Rough Idle, Chugging On Accel – Lambda System Not Working

[klaatu42]

Had to repost this thread, because the first one I posted is throwing a 403 error.

Hi. I'm scratching my head a bit on this one (but admittedly that doesn't take much).

11633 suddenly started shuddering and chugging at a traffic light and I drove carefully, white knuckled home with very little power when starting up from each subsequent stop. My idle is now very randomly up and down (not seeking, nor in any noticeable pattern) and it really wants to die when I try to start moving or accelerate (I've taken it around the block a few times here and there to test).

The odd thing is, after finding that my frequency valve bulkhead connector female pins were so loose they were probably not making contact at all, I found that I could completely disconnect or connect it with zero effect at all on idle. I then noticed the same thing when unplugging my O2 sensor (no effect at all), and was further surprised when I was able to disconnect and reconnect the whole Lambda ECU with absolutely zero effect.

Am I right in thinking that depressing the full throttle enrichment dipswitch should alter idle? Mine doesn't.

Replaced Lambda relay with no effect.

The grounds and power to the ECU seem to be fine.



Video illustrating the erratic idle (turn your sound up): https://www.youtube.com/watch?v=YA0oI4pz-5M

[sdg3205]

Make sure the female spades for the relay pins on the underside of the lambda relay socket have not backed out. The lambda relay is not a standard relay. Are you using a lambda specific relay?

[klaatu42]

Make sure the female spades for the relay pins on the underside of the lambda relay socket have not backed out. The lambda relay is not a standard relay. Are you using a lambda specific relay?

Thanks for the reply. Yup, I checked the pins when I did the swap (with new lambda specific relay). No effect after changing it. Tempted to change it back to remove that variable, but the old one is quite crusty.

[sdg3205]

Check the ground for the lambda system that runs off the RH intake plenum near the back. It's off the side. Is that in tact? It should be bolted on with a ring terminal then becomes a spade terminal junction.

By back I mean closest to firewall

[sdg3205]

Also have you checked the fuse?

[klaatu42]

Check the ground for the lambda system that runs off the RH intake plenum near the back. It's off the side. Is that in tact? It should be bolted on with a ring terminal then becomes a spade terminal junction.

By back I mean closest to firewall

Thanks. Justin from Wells Auto also felt this could be the culprit. I've checked it and the connector that it leads to a couple inches back, but I'm wondering if it is disrupted somewhere further along, and I'm not sure exactly where that ground ultimately goes in the Lambda system. I verified the grounds on the Lambda ECU connector, and the ring ground below the connector, and they all appear to be sound.

[sdg3205]

If you are getting 12v at the relay socket and all your grounds are good my guess is there is an issues at the bulkhead molex connectors. Pins can back out or corrode. Do you have the bulkhead pin schematic? You should find it here no problem, then proceed to clean the male and female pins at the bulkhead with sandpaper and alcohol. It's time consuming but effective.

[klaatu42]

Also have you checked the fuse?

Removed, visually inspected each fuse and socket, and tested each fuse as good.

The Lambda ECU connector is getting power.

[klaatu42]

If you are getting 12v at the relay socket and all your grounds are good my guess is there is an issues at the bulkhead molex connectors. Pins can back out or corrode. Do you have the bulkhead pin schematic? You should find it here no problem, then proceed to clean the male and female pins at the bulkhead with sandpaper and alcohol. It's time consuming but effective.

Thanks. I removed and inspected all of the bulkhead connectors and they are all super clean and tight, with the exception of the aforementioned frequency valve connector, which had female sockets that were incredibly loose.

I'm starting to wonder if the little chipmunk friends I feed outside, and who come to the garage to get me when I forget to feed them, decided to have a little chew on a wire somewhere... I originally ruled that idea out because the problem started near the end of a long drive, but a partially chewed wire could certainly heat up and fail.

[Bitsyncmaster]

Does the FV buzz? The "lambda" relay switches power to the FV and the lambda ECU with separate pin outputs. If the FV does buzz, both the FV and ECU are getting power.