Idle problem

Tiny
NGANT17
  • MEMBER
  • DODGE CARAVAN
I have a 1996 Dodge Caravan with 2.5l 4-cylinder motor. 130k miles. The engine runs fine except at idle. The motor sometimes dies when I come to a stop. I pulled off a vacuum plug and the motor ran a little better, but as soon as I put the plug back on, the motor shuddered a little then it stalls out.

I checked vacuum with a guage, it seemed normal. 15-16 units on the guage. I looked at air filter and it appears okay.

I cleaned throttle body with cleaner.

I ran a scan test with an OBDII code reader, it says the downstream O2 sensor is bad, code: PO140, no activity. I read where the downstream sensor doesn't affect idle, but if the upstream O2 sensor is bad, it could affect idle.

Compression check,

dry wet
#1 205 210

#2 210 225

#3 210 220

#4 210 220

wet test done after squirting small amount of 30-wt. Motor oil in cylinders, compressions taken with all plugs removed. Mininum 4 cranks. Pressure is holding at those numbers on all cylinders.

Haynes manual for 4-cylinder specs are showing between 170-225 psi as acceptable.

Based on those readings, I would say the cylinder head, piston rings and engine bores are good. The car appears to have good acceralation although there are no steep hills in area to test a load.

Should I be looking at replacing the Idle Air Control(IAC) valve?
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Thursday, May 3rd, 2007 AT 6:28 PM

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Tiny
LES DANE
  • MEMBER
Check voltage across MAP sensor.
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Saturday, May 5th, 2007 AT 11:37 AM

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