74 2.0 with 96 mm cyls and Webcam 73, stock FI. Car starts easily, runs strong right up to redline, no backfire or any trouble at all, except that when coming to a stop the engine revs waaaayy down low and sometimes quits. If it keeps running, it rebounds up to 1100RPM and will yoyo a bit before settling at about 450RPM. If it quits, it will start right up again.

The decel valve had been removed by the overhaul shop because they said it was "leaking". I had another one on the shelf, with no leaks, and installed it, but it doesn't seem to make much difference.

The idle adjustment screw shown in the Haynes manual doesn't look anything like my throttle body, so is it the screw at the 7 o'clock position on the throttle body when viewed from the back of the car? How much adjusting does it take? I gave it a turn or two with no apparent effect.

Ideas?

CHTS = Cylinder Head Temperature Sensor

Check the wires leading to it also!

I would check the dwell first 50 degrees, and make sure that the car is hitting on all four cylinders at idle. Webcam may be a bit of a problem as they run richer at idle than the fuel injected camshaft. Also make sure that your advance weights are not sticking leaving some timing advance at idle which is not good for a clean idle

Dr:

It is firing all four at idle, but it is a bit ragged sometimes. I was wondering about the mixture. Which direction do you turn the knob on the brain for leaner mixture? If it is running rich, the plugs should show it, right?

Thanks

Jeff,

Hmmmm, educate me. How would the CHT sensor affect the idle? Mixture misread by the brain? MPC FI is a whole new world for me.

Tim

CHT, if loose, would possibly enrichen the mixture and cause it to lose the idle.

There are a few things to check that have already been mentioned and none of them are a silver bullet.

Your car may not be tuned up correctly, and that will cause this condition.
First, set your valves...when was the last time you adjusted them?
How many miles?
After that, check your points for corrosion in between the contacts...the corrosion will increase your dwell and cause this idel condition.
After you visually inspect the points, and your valves are adjusted, hook up a dwell meter to see what you are reading.
50 is the top end of the scale for proper running and it assumes you will change your points more frequently..or at least check the dwell more frequently...48 is a bit more safe and it allows for the build up of corrosion that will increase you to 50 or more over time...then you get odd running conditions.

Most times the low idle condition is due to the ignition system a tuning not being done and up to snuff. Turning the ECU knob just masks the issues and its most likely why that option was removed on later ECU's.

A fresh tune up, a new set of points, plugs, wires and a cap (about 40 bucks) does amazing things to the motor, and will make it purr.

Points cost $4.00 dollars...I change my twice and sometimes three times a year...when I feel wealthy.
Rotors get cruddy build up and get worn down.
Distributor caps get buildup on the contacts...again replace.

Its all fairly simple to learn instead of paying someone if that is one of your fears...we can help.


Rich

If the CHTS begins to fail it won't be able to sense that the car is warmed up to adjust the fuel/air mixture to be leaner!

Mine had stripped threads and would get intermitant contact so sometimes it would run fine and others it would not idle at all when warmed up!

Agreed.
If its a consitent issue, check your CHT wire with an Ohm meter to verify that is reads the proper amount.
These readings are based upon the year etc.

Look up at the top of this page and click on 914info (way at the top) and in there (click around a bit) is a link to Banders Djet site which has a graph that has all the readings for the CHT in there.
He has a very good troublshooting flow chart to walk through the issues.

The CHT is an enrichment circuit that is driven by the engine temps.
The idle setting is a different circuit driven by the TPS and those sometimes get dirty and give you false readings.

Start with a tune up...dont go down the fule injection troubleshooting road until you know that your car is properly tuned.
If your valves are off...you lose idle.
If your dwell is off, you lose idle
If your cap or rotor are worn...you lose idle.

Its simple enough to check those normal everyday issues before you try to figure out Djet...most likely its not Djet (at least not all the time)

Replacing a CHT is not always a fun project and they can break off inside the head...while the motor is in the car..
Its not a simple place to drill and tap.

Rich

do trigger points effect idle?if yes check those too.

OK, I got a checklist now. Too late to do much more today, but thanks to everyone.

Hey Tim, I can help you trouble shoot some of those items over the weekend. Not able to do the valves though. Maybe one of the other local guys can help you with that, or you can contact Rorey. He does mine. If you pick up a new condensor and points we can put them in and relube the distributor and contact plates.