I believe that particular gasket is a paper one.

and yeah, I wouldn't use RTV. I wouldn't even take it apart unless you know its leaking

 

Bolted a new gasket on today. No RTV and I finally found one!

Now on the coolant temp sensor and the temp gauge sensor, I didn't use any silicon or teflon tape or plumbers putty. Do you think that was a mistake? The etc had a brass washer with it. I read that teflon tape can interfere with it grounding properly.

Does my car (93 240) have Fuel Cut Off Valve? If so, is it possible I should be looking at it as suspect for any reason with these issues?

Thanks you guys. I'm going to get this thing running well if its the last thing I do.

Arne

 

the fuel is cut off by shutting off the fuel pumps. there's no cutoff valve.

the LH2.4 ECU has the following key inputs...

• timing signal from the CPS via the ICU.
• engine coolant temperature via the ECT sensor.
• mass air flow meter
• O2 sensor
• idle switch
• AC on
• full throttle (on some models)

(there's some other stuff but its not as important)

the ECU turns on the fuel pumps via their relay, controls the injector timing, and modulates the idle air control valve when at idle. oh, and it can turn on the electric fan on 1992+ 740/940's.

 

Do you think I should re-install the ECT and the other sensor for the gauge with some kind of sealant or teflon tape? I already put the intake back on but I could remove it easily still. Just thinking if its going to leak I'd rather deal with it now.



Arne

 

the sensors are grounded via their threads. sealant/tape could interfere with that.

 

Well, I put it all back together with new sensors and still "starts then stops".

HOWEVER, I went back to the code reader at terminal 2 (ECU I think) and got code 1-2-1 MAF. So I unplugged the MAF and it runs although rough.

SO, the MAF history is this. I replaced it when a shop told me it was bad and maybe they got the same code as I did. They were certain my problems were over but it didn't help anything. Then just now I swapped a MAF from a 91-240 and no difference. Then I replaced the sensor on the throttle body that I believe connects to the MAF and that didn't fix the problem.

All MAF hoses are solid, no leaks at all. New air filter in front of the MAF. What can it be? The connector harness from the MAF back to the ECU? How would I test that?

HELP!
Arne

 

With key to "on" and ECU terminal 21 grounded
Backprobe the AMM plug wire 5 (orange) and ground- should yield 12V (power)

With ignition "off"
Backprobe AMM plug wire 1 (brown/black) for continuity. (ground)

With ignition "off"
Backprobe AMM plug wires 6 and 7 -Should yield 2.5-4.0 ohms (wire)

These should be performed with cold engine with wires at ambient temperature.
The wire numbers are imprinted into the AMM (MAF) plug on the AMM body. Find the corresponding wire on plug socket, lift back rubber plug boot and test wires from there.

Also make sure no wire connectors are loose/ pushed back in the plug socket. Sometimes they can push back into the plug socket neck and not make contact.

 

First, thanks both to Fochs and Pierce for the many responses and to any other contributors. I had to take a couple weeks off this project but now I'm back. In the meantime, I have gone ahead and replaced the MAF AGAIN! this time with the OEM Bosch and the air box thermostat. The stuttering or knocking I had under load went away and it is now running better than it has in a long time.

HOWEVER, there is a roughness to the idle and also gradually coming out of idle that shakes the car some. I'm still getting the same codes even after clearing them and the check engine is currently on. At least one code is maf related and the others are rich/lean related I think. They are:

1-2-1
1-1-3
2-2-1

TPS is adjusted correctly. Idle air valve replaced. What else? Why am I still getting MAF codes?

Arne

 

With a digital meter I am getting a constant 5 volt reading from my O2 sensor. What does that mean? Are there other explanations for a bad O2 sensor reading such as a bad catalytic converter? Do I need to use an analog meter?
Could this be giving me the 1-2-1 MAF codes?

Arne

 

All problems solved finally with this car relating to this post, so this is a closeout. I replaced many parts and sensors but in the end it seems the problems went like this.

The MAF went out, probably due to the air box thermostat failing and sending hot air to the MAF. I replaced the MAF and it went out again, though I didn't realize that at the time. I replaced the MAF this time with Bosch and the air box thermostat. Still I got MAF codes and lean/rich codes. That was because the new O2 sensor that I had replaced had now become coated with soot and carbon due to the engine running rich, due to the bad MAF.

So, one part definitely affects another part on these cars. If you have a rich problem you may damage other components.

Arne

 

i generally wire that airbox thermostat closed with a bit of bailing wire. I'd remove the heat riser tube entirely but its a smog test checklist item, so I leave it in place and just block it off (they don't check that). AFAIK, its only useful in very cold weather, and then only to help the engine warm up a little faster. where I live, 'really cold' is the very occasional 40F morning