Lambda system 0 dwell and no buzzing

[Nioreh]

My car is not running right. Frequency valve is only buzzing if I press the full throttle switch. Dwell meter is reading 0 otherwise. Idle is high. Does this indicate a bad oxygen sensor? Any easy diagnostic? I was going to unplug the sensor, but where on earth is that connector? Sorry for newbie questions 😀

[Nioreh]

So the oxygen sensor is connected behind the back wheel where I can't really reach with the car on the ground.

[82DMC12]

Yes, the connector is in the driver's side rear wheel well.

Regarding the dwell, if it reads 0 on your meter (no activity) it sounds like you are not connecting the dwell up correctly, or there is no signal at all on the orange wire from the Lambda ECU. If the system is working and you disconnect the O2 sensor (lambda sensor), the dwell meter should read constant 22.5 degrees on the 8 cylinder scale.

Make sure your dwell meter actually works, first, and you have it connected to a good ground and the orange wire that goes to the diagnostic plug.

Also check to make sure the ground for the lambda system is connected to the engine, it's supposed to be attached to the passenger side of the intake manifold and is identified as a thin gauge black wire with some red heatshrink on it and it has a black plastic snap-in plug which is near the firewall behind the engine. Very common for it to get unplugged or someone forgot to attach the wire to the manifold after doing service work back there.

Also check the Lambda relay in the relay compartment. Could be a bad relay or the spades have pushed the female connectors down into the receptacle making bad connections.

Connector on frequency valve could be flakey but if you aren't getting a dwell reading, it could be that the lambda ECU isn't running reliably due to poor ground or poor connections which would of course affect FV operation.

Also check the idle speed micro switch to make sure it is truly clicking in at idle and you get continuity between the two spades on the back when closed. This could be causing your high idle AND strange lambda readings. Another good test of the microswitch is to remove the inner plug on the idle ECU (the black box on the metal tray behind the driver seat) and find the black-green wire. That's coming from the idle microswitch. Set your meter to DC Volts and check between the positive battery post and the black green wire while the ignition is in Position II and you should see 12V if the switch is actually closed at idle. If it's reads 0 then you have a wiring problem at the switch or it's no good. Bad idle microswitch will mess up idle speed and lambda.

[Bitsyncmaster]

If the dwell reads 0 then the ECU is bad or your meter is not reading correct. The minimum dwell the Lambda can set if about 10 deg. Now since you get a buzz pressing the WOT that says your lambda ECU and FV are getting powered.

So even if your mixture is way off it still should not read 0 deg.

[Nioreh]

Yeah, when the WOT switch is pressed I get a buzz and a good reading on the dwell meter. So I am pretty confident the meter and relays etc are all working.

[Nioreh]

Idle circuit tests good. Removing inner connector on idle ecu makes the engine go to 2000 rpm.

I guess I need to fiddle with lambda ecu and see how I can test it.

[82DMC12]

Yeah, when the WOT switch is pressed I get a buzz and a good reading on the dwell meter. So I am pretty confident the meter and relays etc are all working.

Try the tests I told you about regarding the idle microswitch. Note that the microswitch has nothing to do with lambda but could be part of your high idle problem.

The lambda relay and fuse 7 need to be looked at closely for the lambda issue, that is where the lambda system gets its power. If you have reliable power to the ECU (Green/yellow wire), the Lambda ECU could certainly be bad. The ground for the ECU goes through all the grounds on the rear bulkhead behind the passenger seat. Not common for all that stuff to get loose but it's worth a check anyway.

[82DMC12]

Idle circuit tests good. Removing inner connector on idle ecu makes the engine go to 2000 rpm.

I guess I need to fiddle with lambda ecu and see how I can test it.

just edited my last post, check it out

[Nioreh]

Thanks. Hopefully it's just a bad connection somewhere.

