Legacy mega stutter!

[tebbyj]

Okay, i thought the knock would just be because the engine is cold, like Marky said could be some piston slap mistakenly taken as knock or something.

The o2 sensor is reading a constant 0.3v at 600 deg, so am going to replace that.

My cold idle seems to be all over the place at the moment, will go to its normal 1500rpm then drop right down to 300-500rpm until it nearly stalls then come back up again. once warm just idles at a constant 700 ish. Would having an open O2 sensor circuit cause this when cold?

Have cleaned IACV and TPS this morning with contact cleaner, thats when cold idle started doing what its doing.

[Marky]

My understanding is that most ECU\'s run in open loop and ignore the 02 sensor voltage until the car is up to temperature, since it wouldn\'t be of any use until then anyway. If it stays .3v after a couple mins driving then it\'s poked, and 02 sensor faults seem to have a massive effect on subys (most cars all it does is make it run slightly rich, these it seems to cripple half of them)

When you cleaned the TPS, are you sure it\'s adjusted correctly? Couple mm can throw it right off which could mess with the idle too . If it was fine before you played with something, then pretty easy to say it\'s one of those two things at fault I guess.

Seems like when you have one thing sorted, something else goes wrong as well aye

[tebbyj]

Yeah was pretty sure the o2 sensor readings were wrong. Am seeking a new one as we speak.

Never removed TPS, had intercooler off to check for vac leaks etc and sprayed the #%@* out of it with MAF cleaner, same with the IACV (cheap way i know). Voltage readings were in spec for TPS when i checked with Subaru computer.

Tell me bout it.... feels like im just pushing the problem arround rather than fixing it, But thanks for all the suggestions, atleast were making progress :

[tebbyj]

UPDATE:

O2 sensor in, Car seems to be running a lot better, Smother and no more hesitation while cruising thank god.

Car still seems very sluggish below 3000 though,

When is primary turbo supposed to kick in? mine doesn\'t come on till between 2500-3000, is this right?

Mate of mine told me primary should come on pretty much instantly, (around 1200rpm from memory)

[Marky]

Your mate is wrong, that\'s like a diesel or something

2.5-3k is normal

[tebbyj]

Haha sweet, looks like the cars all sorted then, thanks for all the input guys was a great help. ;D

And thank you hijacka for the o2 sensor that saved the day.

[Subirex Automotive]

this happened to my 98gtb. driving at 50kms, steady throttle and the cars starts to stutter. repalced my front O2 sensor and ran sweet after that.

[Subirex Automotive]

by the way your throttle position sensor is a little low on voltage (0.42v) put it to 0.50v and you will have better throttle and turbo response.

[tebbyj]

Sweet thanks subirex, will definitely do that.

[Steveo]

Just a bit of an update on the similar issues I was having with my car, was the AFM in the end and a genuine replacement was less than $200. Not to sure why the one you priced genuine was so much more expensive, maybe they change quite a bit through the years.

[Guest]

 Steveo said:

Just a bit of an update on the similar issues I was having with my car, was the AFM in the end and a genuine replacement was less than $200. Not to sure why the one you priced genuine was so much more expensive, maybe they change quite a bit through the years.

The orange afms are quite dear these days. They like 80-100 for a second hand one that\'s just as old as the car. Price is about right