CODE 34 ON RESTART/ STALLS HIGH OR LOW IDLE SPEED
VEHICLES AFFECTED: 1985-87 5.0L/5.7L PFI ENGINES IN 'F' AND 'Y' CARS (ENGINE CODES F AND 8)
Some 1985-87 vehicles may experience the following:
1. Code 34 on restart. 2. High idle speed. 3. High accelerator pedal effort. 4. Engine stalls at idle or during deceleration. 5. Rough/low idles.
These conditions may be caused by carbon buildup inside the throttle body bores behind the throttle plates limiting air flow. It should be noted that what appears to be just a small amount of accumulation can be enough to limit air flow.
To diagnose this condition, perform the following steps:
1. Measure minimum idle speed using procedures defined in Section 6E3 of the Shop Manual.
2. If minimum idle speed is less than specified in chart, proceed to Step 3. Otherwise, perform activities defined in the Shop Manual under Section 6E3, Section B - Rough, Unstable or Incorrect Idle, Stalling.
3. Remove negative battery terminal.
4. Remove mass airflow duct at throttle body.
5. Cover TPS and IACV to protect from overspray.
6. Stuff IACV air inlet passage with shop towel to prevent cleaner from entering passage (See Illustration).
7. Block throttle lever in wide open throttle position.
*NOTICE: THE CHEMICALS USED IN CARBURETOR CHOKE CLEANERS ARE VERY STRONG. DIRECT CONTACT WITH ANY RUBBER OR PLASTIC PARTS WILL CAUSE SWELLING, CRACKING, OR OTHER DAMAGE. DO NOT USE ANY CLEANER THAT CONTAINS METHYL ETHYL KETONE, WHICH IS AN EXTREMELY STRONG SOLVENT, AND NOT NECESSARY FOR REMOVAL OF THIS TYPE OF DEPOSIT.
8. Spray carburetor choke cleaner around throttle bore(s) and on back side of throttle valve(s). Avoid spraying directly at throttle shaft bearing surfaces to prevent washing out factory lubrication.
9. Use a nylon parts cleaning brush or shop towel to remove heavy deposits. (It should be noted that what appears to be just a small amount of accumulation can be enough to limit airflow).
10. Release throttle lever. Open and close throttle lever several times to make sure it operates freely.
11. Remove shop towel from IACV air inlet passage, and uncover TPS and IACV.
12. Connect mass airflow duct to throttle body.
13. Connect negative battery terminal.
14. Check minimum idle speed, and readjust speed and TPS as specified in the following chart:
Model Speed TPS ----- ----- --- 1985 'Y' (5.7L) *400 RPM in Drive (Auto.) .54 plus or minus .075 Volts 450 RPM in Neutral (Man.)
1986 'Y' (5.7L) **400 RPM in Drive (Auto.) .54 plus or minuus .075 Volts . 450 RPM in Neutral (Man.)
1987 'Y' (5.7L) **450 RPM in Neutral .54 plus or minus (Automatic and Manual) .075 Volts
1987 'F' (5.7L) **450 RPM in Neutral .54 plus or minus (Automatic and Manual) .075 Volts
1985 'F' (5.OL) *500 plus or minus 50 RPM in Drive (Auto.) .54 plus or minus .075 Volts
1986 'F' (5.OL) **400 RPM in Drive .54 plus or minus (Automatic) .075 Volts
1987 'F' (5.OL) **400 RPM in Neutral .54 plus or minus (Automatic and Manual) .075 Volts
* Distributor Connected
* * Disconnect the distributor set-timing connector.
Use applicable operation number and charge 0.6 hours.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
