waaay rich. Anybody know why? I've been fighting this since I changed to a manual trans and put headers on the car. its an 89 TPI 5.0.

 

When you put headers on the car did you remove any o2 bungs?

 

Nope. I used hooker 2055 shorties. even installed a new O2

 

Have you checked out the injectores with vom?
Has any changes been made to the prom?
clogged fuel filter,injectors
Is it possible you accidently shorted out the o2 sensor by touching wires together while battery was connected?Have you adjusted and/or replaced IAC?

 

Have not checked injectors. They are the originals. I've got a set of FICs 22# Bosch IIIs. Can't put them in until I get a chip to support them.

No changes have been made to the PROM to my knowledge and I've owned the car for a long time.

Seems like I changed the fuel filter a few years ago. Its not plugged enough to be the problem, I know that.

NO idea about shorting out the o2 sensor. Seems like it only had one wire anyway.

I have replaced the IAC. How do you adjust it?

Whats that sensor in the plenum towards the back? I forgot to reconnect it last night when I put the plenum back on. Now I've got a 'service engine' light driving to work this morning.

Last night it ran better than it has since changing exhaust and transmission. I took it all apart for an AFPR and put it back together. Idled at about 1000 but rock steady with the IAC connected. This morining, the idle wont go below 1300 and is rough. I've got the butterflies completely closed and still a high idle. I wonder about the throttle body itself....if the bushings are so shot that they're leaking enough air to be a problem.

I've looked for vacuum leaks again and again and don't find any.

 

There is a thread on adjusting the IAC on the main page in the tech articles or just search for it.

I think the sensor in the back of the plenum is the mat sensor manifold air temp.Atleast that sounds like what you`re refering to.It needs to be hooked up.Some people move it further up in the intake track.

I have read of people having worn TB `s causing vacume leak.They can be rebuilt I believe.I forget how the checked it.With some sort of smoke or something.

 

I'll search for the IAC adjust. Can't hurt. Thanks

 

Any luck yet?Just curious,like to hear what the problem was on some of this stuff.

 

Did you change the Prom for a manual tranny?

FWIW, the IAC (which could be your idle issues) has no bearing on running rich/lean...it's justy a controlled vacuum leak to idle up the engine on cold starts, and keep it running when you let off the go-pedal.

Kinda think you have a few seperate issues...running rich-is this at start up? Or once the car is warmed up? If when warmed up, you might (depending where you put in the O2 sensor) need to relo it, or run a heated O2.

The idle issue, I'm dwelling on the manual conversion, as I'm sure the Proms are different for each, so start with a stock PROM form a 305 manual tarnny car and see where your stand.

 

IAC, TPS, O2 are all new. I did not change the prom, though I will in the next few weeks.

I replaced the gasket between the throttle body and the plenum and gooped up the vaccum nipple that goes to the cruise control servo. That line looked to be in good shape, but fit a little loose so I siliconed it up a bit.

After these two fixes, the car idled great...smooth and about 900 rpm (by the dash tach).

Next day, on the way to work, the car would die everytime I coasted up to a stop sign and pushed in the clutch.

Sooo I adjusted up the minimun idle. Now it doesn't die on me, and its all much better. Still idles about 900-1000 however.

Finally I checked the injectors. Found 3 bad (under 12.0 ohms hot).

I suspect they are leaking, causing a rich condition to the ecm, so it's opening the IAC a bit to lean things back up, which is why I have high idle.

I've got a set of Bosch 3s on the shelf, but need to chip the ecm before putting them in since they are 22#.

Once the injectors have been changed, I think I'll be in pretty darn good shape, and be ready for a cam change.

 

You need a chip burned based on the 305 Manual trans calibration. The coast down idle return and IAC throttle follower are all wrong, assuming a 350 Auto calibration is being used. Really its not that hard to make the 350 calibration work with the manual trans or the 305 manual trans calibration to work with the 350. I am assuming you have a fully functional VSS and all. Where around Fort Worth are you? I am in Bedford myself.

Order this from Moates and we can chip your ECM to a G92 TPI 5spd calibration. I am assuming you are still running your stock 165 MAF ECM setup. We will put a nice little base calibration for the 305, stick, 22# injectors and a performance minded timing map.

http://www.moates.net/product_info.p...products_id=41

Here are some of my tuned shots.

http://s243.photobucket.com/albums/f...t=100_1477.flv

http://s243.photobucket.com/albums/f...t=101_1472.flv

http://s243.photobucket.com/albums/f...t=100_1478.flv

http://s243.photobucket.com/albums/f...t=101_1471.flv

Finally, I need gears, transmission work, and stickier tires, but heres the half *** acceleration run.

http://s243.photobucket.com/albums/f...t=101_1468.flv

 

Hey...didn't even notice you're local, Fast. I'm in Watauga up next to Keller just off Hwy 377.

The car was originally 305 auto, now 305 stick. I doubt I have VSS going on since I never hooked the speedo cable back up to the tranny. My car had a cable drive and the T-5 I used has an electric drive. I've got the adapter and stuff, but need a drive gear.

 

I am very local, 377 is not far at all, I am down where 183 and 121 run togather.

VSS for most calibrations are essential to get the proper idle. Without VSS things will definately not run right. In most calibrations the IAC will not reset to 0 counts without the vehicle reaching and maintaing a steady 30-40 mph. Once it reaches and maintains the required steady speed, the computer will pulse the IAC for a couple of seconds to ensure it is fully closed, then re-opens it X counts. In most calibrations it does this many times during a normal drive. This ensures the computer can adequately judge the IACs position. If it will not reset to 0 counts and fully closed, the ECM has no way to know where the IAC is and the idle will be erratic.

Some calibrations also use the VSS calibrations to control BLM cell in use and some run a seperate idle mode fuel/spark mode.