86' GL

 

Driving down the road, the tach will fluctuate 250-500 RPM but the engine doesnt. Once you are at 3000 RPM and above, the engine stumbles. Checked the plugs, they are clean and look good, checked choke. Changed gas filter, check belts incase one slipped. Checked rotor, cap, looked fine.

 

What am I overlooking?

Ok, I guess I'll throw this out there. First of all, let it be know my symptoms were somwhat different (kinda rough idle, no tach fluctuation though, and a stumble between 1500-3500) What did I do? Clean the MAF sensor! There's a much better guide somewhere around here that's better then I could explain it, but it took care of 85% of my issue. If you do a search, I'm sure you'll find it.

Your distributor shaft bushings are worn out. Replace the distributor.

 

GD

Ok, I guess I'll throw this out there. First of all, let it be know my symptoms were somwhat different (kinda rough idle, no tach fluctuation though, and a stumble between 1500-3500) What did I do? Clean the MAF sensor! There's a much better guide somewhere around here that's better then I could explain it, but it took care of 85% of my issue. If you do a search, I'm sure you'll find it.

 

Carb.

Your distributor shaft bushings are worn out. Replace the distributor.

 

GD

 

Ok...gotta find one, thanks.

Ok...gotta find one, thanks.

 

Pretty common - it should have some noticeable play in the shaft if you grab the rotor. It doesn't take much to throw the air-gap off on the reluctor and then the spark timing goes all wonky.

 

GD

Tore it apart....thats not it. There is not a bit of play up/down or lateral.

 

Another thing I notice is the car is charging 17V at 3000RPM.

 

This was an overnight thing, not a progressive increase, FWIW.

Tore it apart....thats not it. There is not a bit of play up/down or lateral.

 

Another thing I notice is the car is charging 17V at 3000RPM.

 

This was an overnight thing, not a progressive increase, FWIW.

Is that 17V with a digital meter or 17 on the dash meter?

Is that 17V with a digital meter or 17 on the dash meter?

 

Dash, but its never been that high. I will get a meter and check it Monday. I am thinking it might be more of an alternator/regulator issue.

Tore it apart....thats not it. There is not a bit of play up/down or lateral.

 

My wife's '84 wagon does this too. I also checked the distributor and it was fine. I also took the disty out of my hatch that I knew worked perfectly, put it in her car, and it still did the tach thing over 3k. Just put in a new (used) transmission and clutch and it still does the crazy tach thing over 3k. I think her charging system is a little messed up, so I am eagerly awaiting anything you find out.

Could definately be a bad regulator in the alt. Bad diodes will cause it to put out AC and that will not effectively recharge the coil at higher RPM. Plus it would explain the naughty tach. AC is no good for your electrical system on a Subaru.

 

GD

+1 on the bad alternator. same thing was happening on my '85 wagon. replace the alt and all the problems were solved.

Make sure that you check the voltage at the back of the alternator as well as at the actuall battery, a difference in the voltage between where its coming out (the alternator) and where it effectively ends up, this can cause the regulator to go into what was commonly called "full fielding" on older externally regulated chevs and fords. The alternator is trying to compensate for a lower voltage reading somewhere else.

It was the alternator. I need another one though, anyone got one?

I'm sure there are tons around. If you don't find one we've got one at our salvage yard, It's in there for 35 but I bet I could sell it for 25 plus the freight, if you need it just post again and I'll give you the number to our yard.

Reading/thinking a GM swap might be the cheapest and most effective route to go now. :/

Would be awesome if you could figure out a way to get a GM 10SI self excited alternator mounted under it.

Reopening this was not what I wanted to do. I yank an alternator off another rig the other day, seemed to be fine. Fire it up and headed to church today, same symptoms. Would be rather odd that 2 alternators went bad.

Got home and yanked the battery feed wire off it and it runs fine.

 

What am I missing here? I need to find a volt meter tomorrow but its fair to say it is charging too high. Is there something that would cause me to lose 2 alternators? Maybe I should run a new feed wire and see what happens?

If there is any resistance in the sense wire the alt will try to keep up with an imaginary load and it will fail in short order as they are not designed for constant high-load. I have fought this on EA81's in the past as the wireing and connectors for much of the harness are old and poorly insulated against water intrusion.

 

GD

If there is any resistance in the sense wire the alt will try to keep up with an imaginary load and it will fail in short order as they are not designed for constant high-load. I have fought this on EA81's in the past as the wireing and connectors for much of the harness are old and poorly insulated against water intrusion.

 

GD

 

Ok, Not sure what wire that is. Would it be possible to bypass [re-wire] the current wire without digging apart the whole harness? In other words, I am not going to tear apart the whole harness for this. Can I replace it with an external wire? Kinda funny, we had a whole whack of rain and a few days later is when it acted up.

Alternator is putting out 18 with the battery wire disconnected. I am thinking something is awry with the fuel pump, which might be toasting alternators......is it possible? Is there a way to diagnose the pump with a multi-meter? [there is 12v getting to the pump]

Edited May 27, 200916 yr by opus

I am thinking something is awry with the fuel pump, which might be toasting alternators......is it possible?

 

Why do you think this?

 

GD

I'm glad you asked. :/

 

Its running lean, backfiring at high rpm. Horribly lumpy idle, if it idles at all. I turn the idle screw up, keep pumping the gas pedal. After it warms up, same idle, I close the choke and it runs better. Plugs are plenty lean looking as well.

 

As you know, once electrical enters the program, I shut down.

 

I have gone through 2 alternators in the coarse of a week. I am not putting another one on until I figure something out. The 2nd alt I put on is charging 18v at an idle. Voltage goes down as the rpm's go up. I'm pretty much stumped at this point in time.

I don't beleive the fuel pump has anything to do with your problem.

 

The alternator has only a few connections but the voltage sensing line is the most vulnerable to problems as it runs through the ignition switch, an idiot light, and a fuse on it's way from the main junction (the fuseable links). I would start there - check the entire circuit for voltage drop from the positive battery post to the back of the alt. If you see more than 0.10v drop across the circuit then you need to find the cause of the bad connection. A high resistance connection in the sensing circuit will cause the alt to overcharge thinking it's compensating for a drain where there is none.

 

And make sure the battery is FULLY charged before installing a new alt. The alt is not meant to charge the battery from dead or nearly so - you will kill it doing that.

 

GD

What would be causing the lean conditions then? I read somewhere here that the fuel pumps were designed in mind with the alternator. Something about if the alternator is defunct, the pump wont. If you get in a wreck and the fuel line is cut, its designed to not pump fuel out if the alt isnt spinning.

 

I checked the power line from battery to alt, no resistance.