rough idle

[dannym]

about a year ago i replaced both head gaskets on my 87gn and car never ran right after that, car is all stock, car has been sitting all this time. don't really have time till today, here are scanmaster readings
AF-05
LB-68
BAT-13.9
INT-128
BL-110
CLT-171
ATS-69
TPS-.42
IAC-00
CC-2
MAL-34-24
R-750

after i ran it for awhile INT and CLT changed

INT-107
CLT-209

thanks

 

[MeanBuicks]

Have you looked for vacuum leaks? Your IAC being 0 is an indicator that you may have a leak.

Also, and this is a stretch, if you used RTV silicone during reassembly, was it marked as sensor safe? If not, it could affect the O2 sensor readings.

Oh, BTW, CLT is coolant temperature. It should go up over time.

 

[dannym]

Have you looked for vacuum leaks? Your IAC being 0 is an indicator that you may have a leak.

I sprayed carb cleaner around the intake, vaccum lines and there is no indications of vaccum leaks. I also check the EGR valve and solenoid for leaks and opperation.

thanks for your help

 

[Ormand]

At the very least, you should try adjusting the IAC to get it off zero. Don't know if that would help, but it will give the ECM one more "tool" to control the idle.

 

[Fakeyankee]

I also noticed that you are throwing codes 24 and 34. Look into what's causing those codes for starters. I think 24 has something to do with the speed density sensor and 34 for the MAF not sensing the proper air flow. As was said above, adjust your IAC within limits, which will cause your TPS to also need readjusting. Get both of those in line first and maybe it will idle much better. Also continue looking for vac leaks. Good Luck and report back.

 

[DonnieShort]

about a year ago i replaced both head gaskets on my 87gn and car never ran right after that, car is all stock, car has been sitting all this time. don't really have time till today, here are scanmaster readings
AF-05
LB-68
BAT-13.9
INT-128
BL-110
CLT-171
ATS-69
TPS-.42
IAC-00
CC-2
MAL-34-24
R-750

after i ran it for awhile INT and CLT changed

INT-107
CLT-209

thanks

INT and BLM numbers are way too low. Also:

Code 24 - VSS Fail


Trouble Code 24 indicates that the Vehicle Speed Sensor (VSS) is reporting an abnormally low reading when other sensors indicate it should be higher.

The conditions for setting this code are:

No Code 33 or 34 (MAF Error) is present, and
The vehicle speed signal indicates < 4 MPH and
Engine speed is between 1400 and 4400 RPM, and
During a low load condition (LV8 between 50 and 99), and
Transmission not in Park or Neutral, and
All conditions met for more than 20 seconds
If the code was logged when the vehicle was in motion, the following should be checked:

Defective or corroded VSS connections
Misadjusted TPS sensor. The TPS should read about 0.42 volts at closed throttle
Defective speedometer cable
Bad or missing speedo drive gear(s) in tail shaft housing of the transmission
Defective VSS
Defective ECM

Code 34 - MAF Low

Trouble Code 34 indicates that the Mass Air Flow (MAF) sensor is reporting less air is entering the engine than makes sense based on RPM and TPS. The MAF sensor produces a frequency output; around 30 Hz at idle to 150 Hz under acceleration. The frequency varies proportionally to airflow. The ECM monitors the frequency and thus determines airflow into the engine. Typical idle MAF is 5 to 7 grams per second.

The conditions for setting this code are:

No Code 21 or 22 (TPS Error) present, and
The air flow reported is < 4 grams per second, and
TPS indicates 10% or more throttle position, and
The engine speed is 1800 RPM or higher, and
The above conditions exist for over 5 seconds.
Typical causes for this code include:

Faulty MAF sensor
Faulty air ducting to or from MAF sensor
Faulty ECM-to-MAF connections
Poor routing of MAF harness (i.e. near coil packs)
Maladjusted TPS sensor
Defective MAF sensor
Defective ECM


You need to get these issues fixed otherwise you'll never get it to run right.

 

[dannym]

how do i adjust IAC?

 

[MeanBuicks]

IAC Reset Procedure

Service Manual Procedure

1. Ground ALDL diagnostic lead (short the top two rightmost pins in the ALDL connector).
2. Turn on the ignition (but don't start the car).
3. Wait 30 seconds.
4. Leave ignition on and disconnect the IAC connector.
5. Remove the grounding from the ALDL connector.
6. Start the car. The car will probably run rough and may stall. Just restart and try again.
7. Adjust the throttle stop screw to set the idle to 500 RPM +/- 50 RPM.
8. Turn the car off and reconnect the IAC connector.
9. Turn ignition on and adjust TPS to proper settings. (.42-.44 at idle is typical)
10. Repeat procedure until the 500 RPM +/- 50 RPM in step 7 can be maintained while TPS is at proper idle setting.