It doesn't happen all the time, but I notice that when I'm on the freeway, cruising at about 3K RPMs, I get little bits of hesitation intermittently. Twice now, I've had trouble starting the engine as well, although it's been a while since this happened last. For the most part, the car runs beautifully for having 190K miles. I changed the air filter, fuel filter, plugs and plug wires, but I'm still having the same problem. Is it possible that the fuel pump is going bad?

It's nothing new, us 90-94 Legacy people have been chasing after it for YEARS.

 

Try these things:

1) Make sure your alternator is good and not giving the electrical system bad juice

2) Change your knock sensor. If you look straight down on the engine on the driver's side of the throttle body, you will see the circular sensor bolted to the block. Chances are, if you find the connector for it, it will be the original gray. These were problematic in that they were oversensitive and prone to cracking. Get a brand-new one from the dealer, and make sure it has a white connector. This is the updated version which has dealt with those problems.

3) Try a fuel-injector cleaner called Lubro-Moly Jectron. It's a German company, their products are widely used in Mercedes and VW's. Run 3 bottles in 3 consecutive tanks, that should help out a bit too.

 

If this still doesn't fix it, learn to live with it. I've improved upon it in literally dozens of ways, but never completely rid myself of it.

Have you checked to see if you have any stored fault codes from the ECU? Mine also hesitates, I believe it is caused by the ECU overreacting to the air con compressor cutting in.

I was interested to read this post, as I have been experiencing a similar thing with my 95 wagon. At first I thought it was just me and my big boots on the accelerator, giving it uneven pressure or something. The first effect I had was as if I had given it a bit of extra gas, in a short burst, which returned to normal immediately. This morning, after 10 miles or so at fairly slow speeds, due to traffic, I felt the opposite effect----it was as if the brakes had been applied for a second or so--again returning to normal immediately. The car has been running fine and starting first time in all temps and no CEL or stored codes.

Talking to a workmate, who drives a Ford, today, he said he had the same strange behaviour with his car. It turned out to be his Cat emmissions sensor going intermittently bad. He did get a light come on though-----which I am not.

Changing the sensor fixed the problem for him.

I believe Josh got a three-wire sensor when he replaced his. The idea is that the third wire provides a good ground connection, which the two-wire setup lacks - it grounds through the exhaust pipes.

 

If you are replacing it, it might be a good idea to go for that type.

I thought the three wire didn't have a ground, and the four wire did.One wire is the sensor signal, two wires are for the heater, and the fourth wire would be ground

Three wire does have a ground, but it's for the heater. The sensor grounds through the exhaust itself. Over years of rust and what not, continuity between the exhaust pipes and the motor will degrade.

 

The four wire has an extra ground for the sensor itself to ground through.

Thanks for all the tips everyone! I'll look into it some more.

 

It's really not that big a deal, the car runs great overall, and is still getiing around 27MPG for having almost 200K miles, so I'm not complaining!

OK, so this problem has been getting worse, and the CEL has been coming on and off. I ran the diag, and got a 21--Water temperature sensor, and 23--Air Flow Sensor. I haven't noticed any problems with overheating, etc, so I'm more interested in the air flow sensor. With the car approaching 200K miles, I'm hesitant to drop $200-300 into it, especially if it's not going to fix the problem. Just wondering if anyone had similar experiences, and what results they got from changing the sensor.

 

Thanks!

clear the codes, and then check again to see what codes come up again.

OK, codes are clear. Now I just have to wait for it to act up again. I'll post an update when that happens....

Hi,

have you checked the spark plugs?