Car runs OK-ish as is, but it is using a lot of fuel. Going on a pretty long trip next week, and would be nice to not burn extra in fuel at these prices 😀

[82DMC12]

Thanks. Hopefully it's just a bad connection somewhere.

Car runs OK-ish as is, but it is using a lot of fuel. Going on a pretty long trip next week, and would be nice to not burn extra in fuel at these prices 😀

Personally I wouldn't drive the car too far until you get all this sorted out. You don't want to foul up everything, do you? Just asking for trouble.

[Nioreh]

Good news is the car made a big road trip this summer without issue. Car still runs as "good" as before. Don't think I fouled it much more than it already was. Either way it was worth it, I had a great time! I decided to get another Lambda ECU just to see if that was the issue. It was unfortunately not. As usual, parts cannon was a bad idea :). Car behaves exactly the same with the new ECU. So there is probably something wrong with my electricals somewhere. There are some other weird electrical stuff happening, so probably one or more bad grounds. I have noticed that when I get off idle, it sounds like a relay click inside the car somewhere. Not sure if this is normal, and I am just listening for stuff more now. Radio doesn't turn on at all (not sure where the fuse is for this, looks like it's inline somewhere in the center console or dash and I have to disassemble half the car to get to it). And the cabin fan will randomly turn off especially on high settings.

[Bitsyncmaster]

Good news is the car made a big road trip this summer without issue. Car still runs as "good" as before. Don't think I fouled it much more than it already was. Either way it was worth it, I had a great time! I decided to get another Lambda ECU just to see if that was the issue. It was unfortunately not. As usual, parts cannon was a bad idea :). Car behaves exactly the same with the new ECU. So there is probably something wrong with my electricals somewhere. There are some other weird electrical stuff happening, so probably one or more bad grounds. I have noticed that when I get off idle, it sounds like a relay click inside the car somewhere. Not sure if this is normal, and I am just listening for stuff more now. Radio doesn't turn on at all (not sure where the fuse is for this, looks like it's inline somewhere in the center console or dash and I have to disassemble half the car to get to it). And the cabin fan will randomly turn off especially on high settings.

Two common problems when Lambda does not work.

1). The ground wires for the lambda are not grounded on the engine block. Little ring terminal on passenger side, near back of intake.
2). The "lambda" relay was replaced with a standard relay. Standard will not work.

[David T]

Two common problems when Lambda does not work.

1). The ground wires for the lambda are not grounded on the engine block. Little ring terminal on passenger side, near back of intake.
2). The "lambda" relay was replaced with a standard relay. Standard will not work.

A couple of more possibilities;
Mixture very rich
O2 senor bad or disconnected
Bad connection at the plug to the frequency valve
Ground wire left disconnected for the frequency valve (already mentioned in the quote)

Usually when the Lambda is not working someone makes the mixture richer to compensate for the loss of the extra fuel the frequency valve would add. Once you get the frequency valve buzzing you should check the duty cycle and adjust the mixture (leaner).

[Nioreh]

A couple of more possibilities;
Mixture very rich
O2 senor bad or disconnected
Bad connection at the plug to the frequency valve
Ground wire left disconnected for the frequency valve (already mentioned in the quote)

Usually when the Lambda is not working someone makes the mixture richer to compensate for the loss of the extra fuel the frequency valve would add. Once you get the frequency valve buzzing you should check the duty cycle and adjust the mixture (leaner).

I doubt that is the issue since apparently it should buzz on warmup in open loop mode. Mine buzzes fine when wot switch is engaged.

I tried to look over the grounds that are easy to access. Everything looks brand new. I did find, however, that my low beam fuse is melted to all hell. It's still not blown, though. Not sure if that could affect stuff. It has melted the actual fuse box pretty bad. Not sure what to do about it, but I have to fix it and see that it hasn't caused something else to short out. I guess that could maybe cause my issues.

[Bitsyncmaster]

Mine buzzes fine when wot switch is engaged.

Then the two things I suggested are not your problem.