Teaching an old dog new tricks K1500 350

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06-03-2015
Psycho_Daleic

Teaching an old dog new tricks K1500 350

*This is my First try at this stuff* I'm a real old-timer so I'll apologize up front for what may be a barrage of simple minded questions. I have been reading the forum for about a month and am eternally grateful for the wealth of information for rank beginners like me.

I've got a 1989 K1500 350 (Transplant, new and balanced) 5 speed (M20), 4X4, 220 TBI (GT4: Rear Axle, 3.73 ratio), with some running issues (new distributer with pickup and module, all new sensors on engine including O2, EXCLUDING, TPS, IAC, MAP, ESC). The VIN indicates that at some point in its life it originally had a V6.

Got an 'ALDU1 and CABL1' from Moates to do some data logging so I can hopefully run down some afterfire/stumble issues. (I haven't checked the fuel pump, which is suspect and next on the list before some serious Timing). Hooked her up and got a good connection, I am using EagleMark's ADX, XDF, and for comparison ASDX 88 C-K Truck 5.7TBI 5 speed manual bin. The current prom is AMUD which appears to be for a 1988 305 manual trans, but was told by a fleet mechanic friend of mine that it shouldn't make any difference (which I kind of question?!) It should be AYUC according to the "BBC" lookup data sheet (thanks by the way for this resource!)

I have data logged a few trips but realized that the results depended on whether I switched the 10 ohm resistor in or out. With it switched on, the idle was significantly higher than when it was off. Is there a preference, since moates says to switch it on and EagleMark says to switch it off? Once I have a definitive answer, I’ll do some more data logging, check the fuel pump, and ask some more questions.

I have some other proms and another 7747 ECM (pulled on my last trip to the yard) to monkey with as required. Is there anyone who could reprogram the appropriate prom for my truck (either the original AYUC or the ASDX 88 C-K Truck 5.7TBI 5 speed manual I found on this site)?

Thanks again for the great resource.:thumbsup:
06-03-2015
joegreen

the current chip for the 305 will not work fine with the 5.7. If they did gm wouldn't have made different proms. I don't know how much of a difference there is though. Also when datalogging dont have the 10k resistor on. When it is on it puts it in some other mode and your data won't be accurate. You want to see the data as if nothing was plugged in so keep it off. Other more knowledgable people will chime in with more info.
06-03-2015
Psycho_Daleic

Thank you joegreen.
06-04-2015
jim_in_dorris

I ran a 305 bin in my 87 4x4 for years wondering why it was so lean all the time. Finally determined that some PO had installed a 350 in place of the original 305. Put in an 350 bin and WOW I couldn't believe the difference. Yes it will run, but you will leave a ton on the table.
06-04-2015
Psycho_Daleic

Quote:

Originally Posted by jim_in_dorris

I ran a 305 bin in my 87 4x4 for years wondering why it was so lean all the time. Finally determined that some PO had installed a 350 in place of the original 305. Put in an 350 bin and WOW I couldn't believe the difference. Yes it will run, but you will leave a ton on the table.

Thanks so much for the heads up Jim! I'll check the fuel pump pressure, run another data log, then I'll be getting back to you. My truck is having the same issue you said you had, BLM 133 or higher constantly, afterfire coming off closed throttle downhill, stumble accelerating uphill under load, (seems the ECM detects a too lean condition and then tries to compensate by dumping more fuel to the engine.):thumbsup:

Moved this discussion to NEW POST HERE.