93 lumina euro 3.1 auto

[kleeven]

we have a 93 lumina mls uknown ran well for a year. replaced battery found out that alt had no output r&r that also now idle lopes rr mat and tps according to the 23 code pulled out
at stop car revs up and down sometimes will die and sometimes not car runs perfect at higher speeds
idles at cold start after will rev up and down will die but will restart
lost for next move need help

[cjslumina]

Try oxygen sensors.

[Kooterskkar]

Replaced the IAC valve yet? Might also try looking for a small vacumm leak by the throttle body.

[kleeven]

if the mat - iac are the same then yes
have not looked for vaccum leaks yet we keep these cars busy

[Kooterskkar]

Ive never heard of a mat sensor. Do you mean the maf/map sensor?
IAC is Idle air control valve. Its mounted to the front side of the throttle body(facing the front of the car). What happpens is they get covered with carbon from the egr and it will get gummed up and get stuck. The ecm tries to adjust the idle and when the valve pintle doesnt move it will try even harder and jump past where the ecm wants it to be. Then it will try to move it back and the same thing happens.

[richtazz]

MAT sensor is manifold air temp sensor, and is not the same as the IAC. The IAC adjust air flow at idle and part throttle, and is mounted on the side of the Throttle body. I agree with Kooter that it is the source of your problem.

[RCSpeed]

Its good that you posted that you replaced the battery. Thats when the trouble started. Your ECM (engine computer) lost its idle strategy when you took away its memory power by unhooking the battery. To perform the relearn, its best to do it in 2 steps. First, clean the throttle body (where the big butterfly is) with carb cleaner. Unhook the air intake hose that connects to it, soak up a rag with carb cleaner, open the throttle wide open, and get in there with the rag and clean out as many deposits as you can. Button that back up. Start the car and let run a couple minutes, until the idle stablizes a bit and slows down. Block the wheels so the car can't move. Put in a forward gear and let off the brake. Let it idle for 10 minutes. Put in park and shut off. Wait 20 seconds. Restart and put in gear, let off the brake, idle for 5 minutes. Repeat these 2 steps again, going 10 min. and then 5 minutes. Your idle strategy is now relearned. If your car gets to surging excessively, you may have to shut off and start over. Good luck!

[kleeven]

well the iac is repaced nochange lot of fuel in the hose after the air filter chkd for vac leaks found none any other insight?

[RCSpeed]

Do the idle relearn as I suggested. That will fix it.

[kleeven]

no idle still surges seems a littlr more stable but still has a surge also seems to be over fueling black smoke a the tail pipe and some coming out the throtle body housing after ignition is switched off

[jeffcoslacker]

Have seen defective coolant temp switch lead the ECM to control the motor as if it was extremely cold (forcing rich). Does it run better before it warms up? Or fuel pressure regulator shot.

[kleeven]

have not checked that sensor yet will idle smooth for about 30 secounds then starts to surge one more question the three vaccum hoses on the side off throttle body are any of the supose to carry fuel to or from the throttle body

[jeffcoslacker]

Vacuum hoses pull air, not fuel. There is no fuel supply to the throttle body. There is a coolant line. If you are sucking air at any vacuum port, stange idle can occur. You can spray water in a mist all around the intake and vacuum hoses. If it is drawn in by a leak, idle will stabilize momentarily. There should be nothing being drawn into the intake anywhere but the air box.

[jeffcoslacker]

Check your PCV valve. Should feel the ball rattling inside it. If not, replace it.

[richtazz]

if you have fuel in the intake, you either have a bad intake gasket, or a leaky fuel pressure regulator.