Error Code P0101 and Idle Air Controller

97 Buick Lesabre Ltd 3.8 L 78890 miles - replaced MAP and MAF sensors, general tune up, air filter. Since replacing MAP and MAF sensors at cold starts car rough idles and dies. What is going on?? Alarm code is P0101.:runaround:

That's a code for the MAF sensor. Did you try putting the old one back in?

I recently encountered an identical situation. The vehicle had been at at least one shop previously, and had a new MAP, new MAF, new PCV, new TPS, new plugs, wires, and coil packs, probably a new ICM (I couldn't tell since I didn't disassemble it, but it was very clean for a 1996) and who knows what else. That was in addition to new brakes, struts, tires, and all sorts of other hints of a well-maintained car. The old MAF was still in the trunk when the apparently frustrated owner traded the car. The new owner nearly stole the car, and I discovered the MAF electrical connector was failing intermittently. The new owner was utterly ecstatic to get a very clean, rust-free, 130K mile PA Ultra for $925 and a few hours of my diagnostic time. (License, title, taxes, and fees extra. Etc. Etc...) I'm thinking the car is easily going to outlast her. She let me keep the old (good) MAF since they are about $145 new, and I'd use one long before she would.

Moral of the story? Hook up your scanner, read the MAF frequency or percent, and start playing with the connections.

don't have the old MAF sensor, but i was told to install a new idle air sensor. do you know where it is located?

does anyone know where the idle air sensor is located on 97 buick lesabre ltd? where can I find a photograph?

Good info at autozone.com, repair guides.

mbhudd,

Your two threads concerning your issue have been merged together and retitled. Please try to keep one thread only on a similar issue.

There is no "idle air sensor" per se. There is an idle air control (IAC) which is used by the PCM to admit extra air and control RPM. The IAC is mounted on the rear of the throttle body, and looks a lot like this:

http://www.finemotorcars.org/files/231V-6ThrottleBodyID.jpg

It is nothing more than a two-coil stepper motor which controls the position of an air inlet valve pintle, just like a digital EGR valve does with exhaust. It has absolutely nothing to do with the Mass Air Flow sensor's ability to measure intake air. Unless there is an intake leak downstream of the MAF, the MAF should indicate actual air intake mass.

It's never a bad idea to make sure that both the throttle body and idle air control are clean, but again, neither of those will affect the MAF reading.

You can also clean the TFT sensors on a MAF. However, since your's is new it shouldn't be necessary. The fact that both the old sensor and replacement sensor are apparently doing the same thing indicates the problem is not the sensor itself. Something is causing a lower than expected MAF reading at a given engine RPM and throttle position.

Verify that there are no leaks in the intake, including the power brake booster, PCV valve, all vacuum lines, the MAP sensor connection/grommet, the throttle body gaskets, intake ducts, and injector 'O' rings. Make sure the MAF electrical connector is clean and fully seated, and that the MAF has a 12VDC power supply on the pink and black (or black/white) wires.

EDITED IMAGE - AARRGGH! BNaylor beat me to the punch.

For what it is worth I just happen to have a pic of the IAC on a SII 3800 engine in my collection. :wink:

http://i5.photobucket.com/albums/y186/lizzywiz/3800tb.jpg
IAC circled in green

Every year around this time Labor Day weekend I clean all MAF sensors with MAF spray cleaner and the IACs with throttle body spray cleaner on all 4 of our GM cars. Plus replace supercharger oil on two of them.

Just trying out the new Sony Cyber-Shot 7.2 mp digital camera today. Gonna take a while to get used to it. :crying:

http://i5.photobucket.com/albums/y186/lizzywiz/iac_01.jpg
SII 3800 Throttle Body with IAC, TPS and MAF sensor


http://i5.photobucket.com/albums/y186/lizzywiz/iac_2.jpg
IAC Removed, Cleaned and Showing two Torx T20 Scews and O-ring Seal


http://i5.photobucket.com/albums/y186/lizzywiz/iac_3.jpg
Cleaning TB IAC seat with STP Throttle Body Spray Cleaner

Uh, can we get this in focus, my 66 year old eyes are enough of an issue.

Uh, can we get this in focus, my 66 year old eyes are enough of an issue.

