Unconnected Wires in idle ECU compartment

[ifelder]

Tonight I found these disconnected wires coming out of the relay next to the idle ECU.

I was diagnosing a idle hunting issue, I found if I disconnected the idle speed motors connection, my idle would steady. The engine was not properly warm, so this might all be speculation, but it lead me to look at the idle ECU where I found these wires.

IMG_20140719_233059736.jpg

Could someone point out on the wiring schematic where this relay is, and what these wires should be doing.

Thanks,

Ian

[Tillsy]

Could someone point out on the wiring schematic where this relay is, and what these wires should be doing.

That is not stock - my suggestion would be a custom solution to make an aftermarket power antenna work.

[ifelder]

That is not stock - my suggestion would be a custom solution to make an aftermarket power antenna work.

I was just looking at my power antenna motor because it sometimes get stuck going out the wrong slot in the faux air intake. The motor body had a DMC sticker, but the sticker looked new, possibly a houston part.

Is the relay to the right of the ecu not stock at all?

[Tillsy]

I just did some checking and it looks like the answer is BOTH yes and no.

When DMC first switched from the windshield and fender antenna options to a power antenna, the first batch of these used an external relay to control it. Subsequent builds used the more common approach of the power antenna having an onboard relay.

So your VIN must fall in the range where there was temporarily a relay added there.

HOWEVER, you also mention your antenna looks new with a brand new DMCH sticker on it. That means you now have a power antenna that has an inbuilt relay.

So perhaps rather than removing the now unnecessary relay your PO simply yanked something out to cripple it?

[DMCMW Dave]

Probably. We always take all the old wiring out but I've seen plenty of cars with an updated antenna and the old relay and wiring in place, with whist the fuse unhooked.


Sent from phone

[David T]

I just did some checking and it looks like the answer is BOTH yes and no.

When DMC first switched from the windshield and fender antenna options to a power antenna, the first batch of these used an external relay to control it. Subsequent builds used the more common approach of the power antenna having an onboard relay.

So your VIN must fall in the range where there was temporarily a relay added there.

HOWEVER, you also mention your antenna looks new with a brand new DMCH sticker on it. That means you now have a power antenna that has an inbuilt relay.

So perhaps rather than removing the now unnecessary relay your PO simply yanked something out to cripple it?

The older style power antennae needed an external relay to run it up when the radio was turned on and put it down when the radio was shut off. Newer power antennas have the relay incorporated inside so they don't require the external relay. It looks like the external relay was added to your car but in a very amateurish way. I don't know if your current antennae needs it or not. If not then just remove it. If it needs it and is working just clean up the wiring a little to make it neater.

[ifelder]

The older style power antennae needed an external relay to run it up when the radio was turned on and put it down when the radio was shut off. Newer power antennas have the relay incorporated inside so they don't require the external relay. It looks like the external relay was added to your car but in a very amateurish way. I don't know if your current antennae needs it or not. If not then just remove it. If it needs it and is working just clean up the wiring a little to make it neater.

Thanks everybody, I'll try removing it to clean up my ECU bay and make sure I don't have any ill effects before trashing it.

So in continuing my search for the cause of my idle hunting issues... Because disconnecting the idle speed motor stopped my idle hunting I figured it might be seizing, so I removed it and blasted it with carb cleaner and verified that it clicked open and closed when I rotated the body of the ISM. When Plugged into the car and the key in the 2nd position the ISM buzzes and the gate swivels shut all the way.

I got the car warm and drove it around for a nice long drive last night and was pleased to find that I was experiencing no idle surging! I went to bed happy thinking I had finally solved my issues.

Today, when I went to drive to the grocery store, it purred right along all the way there with the idle steady just below 1000RPM every time I stopped. I left the grocery and clicked on my AC and the idle went nuts, right back to its old ways of surging to about 1500+ RPM and dipping to around 500. Switching on and off the AC I was able to 'surge on demand'.

