93 GMC K1500 Code 45

[Joey99]

Hi everyone,

I have a 1993 GMC K1500 I bought with 160k miles a little while back, and it has an issue I have been totally unable to fix. My mechanical knowledge is pretty limited, but I figured this would be a good car to learn on.

When I first bought it, it would randomly stall at idle every once in a while. More recently, it stalled while idling and would not start back up until the engine had cooled down. Now, soon after the truck warms up it begins to run very rough, sputtering and surging, and acting like it will stall out while idling. The only code it's throwing is a code 45, a rich exhaust code.

So far I've replaced:
-catalytic converter (with an aftermarket one, was missing cat when I bought it)
-water pump (unrelated to issue)
-radiator (unrelated to issue)
-battery (unrelated to issue)
-icm
-iac
-temperature sensor x2
-tps
-map sensor
-pickup coil
-throttle body gaskets
-Pcv valve and hose
-oxygen sensor
-distributor cap and rotor
-spark plugs and wires
-ignition coil
-fuel filter

-I tested the fuel pump (I believe) correctly and it was within range.
-When I changed the pickup coil I set the timing back correctly
-Swapped out known working fuel injectors, same exact performance
-Swapped out known working ecm, same performance
-When I changed the spark plugs they were pretty black and sooty, clearly indicating a rich exhaust condition

 

[Joey99]

Not sure where to go from here, but any help is greatly appreciated!

 

[Schurkey]

Stop replacing parts at random. Connect a scan tool, look at the data stream. Verify all sensors and outputs, which includes the wire harness connecting them. Coolant temp, O2 sensor, IAC, TPS, and short- and long-term fuel trim would get special attention. Also verify that the EGR valve isn't stuck open.

What are the results of the fuel pressure test?

When you were in the distributor, did you verify the magnet on the distributor shaft? Common TBI problem.

TBI HEI / Small-Cap HEI ignition problem areas

[Note: This is a placeholder for a more lengthly post--a work in progress. More to follow.] Common problem with '87--'95 TBI "Small Cap" HEI distributors. The Ignition Control Module gets blamed for poor performance when the real issue might be in the pickup coil assembly. I'm not saying...

www.gmt400.com

 

[sntrym]

Send some salmon bits from Tony's and I'll tell you what's wrong. Just kidding.

New parts are not always good, so just because it was replaced doesn't mean it's working correctly. We could all harbor some guesses, but like Schurkey said you need a scan tool that can output the data stream. A laptop, TunerPro, and an OBD1 to USB cable will do it. So will the Bosch scan tools and many others you can get at the parts store.

You really need to see what the computer is seeing to determine what the issue is.

 

[Joey99]

Stop replacing parts at random. Connect a scan tool, look at the data stream. Verify all sensors and outputs, which includes the wire harness connecting them. Coolant temp, O2 sensor, IAC, TPS, and short- and long-term fuel trim would get special attention. Also verify that the EGR valve isn't stuck open.

What are the results of the fuel pressure test?

When you were in the distributor, did you verify the magnet on the distributor shaft? Common TBI problem.

TBI HEI / Small-Cap HEI ignition problem areas

[Note: This is a placeholder for a more lengthly post--a work in progress. More to follow.] Common problem with '87--'95 TBI "Small Cap" HEI distributors. The Ignition Control Module gets blamed for poor performance when the real issue might be in the pickup coil assembly. I'm not saying...

www.gmt400.com

Ok thanks! I'll look into getting a scan tool.
I can't remember what the results were but I'll recheck to make sure I did it right.
I've never heard of the magnet problem so I'll pull the distributor back out and check that, as well as the EGR valve.
Thanks again for your help!

 

[Joey99]

Send some salmon bits from Tony's and I'll tell you what's wrong. Just kidding.

New parts are not always good, so just because it was replaced doesn't mean it's working correctly. We could all harbor some guesses, but like Schurkey said you need a scan tool that can output the data stream. A laptop, TunerPro, and an OBD1 to USB cable will do it. So will the Bosch scan tools and many others you can get at the parts store.

You really need to see what the computer is seeing to determine what the issue is.

Ok looking into getting a scan tool now!
Thanks for your help! I'll look into the salmon bits haha