NO!!!! :lol:

Not 'til I figure out how to use it Shep. Auto-focus but it has a mind of it's own. Actually more of just a lighting problem and figuring how how to use the zoom. :tongue:

Nonetheless, the pics are good enough for government work and I believe the OP gets the message. :wink:

For SHAME!

http://i5.photobucket.com/albums/y186/lizzywiz/iac_2.jpg

Not for the out-of-focus photos, but for the apparent lack of anti-seize compound on the screws for the IAC. ;)

And I'm hoping that the IAC gets disassembled so that the pintle rack gets cleaned and lightly lubricated:

http://72.19.213.157/files/IACDisassembled.jpg


BTW - I'm now officially jealous, since my 4Mp digicam no longer makes the grade.

P.S. We can see what your left hand is doing, but where is that right hand? Never mind -I don't really want to know...


As for mbhudd, now that you can find the relevant components thanks to BNaylor's photos, you can see what we've been trying to convey. The IAC can (and probably should) be cleaned periodically to maintain peak performance, as well as the MAF sensor's TFT array. However, but your new MAF should not require it, and a dirty/sticking IAC cannot affect the MAF reading. Only an external leak at the IAC can affect that.

You might want to verify that the throttle body bolts are tight so that there is no vacuum leak (be careful about over torquing the screws) and check all the other vacuum connections on the plenum. Since the MAF will be sensitive to any vacuum leak, the EGR should also be suspected, along with the other items mentioned perviously, and the CCV tube, the oil filler cap, the vacuum supply to the HVAC controls, and anything else which could leak intake vacuum.

You might also want to remove the air inlet hose from the throttle body and clean the TB inlet screen (if there is one) to insure that air flow across the MAF sensor is not obstructed. One errant leaf, insect, or accumulation of varnish or dirt can affect the flow through the MAF tube.

After all that, and verifying the correct voltage at the MAF electrical connector, you may require a scanner to read the MAF frequency to aid in the diagnosis.

the apparent lack of anti-seize compound on the screws for the IAC. ;)

I don't use anti-seize. Actually if you look closely there is old threadlocker on the two Torx T20 screws which was removed and new applied. :wink:


And I'm hoping that the IAC gets disassembled so that the pintle rack gets cleaned and lightly lubricated:

I wouldn't hope too much. :grinno:

Personally, I wouldn't go that far unless absolutely necessary which in most cases it is not. Last member I recommended that to made a mess out of it and wound up buying a new IAC. Mine are in really good shape so I just spray the TB cleaner on the spring loaded pintle and gently wipe off with a rag. Then spray with silicone lube. IMO important part is to get the carbon off that dish at the end of the pintle part and out of the IAC throttle body seat where the air orifice is located as far as routine maintenance. :grinyes:


P.S. We can see what your left hand is doing, but where is that right hand? Never mind -I don't really want to know...

:lol:

Multiple choice:

1. Taking the picture.
2. Scratching my balls.

:rofl:

Thanks everybody. The problem was the idle air control -not MAF, MAP, fuel pump, manifold, etc. Replaced the IAC and she runs like the day she came off the assembly line and I got possession of her. Just wish with all the technology and the on board computer it could have pinned pointed what part was malfunctioning and needed to be replaced before I spent money on unneeded replacements that were costly. Live and learn - go to Advance Auto or Auto Zone and describe symptoms before taking the word of mechanic who is reading the computer read out.

Thanks for the feedback mbhudd and congratulations. Did you at least try cleaning the IAC before replacing? Actually the P0101 DTC was telling you the general area to look at and was not indicative of solely a bad MAF sensor. That requires proper troubleshooting and a good course of diagnostics based on either experience or proper documentation like a GM FSM. However, having said that and contrary to belief a bad IAC or an IAC giving high IAC counts will cause a MAF system/range/performance problem and may show as a P0101 or P0102 DTC. MAF, MAP, TPS, PCM module, dirty throttle body, etc. are other possibilties but possibilities only. Based on what I see sometimes you have to go through all the possibilities before finding the actual culprit so don't feel bad or alone unless you get lucky and hit it on the first try.

Incidently, one of the tests for MAF troubleshooting per the GM FSM is to command the IAC valve to extend fully which will give zero IAC counts. The MAF low frequency and/or range tests are dependent on a proper idle. An IAC driver test fixture J37027 is normally used as part of the diagnostics but not all mechanics or DIY'er have the fixture readily available in their tool boxes. :grinno:

Therefore, IMO a bad IAC is both plausible and feasible as it pertains to your specific problem.