[rfmaster]

Originally Posted by pancake

Hello again, been awhile.

Finally got the blazer running well. Took it out four wheeling for a "test drive" and did ok there, but coming back it had issues.

I adjusted the fuel pressure to ~12.5 psi and made sure everything was tight.
It had two codes when I got back 44 and 24. 24 is the VSS. I do not have a neutral safety switch hooked so I think that is why I got that code.

44 is lean 02 sensor....I tightened up everything and seems to work fine.

Only concern I have is to run good the timing is at ~ 12 BTDC. I tried to set it at 0 TDC but it would backfire through the exhaust and run very poor.

Is 12 BTDC to much? Is there something else I should be looking at?

Thanks for the help.

Hi Pancake

From above it looks like Code 44 was due to exhaust leak which you took care - is that correct???

Timing the TBI system. This is where a lot of people get tripped by ECM controlled ignition system. I am going to assume that you are running 7747 ECM with ASDU calibration. TBI base timing is set with EST connector open! This connector has just one wire (usually tan/white) and hides by the brake booster in OE installation. With connector open the ECM does not control timing - this is when base or initial timing is set. ASDU calibration has initial timing set 0 deg BTDC. The actual and calibration timing values must match! When you open EST set connector idle speed will drop down and engine may have difficulty idling, but since dizzy does not have spring weights idle speed at which you are checking has no effect on initial timing. Once you set base timing shut down engine reconnect EST set connector and clear ECM by disconnecting negative battery terminal. Re start engine and take a look at your idle timing. ASDU calibration has timing tables in the idle RPM/MAP range with 20 to 24deg. This is not a final value since other operational factors may alter the final timing value being sent to dizzy. Usually, I see idle timing bouncing between 18 to 22 degrees in a fully warmed engine.

//RF