Idle Backwards

[Bitsyncmaster]

I started the car in Park. Pulled the plug on the Thermo Time Switch. Jumpered the Microswitch. The Curb Idler Screw is not touching. The Butterflys are completely closed (I removed the U-Pipe and checked).
Once the car got hot the RPMs went up from 775 to 1,500. It starts find when hot. I pulled the center side plug on the ECU and the RPMs went up to 2,200. Plugged it back in and down to the 1,500 (cause the engine was hot). Plugged the Thermo Time Switch back in, made no changes.

Something is telling the car when hot to increase the idle RPMs. What? The ECU, some sensor? Why only when hot?

With all those symptoms, my guess is you have leaking deceleration springs. Did you look at springs?

Here is a photo of bad springs.

[Ricker]

With all those symptoms, my guess is you have leaking deceleration springs. Did you look at springs?

Here is a photo of bad springs.

I have. Here is a photo of mine. Do they look bad?

https://dmctalk.org/images/attach/jpg.gif (not sure how to add a picture)

[Bitsyncmaster]

I have. Here is a photo of mine. Do they look bad?

https://dmctalk.org/images/attach/jpg.gif (not sure how to add a picture)

Hard to see in that photo but I think I see uneven spacing which has shown the springs are a problem.

[Michael]

Edit...found this on the euro forum. It may help

This info is courtesy of Nick T, who imparted his secrets to me in a call last year. I have only just got round to making use of the info, and I must say it has made a real difference to the feel of the car.

It became necessary on my own car when I noticed a high idle, and traced it to the butterflies not closing fully at “rest”. Coincidentally this high idle became noticeable after fitting the new exhaust and Nick helped Dan K set up the mixture. After getting it "ballpark", and adjusting fuel pressures accordingly, I noticed a high idle once the car was fully warm.

(The rest of the D-Intelligence gleaned in the phone call will be written up after I have done it myself).

Following this procedure will allow correct set up of the mechanics of the throttle control from pedal to butterflies. Nothing too radical, just useful information- mine was a definite bodge.

To start from first principles is often the best way. I also replaced the throttle cable, making sure it was well lubed.
1. Disconnect the linkage rod front the ball joint on the throttle spool.
2. Unwind the top grub screw, on the “butterfly actuating lever” away from the idle microswitch
3. Back off the bottom (throttle stop) screw on the same lever, so that its off the stop.
4. Screw this back in, until it just touches the stop. Then give it one more full turn and nip up the locknut
5. Grab the link rod, and open and close the mechanism. It should be smooth and repeatable. You may wish to visually check the butterflies are closing fully. I had taken mine off previously, so knew they were good. If this is all ok, clean and lubricate the return spring.
6. Get a 0.3mm (12 thou) feeler gauge between the closed throttle stop screw and the the throttle stop.
7. Open the throttle very slightly, and adjust the top idle microswitch activating screw, so that it just activates the microswitch (“click”) at this point. Nip up the locknut.
8. Now look at the spool.
9. At zero throttle, it should rest on the zero stop.
10. Similarly at full throttle (pedal fully depressed) the spool must touch the 100% stop
11. If not, adjust the pedal stop in the drivers footwell to ensure the spool fully closes at rest and the spool goes to 100% when the pedal is fully depressed. Ideally, the cable adjustment (where the cable goes through the throttle spool mounting) will be about halfway along the threaded portion.
12. At 100% throttle, the actuator must also trigger the full throttle microscwitch.
13. Now reattach the connector rod back onto the spool. Adjust the linkage (shorter usually) until the spool is just off the closed stop at rest.
14. Next turn attention to the 3 brass screws…. But that, children, is another story!

More to come when I get further into my set up! At the same time I had replaced my fuel lines, and vac pipes so was reasonably confident of no major vac leaks.

[82DMC12]

Thermotime switch should read about 0 ohms (direct to ground) on one pin to ground and the other pin should read 20 to 30 ohms to ground.

[82DMC12]

Notice that the butterfly plates are not supposed to be 100% closed at idle, they will bind if you try to get them perpendicular. See the process I posted earlier - as you turn in the idle stop screw, you are opening the plates. When you let off the gas, the throttle should spring closed and stop on the stop screw.

Agreed that the spring on the left side of the throttle looks collapsed. You could try to use a hot glue gun and glue the decelleration spring plates closed temporarily as you try to sort this out. If your idle is fixed with the plates glued closed, you will know for sure it's the collapsed spring.

I had an issue with idle creeping up when the engine was hot (after starting cold and just idling in the garage). The problem was just the throttle linkage was not adjusted properly.

[Ricker]

I have done everything suggested and the car still idles at 1,500 RPMs when hot (not cold - 775 RPM) and in park/neutral. So a few more questions......

1) Does the ECU control the idle RPMs when a) in drive and b) in park/neutral? I believe it does.

2) What tells the ECU the temperature of the engine? I know it is not the TTS but something does.

[Bitsyncmaster]

I have done everything suggested and the car still idles at 1,500 RPMs when hot (not cold - 775 RPM) and in park/neutral. So a few more questions......

1) Does the ECU control the idle RPMs when a) in drive and b) in park/neutral? I believe it does.

2) What tells the ECU the temperature of the engine? I know it is not the TTS but something does.

The idle ECU does try to hold 775 RPM all the time. It does not know if in park or neutral.

There is a thermistor (changes resistance with temperature) in the Y pipe that provides the measurement of engine temp to the idle ECU. note: the schematic calls that the "IDLE SPEED REG SW".

[FABombjoy]

I didn't see anything in this thread about ignition timing. Have you checked it?

It's easy to get high RPM with too much idle advance. Like if the solenoid is bad, disconnected, maybe vac hoses backwards at the solenoid.

[Ricker]

The idle ECU does try to hold 775 RPM all the time. It does not know if in park or neutral.

There is a thermistor (changes resistance with temperature) in the Y pipe that provides the measurement of engine temp to the idle ECU. note: the schematic calls that the "IDLE SPEED REG SW".

I checked the thermistor when the engine is cold. I do not get any reading with the ohm meter. I believe it needs replaced and possibly this has been my problem. Your thoughts?