Momar

Ok, my idle mixture screws are 7 turns out. I just set the dwell, and it fluctuates, but I have got it so that it goes from somwhere around 47-53 or 54 with the air cleaner on. I was told to set it to 30 degrees dwell on a 6 cylinder scale. 50% dwell is equal to the 30 degrees that was reccomended to me according to the chart with the fluke meter I used. I set the idle at about 750 and did this. I got it set like this and the idle was still at about 750. I turned the car of and went inside for a while. I came back out and started it up and it was trying to idle at 500 again. Well, I went ahead and let it warm up for a couple minutes and the idle came up. After the idle came up I took it out and drove it for a while. After driving a minute or 2 the idle was up to around 1100. It stayed this way the rest of the drive. I parked the car and put it in park and the idle went up to about 1200 and stayed there for a minute. I punched the pedal to the floor real quick and it reved and then started idling at about 750 again. What the heck is going on and how do I fix it?

Thanks

Ben

Momar

anybody?

ME Leigh

Sounds like it could be a vacuum leak?

Riley's35089rs+

What carb you have? Does it have a choke? Electric or manual?

Momar

It is a computer controlled quadrajet. It has an electric choke. When I checked the choke seems to work, but the high idle doesnt seem to work unless its real cold out.

Vader

You know that the engine and carburetor should be a full operating temperature before you adjust anything, right? It sounds like you adjusted the MC solenoid, then let it warm up.

7 tunrs out on both mixture srews sounds like a problem. Has the carb been cleaned out?

BTW - The idle mixture and idle speed adjustments shouldn't necessarily affect each other that much.

Momar

Yes, I did adjust it before it warmed clear up. I guess I will redo that. Yes, the carb is actually really clean. I just put it on recenty. Also, if the mixture doesnt effect the idle to much, what do you think my problem with the idle is? Oh, and by the way, you think 7 turns out on the idle mixture screws is a problem? Thats what I was told to put them at.

Ben

Vader

7 turns out could be about right as a starting point. I know the later E4ME has a lot finer thread than the older 4MV and 4MC Rochesters.

Get an idle vacuum reading while you're adjusting the primary mixture, or use an EGA while adjusting the mixture. Make sure the engine is at full operating temperature before adjusting anything except the automatic choke.

flyway190

While you're doing this testing, you might want to unplug the idle load compensator just to be certain that it's not doing anything weird. It's the one-wire connector on the driver's side of the carb. I really doubt that it's the source of your problem, but it couldn't hurt to unplug it.

Momar

Ok, so if I adjust the idle mixture screws with a vacuum gauge I just go until the vacuum is the highest right. Then after I get that I will need to re-adjust the iac right?

Also, I think these are more of efeciency adjustments than fixing my problem right. What would you guess was causing my wierd idle speeds? Do you think it would be a vacuum leak. Do you think that my idle mixture could actually cause this?

Ben

Momar

Ok, well, I figured out part of the problem. I found that the silinoid was holding it open for some reason. Anyway, I unplugged it and I still have the problem with it trying to idle at 4-500 rpm until it warms up. I reset the idle but did it while it is warmed up and it still idles around 500 when I first start it. The motor can still be hot and it will still idle at about 400-500 when I start it unless I just shut it of within the last minute or 2. What do you think I should do? I could try setting the idle screw when it is idling real low, but I would bet that I am going to end up idling over 1000 when it warms up. Any ideas?

Also, should the high idle work only like the first time you start the car for the day when the motor is completely cold, or should it work anytime the car has sat for a little while(how long?)? Also, what would be causing that silinoid to open the throttle like that? I have another 1 or 2 of them off of other carbs if you think it is the part its self, but I dont know why it would just decide to open the throttle. I would think it was the computer doing it.

Thanks

Ben

flyway190

From looking at the circuit diagram and doing some reading, it seems that the solenoid (throttle kicker is a better name) should come on when the car is running, then switch off when the ECM tells it to. Once it's switched off by the ECM, it should only come back on when the air conditioning is on. I haven't been able to confirm this on my car because my carb decided to start leaking gas all over the place today. I suppose it's possible that the solenoid is sticking, so with a couple of others on hand you might want to change it out. It doesn't seem that it's getting 12V all the time, but you might want to check to be sure. It appears that the ECM, by using a relay, only controls whether it's getting constant power (hot when running, bulb test, or start) or switched power from the A/C.

When I first start my car in the morning, the idle stays at about 1500 rpms for about 2 minutes (unless I get impatient and start driving anyways). Depending on how long I let the car sit, it won't take as long to come down the next time I start it. If I start it immediately after shutting it down, it will only stay there for half of a second.

Momar

Yes my friends dad that I talked to yesterday has 25 yrs experience and he said that that was supposed to comeon when the air conditioning was on.

Say maybe your car had sat for 20 minutes, does or how long does the high idle come on?

Ben

RB83L69

The "fast idle", as far as anything temperature-controlled, is a function of the choke. If the engine doesn't cool down enough for the choke to come on, it won't go into fast idle. 20 minutes should not be enough time for the choke to cool down and come on, unless you're parking the car in sub-zero weather. Oh wait.... you do live in northern Illinois....

