Poor performance when warm

xabi

Folks,

Recently my car seems under powered when warm, its fine when cold, great pickup from low revs, but whe the engine warms it seems under power until 3000rmp, the it takes off like i expect. Is the engine getting air from a different source when cold? Could there be a leak in the air induction somewhere meaning the engine thinks its getting more air than it really is? What about the MAF?

Car = BMW 320ci E46

X.

xabi

Are there any mechanically minded people here?

craichoe

xabi wrote: »

Are there any mechanically minded people here?

Sounds like it needs a diagnostic kit hooked up to it, Mr.Diagnostic has been recommended as very good.

Mr.Diagnostic

xabi wrote: »

Folks,

Recently my car seems under powered when warm, its fine when cold, great pickup from low revs, but whe the engine warms it seems under power until 3000rmp, the it takes off like i expect. Is the engine getting air from a different source when cold? Could there be a leak in the air induction somewhere meaning the engine thinks its getting more air than it really is? What about the MAF?

Car = BMW 320ci E46

X.

It is difficult to say. There is more than one engine fitted to a 320Ci. Even knowing which engine it is doesn’t really narrow it down much. It could be a valvetronic issue or as simple as a vac leak. It really needs to be plugged in.

cantdecide

Hate to hijack but could a vac leak be interpretable from a diagnostic check?? I've had intermittant imperfect idle in my A6. It's been plugged in twice and all that's shown up is a knock sensor fault. It's irritating cos I've attempted twice to have this fixed but I've gotten nowhere...

Mr.Diagnostic

cantdecide wrote: »

Hate to hijack but could a vac leak be interpretable from a diagnostic check?? I've had intermittant imperfect idle in my A6. It's been plugged in twice and all that's shown up is a knock sensor fault. It's irritating cos I've attempted twice to have this fixed but I've gotten nowhere...

That depends on what you classify as a diagnostic check.
With a code read a vac leak will often cause a code to be set for lambda sensor signal out of range. As part of a diagnostic check it is possible to look the processed data as reported by the ECU to a suitable scan tool. There are “fuel trim” values there which could give a hint too. There are also idle adaption figures which are quite telling. Also exhaust gas analysis will show excess O2. If after all this a leak is suspected the complete system can be smoke tested.

The knock sensor fault could be telling you that the signal is missing or that it has reached its threshold. So anything that could cause it to pink could possibly throw that code.

cantdecide

This is my problem, mechanics giving me vague conclusions and I don't know what level of information they're using. I've been told twice that nothings wrong but obviously there is because it idles anywhere between almost perfect up to rough and recently slight backfire (twice in last month) and back to near perfect idle the very next day.

I witnessed a mechanic using his diagnostic gear to suss my 325i and he was able to tell me the lambda was knackered (he replaced it- big improvement) and then that the MAF wasn't working 100% causing a slightly uneven idle.

I'm down in Cork but I might give you a shout at some stage, cos I'm a little sick of having to put up with mechanics that are powerless to help...

Mr.Diagnostic

If your problem is intermittent then that makes it more difficult to diagnose. There could well be a diagnostic trail to follow even when it is running right but it is much easier to find any problem if it is there to be seen.

Your are welcome to book it in at some stage but for your own sake there must be someone down there who could sort it. Have you tried Des Golden? Don’t know him but I hear he is pretty good.