rusnak

Doug, I didn't see the part where you said you left the key on helps. It might be coincidence.

If it were my car, I would try to have the coil tested outside the car before buying a new one. The other thing is to take the car to a shop with an ocilliscope, and they can do much better testing than you can at home.

P.S.: I have a amp meter that works like a multimeter. It tests ohms, DC volts, amps, etc etc.

Let me know if you'd like to borrow it, and I'll send it to you free of charge, just send it back when you're done - no rush. I have three others.

Amber Gramps

Coincidence if it happens one or twice. This has been going on for years. Now that it has escalated to stumbling off of idle I have to address it.

I did order a coil today and should have it by this time tomorrow. Thank you for the meter offer. I've got two of this kind: http://www.google.com/imgres?imgurl=...ch&um=1&itbs=1

I refuse to take her to a shop until all else fails.....Besides, if all else does fail, I've got Peter Z's phone number.

rusnak

Doug, does it run better with the O2 sensor disconnected, or the fuel pressure regulator vacuum line disconnected?

Stumbling off idle sounds like fuel pressure, but you have plenty. Could be weak spark, or also vacuum leak. Does it have good torque if you mash the throttle?

Amber Gramps

This thing is a demon fish when running. I think we are on to something here....

School me on the ohm meter please. I'm confused again. (when am I not)

Testing across terminals 1 and 15 should give me a reading of 0.4 - 0.7ohms.

with the meter set as follows I get:

2000k = 000

200k = 00.0

20k = 0.00

2000 = 000

200 = 00.6

Testing across terminals 4 and 15 I should get 5.0 - 8.7K ohm

2000k = 005

200k = 05.9

20k = 5.97

2000 = meter stays at 1

200 = meter stays at 1

Here is what has me freaked out....See the white calcium looking crud next to terminal 15? Leakage??


...and come to think of it the fuel pressure actually goes up (after a momentary dip) with higher RPM. Perhaps the system has more juice going to the pump at that point.

User 4221

Your ohmmeter says you are getting 5.9kOhms across the coil.

Use the 20kOhm setting and the number you see will be the actual resistance.

Mind you, this is a static reading. With current, vibrations and dynamic loading, the coil could short or becoming high-impedance and will interrupt spark..... Especially at higher RPMs.

My 911 cents is on the coil.

Amber Gramps

Mine too.

On 20k I get 5.92 testing 1 - 4 or 15 - 4

rusnak

A bad coil used to make noise on the radio, back in the day. On a hot day under load, a bad coil will get weak. If the thing has lots of power under load at high rpm, then I'd tend to think it was ok. You'd probably hear it missing if It wasn't. I wonder if there is a huge vacuum leak somewhere, like in the brake booster hose or something. Or maybe the CO% screw is just way off. Or the cht sensor not right. I am out of town without the Bently manual. There is a description of the cht failure modes.

Amber Gramps

New coil tests out at 7.59ohms and will be going in the second I get home from work.


....and Rusnak, one system at a time.

Amber Gramps

Well, that wasn't it.

Runs fantastic, starts for crap. So.....not a total loss.

I need a helper so I can turn the key and run the multi-meter at the same time.

It's time to take another long hard look at the schematic.

User 4221

I know this has been asked but have you checked the reference sender and CHT sensor?

These two items are key for clean starting.

You can diagnose the CHT by one of two methods:
1. Jumpering the sensor to make the DME think it the car is hot. This will probably make the car start even harder if cold. It will provide a lean mixture into a cold engine
2. Get a resistor from Radio Shack that corresponds with the approx. air temp (or really cold temp) and jumper the CHT with the resistor. This will enable you to pinpoint the CHT as go/no-go.

Have you checked the fuses and cleaned the terminals? Perhaps the coil fuse is not clean/happy.

What about the throttle position switch? Is the FT switch shorted? This would also present itself as rough running

Amber Gramps

Thank you Scott,

The next step is definitely testing the reference sender.

I changed out WOT TPS and whatever all switches a year or two ago. All that throttle body stuff is new. I gotta get a second set of hands to do some of this other testing you and the Bently are calling for.

rusnak

Doug, I was surprised that you went and got a new coil.

There is a cheap remote starter switch that you can get at any FLAPS. You connect the two leads to the solenoid, and when you pull the trigger, it engages the pinion, and the engine cranks over.

I can let you borrow either the Fluke multimeter or the Craftsman amp meter/ multimeter if you for some reason want a second opinion. That's why I bought so many myself, haha!

Loren likes to use a paper clip to jumper the cht connector. Or you can get fancy and use a real wire.

I would like you to check the reference sensor gap. It's real easy, and quick. You just have to remove the left rear shock absorber.

rusnak

speed/ ref sensor location:

Amber Gramps

Dude, one of these days I'm gonna have to buy you a Dr Pepper. I really, really, really, want to get this done, and I know I shouldn't have spent any money 'til I knew exactly what was wrong, but I've very limited on time and space. (Ya Ya, 13,911 posts, and no time, sure Doug, whatever)

rusnak

I'll tell you a quick way to check the sensor, that I remembered just now.

If you have a known good sensor, you can use it to start the car. Just plug it in the bottom connector, and pulse it against the engine mount while cranking. If the car starts, then it's either the sensor or the gap. I think I still have my old sensor lying around if you wanna use it. Otherwise, you can try to pull your old sensor out of the holder, and wave a wrench over the end while cranking, to test the gap.

But first, I think you should check the sensor resistance. Even though that test is not conclusive. A bad sensor can ohm out just fine.