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'97 Legacy GT no spark to two cylinders.

I have a '97 Legacy wagon GT, 2.5L engine with about 72k miles. My car was going along just fine on the freeway at 65mph when all of a sudden it lost power. I was able to safely coast to a stop away from traffic. I had the car towed to a local mechanic. He called me the next morning when he had time to debrief me about the failure and whether or not it had overheated or I heard any unusual mechanical noises. I told him the temperature gauge never moved above where it usually sits and there were no extra noises. He said he could not pinpoint the trouble right away. The engine check light did not come on. The timing belt was good and nothing else seemed wrong at first glance. Later that afternoon he called back and told me that two of the cylinders were not getting spark. That made sense because when I tried to restart the car after it shut down, the engine was shaking pretty good like it was missing on two cylinders. It would not run like that of course. The mechanic decided to replace one of the coils as an educated guess. It took about a day to order and receive this coil. He said that there are two coils and each coil is responsible for firing two cylinders. The new coil however did not change the situation. Still two dead cylinders. Now the mechanic seems a little bit lost as to what to do next. He works on all types of cars and probably doesn't get very acquainted with any one type very well. My feeling is that it should be fairly easy to hook up a scope and see if there is signal getting to the coil that is not sparking. My guess is there isn't any input signal to the coil since the new coil did not fix the problem. Tomorrow will be day 3 in the shop for my car and still no correct diagnosis. So my questions are these. What part of the system sends the signal to the coil to fire? I know there's a cam sensor but is that responsible for the ignition firing? If so, is there a cam sensor for each coil? Any explanation of this would be appreciated. The last time I worked on cars they had points and a distributor. (-;

Thanks for your reply.

Reply to
David Farber
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Reply to
Tcassette

Take it to a good mechanic that won't charge you for all the parts, just labour for ripping sensors out and putting the "good" ones back in.

If you have absolutely no indication which sensor is gone, it's gonna be like trying to replace the blue christmas light that is blown when you pull them out of the box each year - keep goin and goin until you find it.

-mark

Reply to
mark jb

Hi Mark,

Are the sensors in an easily accessible location or does the engine have to be torn apart? I believe my mechanic is honest enough not to charge me for parts that don't repair the problem. I was just hoping the job would not have been so involved.

Thanks for your reply.

-- David Farber

Reply to
David Farber

I looked thru the wiring diagram for the '02 2.5 Impreza, (probably not identical, but similar I'll bet) and it appears that both the cam sensor, and the crank sensor (_all_ of the sensors for that matter), and the ignition coil (only one on that engine), are connected thru the ECU. There is also a module labeled "GE" associated with the coil; perhaps a resistor? I would be surprised if connecting an OBD scanner didn't pinpoint the problem, but if not, look for open connectors or bad wires in and around the engine wiring harness. See if you can find the resistor module(s ?), and check for continuity. Try swapping the ignition coils to see if the problem follows the coil. You should be able to put a scope on the cam/crank sensors; IIRC they are magnetic pickup thingies, and there should be pulses as the engine rotates. Eventually, you will probably want the shop manual/wiring diagram specific to your car. I don't have one, but perhaps someone on the group does, and will share. If nothing else, I think Subaru has them available for down-load for a modest fee; check their web site. Hope this helps a bit.

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

Reply to
S

Hi Steve,

It's now the beginning of day 4 in the shop. Still no progress. I just called my mechanic and he is going to get some troubleshooting assistance from a more experienced tech. One thing he said was that the OBD scanner is not of much help because the car won't start. I find that hard to believe. I looked up the Subaru link for the service manual. To download the pdf from Subaru there is a fee. However, where I grew up, $200 for a paperless service manual doesn't seem so modest. Do you think the independently published service manuals are detailed enough to provide some help with electrical problems?

I've been busy with my work and have not had a moment to even look underneath the hood. Otherwise, I would park myself in this guy's shop and get an idea of what the big mystery is.

Thanks for your reply.

-- David Farber

Reply to
David Farber

The OBD II Website might be some help to your "mechanic" I use the term loosly. You may not have time but factory service manuals can be bought on CD ROM at the Ebay site for $10-$30. ...I'm still thinking coil pack and would swap them and see if the miss goes to the other cylinders. TG

Reply to
TG

I got a call back today from the shop. The more experienced mechanic told me there was no compression on the cylinders not firing. I had a poor cell phone connection so it was difficult to tell if he said both non-firing cylinders had no compression or all the cylinders had no compression. He also said that it appeared the cam timing was off and the valves were suspect even though the timing belt was good. He is going to remove the head and check the valves. He also expressed concern because he can't figure out how the timing shifted without the belt braking. In other words, he doesn't want to have the problem happen again to me. I'm waiting for the next update.

Thanks for your reply.

-- David Farber

Reply to
David Farber

The car was finally repaired two days ago. There were eight bad intake valves which were caused when the timing went out of sync. The parts replaced included the timing belt kit with bearings, pulleys, and hydraulic tensioner. Also replaced was the water pump, thermostat, spark plugs, and of course all the gaskets and seals. I saw the old belt and it did look in good condition. The car runs quite smoothly now. The repair cost $1,618.

-- David Farber

Reply to
David Farber

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