MB

Morning all

My S is not behaving itself.

Symptoms are that it feels like its no performing as it should when flat out, it just feels trangled and in traffic its bordering on unbearable. It hesitates VERY badly and also when pulling away it kangeroo's like a , well, a kangeroo.

While i'm no expert, hopefully this might help someone esle who has a problem There is the thread in my signature to give some pointers, but this might be a more practical example.

So I like to check the simple things first and the important thing in understanding what's up with it is do do things one at a time, test it, then try something else if it didn't work.

So I have poor performance - hesitation and kangerooing. Its pretty important to know what probs you have because that helps where to look. For example, if it was performing fine i could rule out a few sensor issues and look at other things.

1) I know it has good fuel as the probs have been there for a while. This also wouldn't cause hesitation and kangeroo probs.

2) Tapped the MAP sensor

3) I have reset the ECU and this hasn't helped.

4) Checked all around the manifold to ensure all the hoses are secure - this in another unlikely as I dont have an idle problem, which it would should there be a vac leak.

5) Removed intake and checked there were no animals in there - there weren't A strangled air intake could cause the performance problem, but prob not the kangeroo.

6) Throttle cable - now a slack cable is a favorite for kangeroo and hesitation, but it wont affect the performance when you are flat out - checked it anyway and its all fine. Should be taught, but not tight.

7) Air intake temp sensor - Now I have ruled out all the easy ones, im starting to look at engine sensors - these are what I find to be the majority of all problems - novelties and gadgets! The AIT is an easy thing to remove and clean. It could definately be a cause of all the problems. The AIT checks the temperature of the air going into the engine, and provides a signal to the ECU depending on what it sees. The ECU uses this to retard and advance igniton etc, so if its reading something funny, it might be causing the car to hold back.

Normally I would check and monitor the AIT signal and ignition advance but I haven't got a reader or software for the S

So I removed it and gave the tip a clean Be very careful with it! I used a soft cloth with some electrical cleaner on it. It was quite oily - but prob not enough to affect it but we shall see... it lives on the manifold back from the throttle body.



I am just off to try it! Bear in mind that after correcting a sensor fault, it can take several miles for the ECU to pick up on it, depending on the sensor. So you can either reset the ECU or drive around for 10 odd miles and let the ECU do its thing. Im going to drive it in this case.

If its not that then I have a cunning plan of more things to check.

Things like MAP sensor, injectors, plugs, throttle lines and body cleaning etc.

gaddafi

MAP/MAF thingy

needs whacking/replacing

betcha

MB

Don't worry Pete, its on my list

I don't believe in whacking it though - if you damage it, it has the potential to destroy your engine. I have seen failed MAF's do this on dozens of Impreza's

I have given it a good tapping and it didn't make a difference.

I have a new one ready to go on should it be that though.

lower

Does it feel almost like its dropping in and out of vtec when revs are between 6-7k? If so then its the map sensor. I had the exact same symptoms you describe, with the above problem in vtec.

I took the map sensor off, it was clean, put it back on and tapped it with the handle of a screw driver a couple of times and the problem disappeared.

Didn't come back in the remaining 12 months or so that i owned the car.

s2k_Nut

How do you reset the ECU what is it, and why do it?

MB

I know all the potential issues - thread was designed to help others in how do methodically diagnose things in a thought out order.

I know it may well be the MAP, but for the purposes of this thread im saving it til later...

Simmo - resetting the ECU clears all its fuelling / idle / ignition timing memory which it learns as you drive. When you reset it you wipe the slate clean, and its a bit like defragmenting your hard drive. The ECu can pick up funny quirks along the way, and a good starting point of you have any problems, can be an ECU reset.

There are 3 ways to do it.

1) Remove ECU fuse - will find a link shortly
2) Reset using an OBDii code reader from Ebay
3) Disconnect battery for half an hour

Once its reset the idel will be ppor and it will cut out - it has to run for about 2-3 fan cycles (cooling fans come on and off) before it sets the idle. Ir you can just drive it and it will learn anyway.

lower

talk about doing it the hard way.......

MB

I said I tapped it already... But I will add it to the first post.

(plus the previous owner has bored out one of the screw heads to I cant get it off at the mo )

gaddafi

some people like fixing things

some people like 'problem solving'

not necessarily the same thing.......

s2k_Nut

Thats some great info right there, thanks. Theoretically then, would it be a good idea to reset the ECU when buying a second hand car, or only do this if there is a problem?