84delegance
05-12-08, 11:55 PM
my 84 fleetwood brougham with the HT4100 runs real good on start up and starts to run rough once it starts to warm up anyone what sensors are being used until it warms up and what would cause it to feel like its missing and runnung rough?
Check the oxygen sensor. Sounds like open loop is OK, but the closed-loop signal from the O2 sensor may not be reacting fast enough. You can measure it with a VOM on the millivolts scale; one wire to body ground, the other to the O2 sensor wire. Or just disconnect it with the engine cold, then warm it up, and if it makes no difference then test it. The voltage should change rapidly from .9 to .1; and will only react this way once it is warm (thermostat opens). If it seems to level off at any specific value, it's defective.