New TB & backfire

[ChuckG]

Installed the new 52MM throttle body this week. GREAT upgrade and very smooth. Really opens up the lungs that felt so restricted after 3500 RPM.

There are some concerns though. It does cough and sputter a bit when I accelerate somewhat hard when cold, or after it's been sitting for a little--like when I run into a store. Just a hint of backfire now and then under acceleration.

I've driven about 100 miles on it, so I think my ECM has adapted--though the negative battery cable was never unplugged.

No codes, smoke test came out fine, TPS set at .54 and idle at about 750 RPM.

Any thoughts?

[markw8]

Lean symptoms.

Mark

[ChuckG]

Really? My fuel pressure is set at 40PSI. Should I bring it up?

I have new Gen III Bosch 24lb injectors too, by the way.

[Bronze85]

Maybe a scantool instead of guessing.

[ChuckG]

They're $800--adjust the fuel pressure is free.

As I said, it throws no codes.

[Bronze85]

A scantool allows one to view the ecm's data stream so you can look for fuel trim / block learn numbers to decipher whether it is running lean or rich and then look for the causes. 1985 OBD I ecm's need a failure to set a code whereas OBD II can detect fuel trim abnormalities i.e. PO 171 System Lean and set a code or even a soft code (no light)

[ChuckG]

When Paul scanned it at Cruisefest in June, it had a "lean" code, but the injectors and now the TB have been changed out. It also said the CalPack/or ECM was improperly seated and there was a ground problem.

The ECM is new, the CalPak, chip, and ground have been checked, the MAF replaced. The burn-off relay (OE!) still works, so that's not it. The MAP, TPS, the IAC, Manifold Temp Sensor--all new.

I did dial back the fuel pressure to 40PSI before the new throttle body and it never before popped. My best guess now reading that's a lean symptom is that I've added airflow, but kept the same fuel flow which needs addressed.


I never before heard the theory this condition was a "lean" situation, but it makes sense and I now have a quick "just maybe" solution to try before I get too nuts.

My buddy has a very expensive tool of some sort (it's blue or grey, if that helps), but no OBD I software he says is available. I may buy the add-ons and borrow the scanner as a cheap work around, but still, how much is adjustable or within my ability to control on this system?