idle problem. Vacuum? MAP sensor? Brake Booster?

[jdyates]

Not all the time. Lots of factors. Engine temp, mixture, compression, throttle blade % open, load, etc all affect vacuum. Check the difference between low and warm. I swear you've got a vacuum leak, if you're idling warm at 975rpm, lol.

It was the scanner. Both seperate scanners ive used have a diagnostics mode that makes the truck idle higher when making the graphs. Normally idles at like 400-500 when its popping out of the exhaust and hesitating.

 

[great white]

Snap on scanners suck for anything but pulling DTC's IMHO.

I'm going to guess you have not DTC's present in either active or history?

If you do have some in history, pull the freeze frame data....

 

[jdyates]

Snap on scanners suck for anything but pulling DTC's IMHO.

I'm going to guess you have not DTC's present in either active or history?

If you do have some in history, pull the freeze frame data....

No sir, not a single one.

 

[1997chevydriver]

Here's mine in park

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[jdyates]

Here's mine in park

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Wish mine wasn't obd1 . Give me few mintyes, i'll post up some data.

 

[jdyates]

Here's a few pics I snapped while it was hooked up. Idle, in park. Sorry for the glare.

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[jdyates]

Got another symptom. I'll admit I was getting a little too exited with the throttle tonight, and went WOT under an overpass (wasn't showing off or anything, I was the only vehicle on that road), and all of a sudden, the check engine light came on. Drove home carefully, and I didn't notice any change in the way it was driving. Got home and came up with these codes:

34-MAP sensor problem, the scanner shots above show the data for the current sensor.
and
43-ESC circuit malfunction.

Any ideas?

 

[Yeti_Owner]

A massive vacuum leak can throw the MAP code.

Did you ever try to disconnect and plug the vacuum line for the brake booster, to see if that helped?

 

[great white]

In this case, code 34 indicates high vacuum, not low:

33
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR (VOLTAGE HIGH-LOW VACUUM)

34
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR (VOLTAGE LOW-HIGH VACUUM)

code 33 is the one that could be associated with a vacuum leak, not 34.

Conditions for setting code 34:

1.Engine RPM less than 700.
2.Manifold pressure reading less than 13 kPa.
3. Conditions met for .22 second.
OR
1. Engine RPM greater than 700.
2. Throttle angle over 20%.
3. Manifold pressure less than 13 kPa.
4. Conditions met for .22 second.

MAP sensor could be at fault. Whacking open the throttle blades normally results in low vacuum, not high.

43
ELECTRONIC SPARK CONTROL (ESC) CIRCUIT

This could be a red herring, potentially a transient condition as a result of your "friskiness". Or it could be a valid fault.

Clear the ECM and see it they return. I wouldn't trouble shoot them until you prove they are actually there as faults. If they are actual faults, the codes will return....

 

[Yeti_Owner]

Gotcha - I defer to GW, he's the guru