Is it possible my CO adjust is set in such a way that my ISM is fully closed in normal operation and does not have enough adjustment range to properly maintain idle with the AC load on the engine? I have not checked the voltage the ISM is receiving when the AC is on, but the ECU was outputting ~12-13 V to the ISM when I was testing the leads when It was idling smoothly.

Thanks again for everyone's input.

Ian

[ifelder]

Thanks everybody, I'll try removing it to clean up my ECU bay and make sure I don't have any ill effects before trashing it.

So in continuing my search for the cause of my idle hunting issues... Because disconnecting the idle speed motor stopped my idle hunting I figured it might be seizing, so I removed it and blasted it with carb cleaner and verified that it clicked open and closed when I rotated the body of the ISM. When Plugged into the car and the key in the 2nd position the ISM buzzes and the gate swivels shut all the way.

I got the car warm and drove it around for a nice long drive last night and was pleased to find that I was experiencing no idle surging! I went to bed happy thinking I had finally solved my issues.

Today, when I went to drive to the grocery store, it purred right along all the way there with the idle steady just below 1000RPM every time I stopped. I left the grocery and clicked on my AC and the idle went nuts, right back to its old ways of surging to about 1500+ RPM and dipping to around 500. Switching on and off the AC I was able to 'surge on demand'.

Is it possible my CO adjust is set in such a way that my ISM is fully closed in normal operation and does not have enough adjustment range to properly maintain idle with the AC load on the engine? I have not checked the voltage the ISM is receiving when the AC is on, but the ECU was outputting ~12-13 V to the ISM when I was testing the leads when It was idling smoothly.

Thanks again for everyone's input.

Ian

Upon further investigation, I'm having my idle stick at 1500RPM occasionally with the AC off. Could this mean I have a bad Idle ECU, or would I not have this intermittently stuck idle? I was reading some posts saying a stuck high idle can be evidence of a bum ECU.

Is there a resource available with the schematic of the idle ECU innards?

[Bitsyncmaster]

Upon further investigation, I'm having my idle stick at 1500RPM occasionally with the AC off. Could this mean I have a bad Idle ECU, or would I not have this intermittently stuck idle? I was reading some posts saying a stuck high idle can be evidence of a bum ECU.

Is there a resource available with the schematic of the idle ECU innards?

It is probably your throttle cable sticking so the throttle plates don't always close. Next time it happens, open the engine cover and push on the throttle spool to see if that fixes it.

[ifelder]

It is probably your throttle cable sticking so the throttle plates don't always close. Next time it happens, open the engine cover and push on the throttle spool to see if that fixes it.

Today I found that the vacuum advance solenoid had come unplugged. Plugging it back in caused the idle to surge all the time, like when the AC was turned on before. I bent the pins a bit so the plug wouldn't slip off so easily.

I must have tuned the idle to run smooth without the vacuum advance and had to start from scratch with my CO adjust.

I let the car warm up then turned the CO adjust lean until it started to shudder and then tuned it richer until it would hold a steady idle. Drove it around the block a few times readjusting trying to find a happy adjustment. After all this I was able to get it to hold a steady idle with the AC on or off. This was probably my issue all along, and I'll have to plug my O2 sensor back in and see if I can properly adjust the CO using my dwell meter and get my lambda system running again. Overall I'm a pretty happy camper now that it's running smoothly. Fingers crossed I won't find any more idle gremlins.

There was some heavy rain last week, and I found my carpets on passenger and driver side were soaked. I had pulled the carpets last night and had them drying in the sun today, but I found more water in the fiberglass tub after doing all my adjustments with the idle and AC. No rain today, so I'm thinking my AC drain tube is clogged and i'll have to try and clear it out tomorrow night.

I think i'll be able to find the drain from this post http://dmctalk.org/showthread.php?39...ter-everywhere but what is the best way to clear it out? Do i need to snake the drain from the other end (I assume connected to the condenser), or can I just use something like a coat hanger to clear it from the output side on the trunk side?