High idle troubleshooting

[Jonathan]

For understanding that "upper screw, lower screw" idea, have a look at this pictures in this post:

http://dmctalk.org/showthread.php?10...l=1#post152181

You can see it best in the 3rd and 4th pictures. The bracket holding those two screws (upper to engage the microswitch, lower to bottom out or come to rest at a zero point/curb screw) pivots together with the butterfly valves that are inside. As Dennis was saying, you want the lower curb screw to rest against its stop right where the butterfly valves are fully closed (i.e. in a vertical position). Once you're happy with that, adjust the upper microswitch screw to just activate the metal tab on the microswitch and then make it protrude perhaps another quarter turn or so.

When you're sitting at idle at a red light or intersection, you want the microswitch to be engaged at the same time the butterfly valves are completely closed and not letting any air by them. What I think can happen to change things slightly (and inconsistently), is if your pivot point and linkage aren't cleaned up well or lubed to some degree, the resistance normally put on by that spring to get it to go back to zero is countered by grime or rust or whatever and then it doesn't come all the way back.

This seems to happen more when the engine is warm or hot which is either affecting the spring or the grime by it expanding or swelling in the heat or it's being affected by the vacuum system somehow getting stronger as the engine has warmed up. This "sticking" idle is what you'll be dealing with if you need to "snap the gas" to get it to come back down. If giving the accelerator a quick snap or two to get it to come down works, then something in that throttle assembly and linkage isn't rotating freely. If the high idle is perma-stuck at 2,000 RPM or something similar, it's generally going to be an electrical connection gone bad.

Speaking of which, you mentioned your connector on that microswitch. Do you have a manual trans? I think you do, wasn't sure though. The automatics also have a "full throttle microswitch" which is very similar in terms of the switch and connector and it is mounted on the side of the throttle spool at about the 10 o'clock position looking down on it.

On the automatics, if you hammer the gas say in 3rd gear while out on the highway pulling out to pass someone, it will kick down the trans to 2nd to give you some more oomph to pass. I don't think the manual trans cars have this microswitch but I think they may still have the connector (not sure about that though). Some owner before you might have confused the two microswitches or connectors to explain why yours was unplugged. Hard to say though for sure.

[DMC5180]

All D's came with a full throttle enrichment switch. The automatics have an additional kick down switch. Manual cars just have the unused kick down switch connector stowed.

[Jonathan]

All D's came with a full throttle enrichment switch. The automatics have an additional kick down switch. Manual cars just have the unused kick down switch connector stowed.

Thanks for clarifying. Those two switches on the autos are "stacked" on top of each other, aren't they? The kickdown and full throttle ones that is.

Are any of the electrical connectors for these two or three switches universal such that the OP might have them plugged in to the wrong spot accidentally?

[DMC5180]

Stacked? Yes.

Connectors are the same style, but different colors. One black (kick down) and one white (enrichment).

[Trstno1]

Just ensure the lower adjusting screw is not contacting the bracket (throttle plates closed) and make sure the upper screw still triggers the micro-switch.

Your cold start issue could be attributed to a leaking injector. The next time your do a cold start try pressing down on the the gas pedal a little after it the engine fires. See if that clears the initial rough idle then let off the pedal to see if the idle is stable @ 775 +- 25.

Ok, it appears as though the curb screw is just barely making contact with the plate when the throttle is fully closed. So I don't want to mess with it quite yet. At this point it appears to be idling at 775-800 rpm after a second test from plugging the micro switch back in. That's good. Now, back to the original issue. Rich running. The dwell tested at 42-48 warm. Is that good or bad? I have never heard my FV buzz at all, ever.... I have verified power to the FV and the lambda ECU when the engine is running so my lambda relay, rpm relay, and lambda ecu should be working right? The only thing that seems weird is that after it warms up (still running rich) I can unplug the O2 sensor with no change to idle or running rich smell. Same story for the idle control valve. Is that normal? Meanwhile the FV never seems to buzz. Though I must admit I'm not sure of what the sound should be simply because being over a running motor with a type 1 exhaust installed is already a bit loud. I assume if the FV is not obviously buzzing, the ECU already thinks the car is running rich right? Is there a test I can conduct to lean things out a bit to see if that helps the running rich smell and turns the FV on? i have a pic of the throttle plate I'll attach, and I have some videos as well that may help in diagnosis if I can figure out how to attch them....

