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new 4/15/2004

Well got a SES light this morning and pulled into Autozone to get the code pulled. It was P1121, Idle air control. The price at Autozone is $39.99.
Could this be the reason that my car has been cutting off right after I crank it? It will run for a few seconds, then die. After i cut it off and restart it, it will run fine. Also having a problem with it cutting off sometimes while going down the road. Most of the time it will happen after a hard acceleration. Any comments or suggestions will be appreciated.

Mike Bouchillon
97 Pacific Green


Sounds reasonable. Basically, what the IAC does is allow some air through to keep the engine running when the throttle is closed. If your engine dies when the throttle isn't depressed, this would be the problem.

Wait a minute. P1121 looks like a TPS problem, see below.



Code P1121 in my book reads
Throttle Position Sensor "A" Inconsistent With Mass Air Flow Sensor. If
that's of any more help.



I concur with Paul. Per the website, P1121 is "P1121 TP Sensor Inconsistent With MAF Sensor "

P1501-1511 are the codes related to the IAC. Was the code reader being read in a mirror or something? That would get you 1121 out of 1511. If it was upside-down, you'd see 1211, which is related to injector pressure.

If the code hasn't been cleared out of memory yet, you might want to have it pulled again and verified.

-John Breen III


Indeed if the IAC were acting up it would cause the engine to stall,
especially after the initial start. I would take it off and spray it with
some cleaner first before replacing it.

Paul Nimz


The IAC is actually a duty cycle servo. There is a pintle and seat controlled by an electromagnetic servo. The % of IAC is a representation of the duty cycle and the pulsed ground from the PCM. The more duty cycle, the farther open the IAC valve is pulled and the more idle air is allowed into the engine.

Remember too that the data stream is not a I/O interface. It's a representation of what the computer is seeing and commanding.

Doug Lewis


 IAC should not be in play except at idle or other closed idle situations. But even if it was malfunctioning then the IAC would have no effect when the throttle is open.

Paul Nimz


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