98 K2500HD runs rough, possible IP?

[GM Guy]

OK, swapped ECMs today, and that helped, dash lights up and she will fire up every time now. The swap got rid of all the codes except P0251, which probably means its IP time, unless I want to risk a runaway and do the optical sensor myself.

It will run for about 30 seconds and then stall. Security light doesnt come on after the initial bulb check, so I think I did the re-learn correctly.

 

[ak diesel driver]

if the relearn didn't work it wouldn't start or at least stay running

 

[ak diesel driver]

now might be the time to try the sensor check

 

[GM Guy]

unplugged the crank sensor, and she ran continuously, so it seems passlock is not an issue.

Still stumbles and runs rough, fluctuating RPM, etc. with the crank sensor unplugged.

 

[Husker6.5]

With 220K on it and the symptoms you are describing, which were very similar to what I experienced with my 98 Burb when its IP went slowly to hell, from 180K to 225K, when it finally took out my 4L80E due to the pump's ever increasing RPM fluctuations. I really hate to say it, but you're most likely still running on the original IP and it's time for a new IP and possibly a set of injectors, too.

 

[GM Guy]

I have a 99 engine that I snagged from an auction with a hole in the pan that I plan to get the IP off of, but the injectors may have been the cause of the hole, so I better have them re-done.

 

[ak diesel driver]

now try unplugging the optic sensor

 

[Husker6.5]

How many miles on that 99 engine?

 

[GM Guy]

How many miles on that 99 engine?

Pretty low

 

[Husker6.5]

That's good. Then at least you should be swapping in a "better" used IP. Sometimes newer doesn't equate to less miles. As long as that "new" IP out of the 99 is 100K miles or less, you should be good to go for another 50K or so. Pulling IPs is such a PIA!

 

[jrsavoie]

I have a 99 engine that I snagged from an auction with a hole in the pan that I plan to get the IP off of, but the injectors may have been the cause of the hole, so I better have them re-done.

I would not go through the trouble of installing injectors or an IP without having them tested first.

With 220K on it and the symptoms you are describing, which were very similar to what I experienced with my 98 Burb when its IP went slowly to hell, from 180K to 225K, when it finally took out my 4L80E due to the pump's ever increasing RPM fluctuations. I really hate to say it, but you're most likely still running on the original IP and it's time for a new IP and possibly a set of injectors, too.

We just went through that with the 1996 K1500 Suburban. I am guessing twice

The trans went out on the Burb. Had it rebuilt and it was out again 20,000 miles later. It had about 300,000 miles on it the first time, so I do not know if it just gave up or the IP took it out then. the 2nd time, it was definitely the IP