1991 R2500 454 suburban drive ability issue

[rampage]

Checked y pipe temps / converter temps today and all over 600 degrees with truck off checked with my Fluke infrared temp gun. All Stock original exhaust on this one, has the muffler in front of the converter........ stay tuned

What were the temps before and after the converter when it was running at normal operating temperature? That’s how you know if it’s plugged up. And what the temp of the converter itself?

 

[Klink K5]

Do you have the old pcm still? I assume these still have easily removable proms, swap the old prom into the new pcm if you think it's along those lines. Not convinced that's it. What pcm number is this, and what bcc? Bcc is four digits, usually alpha, not numeric.

Old pcm is gone..... part number for delco replacement above in thread 88999179

What is the bcc? Prom Id scanner said 5081 I believe

 

[Klink K5]

Do you have the old pcm still? I assume these still have easily removable proms, swap the old prom into the new pcm if you think it's along those lines. Not convinced that's it. What pcm number is this, and what bcc? Bcc is four digits, usually alpha, not numeric.

My old pcm has been turned in (core) and is gone....... was no good. Replacement delco unit is 88999176 that is in it now.........

Scanner prom I’d is: 5081 ( going off memory)

Truck is put away until next weekend my brain is shot from thinking on it.

 

[dyeager535]

Nah, bcc will be something like abcy. Normally printed either/also on the pcm label stuck to the outside of the case, or visible on the prom when you pull the inspection cover on the pcm.

I'm just curious if the code data (.bin) is out there for this app. That seems like a lot of advance, but maybe that's a big block thing? I don't recall my dad's TBI 454 running that much but I've got that info floating around, I'll have to look for it.

 

[black dawg]

there is a cross reference book that will cross the scanner id# to bcc letters, I cant seem to find mine though.

 

[1-ton]

Sometimes those old BCC codes are superseded to new ones when trying to find the proper .bin files out there. The original BCC code on my 1991 Chevy V3500 ECM ( PN# 7760) is AWBP, but I had to use the .bin file with the superseded BCC code of BAJW, in order to get Tuner Pro R/T to communicate with my ECM.

 

[dyeager535]

Yeah, they do run pretty high timing in this application at light load and when the EGR starts to come into play. Nothing weird about 50* apparently under the right conditions. As soon as EGR starts to open it looks like it adds 10*. And the timing is pretty high under light load/higher RPM (freeway driving I'm guessing with the right gears) ~35-40* is to be expected.

 

[Klink K5]

Yeah, they do run pretty high timing in this application at light load and when the EGR starts to come into play. Nothing weird about 50* apparently under the right conditions. As soon as EGR starts to open it looks like it adds 10*. And the timing is pretty high under light load/higher RPM (freeway driving I'm guessing with the right gears) ~35-40* is to be expected.

Well I’m going to put on scan tool again today....... but I agree with you under light loads / egr valve opens up and ........ my 454 / 4L80 jerks & shutters like crazy at cruising speed........ no codes either. Looks like lock up converter goes nuts or? I’ll test drive some more today ......... but on scanner , the jerking acts up when ignition timing jumps from 40 to 50 degrees and that’s when the problem comes to life / acts up in those seconds .........

 

[Klink K5]

Well I’m 90% certain my transmission is the culprit

Unhooked all my egr circut abs problem still exist.under very light load in 2,3&4th gear, shutter occurs and scanner says trans slip from 0- 600 rpm ........... Lock up converter is going nuts and I believe that’s where my problem lies...... I’ll follow up when I tear into it

Thanks