[av8r115]

Simple household test. Take an incandescent bulb that has cooled off and measure across its contacts (between the threads and the center contact). When cold, should be about 0.5 ohms or so.

I tried the meter on a bulb that I know works, and got the same results. The decimal point marches across the bottom from left to right (which I assume means its changing ranges), and the screen alternates between the letters O.F, a string of dashes, or a string of zeroes. If I select a range, I get the letters OF or a string of zeroes. A new battery did not make any difference.

Sounds to me like something is wrong w/ this meter.

 

[Bob Lincoln]

Sounds likely.

 

[av8r115]

It died again on the highway. This time it did some serious bucking before it quit. I was able to drive it like that about 3 miles. It would lose power, buck a bit, and then suddenly pick up again, but not to full power. Eventually is slowed down so much that I had to get onto the shoulder. When I put it in neutral it died completely, so I guess the push from the tranny was helping it stay running.

It started immediately, and when I revved it up it just poured black smoke. I revved it until the smoke cleared, and then drove the remaining two miles to my home w/out a hiccup. I also notice my milege has dropped big time from a little over 15 to approximately 12. (4 gallons got 50 miles before the low level light came on again. Yes, I know that's not an exact measurement.)

I think this is something electrical, like a weak or intermittent spark. If it was just the mixture too rich, I think I'd be getting black smoke all the time. I have to go to work soon, but in the morning I'm going to the parts store and have them test the old coil. If it tests ok, then I'll replace the distributor pickup. I'd like to replace the O2 sensor, but it's out of the budget right now.

 

[valiant67]

That is exactly how my 1987 Dakota acted when the O2 sensor failed on it back around 1991. It would buck and smoke black then run like nothing was wrong. Then repeat at random.

 

[av8r115]

That is exactly how my 1987 Dakota acted when the O2 sensor failed on it back around 1991. It would buck and smoke black then run like nothing was wrong. Then repeat at random.

Any problem using a universal O2 sensor? Parts store says its the same but I have to modify the connector on the engine. Hate to do that but it's $30 less.

 

[av8r115]

There's only one O2 sensor, right? On the left manifold?

 

[Bob Lincoln]

There is a special O2 sensor socket that you can essentially rent at Autozone - they have a policy where you can return it for full refund when done. The socket has a slot up the side to accommodate the wiring. I would NOT use a universal sensor for several reasons:

1) You have to splice the wiring, and can't ever use an OEM fit again.
2) The brands are often inferior. Bosch invented the O2 sensor, and I've had good luck, but it's 1/8" longer than OEM, and the socket won't reach completely over it, and will round off the hex. Others report poor performance with Bosch. Bosch uses four long slots in the sensor tip to sense the exhaust gas, where other brands such as NTK and Denso use 16 holes placed all around the tip for more uniform exposure to the gases.

Denso for this car is only about $47, well worth the price. At one time they were $70 to $90.

Critical: Do NOT get the anti-seize compound that is supplied with it on the tip of the sensor - make sure it's on the threads only. The compound contains sulfur compounds that will destroy the sensor quickly.

Be careful removing it. If it's stuck, run the car until warm, then as it's cooling down, spray PB Blaster or similar penetrating oil around the base of the sensor while the car is cooling down. It will be drawn into the threads while the sensor body contracts. Repeat a few times if necessary.

Having said all that, with no O2 sensor fault code, I'd check other things first. Did you check all of the ground connections?

 

[av8r115]

How many grounds should there be for the engine? I can think of one to the firewall on right side - where are the others?

I'll look at getting the Denso - right now $47 is a lot of money. But like you said, if I use the Uni I can't install the Denso later on.

 

[valiant67]

Having said all that, with no O2 sensor fault code, I'd check other things first. Did you check all of the ground connections?

There are no fault codes on a 1987 Dakota. It's carbureted and no self diagnostics are provided.

 

[av8r115]

I think the coil is weak. The primary tested at 1.6 and the secondary tested at 10.55 on the 20k scale. That's going to create a weak spark, correct?

Also, another theory has been floated that a rich running engine would clog the converter and cause the bucking and jerking that happened yesterday. But if the converter was clogged, how could the engine start again immediately? That's the part of this theory that doesn't make sense to me.

Let me know what you guys think about the coil and converter idea.

Thanks!

