95 Legacy- runs great until it warms up?

Hello all,

 

New to the forum, although I've been getting useful info for years, so thanks!

 

Here's the issue, I just bought a 1997 Legacy Brighton, the car runs great when its cold, purrs like a kitten, revs smooth. As soon as it warms up completely, it starts idling rough, sputtering, falling flat and bucking on acceleration.

 

When I first got it home, it had a cel, throttle position sensor. I tested it and its smooth, no flat spots. So I've been playing with its setting, I read somewhere here that if its a 3 wire TPS, there is no adjustment needed, that the computer reads closed throttle at each start up? True/False?? Either way, I don't think that would cause the run good when cold, bad when hot problem.

 

Anyhow, depending on where it is set, it is now throwing cam sensor codes sometimes when the idle gets real low and rough.

 

I changed the temp sensor with a new one, changed the cam sensor with a used one, swapped the MAF sensor with a used one, cleaned the IAC and throttle body with seafoam. No change when running after warmed up. Still runs awesome when cold though.

 

I've read through a lot of posts, haven't really got anywhere. Anyone have any known fixes for a 2.2 that runs great when cold, and bad when warm?

That used cam sensor may be failing, when the get hot they throw codes and no longer read. The tps on my motor can be adjusted, I'm sure its the same for you, don't know if you want to play around with it. I moved mine a little and it ran completely different.

i would check the timing to eliminate that as a cause.

 

how old are the plugs and wires?

replacing them can't hurt.

 

if you have played with the TPS it should be reset to the correct standard.

i don't know off hand what that is , but it is not hard to do with a volt meter.

 

the difference between cold and hot is open loop vs. closed loop.

i open loop the ECU / engine runs on default settings designed to get it started.

in closed loop the ECU / engine runs on setting based on the response from the sensors.

incorrect info will call for incorrect settings.

 

if you are getting a cam sensor code i would start there.

if you have replaced it once i would look at the connector and wiring.

what code, pxxxx number, did it throw?

 

you need to reset the TPS, and re-read the codes.

Ok, checked timing with an induction meter, 16/17 degrees BTDC. Checked the pigtail harness for the cam sensor from the sensor plug to the plug labeled B20 in the service manual, ohm'd out good.

 

The code is P0340.

 

No idea on the plugs and wires, I'm going to switch the wires out with the set off my 92, and I think I have a coil pack to try also. Maybe I'll run down and get some plugs to try.

 

It sounds so nice when you first start it! I can't wait until it runs like that all the time.

 

Any thoughts on an O2 sensor, I tried unplugging it and it threw the code right away. Does that mean its ok? Or can it be bad without throwing a code?

Just dug out the ecu and used the sewing needle trick to get to the backside of pins 6 & 20. Voltage was at 0. Adjusted to .48.

 

Turns out my '92 coil and wires are not compatible with my '97, so I couldn't swap those around to test them.

Ok, after resetting the TPS, it is now giving a P0341

Is the cam sensor wiring touching the spark plugs at all?

Zues- not touching, looks like it is in the stock place, close to the plug boots, but not touching.

 

I've been working on it for the last three hours, testing voltages, and ohms, and swapping cam sensors because I couldn't imagine having two bad ones.

 

Here is what I found. I started messing with the sensor, for the heck of it I loosened it, and the idle smoothed out and it started running better. I cleared the code and waited, revved it up and re-read the codes, no codes.

 

I retightened the sensor, and it started running rough again, I checked the codes and the P0341 was pending. So I loosened the sensor again, cleared the codes again, and everything was better again.

 

So knowing I couldn't leave it loose, I thought if it wanted to be loose, maybe a small washer would suffice. After many tries of different thicknesses of washers, I couldn't find the sweet spot.

 

So I tinkered some more, and realized that it wasn't just being loose, it was also tipped a little. So with some more playing, I found the sweet spot by putting blue electrical eyelet between the sensor and motor at the top, and snugging the bolt down. She purrs like a kitten now!

 

I took for a test drive, and no more hesitation or bucking, just takes off smooth, accelerates smooth, runs smooth, it's all very exciting!

 

But of course, it's not fixed, it's just fixed temporarily. So I pose the new question -

 

Is the sensor bad?, or is there something wrong with the pickup on the cam pulley?, or is there a problem with the mounting surface of the engine where the sensor mounts?

 

I'm going to pickup a new sensor, just because that seems like the easiest test, anybody have any recommendations for the best and cheapest place to get a new cam sensor?