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I am not sure my additional A/C air valve functions correctly pictured below.

My understanding is that it is non functioning until the A/C is turned on but with just the engine running without a/c and I unplug it my rpms drop and the idle roughens. Does this sound normal? Should the idle stay stable.

When I do turn ac on, the rpms drop also about 200 rpms.
Does it sound like this ac additional air valve is bad?

Thanks...always seeking smoother idle and better mpgs.

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It sounds like it is functioning in reverse, for some other yet unknown reason. It also sounds like your idle setup is incorrect, as it is depending upon the valve being open to provide a smooth mixture via the AFM setup.

The valve should stay closed until the A/C switch (and associated relays) closes the circuit, energizing the valve thereby opening it.

You first need to chase the reason the valve is functioning incorrectly, then redo your idle setup.

My cousin also said it sounds like it's operating in reverse.

I did flip it around once but still got the same results.

You mentioned a relay, could that be causing the "always on" symptom or should I start tracing a wiring issues?

I have always had a bumpy idle but I have read where many e12 owners have the same issue. Goes down the road real good...but not great MPG.

Thanks for advice.

Just figured it out!

Somewhere along in time the wires were crossed from the throttle control switch and the ac valve.

Had to really adjust the idle screw out a lot as the ac valve has been running on for a lot of years. I hope this helps w/the mpg log as the throttle switch should be sending the correct signal now.

Thank you Lenny for you assistance, your thoughts (and some posted pics) led me to the incorrect wiring.

Wow. Trying to get my head around what a swapping of the wires for the aux. valve and the throttle switch would do to engine (mis)management (which one? - there are two sets, one for idle and one for WOT). That would be rather buggy weird!

I refrained from saying that A PO might have buggered stuff, you never know... Anyway, glad you figured it out.

Reset your main idle screw (big one on top of the manifold) but I'd reset your AFM idle after things settle down with the instructions found here:


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Yeah it's running real rough now Lenny. The Wot wires were the ones switched so I think it"s been running real rich because I had to open up the idle screw a good 3-4 full turns.

It sure feels like it isn't running on all 6. I haven't tried adjusting the AFM yet but I need to replace the #6 injector plug first as I noticed it is broke and just hanging on the connectors. Will report back on progress.

Thanks again for your tips, any other are welcome.

Lesee... I'll take a WAG that a PO swapped those leads on purpose, so as to 'make it run better' by making it excessively rich (does it smell that way?) in an effort to get around the real problem of an out of calibration AFM. Or maybe they messed it up trying to 'fix it' and came up with your previously current situation.

Did you have a chance to read the AFM calibration procedure yet? Are you comfortable with using the O2 sensor and a DVM to set it up per the instructions?

I would, at this point, fix your injector connector, take out all the plugs, clean them and gap them, while you're there, do a valve adjustment .012 cold. That will give you a good starting point. Get the engine running, hopefully able to idle, disconnect the O2 sensor (is it new enough within reason to trust the readings?), hook up the DVM per the instructions and see what value you're seeing at idle. That will give a good determination of where to go from there using the calibration instructions as a guide on how to make adjustments.

Please Google on this site my other rants on engine and L-jet grounds, they are vitally important. It may not be quick or easy but persistence will eventually cover all the issues to give you a smooth running engine, they love to run (and like rich) but engine management has had issues (mostly age-related, but fixable) making it seem insurmountable. Best of luck -

You are absolutely right Lenny...the shop that did my head gasket some 3 yrs ago were having a problem getting everything back together and running right. Took them 3 times to get get that head back on right so I suspect they did it.

I already thought about cleaning the plugs and checked the timing also. So far have noticed a little improvement and is idling pretty good but my rough idle has always been while in Drive, not so much in park (if that makes a diff.) Not too comfortable messing with the AFM calibration for now. Will see how she runs for a while and see if MPG improves then take it from there.

Big thanks again for your tips and time!

I pulled a spare AFM and tried the adjustments that Lenny D provided (very much appreciated) but have not gotten any better results. Still hesitates on take off and idling rough as ever. Put newer AFM back on and still very similar results (slight improvement), reluctant to open up this AFM.

Not sure where to go next as I have cleaned sparks, double checked timing, cleaned the major grounds as Lenny has written about and still no improvement.

I thought correcting the wire switch-a-roo was going to improve the running but actually made it worse. Has to be a throttle/vacuum issue as that's where this bug started I'm thinking.

Checked function of idle control valve, temp time switch, coolant temp sensor to ECU, cold start valve, and all checked out good.

Any ideas/suggestions still welcome.

You have to determine if it is too rich or too lean. I would advise you to go through the entire system looking for unmetered air. If pressing the WOT switch at idle improves the idle then you are too lean (for any of a number of reasons that you have to eliminate one by one). It's not difficult but it is time-consuming to only change one thing at a time and evaluate the results. Please look at Peter's L-jet piece on the site for places that unmetered air can exist.

Yes Lenny I did push the WOT switch in the other day and it did improve idle so I just have to find the source of why it's running lean.

It's really getting hot and humid here in Orlando so I go to the garage less and less this time of year but just need to get up earlier and get through some more testing.

Thanks for your help Lenny.

Still runs best with the WOT Bosch throttle switch connectors plugged into the AC "additional air valve" i.e. no hesitation/trailer hitching and power seems magically restored when wired this way.

When hooked up like it should be I am getting severe cold engine hesitation/trailer hitching and still not fun when warmed up (but better), noticed also much more engine braking when lifting off the gas pedal(coasting), most likely because of fuel cutoff/lean condition. Have to put it in neutral at stop lights because it idles so rough in gear.

I have gone through Peter's L-Jetronic Throttle FAQ and all the adjustments (much more than once) and cannot pinpoint my problem. I have also taken all of Lenny's advice in this post but have had no luck solving the issue.

I was thinking that I might replace the ICV (aka additional air valve) as I read in a post that it solved someones similar problems, does this sound like a solution? I have tested it and it appears to be functioning properly but maybe out of calibration?

Sorry for the long rant but just trying get some help resolving. Any suggestions welcome as the weather is getting a lot nicer here in O town and is the time to drive the e12 more.

You need to set it back to stock and work from there. The A/C AAV is just a dumb valve, on or off. It does work remarkably well in my experience though providing essentially perfect idle regulation with the A/C on. But it's basic on or off, 100% of either.

Put the connectors back on the right switches. Hook up a meter to the O2 sensor up by the firewall. What does it say? It should be right around half a volt, up and down, back and forth all the time once it's warmed up. Low is lean, high is rich. If that's right, lets move on. Are the vacuum hoses hooked up right. Do you have the one to the distributor going to the correct side of the throttle body? That will screw you up if it's wrong, one side is for vacuum advance the other for retard. Next check fuel pressure. Make a $10 gauge with a $5 gauge for water from the hardware store and a couple of brass fittings.

Check all that and we'll go from there if you still have a problem.

The O2 is good and the vacuum hoses are right and have switched out the fuel pressure reg. but have not tested the fuel pressure. I will need to get a gauge rigged up and get back w/you. Thanks Mike.

Made the fuel gauge this weekend and hooked it up on the line to the cold start valve per the repair manual and it read perfect, 2.5 bar with vacuum hose off the regulator and 2 bar hose on.

I have also checked each fuel injector and connectors. Have no fuel leaks that I can see or smell. Fuel lines are newer (around engine).

I have also checked all the heat sensors, grounds.

Still don't get it :/