Tuning for a rich 305ci sbc

[brettinator]

Hey all,
I have a 1988 c1500 305ci with long tube headers, a k&n intake, and a holley 670 cfm tbi throttle body. (Also have a new fuel pump).

It is running rich and I have read that folks have that issue with the holley throttle body. I would love recs for a tuner, module or a convenient way to tune the ecm. I have read about black bear but they start at 1998 I believe.

Looking for recommendations.
Thank you

 

[RichLo]

Hopefully PlayingWithTBI sees this thread.

That seems very large for a 305 but a TBI should still be able to control fuel in closed loop through the o2 sensor and other sensors. I assume you put in a new o2 when you put long tubes on it? Did you upgrade to a heated o2?

 

[L31MaxExpress]

Biggest issue with the Holley is the vacuum port on the back should not go to the MAP. MAP needs to connect to the manifold vacuum port on the front. The rear port is connected to the IAC passageway and causes the MAP to read wrong especially on a cold start.

 

[Schurkey]

HOW do you know it's "rich"?

Is it really rich, or is it merely in lean-command?

 

[PlayingWithTBI]

Is it really rich, or is it merely in lean-command?

^^^This, before we get into programming you need to put a scanner on it and see what the sensors and commands are doing, especially the O2 sensor. Where is it located, in the collector of the LT header? Is it a heated O2 sensor? Is it going into Closed Loop?

 

[brettinator]

Thank yall. Keep in mind this is my first project if I sound ignorant (I am).

I did reinstall the original o2 sensor in a new bung in the LT header reducer. I have a new one coming but had not heard about a heated sensor before.

I suppose the truth is I don't know it's rich, but was inferring due to the increase in wet exhaust.

Should I move the MAP to the front vacuum port?

I've ordered a scanner

 

[BVRPLZR]

Are you familiar with the Flash EBL system?

Brings the TBI computer into the 21st century.

 

[PlayingWithTBI]

Are you familiar with the Flash EBL system?

Brings the TBI computer into the 21st century.

Agreed, I'm running one too. My point with the OP was, tuning an ECU won't cure a mechanical problem. It may mask the symptoms for a while but the engine will never run at its best.

 

[brettinator]

The EBL flash from dynamicefi? I will get more familiar.

Agreed, I'm running one too. My point with the OP was, tuning an ECU won't cure a mechanical problem. It may mask the symptoms for a while but the engine will never run at its best.

I appreciate this sentiment and would like to correct whatever issue is underlying. I ordered a retrofit heated o2 sensor today to replace the factory one.

I will move the MAP to the front vacuum port like l31maxexpress suggested.

 

[L31MaxExpress]

You definitely want to move the MAP port. The rear port opens right to the IAC passageway. If you follow the passageways you will figure out the difference. The GM MAP port is away from the IAC vacuum leak, where the Holley MAP port dumps right into the IAC vacuum leak. What that means is lower vacuum reading to the MAP anytime the IAC is open. What happens on a cold start is the IAC opens, the vacuum to the MAP drops, the MAP drops, the ECM overfuels the engine, which then causes the ECM to open the IAC even more which causes it to overfuel even more until the system is just dumping fuel and the IAC is wide open.

Holley

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GM

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