98 C1500 stalls , won’t run when hot

[Alex]

Howdy fellas . Hope someone maybe ran into that issue before so here it goes . 98 4.3 Vortec , around 244xxx miles . Bought as a project knowing it needs head gaskets . Got new heads on it , runs good when cold , as temp comes up to operating level it starts to emit faint black smoke that progressively gets worse until it finally stalls . Once it stalls it will crank but won’t start till it cools off . I’ve been scratching my head for awhile on it . Got multiple new sensors on it . Fuel pressure stays perfect for the entirety of it running and when trying to crank it . Could a bad PCM cause this ? Could it be bad gas ? ( truck did sit few years till I bought it ) . It’s like once it exits cold running algorithm and gets out of the fuel enrichment state it goes haywire . No restrictions in the exhaust , cat was gutted by previous owner . Just would like for this old girl to live again lol

 

[chris032188]

Any codes? Def. Seems like it is running rich. Does have FI or TBI?

 

[Alex]

Any codes? Def. Seems like it is running rich. Does have FI or TBI?

Throws no codes at all when it does it . It’s a FI spider set up . It’s most definitely starts running rich and chokes itself but it has me puzzled as to why . What comes into play or what sensor is going wild .

 

[Schurkey]

The Usual Three:

1. Verify fuel pressure at prime, at idle, and under load. Most fuel pressure gauge assemblies have a push-button pressure release connected to crappy vinyl tubing. Route the tubing so it empties into a drain pan, then push the button while the engine is running. This simulates higher fuel demand if you can't check fuel pressure on the highway. Fuel pressure should remain steady even with fuel flowing down the pressure-relief tubing. How old is the fuel filter? Have you ever dumped a bottle of Chevron Techron Complete Fuel System Cleaner into the gas tank? (Recommended at every oil change.)
   
2. How old are the usual “tune-up” parts and procedures? Inspect/replace distributor cap, rotor, plug wires, spark plugs. Make sure the ignition coil will reliably fire a spark-tester calibrated for HEI when the coil is fully warm, and misted with water from a squirt-bottle. Cranking compression test of all cylinders while the spark plugs are removed. Verify EGR, PCV, EVAP, and Heated Air Intake (if used) systems for proper operation. Verify proper initial timing (TBI) and electronic spark advance (TBI and Vortec). Replace old O2 sensors unless you can PROVE that they're working properly—old O2 sensors get lazy, they don't provide accurate data, but they do provide “data” that fools people into thinking they're “working”.
   
3. Connect a scan tool (NOT a crappy “code reader”) and look for “codes”. More important, look at the data stream to verify EVERY sensor and computer output. Verify fuel trims during the time that the vehicle is not running properly. Look for misfire counts for each cylinder (OBD2 only.) “Codes” have official diagnostic procedures that will be found in the service manual set for your vehicle. The service manual set can be downloaded from the links in the Sticky thread section of the Engine forum on this web site.

 

[Alex]

Just to keep everyone updated . Ended up replacing few more sensors , some ended up defective out of the box & had to be sent back to Amazon . After exhausting all of the options I ended up getting a used PCM off 2000 GMC Safari van , the only thing was to do there is swap the eprom & go through security procedure . No more issues starting while hot & no more black smoke , truck runs better then it ever has . Hope that helps someone out there .