Quote:
Originally Posted by CSHADES
The first thing I would check on this before throwing more parts at it is the actual vacuum reading. Do you have 18 inches of vacuum at idle or at least close to that and what is the reading at about 2500 rpm? The MAP sensor is one of the main inputs as far as fuel delivery on these old obd1 systems, the ecm will ignore the o2 sensor readings if it thinks you are under a heavy load/low vacuum situation i.e. wot or close. If the vacuum is low I would look at either a timing chain problem or maybe a outer ring slippage on the balancer that make the timing look correct when it isn't.
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Finally got around to checking the vacuum. Gauge reads 21-22in at idle and right up through 2500rpm and beyond. Is that okay? Should it be varying more throughout the throttle range?
Going to be checking the ignition timing and injectors next.
Edit: This was tested at a stand-still with the truck running.