Fast Idle and more

paulhagedorn · 11-15-2000, 12:43 PM

Ok, so I get in my car and start it this morning. It was probably 40 degrees. Once warmed up, the car has a very fast idle, probably around 2500 or so(tach doesn't work because i haven't gotten the thing for the MSD). Also, it does it when cold as well. I would say that it is the vacuum advance, but not sure.

The idle is high and rough, but once the car gets moving and above that rpm, it smooths out...but will continue to idle there if I push in the clutch. Car is a 73 2.0.

How much does a rebuilt distributor cost? What about just the vacuum canister on the side of the distributor. Oh, and I do have the original fuel injection with MSD-6A.

I am completely perplexed...other than pulling the distributor and rebuilding it.

Thanks,
Paul

John Rogers · 11-15-2000, 12:54 PM

You can pull the distributor cap and turn the rotor to see if it advances and retards freely. I'd guess it's a vac leak, try the carb cleaner spray around all the hoses to see what happens. Whne it gets real cold, metal shrinks and will pull loose from push on hose connections. Good luck.

bowlsby · 11-15-2000, 06:42 PM

It could also be other things.

The idle should be higher on days below 50 degrees for warm up. Under those conditions:

the aux air valve will be open for 5-12 seconds...giving more air

the cold start valve should be operational for the same time period...giving more fuel

the CHT sensor will be cold, and richen the mixture

the air temp sensor will be cold and richen the mixture

throttle switch properly calibrated?

As to why the idle is *lumpy* I don't know...

timing misadjusted?

trigger points worn?

Like was said before...verify the integrity of all possible intake manifold air leaks and check the operation of all FI components

CGNJ · 11-16-2000, 05:11 AM

I am curious about your MSD6. I have installed without the tach adapter and it does work. I am running carbs with a 009. I originally intalled the tach adapter and my tach didn't work, so I just used the tach output.

Pritchard · 11-16-2000, 06:32 AM

Bowlsby-

I am curious about the length of time that you have showing for the Aux Air Valve to be open. Is 5 - 12 seconds correct? Mine stays open for several minutes. 5 - 12 seconds would be great. My MPG would improve some.

If this is correct, I guess I need to check my AAV for power and then corrosion inside.

Thanks

Pritchard

[This message has been edited by Pritchard (edited 11-16-2000).]

Dave at Pelican Parts · Dave at Pelican Parts's Garage

I think he meant 5-12 minutes. Also, the cold start valve should only be spraying fuel while the starter is cranking.

--DD

paulhagedorn · 11-16-2000, 08:15 AM

Sorry for not responding any sooner...thanks all that have responded. For one, the cold start valve on my car should not work. I don't have the ambient air temp sensor. Mine failed a while ago, and the part is no longer available. Anyone have a working one off a junk car?

I tried plugging the tach straight into the msd box and nothing worked. I haven't really had the time to do a search on MSD's site to find the adapter.

I have checked the vacuum hoses and all of them are intact, for the most part. Meaning, the ones that were loose a little before are still loose. The hoses definitely need to be replaced between the filter box and the thing right next to the oil dipstick. As well as the one that goes to the driver's side head. I haven't checked the distributor yet. I will be doing that tomorrow afternoon when I have more time.

Again, thanks all for the responses. I will also try to get some carb cleaner to check for vacuum leaks.

Eventually I will get around to cleaning the TPS(any quick easy ways to do this? also, where is it...do have a Haynes to look at, though) I would love to get my hands on a factory manual.

Don't have a reader, nor any place to put it for the microfiche.

Anyway, enough banter for now.

Oh, and I definitely need to check the AAR...please let that be alright.

Thanks again,
Paul

John Rogers · 11-16-2000, 10:09 AM

The hose to the thing next to the dip stick is the PCV valve, which is no longer available either as far as I know? There are several places that can cause vac leaks here, the PCV valce can be loose or cracked, the hose can be loose or the gasket at the base of the breather box it sits in can be bad or loose and air will most definately leak in there. The wire bale that clamps the breather can get deformed and is easily bent to get pressure to seal the box. I do have a PCV valve for sale for $5000 if anyone is interested????? Good luck.

paulhagedorn · 11-16-2000, 10:52 AM

Well, one more stipulation to the problem. I turned the key to the off position and the car didn't turn off....it didn't turn off until i pushed in the clutch a little then tried to turn it off again. Ugh...now i think it might be the ignition switch. Someone please help me!

This weekend will definitely be troubleshooting weekend.

mejulihn · mejulihn's Garage

I hate to say it, but I think you are dealing with more than one problem here. If the motor does not turn off when you turn the key off, that sounds like a problem with the ignition switch. I don't think your fast idle problem is related. I would start with replacing vacuum hoses and eliminate them as a possible cause first. It is relatively inexpensive to do and if the fast idle is still present, you have done a valuable periodic maintenance item anyway.

bowlsby · 11-16-2000, 07:54 PM

I reviewed the book "How to Tune and Modify Bosch FI systems" and I made a slight error in the previous post...

The Thermo-Time Switch and Cold Start Valve only operate when the engine temp is below 95 degees F and the engine is cranking. The CSV is powered because the ground path runs through the TTS. The TTS has a heater element in it that quickly opens the circuit to the CSV (shutting it off) in what that author said is 5-12 seconds.

The AAV also has a heater in it but the book does not indicate how long it takes to close. The AAV requires an ambient air temp <95F to be open, it closes above that temp.

Other unofficial sources have said the AAV and the CSV only operate when the air temp is about 50F and below. hmmm.

One thing I find interesting is that both the TTS and AAV have heaters in them which run full time while the engine is warm, so they continually tell the ECU how to respond, keeping the TTS circuit open and the AAV closed. No wonder they burn out.

JP Noonan · 11-16-2000, 08:54 PM

Use a "mity-vac" vacuum pump on the ports of the dizzy. You can see the advance plate move, if the diaphram is still good. I do have a dizzy that looks better than my working one but has a ruptured diaphram so it does happen.

Try removing the hose that goes from the manifold to the PCV and plug it. That will rule out the PCV sustem from being the leak.

bowlsby: sorry to be nit-picky but the CSV and AAR aren't hooked up to the computer in any way. They both just get power and ground. The MPS will notice the change in manifold vacuum as a result of the AAR being open or closed, but there is no signal from the AAR to the brain.

paulhagedorn · 11-17-2000, 12:54 PM

Problem one solved. Idling normally and running like a champ. Oh, and for anyone that is thinking about getting an MSD system...I would definitely recommend it. The difference between the power under load in the upper rpm's is like night and day. You can actually feel that it is pulling more. Maybe it is just me though. Anyway, thanks to all that helped. What I did was make all the vacuum hoses tight by cutting some of the length. Also, one of the spring loaded things that holds down the distributor cap came loose. Fixed and all is happy.

Now, we shall see if the ignition switch problem resurfaces.

Thanks again,
Paul