325i low idle speed

[sweep]

My 89 325i is idling at around 600 rpm everythimg seems to be working ok,but the engine is slightly uneven.tps is working and set up correctly,any ideas?

[mrLEE30]

TPS is not where you should check, the idle control valve would be my first port of call, then i would look for airleaks and then the AFM

[StuBeeDoo]

everythimg seems to be working ok,but the engine is slightly uneven

I don't like to worry you, but what you describe is very similar to the symptoms I had.
Turned out to be a knackered bore. I'm currently in the process of building a new engine.

[sweep]

It has only done this since the other day when i changed the throttlebody.

[sweep]

The throttle is resting on the stop,if i wind the stop in so the linkage is just glancing it it slows it down even more,im wondering if somebody has set the tps with the stop screw wound out holding the throttle slightly, so its not giving a correct reading

[stonesie]

Air Leak test

Remove the oil filler cap with the engine at idle, if this has no effect or very little then it's time to get the carb cleaner out and track the little sucker down.

[sweep]

Im going to remove the throttle body and do this tomorow,thanks

[sweep]

Tried this and its still the same,im going to try a airflow metre next.strange one this as it drivers as normal.

[sweep]

Tried another airflow metre and set co.put new ngk plugs in and its still the same just needs to increase in rpm by 150.any ideas?

[StuBeeDoo]

Mate, check your compressions.
I really don't like to be a prophet of doom, but everything you've posted is what I did before I ended-up pulling the 'head off.

[sweep]

What did it end up doing ?

[StuBeeDoo]

What did it end up doing ?

everythimg seems to be working ok,but the engine is slightly uneven

I don't like to worry you, but what you describe is very similar to the symptoms I had.
Turned out to be a knackered bore. I'm currently in the process of building a new engine.

[sweep]

Would low fuel presure cause this?

[davidt]

It has only done this since the other day when i changed the throttlebody.

What was the reason for changing the throttlebody and if you still have the original put it back and see what happens.

[sweep]

I have done this but its the same i think its just a coincidence.

[e30gazza]

I agrre with MrLee. I had the same with mine a few weeks ago. I sprayed carb cleaner in the idle control valve, and hey presto! - Its now running as good as ever!

[sweep]

I have cleaned this today and still the same this is a real baffler it just needs the rpm up by 100rpm and it will be smooth.i was thinking of trying a presure regulator.the performance is still spot on though.

[murran]

air leak would cause a high idle surly. id check the compressions too.
if youve got 6 cyl. contributing to an idle of 800 rpm say. if your a cylinder down then your 133 rpm down. ticking over at 666 rpm or there abouts......

[sweep]

Will do tomorow/but if compression is down rings?burnt valve?

[davidt]

This idle issue only started after changing the throttle body so it may be worth looking at what connects to it, if you have a spare idle control valve change it and check the vent pipe from cam cover.

[sweep]

I have put a new breather from rocker box to throttlebody ,i put a powder coated inlet on and disturbed the injectors but the sealed ok and also i put a inlet manifold gasket on .on the odd ocasion it ticks over at 700rpm but steadily slows back to 500/600rpm.

[StuBeeDoo]

Will do tomorow/but if compression is down rings?burnt valve?

Lots of reasons why a compression would be down. IF you have a low compression, 'head off is the first job and then take it from there.

Did the problem arise immediately after you'd been playing about with the TB/breather/injectors? If it did, then that's where your problem lies. If the car ran alright at first, then I doubt that any of what you did is responsible.

[sweep]

Yes thats right it ran ok before stubeedoo...i understand your compresion check idea though im not dismissing that.did you loose any performance with your problem?im wondering if the injectors may need refurbing its done 72,000 miles .

[e30topless]

comp test it pete just to be sure...
I have to work tommorrow or I would have nipped down

[sweep]

Steve it maybe going down a ditch with no interior or wheels on if it carries on and a gallon of something up it!

[StuBeeDoo]

Other than the low idle speed and the engine not being as smooth as it should be mine was going well.

It just suddenly started coming home from work one day. It had run well for 21k miles then I pulled-up at a junction and it nearly stalled. I thought it was a fluke, but it happened again at the next junction as well. The rest is history.

Stop clutching at straws until you've done the compression check. Then, if they're all within 10%, that's the time to be wondering WTF is up.
If they're not all within 10% - there's your problem.

[sweep]

Yes i will check compresions at 8.30 in the morning then sulk....and go from there. all this and ive got a e plater which is smooth as silk in a garage with 120k on .

[murran]

when i first rebuilt the 325i head on my old touring, it had a low engine speed misfire, low tickover. couldnt work it out, plenty of power with no missing above 2k.
did a comp test and one of them was like 50 psi.
thought eh?
took it back apart, with the head upside down, did the old wd40 pooled in the combustion chamber test. over about 5-6 minutes it had drained out of the inlet port. others would hold wd40 over night! valve must have got bent while it was on the bench at work, with other careless people moving it around etc. after id built it up! 1 new valve it was gone, as good as new.

this was after id changed the fooking bottom end mind!

you might have a slightly burnt out valve seat?

[murran]

might pop down in the morning for a chin wag if its not bloody raining!

[sweep]

If this solves the problem im not bothered i dont mind removing the head as its had all new exhaust studs etc and everything will come undun,its a strange one john.this has a slight off beat tremor /un eveness at idle.

[e30topless]

Steve it maybe going down a ditch with no interior or wheels on if it carries on and a gallon of something up it!

no chance of that !
if the comp is low it's a perfect excuse for a re-build

[sweep]

If only everything in life was as reliable as a volkswagon....cars are like women TEMPREMENTAL..
Facelift vs pre facelift at present steve..

[murran]

with mine above 2k it wouldnt have had enough "time" on the compression stroke to lose the compression thru the valve before the spark plug fired. below 2k it did, but even at idle when you pulled the plug lead off (with insulated pliars i might add!) it still made a difference to the idle speed, so the cyl. was still "helping/doing something"
thats why it confused me into thinking it was the bottomend somehow. bent rod or oval bore or a ring problem.

wierd, i'll pop down and stand around while you look at it.

im still not up to full health yet after my thyroid operation. so im not doing any star jumps, hopping under cars etc.!