Having some trouble with my idle following the installation of my new shortblock/cam (230/224). Just checked Autotap, and I'm throwing code P0107 (MAP Sensor Circuit Low Voltage).

I've not thrown this code (or any like it) before. I'm guessing this code could be the cause of my idle issues? Specficially, my idle is "hanging" (typically around 1100-1200rpm) upon deceleration until the vehicle is perfectly stopped (specifically, when the speedometer reaches zero).

Also, I was having the idle hang as high as 2000-2500rpm It would also climb that high whenever I took the car out of gear and stay there until I put it in gear (it still stayed high and tried to pull pretty hard). Just noticed that the TPS was staying around 0.4%, so I went ahead and loosened up the throttle cable a hair; now it's sits at zero and I haven't had the 2000-2500rpm yet (knock on wood).

Anyway, any ideas on how to fix the P0107 code and cure my idle issues would be greatly appreciated!!

Sorry for the long post; I've done quite a bit of searching and haven't been able to find anything specific to P0107.

*** EDIT ***

Also forgot to mention; I'm seeing something pretty weird with my IAC counts. When idling, they typically start in the 30s or 20s and then slowly start dropping by 2 until they stop at 0 I'm not an expert, but that doesn't sound quite right. Should also probably mention that I went ahead and installed a ported throttlebody with my new shortblock, so I'm wondering if this could be causing the IAC problems??

Help!!

*** EDIT ***

TIA

 

Just made another run and logged the only MAP-related thing I could log (Manifold Absolute Pressure). Read steady at 10kPA the whole time..

Does that sound right??

 

sonds to me liek you drilled your TB hole too big. fix that first get IACs doign what they should be and make sure there are no vacuum leaks

 

02bluess,
Just wondered if you ever found out why your IACs slowly drop to zero? I'm having the same problem!

 

With the engine running, the MAP output V should vary from about 1 to 1.5 V at idle. At wide-open throttle it should be about 4 to 4.5 V. This signal is sent to the MAP sensor input signal terminal on the PCM. With the engine off and the ignition on, the manifold pressure should be equal to barometric pressure and the signal V will be high, close to 5 V at sea level. This 5 V is based on the 5 V reference line.

First, check the fuses in the two fuse panels located under the hood. Then check your V, REF and GND for problems.

As for the IAC, verify that no air is leaking around the IAC motor. Also try resetting the PCM. If the IAC valve is disconnected or reconnected with the engine running, the PCM will loose track of the actual position of the IAC. Also, your readjustment of the Throttle cable might have caused this. Now, to explain why I think this, the reset procedure goes like this:
The PCM commands the IAC valve to shut the idle air passageway in the TB. It does so by issuing enough extended pulses to move the IAC valve pintle fully shut in the bore, regardless of where the actual position was. Then, the PCM calculates the IAC valve is at a fully shut position, and calls that position 0. Next, the PCM issues retract steps to properly position the pintle.
Otherwise, you might have a bad IAC motor or TB drilled too large.


Added: If you turn on your AC, the IAC should rise to compensate.

 

Thanks for the ideas, Cat. I just backed out the 5 degrees of extra timing I had put in both the base spark tables at 1200 rpm and below to address the big cam lope. Now I'm doing a PCM reset (battery disconnected for 30 minutes.) Hopefully, this will help. MAP output looks good. I did drill the TB out to 13/64", but the problem existed before that. I have so much slack in the throttle cable that I can't even get 100% TP anymore, so I don't think that is it. I'll try resealing the IAC motor tonight. With EFILive5 I can see the IAC trying to do it's job, but it falls short on both ends. With the AC on, it can't seem to flow enough air to keep the idle at 950 rpm, and with the A/C off, it can't seem to stop enough air to keep the idle down to 950 rpm. This all started when I bumped my idle up from 800 to 950 for the new cam.

 

Not correct, as engine RPM increases so does MAP in KPA.
At idle it should be around 30 to 40 KPA depending on mods you have and when your in WOT would MAP be 80 to 100 KPA.

Being it is staying at one value I would 1st check to see if MAP is still connected or its wires broken or

You have vaccum issue from install of internal engine mods ?