Timing advancing too far

[Ben Osborne]

Just replaced the original TBI 350 in my 89 Suburban with the Blueprint Engines drop in replacement. Also had the transmission rebuilt and installed shorty headers with a new exhaust system. Nothing crazy in the exhaust. Just didn't want it leaking from every joint.

Set timing to 0 with computer unplugged. When I check initial and total timing per the engine install instructions I'm getting 20 deg at idle and 40 at higher RPM (when it quits advancing).

What could be causing the computer to advance timing this far? Blueprint engines wants total between 32 and 34. Initial between 10 and 16.

 

[Ricko1966]

Blueprint sells these engines assuming you have a conventional distributor. TBI all the timing is controlled by the ECM. First thing I'd do is contact blueprint and tell them your situation. You may end up needing a chip burned,or a different distributor. GM set that ecm up for what they wanted for those heads that compression that cam,not for what you may want or need in the future. And TBI does not play well with very much cam. It is manifold pressure controlled,that means of your vacuum is to low its going to run rich.

 

[Ben Osborne]

I checked with BluePrint Engines. The tech said that he was surprised the instructions would say to set total timing for my engine and agreed that it should be at 0 with the computer unplugged.

Between then and now I got a USB OBD1 scanner and started playing around with it.

With this plugged in I notice a few more things.

I am idling faster than I thought (1k RPM). This drops down slightly if I put the truck in gear.

After driving around some if I put it in park it will start idling at 2k RPM. This corrects itself (back to 1k) if I turn the truck off and right back on.

Knocks are being detected when I turn the truck on or off but not while it is running.

Screenshot from TunerProRT attached. This was mostly me learning how to use it.

SparkAdvance always reads 0
HiWay AFR always reads 0
It will go in to CLOSED loop. It just hadn't yet when I took the shot.

I don't know enough yet about what these should be reading to know if anything here could be telling the computer to advance this much or idle fast.

 

[gmbellew]

TPS voltage is a tad high, but likely not causing you any issues. You can slightly bend the tab to lower the voltage to a little closer to 0.5v at idle, but not critical.

IAC counts seem high for sitting at 195deg temp and warmed up. You may try a reset on it. Jumper A and B on the ALDL with a bent paperclip. Then turn key to "on" for 30 or 45 sec. This will force the IAC all the way closed. You should be able to hear the stepper motor clicking. Then turn the key to "off " and remove the paperclip. Then start it up and see how well it idles down.

IAC counts should be in the 5-35 range for a stock tune and idle ought to be in the 550rpm range.

If that doesn't help, you may pull the ECM out and see if it looks like somebody has put in a different PROM chip. It could be its not on the stock tune.