PS, I remembered that the air injector pump does not work. It froze up on me about two years ago.

 

[av8r115]

Haynes lists a variety of mfrs of coils for the Dakota, each w/ different resistance. How do I tell which one is on my truck?

 

[Bob Lincoln]

Coil is within spec.

http://www.rockauto.com/catalog/moreinfo.php?pk=940163&cc=1087343



O.E. Replacement

Resistance in Ohms:
Primary 200 Scale 1.2 - 1.9
Secondary 200 Scale 6.5k - 12.5k

 

[av8r115]

Coil is within spec.

http://www.rockauto.com/catalog/moreinfo.php?pk=940163&cc=1087343


O.E. Replacement Resistance in Ohms:
Primary 200 Scale 1.2 - 1.9
Secondary 200 Scale 6.5k - 12.5k

Thanks Bob!

 

[Bob Lincoln]

http://www.dakota-durango.com/forum/archive/index.php/t-40201.html

The gap between the reluctor teeth and the pickup's metal tab should be .008 inches, measured with a brass (non-metallic) feeler gauge, with the tooth rotated so it's in line with the pickup coil.

http://www.google.com/search?q=reluctor+gap&hl=en&tbo=d&source=lnms&tbm=isch&sa=X&ei=RtoKUfzfLKqB0QGW2oHoAw&ved=0CAcQ_AUoAA&biw=1280&bih=875#imgrc=YfOaiakRtV7mNM%3A%3BGngSMKyAv_IaOM%3Bhttp%253A%252F%252Fwww.binderplanet.com%252Fphotopost%252Fdata%252F604%252F1534Mopar_dist_3763.JPG%3Bhttp%253A%252F%252Fwww.binderplanet.com%252Fforums%252Fshowthread.php%253Ft%253D87117%3B640%3B480

 

[valiant67]

Also, another theory has been floated that a rich running engine would clog the converter and cause the bucking and jerking that happened yesterday. But if the converter was clogged, how could the engine start again immediately? That's the part of this theory that doesn't make sense to me.

When the converter clogs, the engine can't move exhaust out. Since it can't move the exhaust out it can't pump in fresh air so the engine strangles. It the clog isn't too bad, when the engine stalls the exhaust pressure dissipates and it will start again. But though the engine is running rich (because there is no fresh air) the clog makes it less likely you'll see lots of black smoke out the exhaust.

 

[av8r115]

When the converter clogs, the engine can't move exhaust out. Since it can't move the exhaust out it can't pump in fresh air so the engine strangles. It the clog isn't too bad, when the engine stalls the exhaust pressure dissipates and it will start again. But though the engine is running rich (because there is no fresh air) the clog makes it less likely you'll see lots of black smoke out the exhaust.

So the problem might be a partially blocked converter? I had similar problems with it today on the highway, although no bucking/jerking. It would start losing power, I would pull over & rev the engine, get a little bit of black exhaust and then go a mile or so. But I couldn't get back up to 60mph without it starting to lose power. Eventually I was down to 45-50mph.

 

[valiant67]

I think further diagnosis is needed. As far as I know, the only way to test the O2 sensor is with an electrical meter on that truck. To test for a clogged exhaust the best test is to use a vacuum gauge. The blocked exhaust will cause very low vacuum.

 

[av8r115]

I'm guessing the only repair for a clogged converter is a new converter, plus whatever is causing the mixture to run rich.

 

[Bob Lincoln]

Yes.

 

[av8r115]

Well, the converter is definitely bad. I didn't know the test was so simple: punch a hole fore & aft of the converter and see how much difference there is in the escaping exhaust. There is a HUGE difference - barely any exhaust coming out aft of the converter. I'm not required to put a new converter on since the truck is so old, but right now I don't have the $40 for the guy to weld in a new piece of pipe.

Getting rid of the converter doesn't change the fact the engine is running rich. I read on the internet how to test the O2 sensor, but since my multi-meter crapped out I don't have any way to test it. The sensor is so old, I think its a safe bet that it's bad, though. A/Z has a new OE Denso sensor for $35.99. A carb rebuild kit is only $19.99 from A/Z, so probably ought to do that as well. In a few more weeks I should be able to buy those items.

So that's the plan. Thanks for all of the help guys!!! While I enjoy figuring things out, obviously I'm no mechanic. I appreciate the expert input!