I have a 2004 GMC Jimmy SLS 4WD, with the 4.3 V6. It’s currently got approximately 126000 km (which works to about 78,000 miles) on the body, engine was swapped approximately 15000km (9300 miles) ago for another used one with almost the same miles. Ever since the engine was swapped it’s had an occasional hard start condition. It only occurs when a) the engine has been warmed up / brought to operating temp, or b) it’s warm outside. In the winter, it rarely happens. When it happens it usually will crank for about 2-3 seconds longer than it does when it starts normally before it fires up. Either that or it will fire and run at a lower RPM for a few seconds before smoothing out. But, it always starts eventually. I’ve replaced the following: fuel filter, injectors, regulator, maf and iat sensors, distributor, spark plugs, wires. I might be forgetting one or two things. Anyway, the problem still seems to be there. Just wondering if anyone else has had this issue and what might be causing it. I’ve stumped a number of mechanics that I know (however none of them own blazer!) Any suggestions are appreciated!

 

So no codes from the OBD?

 

Nope, no codes. Engine light hasn’t come on at all.

 

Ive walked due to this problem.... distributor module went out...when hot is typical, intermittent engine start problems.

Also, on old vehicles especially when the wiring has been disturbed, ALWAYS suspect poor wiring connections. Verify 14.8 V from alternator ALSO to the distributor module. There MUST be something like 11V cranking and 13 or more running. INsufficient voltage to the module = weak spark and hard start, and also appears as excessive fuel condition.

Electrical problems are often extremely difficult to diagnose, especially intermittents, and mechanics rarely have any training or experience in electrical or electronic things. So they usually get overlooked.

The Honda CR/ATCs were famous for weak, orange spark and poor running due to a corroded ignition module connector. Solder the wires together- voila, white hot spark.