New O2 sensor, and a strange burning smell

[Jonathan]

Hey, don't mention it! I asked many of the same questions over the years since getting my car in 2007 and so if I can now help answer some of those questions for a newer wave of owners, then giddyup.

http://dmctalk.org/showthread.php?11...l=1#post181425

Now, this thread I referenced is admittedly confusing and a lot to read. I wanted to include it because the post I linked to in it mentions an O2 sensor ground reference wire than can be a problem. It is on the passenger side of the manifold, towards the front of the car and sort of above the frequency valve location. It normally has a solid red coloured wire to help identify it. I found a problem with my own and it helped, but it wasn't the only thing going on.

This thread was in late 2015 and I did my thermistor and valley work in the winter of 2014 (before this thread's season). So while I got the thermistor issue sorted out, I still had a mixture setting problem. A new oxygen sensor and a mixture setting by a local mechanic who had experience in knowing how to do it for me solved my problems of poor idle.

Just some extra reading material in case the next thing or two you try or test isn't the entire solution.

[NckT]

Alrighty, last post for the day, I'm gonna wrap this up and dig in tomorrow after this:

I thoroughly cleaned and reseated the white 9 pin bulkhead harness. Upon re-reading at the ECU, i got 18.7k Ohms across black/yellow and black/grey.

The car idles solidly at roughly 2300-ish RPMs. Hope this piece of data is relevant: if I unseat the white 4 pin harness at the ECU while its running, I get NO change in behavior of the idle. It sits bang on at 2300-ish; it did not even slightly nudge up or down when I unseated it.

So...does it look like I am revisiting the VoD?

Morning. As you now get a resistance reading at the ecu it shows that you now have a connection at the thermistor. No point in stripping the engine down to something you've just fixed!

I'd start diagnosing the wiring and operation of the idle ecu:

First check that the black switch at the throttle is closing with a positive click when the throttle is closed. This negative switching goes through a diode located in the wiring loom just being the idle ecu in a small battery sized cylindrical black plastic container before going to the ecu.
For testing purposes get a link wire and with the white plugs still connected to the ecu, connect the link wire from earth (ground) to the black/light green cable. If the idle goes back down to normal idle speed then there's a problem with the switch or diode or its wiring. If it doesn't then your problem is elsewhere. At this point pull the black plug from the idle motor and check to see if you get 12v at the centre pin of the multi plug with the ignition key in position 2.

I'll assume you've checked the fuses first etc

[rjd2]

NckT-Thanks much!!!! WHEW!!! Great news, re: engine strip down. I really didn't want to do that again(I also believe that the video I posted a link to shows a visual on the harness being seated properly).

I will do this test at the ECU today. That's great. Before testing, I do want to jump in on the fuse box: a problem introduced itself after I did the thermister job; I seem to be getting several intermittent connections at the fuse box; I pulled all the fuses and tested their continuity, and can recreate the problem sometimes by picking up the fuse box and physically shifting it with the key at position 2. It's a problem I don't really know how to fix, as it seems to be local to the actual contact points of the fuse box.

Ok, back later today with more info. Thanks!

Morning. As you now get a resistance reading at the ecu it shows that you now have a connection at the thermistor. No point in stripping the engine down to something you've just fixed!

I'd start diagnosing the wiring and operation of the idle ecu:

First check that the black switch at the throttle is closing with a positive click when the throttle is closed. This negative switching goes through a diode located in the wiring loom just being the idle ecu in a small battery sized cylindrical black plastic container before going to the ecu.
For testing purposes get a link wire and with the white plugs still connected to the ecu, connect the link wire from earth (ground) to the black/light green cable. If the idle goes back down to normal idle speed then there's a problem with the switch or diode or its wiring. If it doesn't then your problem is elsewhere. At this point pull the black plug from the idle motor and check to see if you get 12v at the centre pin of the multi plug with the ignition key in position 2.

I'll assume you've checked the fuses first etc

[rjd2]

More data:

1-with an alligator clip coming off the negative terminal of the battery, while the car was running, I tapped the black/green pin of the white 4 pin harness at the ECU. no change in idle speed.

2-with the key at position 2, i am getting 10.5V at the center pin of the idle motor harness. I can hear it buzz with the key in position 2. I am almost sure at one point I got a visual on the little rotating motor thing opening and closing properly last year during some diagnosis.

Hmmm.....I do know for sure there are some gremlins at the fuse box. Are there any tests to be done there, or elsewhere? thanks again, gonna get this sooner or later!

[NckT]

Remove your idle motor and see if it's physically stuck inside. The valve should be free floating.

Use a multi meter and measure the resistance between the centre pin of the idle motor and one of the outer pins. Take a note of the reading and then do resistance test between the centre pin and the other outer pin.

[rjd2]

Idle motor: by taking the hose clamp off the "rear" side, i can see the cylinder swings open when putting the key into position 2. should I pull the idle motor and inspect it when removed from the car?

the resistance readings across middle and outer pins of the idle motor harness: 160k, and 33k.

[NckT]

Not the harness, the motor windings themselves.

If you apply 12v to the centre pin of the idle motor and temporarily earth (ground) one of the outer pins (for no more than 1 second), the valve should fully open or fully close. Repeat the test bit then earth the other outer pin in the same way and it should move to the complete opposite way ie fully open or fully close

[rjd2]

Ok, gotcha. So at the motor, I get 10.8 ohms from center to right pin, and 9.1 ohms from center to left pin.

If i disconnect, and bridge the center pin, and tap either right or left pin at the motor to ground, I get a whirring sound. It's really hard to catch a visual at the actual motor, but it sure sounds like something is moving.

That help?

Oh, also-one other thing to mention. the brass L pipe that goes into the manifold: I had issues with it upon reassembly. the o-ring fell out. i believe i got it in place, but i cannot be sure it stayed when i reassembled. one other thing to consider. thanks!

[NckT]

Ok, gotcha. So at the motor, I get 10.8 ohms from center to right pin, and 9.1 ohms from center to left pin.

If i disconnect, and bridge the center pin, and tap either right or left pin at the motor to ground, I get a whirring sound. It's really hard to catch a visual at the actual motor, but it sure sounds like something is moving.

That help?

Oh, also-one other thing to mention. the brass L pipe that goes into the manifold: I had issues with it upon reassembly. the o-ring fell out. i believe i got it in place, but i cannot be sure it stayed when i reassembled. one other thing to consider. thanks!

The motor shouldn't 'whirr', as it moves fully open or fully closed, you should be able to hear/ feel the valve give a slight clunk. Remove it from the car to test and look

[rjd2]

The motor shouldn't 'whirr', as it moves fully open or fully closed, you should be able to hear/ feel the valve give a slight clunk. Remove it from the car to test and look

"a slight clunk" is a much better description; it wasn't a slow whirr. it was kind of loud; it sort of startled me. i tapped it once on the right, and it made a metallic clunk. i tapped right again, and it didnt do it. i tapped left, and it made the same clunk. i tapped right, the same clunk. i'll pull it and inspect.

the brass L pipe that seats into the bottom of the fuel distribution unit, if that leaked air, could it cause this high idle problem?