The "kicker" solenoid serves 2 functions; one, as described, is associated with the A/C. The other is as a "dashpot" to slow down the throtttle closing when the driver takes his foot off the gas. The ECM will power it whenever the engine speed is above about 1400 RPM, and remove power from it when the idle drops below that. It should be adjusted so the the idle is about 1250 RPM with it extended. It prevents the throttle from slamming closed and casuing high HC emissions at that critical moment; it also keeps the motor from dying so easily. You can tweak it fir smoothest operation when you take you foot off the gas.

Don't waste your time fooling with the "idle mixture" screws, they basically don't do anything. Put them at 7 turns out and forget they exist, and use the IAB valve in the top of the air horn to adjust the idle mixture. Adjust it in small increments, like ¼ turn at a time; CW richens the idle and should cause the dwell meter reading to increase (ECM attempting to lean the mixture out) as you adjust it, if the whole feedback system is working correctly. The car will probably run best with the MCS duty cycle at somewhere around 60-70%; factory spec is 50% (tends to be a little too lean under some conditions). That corresponds to 30° dwell on the 6-cyl scale of a dwell meter. Aim for a setting closer to 40° with the car fully warmed up, and the idle speed set to 750-800 RPM.

Momar

Ok, I actually am right about in the center of illinois, not really northern. Anyway, it is about 50 out in the mornings right now and gets up around 70 or so. I have figured out how to adjust the choke, I just didnt know where to adjust it to.

Anyway, as far as the mixture, I have it set to about 50% duty cycle because the fluke meter I had actually gives percent duty cycle and has a conversion chart to convert it to dwell. Anyway, I have the screws about 7 turns out. When I adjusted the iac, I have it about 50%, but it fluctuates about 5% up and down from 50.

Anyway, I think I can figure out the choke/high idle fine, but my main problem still exists. What I really want to know is why my idle is low when I first start it and raises up. It does this to an extent even with the silenoid unplugged. With it plugged in it has about 3 stages it would start out idleing about 4-500 and then go up to 750(which is where I set it with the motor warmed up) and then when i drive it it goes up to about 1200(which I tracked down to the silenoid). If I unplug it it doesnt go up to 1200, but the idle is still low when I first start it. I have it unplugged right now and have the idle turned up a bit so it is about 700 when it first starts, and then goes up to about 1000 when it warms up, but want to get it so the idle is the same when I start it as when it warms up. It seems to go up when it hits closed loop. It will idle lower again even if I just turn it off for a few minutes and start it back up. It can still be up to temp, but when it hits closed loop again the idle will go back up. Does anyone know what I should look for to fix this?

Thanks

Ben

Damon

Ben, I think your choke isn't working right.

Here's how it SHOULD work:

On a cold engine you tap the gas pedal to "unload" the choke linkage. Choke plate should "snap" closed and this also engages the fast idle cam which should raise the idle speed anytime the choke is not FULLY open. On a cold motor it should idle about 1200 RPMs, drop down to about 900 when partially warmed up and then down to normal idle speed when fully open/warmed up.

Once started the choke plate should slowly open until it's completely open in about 3-5 minutes of run time. Once the choke plate is fully open the fast idle cam disengages and you drop to normal idle speed as set by the idle speed screw on the driver's side of the carb.

If your choke pate is closing when cold and opening when warm like you would expect then I'd say the fast tidle cam either isn't engaging (unlikely) or the fast idle speed screw is backed too far out to kick up the idle speed when the choke is closed. The fast idle speed screw is located under the choke linkage on the pass. side of the carb and can be seen from the front of the carb by looking underneath the choke linkage carefully when the choke is on (closed) AFTER you tap the gas to let the linkage engage. Turn clockwise to increase the fast idle speed, CCW to decrease it.

Remember, this screw ONLY affects idle speed when the choke is on. once the choke opens fully the linkage disengages and the idle speed is set using the normal idle speed screw on the driver's side of the carb near the throttle arm.

I suspect that what's happening with your motor now is that you are having to "compromise" on the normal idle speed screw. It's idling too low when cold but too fast when warmed up. A single idle speed setting won't cover everyting from ice-cold to fully hot, as you have experienced. That's the reason for the fast idle speed system.

Momar

Well, I am pretty sure I have already figured out what is causing my high idle not to work. I think that my choke is set so that it wont open unless it is really cold out. It worked when it was under 20 degrees out but wont now that it isnt getting that cold. I can fix that(which way do I turn it to get it to come on easier?). The thing is, I am not sure that is the full problem. I turn the car off and wait a few minutes like maybe even only 5 and start it back up and it is idling to low(around 500 when I have it set to idle at about 750). It will do this for a couple minutes until it hits closed loop and then go up to the 750 idle I have it set at. I think that when i get my choke set it should get rid of the problem when the car has been sitting for a while, but when it hasnt been sitting for long enough for the high idle to kick in I think I may still have a problem with it trying to idle to low.

Ben

Momar

I got the choke set so it will work(with high idle) the first time I start it in the morning, but I think I need to do a bit more adjusting because I let it run for like 1 minute and shut it off because I realized I had a flat tire, and then the high idle wouldnt work again after setting for a couple hours. I guess I will mess with it some more.

Ben