yo,

My car is running great, getting 23-25 mpg highway, strong acceleration, solid starts etc etc.

HOWEVER! My OBD is still showing code 2-3-1 (no check engine light though)
If im not mistaken, 2-3-1 means "fuel system compensating for rich/lean mixture at cruise"

Having just recently fixed my flapper/thermostat assembly in the airbox (and by fixed, I mean i ripped it out and blocked the hot air inlet) and because of that, I have no idea how long hot air has been coming into my engine, thus slowly killing my AMM.

What do you think? AMM? Suggestions? oh by the way, the rest of the fuel system is great and recently serviced (everything from pumps, relays, FPR etc.)

Thanks in advance
--
Spencer 1992 244 190K

I had the same code, with engine seemingly running well. Didn't get back to it, then when I started getting stalling recently, I threw in a spare AMM. (It was still borderline stalling, but then, it went away. Must have been bad gas or something).

Anyway, I checked the codes later and it was clean: 1-1-1. I'll have to put the old one back in to be sure, but I'm thinking that maybe the AMM replacement stopped the 2-3-1 code.

--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

the O2 sensor was just replaced about 2 months/3,000 miles ago, and it's putting out perfect voltage.

Also, the the vacuum and intake air tubes should be intact, but again, if anyone has anything else, let me know...

Thanks!

--
Spencer 1992 244 190K

If that is the case, and you know there is no air entering downstream from the AMM ( bad intake gsket etc), or exhaust manifold or headpipe gaskets leak ( more air confusing o2 sensor), then it could be a blinky AMM.
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Gary Gilliam Sumerduck VA, '94 940 na Regina 160k '86 240 190k

I'm guessing your engine setup is not too different from my '94-940 (LH-2.4)

I got the check engine light, a drop in fuel economy, and codes indicated fuel trim, missing or bad signal from O2 sensor, and missing signal from TPS. After I disassembled, cleaned and readjusted, and tested the TPS I got the same codes again, along with the light, so gave up and took it (and the proceeds from a second mortgage) to the dealer. I smugly showed the list of codes to the service rep...(message: "here's a guy who knows a thing or two...").

A day later they gave it back with a new EGR solenoid - the little ECU-operated electric valve that directs vacuum to the EGR Valve. No other action taken. And...no check engine light, smooth running, good fuel economy...4 months now. This fix seems to have had nothing to do with any of the codes! But worked perfectly. I'm humbled.

Point being - the codes from the OBD-1 system can be helpful, but are not guaranteed accurate.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and a few old motorcycles)

Could be an air leak, or a lazy O2 sensor. Check all the vacuum lines, air snorkel tube and intake manifold gasket. When was the last O2 sensor installed.
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Gary Gilliam Sumerduck VA, '94 940 na Regina 160k '86 240 190k

Is it more beneficial to the car to block that hot air hole completely, or just replace the little doohicky that keeps it closed? I have a 93 240 and I have replaced AMM before on a older 240, I dont feel like loosing another one. I know that shock is supposed to open the flap at a certain temp, but if it easier just to block it all together?

I'm interested to know if later ECU's store info and need to 'relearn' when something changes - if so disconnecting the battery will do it, then warming up at idle and driving normally - but I've no info on this for a 92.

BTW in the UK we didn't get OBD until much later (if at all).

Doh! I've now seen the other thread on 'codes reset' which answers this question!