All help is greatly appreciated!

image.jpg

[Trstno1]

For understanding that "upper screw, lower screw" idea, have a look at this pictures in this post:

http://dmctalk.org/showthread.php?10...l=1#post152181

You can see it best in the 3rd and 4th pictures. The bracket holding those two screws (upper to engage the microswitch, lower to bottom out or come to rest at a zero point/curb screw) pivots together with the butterfly valves that are inside. As Dennis was saying, you want the lower curb screw to rest against its stop right where the butterfly valves are fully closed (i.e. in a vertical position). Once you're happy with that, adjust the upper microswitch screw to just activate the metal tab on the microswitch and then make it protrude perhaps another quarter turn or so.

When you're sitting at idle at a red light or intersection, you want the microswitch to be engaged at the same time the butterfly valves are completely closed and not letting any air by them. What I think can happen to change things slightly (and inconsistently), is if your pivot point and linkage aren't cleaned up well or lubed to some degree, the resistance normally put on by that spring to get it to go back to zero is countered by grime or rust or whatever and then it doesn't come all the way back.

This seems to happen more when the engine is warm or hot which is either affecting the spring or the grime by it expanding or swelling in the heat or it's being affected by the vacuum system somehow getting stronger as the engine has warmed up. This "sticking" idle is what you'll be dealing with if you need to "snap the gas" to get it to come back down. If giving the accelerator a quick snap or two to get it to come down works, then something in that throttle assembly and linkage isn't rotating freely. If the high idle is perma-stuck at 2,000 RPM or something similar, it's generally going to be an electrical connection gone bad.

Speaking of which, you mentioned your connector on that microswitch. Do you have a manual trans? I think you do, wasn't sure though. The automatics also have a "full throttle microswitch" which is very similar in terms of the switch and connector and it is mounted on the side of the throttle spool at about the 10 o'clock position looking down on it.

On the automatics, if you hammer the gas say in 3rd gear while out on the highway pulling out to pass someone, it will kick down the trans to 2nd to give you some more oomph to pass. I don't think the manual trans cars have this microswitch but I think they may still have the connector (not sure about that though). Some owner before you might have confused the two microswitches or connectors to explain why yours was unplugged. Hard to say though for sure.

I do have a manual yes.

[Trstno1]

Just ensure the lower adjusting screw is not contacting the bracket (throttle plates closed) and make sure the upper screw still triggers the micro-switch.

Your cold start issue could be attributed to a leaking injector. The next time your do a cold start try pressing down on the the gas pedal a little after it the engine fires. See if that clears the initial rough idle then let off the pedal to see if the idle is stable @ 775 +- 25.

Ok, so I've tested it a couple of times with the same results. I can barely press in on the accelerator when I cold start it and it will stay running, when I let off of the peddle after it appears as though it should be fine it bobbles down to about 500 rpm for a second almost dying then stabilizes back up to around 775 rpm. What do you think? Vacuum issue, fuel pressure issue, or leaky injector?

[Bitsyncmaster]

Ok, so I've tested it a couple of times with the same results. I can barely press in on the accelerator when I cold start it and it will stay running, when I let off of the peddle after it appears as though it should be fine it bobbles down to about 500 rpm for a second almost dying then stabilizes back up to around 775 rpm. What do you think? Vacuum issue, fuel pressure issue, or leaky injector?

Have you looked at the screen filter in the warmup regulator?

[Trstno1]

Have you looked at the screen filter in the warmup regulator?

I have not. Is that something that can be got
To fairly easily? What does the warm up regulator do exactly, and what would the symptoms of a clogged filter be?

[Bitsyncmaster]

I have not. Is that something that can be got
To fairly easily? What does the warm up regulator do exactly, and what would the symptoms of a clogged filter be?

You pull the fuel hose from the fuel distributor to the WUR and look down into the WUR. If it's dirty, you use some air and a brush to clean it off while still in the WUR. Probably best to pull the WUR out of the car so you can see what your doing.

The WUR sets the mixture rich when the engine is cold. It does what a choke does on a carburetor.