Engine - Poor Performance After A Cold Start
Group1
Number
8402
Model
944
Part Identifier
1560
November 19, 1984
Subject:
Engine Performance After Cold Start
Cars which are mainly driven short distances may incur excessive carbon build-up on the intake valves.
This in turn will create engine performance complaints for the first 1 to 2 minutes of operation after a cold start.
The following procedure should be utilized to diagnose this condition.
- Assure correct CO and idle adjustments.
- Check air flow meter for binding flap, for air leaks on the hoses and o-rings on the fuel injectors. Also, check complete intake system for possible air leaks.
- Check fuel injectors for proper operation. Since no special flow tests are possible at dealer level, it is advisable to install. as a test, a new set of injectors and seals.
- A good indicator for partially restricted fuel injectors is if the CO adjustment screw in the airflow meter is turned all the way in (rich) and the CO reading is still on the low side.
(NOTE:
If the new injectors do not correct the problem, reinstall old injectors!)
If the above mentioned points do not correct the complaint, remove the cylinder head and intake valves. Clean the carbon off, lap valves and seats, and reinstall into the same valve guide.
Readjust CO and idle RPM.