Cracking noise and missing. Tach also jumping. Help!

[81dmc]

Could this be a bad distributer cap?

Car wants to stall in gear (600 rpm), and I'm 40 miles from home now...:bigcry:


http://www.youtube.com/watch?v=17AwUzfhvB8

[Bitsyncmaster]

Do you have a stock ignition? I ask because I had a GM unit that needed a capacitor and it made a skip like that.

[81dmc]

Do you have a stock ignition? I ask because I had a GM unit that needed a capacitor and it made a skip like that.

I have the gm unit with the capacitor you sent me...

With further testing it actually seems like your idle ecu is malfunctioning. AC will no longer bump idle and the clicking is actually coming from the vacuum solenoid.

Idle is randomly jumping now too, but if I unplug the ecu, it just stays low.

[Bitsyncmaster]

I have the gm unit with the capacitor you sent me...

With further testing it actually seems like your idle ecu is malfunctioning. AC will no longer bump idle and the clicking is actually coming from the vacuum solenoid.

Idle is randomly jumping now too, but if I unplug the ecu, it just stays low.

At least you can bump your idle up with the curb idle screw to get home. PM me your address and I will send you another ECU and you can return the old ECU in the same box. Let me know if you have the 9 or 11 pin ECU.

[Ron]

Weird noise!
In the video, were you pinching off the line that goes to the distributor (it should be the furthest port from the electrical plug on the vacuum solenoid, iirc), or was it the feed line to the vacuum solenoid? The reason I ask is
I don't think pinching either one should have changed anything since the vacuum solenoid should be shut and not supplying vacuum to the distributor at idle.
Are you sure it is the vacuum solenoid causing the noise...ie not something else causing it to flutter...or maybe the vacuum advance diaphragm has a hole in it...or the plate loose?

Just throwing out ideas...

[81dmc]

Went ahead and installed Dave's new ecu. Unfortunately, it did not fix my issue. I was at a loss.

However tonight, while I was fixing a bad led tail light, I had my ignition set to run for about 30 minutes. In that time, I could hear the damn clicking noise! Turns out the clicking is coming from the idle speed motor, but also every time the idle motor clicks, the vacuum solenoid clicks open. I confirmed this by unplugging and repplugging the solenoid while the issue was occurring.

So what could be the issue? Is it a sticking idle speed motor that causes Dave's idle ecu to reset?

Here's a quick video while the anomaly occurred. Also, after a key cycle, it didn't happen again....


https://www.youtube.com/watch?v=3quE6EIh7Xs

[Ron]

The noise going away when you pinch off the vacuum line is the main clue, imho.
You didn't answer- Was the vacuum line you pinched in the first vid going from the vacuum solenoid to the distributor?

[Bitsyncmaster]

We just had another owner have a problem with advance coming on at idle. It would come and go. After 3 idle ECUs and a new vacuum solenoid it still was intermittent. It has to be an intermittent connection to the solenoid. What he did was just leave the advance hose off (plugged the free hose). I will have to re-due his wiring when I get a chance but he found no problem running without the advance.

Note:
You get advance when the solenoid has no power as long as your engine has warmed up.

[Ron]

Note:
You get advance when the solenoid has no power as long as your engine has warmed up.

Yes! So I'm guessing, since pinching off the vacuum advance line makes the noise stop, the vacuum switch is fluttering because it is defective or being powered on and off, OR, the the vacuum switch is always passing vacuum and the distributor has a problem (eg advance diaphragm torn and fluttering, or ??).
...or am I missing/forgetting something?

[Bitsyncmaster]

Yes! So I'm guessing, since pinching off the vacuum advance line makes the noise stop, the vacuum switch is fluttering because it is defective or being powered on and off, OR, the the vacuum switch is always passing vacuum and the distributor has a problem (eg advance diaphragm torn and fluttering, or ??).
...or am I missing/forgetting something?

I've never pulled an advance solenoid apart. All I know is when not powered, the advance is on and the vent is closed. When powered the advance is off and vent is open. I did find one solenoid that only provided half the vacuum so I guess that vent was always open on that one.

[NckT]

You could do a test and check if the throttle closed switch is not intermittent too, as this would effect both circuits.

[81dmc]

You could do a test and check if the throttle closed switch is not intermittent too, as this would effect both circuits.

I actually deleted that switch when I rewired my engine harness. Maybe I'll reinstall that when I get the chance...

[Ron]

I actually deleted that switch when I rewired my engine harness. Maybe I'll reinstall that when I get the chance...That would be most if not all of the problem...The vacuum solenoid passes vacuum all the time at idle since the micro-switch is normally On at idle -- Vacuum solenoid power Off means distributor vacuum On, as Dave mentioned.

[81dmc]

That would be most if not all of the problem...The vacuum solenoid passes vacuum all the time at idle since the micro-switch is normally On at idle -- Vacuum solenoid power Off means distributor vacuum On, as Dave mentioned.

It does not always pass vacuum at idle though, and Dave's ecu is supposed to run without the switch installed.

Wonder if Dave's ecu just doesn't like the noise from the new 200w fans I installed... It seems like my ecu issues began after I installed those.

[Bitsyncmaster]

It does not always pass vacuum at idle though, and Dave's ecu is supposed to run without the switch installed.

Wonder if Dave's ecu just doesn't like the noise from the new 200w fans I installed... It seems like my ecu issues began after I installed those.

I would not think your 200 watt fans would affect my idle ECU even if the voltage to the ECU dips quite low.

Have you noticed any other problems since you installed those fans?

[81dmc]

I would not think your 200 watt fans would affect my idle ECU even if the voltage to the ECU dips quite low.

Have you noticed any other problems since you installed those fans?

The voltage fluctuates about 1v when initiating the fans, and in drive with AC on, voltage drops from 14.6 to 12.5.

Other than that, I've noticed no other issues.

[Ron]

It does not always pass vacuum at idle though, and Dave's ecu is supposed to run without the switch installed.

Wonder if Dave's ecu just doesn't like the noise from the new 200w fans I installed... It seems like my ecu issues began after I installed those.
Sorry, I reworded that post and wound up contradicting myself.
Looks like you caught it tho...
I meant to say:

That would be most if not all of the problem...The vacuum solenoid blocks vacuum all the time at idle since the micro-switch is normally On at idle -- Vacuum solenoid power Off means distributor vacuum On, as Dave mentioned.

=======

Ah!...I didn't know using Dave's unit eliminates the micro-switch.
But, again to be sure, it should NEVER have vacuum advance at idle. But it does in the first vid (even if it is coming and going)...

Maybe pull the solenoid's plug and put a meter/bulb in it...

[81dmc]

After installing new plugs and wires and checking the distributer cap, the car still had issues. At 4000 rpm or so, it would misfire like crazy. So as a test, I disconnected the vacuum advance hose and tried again, and the car now runs great with no misfires!

I guess timing is too advanced then?


https://www.youtube.com/watch?v=rg1G5BRkI2I

[NckT]

Timing for oem Delorean distributor is 13deg btdc, with the distributor vacuum hose disconnected and plugged.

Unless Daves ecu operates the distributor vacuum advance solenoid, you may still need this switch. To verify,
still perform the test as what Ron said to confirm the correct operation of this solenoid to verify that the pipes are on in the correct order on the solenoid, this is important.

[Ron]

IIRC, At 4000 RPM it should have 13° initial + 20° vacuum + 20° centrifugal = 53° Total advance +/- 2°.