Engine dies at an idle (TPS?)

[blkfordsedan]

Well, this is the FIRST real problem I've ever had in 147K miles of driving.. This is my '93L, B3 EFI, 5SP, no A/C.

I noticed the engine would occasionally die when idling and the idle was a little erratic, but only once in a while. It was that way for several months until yesterday. Now, every time I stop and take my foot off the gas it just dies. In addition, if you try to apply more than 3/4 throttle during acceleration the motor misfires and blows a cloud of light blue smoke out the exhaust. I'm thinking it was loading up on gas, but the smoke is not the typical black associated with over-rich condition. My first thought was a bad TPS or coolant temp sensor. I installed a used TPS off my parts car (which ran fine when I parted it out) and the problems were fixed...OR SO I THOUGHT!

Later today it started acting up again. The idle drops and the engine dies as soon as you let off the gas. However, the 3/4 throttle issues appear to still be fixed. Also, I just noticed that the idle issue ONLY happens when the headlights or fan blower (heater) are running. If no accessories or lights are on, it idles perfectly smooth at 750RPM. I have 2 guesses that I'm thinking of:

1) I need to adjust the new TPS sensor (but I can't find my Haynes manual for the specs)

2) The IAC is suffering from a lack of voltage when I turn on the lights or blower motor. That means I have a bad connection or electrical issues with the battery or alternator or something.

If anyone has any other ideas or experiences, please share!

[eurotiva]

Just for jollies check your pcv valve.

I'd try to check the alternator also. I've had similar problems with a weak ALT.

[blkfordsedan]

Just for jollies check your pcv valve.

I'd try to check the alternator also. I've had similar problems with a weak ALT.

I'm 99.9% sure the battery is junk. With the car off, no load, it shows 12.4 volts, but as soon as I turn on the headlights the battery voltage starts dropping faster than Obama's approval ratings. It drops below 10.00 Volts in a matter of seconds. It's gotta be voltage starving the computer as soon as I turn on the lights. I'm gonna get a new battery @ WalMart in the morning and check out the alternator, just in case it's weak and caused the battery to crap out. I'll post when I get it fixed.

[doylerl]

I would have to agree with the PCV valve comment by Euro. My '92 was doing this when I got it, and that seemed to fix it. The rubber gromet it goes into may be brittle and falling apart as well. They sell replacements at Advance Auto. Good luck, and let us know what happens.

[blkfordsedan]

Quick update:

The battery checked out O.K.....so I cleaned all the terminals and reinstalled it. Once again, it seemed as thought the problem was solved. I took it for a test drive and it will now stay idling with the lights & heater on, but the rpm drops to almost 100 RPM when you push the clutch in and let off the gas and then recovers back to 750 RPM.

I figured it would be wise to clean out the IAC, so I pulled off the air intake tube that goes from the VAF to the throttle body. As soon as I pulled it off, at LEAST half a quart of oil came pouring out of the tube and all over my shoes! There was oil puddled in the throttle body and the flapper door area of the VAF. I pulled the throttle body off and cleaned out the air intake tubes & all the hoses connected to it. The IAC was full of a lot of carbon as well. Tomorrow I plan on changing the plugs and putting it all back together. Then I'll figure out a way to keep the "blow-by" from pushing oil into the air intake tube. I'm thinking about just connecting a hose from the nipple on top of the valve cover (by the filler cap) directly to the extra vacuum port on the intake. Hopefully, after a few thousand miles of conventional oil and a treatment of Restore, the blow-by will improve. If not, then it's time for a B6 or B8EM swap. I just hate to give up the 48.3 MPG I got on the last tank!

For those who are not familiar with my other thread in this section about Pennzoil Platinum Full Synthetic and a high mileage engine, you may want to take a look at it........

http://www.fordfestiva.com/forums/showthread.php?t=29664