First Post, First adventure working on one, some fuel related issues I need help on.

[Peno67]

To follow on, the cleaned valve was installed. The car was started in a cold condition and the rooms would steadily fluctuate between 1000 to 2000 rpm. After warming up for a good period the rpm settled in arou d 170p. Disconnecting the onboard ECU plug resulted in the engine going to around 3000 rpm. Based on input this would seem to indicate the valve is working? If so what should we be looking at to get the rpm in check?

[David T]

Verify the throttle arm is returning ALL the way to the idle position and the throttle plates are closed. Inspect the decel valves and springs on the throttle plates to make sure they are held closed. Try to fix any vacuum leaks.

[NckT]

Check that the ecu has reference to the thermistor (engine coolant temp) resistance. Unplug the 4 wire multi plug that's on the bank of the black ecu behind the drivers seat and use a multi meter to measure the resistance between the black/light grey and the black/yellow cable. You should get a resistance to temperature ir approx 8k ohm to 14k ohm on warm engine. If you get open circuit then shove in the back of the multi plug a 10k ohm resistor so it touches the metal pins and reconnect. If this fixes the idle then you may have a bad electrical connection, usually at the church window electrical multi plugs that is located behind the coil cover at the back right of the engine.

If not then you'll have to back probe the wiring from the ecu to the device, but take note that from the throttle(closed) switch to the ecu there is an interposing diode that is in the wiring at the back of the black idle ecu towards the firewall moulded in a black plastic connector. This is to prevent back feed from another circuit that the micro switch operates, so don't bypasd/short out/ shunt this out.

Good luck

NickT

[Peno67]

Here is what I have figured out. I mentioned an oring found in the intake. Pretty sure this is for the airtube from the idle motor. Got a he'll of a vacuum leak under the intake area. Also found the cold start injector is pooched. Verified voltage and ground at the plug. Also confirmed the idle valve and ECU is operating although the thermsistor is open or at least the circuit is and will likely require a pull of the intake. Thanks for the resistor idea at the plug. Tried this just shorting a wire and after finding out restance is needed I will give this a shot. We are going to park this thing in a barn till spring as we got other work piling up as well as snow.. Thanks for all the help. I will report back

[Peno67]

Well it has taken a bit longer than spring time to get the owner to get some parts. As a follow on to above items, we pulled the intake and confirmed the thermistor was bad and replaced. Checked all related vacuum lines under the intake for any leaks. While we were in we also checked the other coolant temp sensor, replaced all the intake o-rings and gaskets and reinstalled. We also replaced the CSV and confirmed it was operating. Also replaced the vacuum advance control mounted on the firewall (forgot what this is called). Now when the engine is cold it will at least try and start but immediately dies. After a few attempts it then won't fire at all telling me the heater is working properly to prevent flooding. If once it starts we feed gas through the intake to keep it running, after it warms up this is no longer necessary and the engine runs fine albeit at around 1050 rpms. Ended up out of curiosity, pulling apart the pressure regulator and found a bit of a mess, all insulation on heater wires were gone and one wire melted in two. Confirmed the heating resistor was good and a repair was done. I will assume the only way to check this entire regulator out is with pressure gauges and adapters which I am sure we could make if required. So this entire mess has me asking more questions. First off it is apparent we have a fuel delivery issue when cold, just don' t know the cause. I am also concerned with how much the fuel air mixture was messed with. Here are some questions:

1. Is there a ground zero starting point to go with on the fuel air mixture screw. We do have a dwell meter although I wanted to know if someone can confirm something. It is an older craftsman unit that has scales for 4/6/8 cylinders. I read somewhere where one should use the 4 cylinder scale or half of the eight and I question if this is tester specific or for all? I read that another way to get a good staring point is to remove a injector and adjust the mixture screw with the engine not running until a injector starts to break open. Not sure if this is such a good idea.

2. If we crank in the fuel mixture screw clockwise enough we can get it to start cold although it sure seems like it is running rich after warmup based on our eyeballs burning out in the garage in a very short time frame. Also this increases the rpm. I wouldn't think if electronic idle system was working right that this would happen. If after it warms up I back the mixture screw out to get it down to 750 then it obviously is not going to start cold and then it runs pretty rough at the 750.

3. Would greatly appreciate some guidance on Step 1 thru Â…. on check this part of the system and then next and so on. I would like to take the logical approach to getting down to the bottom of this as we must be getting close and much has been repaired.


Any input is appreciated. If you can tolerate 3 previous pages of back and forth it may answer some questions of other items already addressed.

[82DMC12]

Peno,

Yes, the suggestion to close the mixture screw until the injectors stop, and then open it until the injectors just barely crack open, is correct to get to a baseline where the machine will idle well enough so that you can adjust the mixture with the dwell meter. As to which scale to use, sorry, it's been over a decade since I did it last time I don't remember, but my meter only has 6 cyl and 8 cyl scales. I THINK I used 8 cyl somehow...

Regarding the high idle, Have you confirmed the idle stop screw and the microswitch trip screw are not adjusted too aggressively so they are interfering with the throttle closing completely? There is also linkage between the idle spool and the throttle which can be lengthened or shortened. maybe someone adjusted that linkage so that the throttle won't close all the way. I would consider taking this whole throttle system apart, clean the spool and spring, grease the linkage, and set the stop screw and microswitch screw again so you're confident the throttle will close at idle.

[Peno67]

Thanks for the feedback. Seems like I remember reading that one can use 8 cylinder but I think you divide by 2. Maybe someone else will comment.

[Ron]

Yep, 4 cylinder or 8 cylinder / 2

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