Sewer Rat

I apologize for this not being an Accord specific problem, but I've posted in the Acura section and haven't gotten any answers so thought I'd try here.

I've got a '94 Vigor that started idling rough after warm-up and occaisionally coming up with a bad crank position sensor code. I replaced the crank sensor with OEM parts, but still have the same symptoms.

Since then I've checked the wiring between the crank sensor connector and ECM and checked the harness for shorts/opens. The only strange readings I get are when the harness is connected to the ECM, then I get 400 ohms to ground on one pin and about 7k ohms on the other. I have to assume that is just normal cicuitry inside the ECM, anybody have any ideas on that theory?

I've also replaced the following parts: ignitor, coil, temp sensor and cap/rotor/wires/plugs. Oh yeah, I've also removed and cleaned all of the grounds I could find, about 8 of them I think.

I have found that disconnecting the throttle position sensor will get rid of the miss at idle, but it also kicks the ECM into limp mode. The engine idles ok when the crank sensor kicks it into limp mode, so I'm thinking maybe the TPS is doing the same. Also, I get a crank sensor code along with the TPS code when I unplug the TPS. Is this normal or is the ECM trying to tell me something? Like give me 5 gallons of gas and a match?!

This problem is driving me nuts, worse it's burning up my snowmobiling money and time! It's almost to the point of taking it to the stealership, something I've haven't done in thirty years of messing with cars. Somebody save me, please!

Perfectionist

Just a wild shot in the dark, but what does your primary oxygen sensor read? It could be slow and lazy enough to cause an incorrect A/F ratio which could cause your rough idle which could cause your CPS code??? In my experience, lazy O2 sensors won't set a code because they still put out enough activity to satisfy the ECU, just not at the right time for a properly running engine.

I'd suggest disconnecting the O2 sensor, but it probably has a heater in it and that would probably set a code and put you into open loop or limp mode.

Sewer Rat

I suspect that you're right about the sensor being heated, the damn thing is 170.00 at the parts store (and not in stock). I'll check it out when I get home tonight. Anybody have experience with generic sensors or different model compatability like maybe an Integra or Accord sensor used in a Vigor? Thanks for the help!

Dmc1

An accord O2 sensor may be the same.But I'm not sure.

notoriousB

why in the world would an o2 sensor cause a crank position sensor code? I am pretty confident that this has nothing to do with your o2 sensor. (which is, in fact, heated)

strange tho, you've replaced the CPS and still are getting the code? is your timing belt dead on? if it jumped a tooth or two it could cause some erratic behavior. I'd check the cam/crank timing to ensure it's perfect.

Sewer Rat

I don't know why an O2 sensor would cause a crank position code either, but unplugging the throttle position sensor gets me a crank code along with the TPS code, so maybe anything is possible?

The cam timing problem is a good idea, and since I can't go snowmobiling this weekend, I think I'll tear the front end apart and re-check it.

I did forget to mention that most of the time the car runs fine, especially before it gets warmed up. I can break into triple digits on my way to work in the morning and don't notice anything wrong until I get into town and hit the first stop light. If I'm going to have a problem, it seems that is where it's going to start, but there are days that I make it all the way without a hitch. However, there are also days that I have to pull over and reset the ECM a couple of times to make the same trip. Very aggravating! I have heard that Honda ECMs are bulletproof, but I'm starting to wonder about mine. Thanks again for the help, keep the ideas coming!

92ehatch

hitting triple digits all the time, is not only stupid and irresponsible but probably not helping your car any.

Sewer Rat

Hmmmm.....I missed the part where I said I did that all the time. Plus, this is my wifes' car, I guarantee she doesn't break 70. I'm only driving it because I don't want her to have to hitchhike home when it finally dies for good.

As far as irresponsible, you're right. But if there are any cars in sight in front of or behind me, I don't go that fast at all. I don't like it when people drive like that around me so I don't do it to them. The speed thing is just between me and the deer.

As far as the speed hurting the car; the fluids are fresh, grease is good, bearings and brakes are good. I don't know what rpm's it's turning at that speed, I actually watch the road instead of the gauges. However, the car is quiet and I'm sure I hit higher revs just downshifting and merging with traffic on some of the short on-ramps around here (why do engineers put in 40mph curves 150 feet before you're on the interstate?)

Now about the car. It has run fine for the last two days, except for sometimes it has a very slight stumble coming off idle. Maybe I should replace the throttle position sensor if I can find one? I'm going to check out the O2 sensor and the cam timing this weekend too. Hope you guys have more fun than me this weekend!

Sewer Rat

Well...the cam timing wasn't right on, but it was pretty close. About a half a tooth off. I foolishly followed the Chilton procedure for setting the tension which states "loosen the tensioner bolt, allow the spring to apply tension, and re-tighten the bolt". Seems that the right way to do it is to rotate the crank until the cam turns a little bit, then tighten the bolt. That might account for the half tooth difference. Lesson learned: Throw away the Chiltons manual! I've also found torque specs to be way off, like 36 lb/ft for a 6mm water pump bolt?! Oh well.

The bad news is the timing didn't affect the running problem at all.

The good new is maybe I found something last night. After the car has been idling for awhile, turning on the headlights makes the engine stumble. The tach drops to zero, then it catches and idles ok for awhile. Turn on the fog lights, high beams, and heater, and it will kill the engine.

I found out there is a feedback circuit (FR circuit) between the alternator and the ECM. The ECM is monitoring electrical load, battery charge, engine speed and alternator output all the time. If the load is low and the charge is good, it actually turns off the alternator to save some horsepower. Apparently when the idle is low and the alternator is charging, the ECM should be bumping the idle up to handle the load. Or is it supposed to turn the alternator off? Or is the feedback signal from the alternator supposed to be different than what it is?

So here's my latest question. Anybody have experience with this and how do you verify which is at fault? Thanks!

Sewer Rat

Just in case anybody else runs into the same type of symptoms, the feedback signal from the alternator was the problem. The alternator was charging fine (14.5 volts) and didn't seem to have any problems, but I checked the feedback signal at the ECU with a scope and is was bad. Replaced alternator and car has been running fine all week! Thanks again for the help.

VspecSiR

post back from the dead, so what was the FR wire supposed to read? what are normal readings?

I have the same problem. Car is in limp mode, wont go above 3000rpm, ECU is throwing CEL code 04. Car drives fine, untill lower RPM's car stumbles and bogs out (I assume the extra fuel being dumped from the car being in limp mode is the cause of this) At low RPM's with the car at idle, Air conditioning, lights, radio, etc all on the car sometimes dies out because of the load. At night when the lights are on, reving the motor does increase the intensity of the light output so I'm sure there is some kind of voltage drop accross the alternator. distributer assembly was changed out 30k ago, and for some reason I doubt that the Crank Angle Sensor is the problem.

Havent' checked timing, but could a car so out of time throw CEL 04? car previously ran just fine so I'm sure timing is ok, will check. Any info on how to diagnose the CEL code 04 / alternator problem would be helpful. I've arready read about the alternator triggering a CEL 04 code.