rowden

1985 gsl-se
I posted this before and got no response, so I'll try to simplify.
My car is running way too lean. I can't get the idle below 1300 rpm and there is some fluctuation at low idle speeds. The header is heating up and glowing red, but the exhaust is not plugged.

I've cleaned the intake and all associated parts (bac, acv, etc). Replaced all vacuum lines. New intake gaskets. Checked all the solenoids, valves, temp switches. My ecu has all the correct voltages when the key is on, engine warm, but not running. When I start it up, several voltages go low including vacuum switch, relief solenoid valve, switching solenoid valve. The BAC system is operating wide open, letting in way too much air. Spark plugs color is brownish, slightly white.

Who is a likely culprit to tell the ecu that the system needs so much extra air?

lastphaseofthis

iTrader: (8)

red hot header, means it's running rich.

thunkrd

iTrader: (1)

check your timing, make sure plugs are firing

Rx-7Doctor

iTrader: (13)

Wrong! Red header or exhaust is lean situation.

If your idle will not go below 1300 RPM you have a vacuum leak . Find the leak.

Did you just do some work to the engine and this started right afterwards?

rowden

Lots of recent work. I've had the car for only a few months. Emissions were all disconnected and disfunctional when I got it. I'm bringing it back to life. Former owner had just put this engine in and did not finish the details.

Timing is good on trailing and leading, but since I can't get the idle to 800, it's questionable. Distributor is turned as far couterclockwise as it can go. I pulled it, cleaned it, and put it back noting that it could not be off a tooth without being far out of adjustment. New plugs, rotor, wires.

The header is getting red in just a few minutes at idle. I can't let it run more than a few minutes for testing without risking overheat.

rowden

There could be a leak through a malfunctioning part, but it looks like the ecu is wrongly telling the emissions components there is a leak, therefore all is screwed. So which part could be giving such a bad signal to the ecu to do this?
Air and water sensors have the proper resistances at specified temps, but the behavior is like something thinks the engine is cold and needs more air for proper combustion.

Rx-7Doctor

iTrader: (13)

Your running way to retarded on the timing causing your lean situation.

Check the vacuum hose that goes to the BACV or by pass air control valve that is located on the driver side of the engine attached to the side of the plenum chamber to make sure that it is connected to the vacuum port.

lastphaseofthis

iTrader: (8)

I've seen plenty of glowing headers that i knew was running rich!

mjm4jc

Some time ago, my SE had to be the richest running 7 out there. You could not stand anywhere near it without your eyes burning-----My exhaust never got red.

Rx-7Doctor

iTrader: (13)

That's because I already stated that running rich cannot cause the issue, only running lean.

rowden

Problem solved. I had run through all the checks for all of the solenoids and valves under the hood. It was a vacuum leak, but not from a break. This morning I checked the vacuum and vent solenoids that control the BAC again. In my previous test, I had disconnected the vac tube that runs to the bac from behind the solenoids. So I did not notice that the metal tube that feeds the BAC was plugged with the tiniest bit of rusty crap, disabling vacuum control of the BAC and allowing it to open completely, blowing huge amounts of air into the intake. The tube has a much smaller opening than the rest of small vacuum lines. My condolences to anybody else that gets sucked into this problem for many hours of their life.
For the first time since I bought the car 5 months ago, it runs great!