I've noticed a few oddities after converting my v6 camaro to a '165ecm running 32B. Oppinions? Ideas?

1)My engine leans out when I apply the brakes. Looking at the datalogs it seems like it's purposely leaning because it seems to lean and correct at a consistent rate.

2)Lean operation when the tcc locks. It continues to lean in proportion to the amount of throttle applied and runs at about 15.5:1 with minimum throttle applied. Not really a problem because it's kind of like having highway enleanment, even though 32B doesn't.

 

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Anyone?

 

Does it lean if throttle is low or just when brakes/TCC are on?

Check your ecm grounds. It sounds like when something electrical is on/off things change and than change back. Had a car that the radio and dome lite would on/off when the blinkers where on. Ground strap on block was a little loose. Body grounds to engine block would be a place to start. Check with a volt meter between battery neg and someplace on the body. Hit the brakes when lites are on does the volts go up? Ground to ground should always be less than a volt.

Enleanment decel may be invoked because of low air/throttle position.

 

Actually I took out the whole harness about a year ago and cleaned it up (and replaced a few bad spots). The engine's actually leaning out, the difference in power is noticeable. I don't think d.e. is what's affecting tcc locked operation, I've had it up to 10% throttle and it continues to lean out.

The only possibility I can think of with the brakes is that the booster is pulling enough vaccum to suck in more air when the pedal's depressed. The plenum's small enough that it might be possible. It shows up in the datalogs too- I press the brakes, there's a small jump in airflow and things level off again. What I don't understand is why the ecm isn't compensating for it.

 

Any air that enters the plenum and not measured by the MAF will cause leaning. Check that there is a restriction valve in line with the brake booster vauum line. It may also be part of the booster check valve.

RBob.

 

The check valve is also the restrictor. It's smaller on the booster side.

The MAF is reading the extra airflow when I press the brakes. It's small- only about .15 grams or so, but it shows up in the datalogs. Probably an indication of something else going on. Like a bad diaphragm.

Any ideas on the leaning while the tcc's locked?

 

But is the ECM really reading the extra airflow from the brakes? Maybe what you are seeing is the extra airflow from an increase in RPM or load?

RBob.

 

I've done this in park and cruising and it always shows up as brake --> airflow increase --> lean out --> rpm change. Load change is minor, only about 3 LV8, if any. Is the IAC supposed to open with the brakes?

 

Disconnect the Vac line from the booster. plug to the manifold try the brakes in park. There is a vac line for cruise at the brake switch. could be a leak.

 

It stops leaning without the booster hooked up. There's no vac line on the brake switch, so it's probably a bad diaphragm. So, why is it leaning with the tcc locked?

 

Its sucking in a large puff of air that is not read by the MAF. My MAF TBI setup did the same thing. The engine would skip a beat when the brake was applied, but quickly recovered. I added a little MAP AE in my setup, but on a MAF only system, I do not know how you would compensate for it.

 

Grrr! Must be a result of all the filtering in the maf masks.

Any word on your t-bird maf setup?

 

If your a brave person leave the booster plugged and drive the car and see if the tcc still has a lean spot. The two leans could be related.

 

No, it is the result of un-metered air entering the plenum. The PCV is another source of un-metered air. Along with the vacuum controlled doors for the HVAC and cruise control (if present).

For the leaning when the TCC locks, does the commanded AFR change? Since the RPM drops the gms/sec reading probably changes along with LV8 and the SA.

RBob.

 

Doesn't have cruise control. I plan on swapping in a hydrabooster so it's not really a big issue, just curious why it was happening.

The commanded afr stays the same. As soon as the tcc unlocks things go back to normal (stoich).