help repost: ECU codes and air leaks

[jimdoc23]

An update ... I have been able to profile my intermittent engine light problem. The 02 sensor appears to be working fine. At idle the DVM reads around .5 volts then slowly drops to close to zero. At around .1 the check engine light comes on ... I stab the throttle ... the voltage goes up ... the light goes out ... and then the sequence starts over. The ECU codes are 1223 and occasionally 1224.

I have replaced all the hoses (with the exception of the brake booster hose)including the bellows and have even smoke tested the car to find the leak... no luck ... no luck.

Any other suggestions as to why the CE light keeps coming on? Other than this ... the car runs fine and has about 95K miles on it.

[ghnl]

I don't know the Motronic system so well (but I'll reply anyway...)

Do the readings from the O2 sensor vary a bit - wavering about and averaging ~ 0.5V at idle or is it a steady ready of 0.5V? It should be the former, not the later. A steady reading might indicate a faulty O2 sensor. What do the codes indicate?

What does the sensor read at higher rpm's?

[ghnl]

The chart in this link suggests 1223 & 1224 both mean Lambda (O2) sensor problems. How old is the O2 sensor? They don't last forever.

[Tifosi]

By the description it sounds kinda like the heating element has failed. (cooling off when at idle making for funny numbers)

Likely in conjunction with a failed/failing sensor as Eric mentioned.

@ 95k miles, if it's never had the sensor changed you got better than 3x the expected lifespan out of it.

[jimdoc23]

Thanks for the information. I will try replacing the O2 sensor

[Tifosi]

Make sure you pay a proper price rather than the 'special because it's for an Alfa' price....

[jimdoc23]

Darren ...

Thanks, I read the attached thread. Since I have a 90 with the S4 engine and the 3-wire O2 sensor, Is the $53 Bosch just plug and play?

[Tifosi]

Yes and no.

The sensor proper, yes, straight up swap, but the wires aren't exactly what you need.

It comes with this goofy connector thing that seems way high on the 'junk' scale, and the wire lengths might not be exactly what you need.

Ideally you'd crop the wires on your existing sensor relatively close to the sensor proper, (say 6-12"), then solder and shrink wrap those cut ends to the wire ends on the new sensor.

That way you can use your existing factory connectors with no 'intermediate' <strike>buttplug</strike> butt end connector along the way.

It'll also give you quite a bit of extra slack so you can more easily route the wiring under the car well away from the exhaust.

Of course you can trim back the wire length on the new sensor, or shorten the existing stock wires beforehand to get things to a more manageable length, but the most important part is the solder and shrink wrap.

Side note:

Depending on where the solder joint is to be AFA 'easy to get at and work with' you can install the new sensor before soldering using a box end wrench prior to doing the actual soldering.

Makes life a bit easier when you don't need to buy a (practically) one time only use special socket for putting the things in. Well, taht and you don't have a yard + of wire twisting itself up as the sensor is being screwed in.

[aldo]

As a side note,
An alternative to regular crimp connectors and shrink tubing, crimp connectors are available with shrink skirts built in and best of all they incorporate a sealing compound which liquifies as the heat shrink contracts. It produces a liguid tite foolproof connection. I've seen them at some auto supply houses and all marine supply stores.

[ghnl]

Another useful item for splicing wires are Posi-Locks. A little bulkier than crimp on connectors but they're easier to use and re-usable. They also have a water-tight connector (not sure it they are re-usable).

[Tifosi]

If the compression seal material is something plyable that doesn't take a permanant set, it likely could be reused.