low rev/idle runs poor?? please...

[mhardy]

As the topic said my '90 350i runs bad! at low rev (2000rpm) it's holding back and idle is erratic.

When cold start it's ok and when coldstartinject. did his job the problem comes. sometimes after 30 or 50 miles runs perfect at low rev/idle.

new plugs ngk b7ecs,leads magnecor and airfilter. checked airleaks, coolant temp.sensor,throttle pot. and all seems o.k

question: how to set base idle versus co2???

what should it read for co2??

WHO HAVE A IDEA ?? i must 20 august to U.K. for a weektrip with TVRCCHOLLAND (24 cars lake district) and will drive with my friend WEDGE...

Thanks,

Matthijs

[wedg1e]

Might be the soldering on the ECU... especially since you say it is intermittent - I'm assuming here that you don't have the 'hotwire' fuel injection setup.
CO can be anything you want it to be: mine is about 1.5% but I've had it as high as 3.7% and as low as 0.5%. Affects the power delivery!
Idle speed should be about 800rpm when warm. Ignition advance at about 8 degrees BTDC as a starting point. You should just be able to slide a 0.002" feeler gauge under the throttle plate when fully closed. Throttle pot should give you about 300mV (green to yellow wire)with the throttle closed. If you have all these correct the car should be basically right. I had a 350i a few weeks ago that ran very badly and the first thing we did was check all of the above. A quick way to check is to plug your ECU into a known good car and see if that causes the same problems (that's what we did in the end). Also see if unplugging the coolant temperature sensor with the engine running, causes it to stop (it should).
The Lake District is one of the nicest parts of Britain: which way are you travelling? Harwich, Newcastle, Hull, Dover? I may be in the Lakes that weekend - hope to see you guys!

Regards Ian

[danny hoffman]

Try unplugging the throttle pot and see if it runs smoother at low revs/light throttle. Check the multiplug is firmly home on the ECU.

[plewis66]

Maybe just try resetting the base idle?

Turn the screw on the throttle bosy until it is all the way down (don't tighten it, just till it stops - it's in aluminium), then open it by two and a half turns. That, I believe, is the factory setting.

ALSO, what's this about TVRCC Holand and 24 cars in the Lake District? Is that 24 cars from Holland? Or have you arranged to meet with some guys from the UK?

Either way, it sounds like if you are coming that distance, we ought to do something to make you feel welcome...

[mhardy]

Thanks for that guy's, will try ecu,throttle etc.

More idea's ??????????

Yes, TVRCC HOLLAND is coming over at 21 august we will arrive in New-Castle and drive to Cleator (ennerdale Country house hotel). 24 august we travel to Boroughbridge (Crown hotel) near HARROGATE.26 august we drive back to Newcastle.

24 TVR's incl.5 wedges
all dutch people

Hope to see you there.

Matthijs

[boltontvr]

Oh boy! Of all the weekends you could have chosen, you have decided to come over on a bank holiday weekend. Make sure you do all your touring of the lakes on the Friday, before the mad rush begins.
Ennerdale is a quieter part of the Lake District so you should be OK there. Whatever the traffic situation is like, you'll have a great time because the Lakes is a great place to be. Don't forget to sample lots of Jennings Snecklifter.
Hope you get your car sorted before then as well.

[wedg1e]

If you're staying in Ennerdale, make sure you get round to Wastwater (Wasdale). All of England's highest mountains are around that lake: it's the least touristy part of the Lake District and the most spectacular (in my opinion). A very tranquil place when the tourists are away.

Ian

[dexy]

I had similar problem on my 350 running like a bag of pants .Ian (wedg1e)fixed the problem after he went through a fault finding on the engine taking things out and putting them back .Then he placed his ecu into mine and it ran perfectly .He then resoldered the board and hey presto it goes like a dream.Hes a star
I keep him fuelled up with beer everytime we go out.
So your coming over in August we will have to meet up maybe at Boroughbridge for a drink not to far away from Middlesbrough .
CHEERS NEIL

[dickymint]

Sound to me suspiciously like the ignition module on distributor.

[mhardy]

dickymint said:

Sound to me suspiciously like the ignition module on distributor.

can you explane ??

Also, ian said maybe ECU resoldering . If i take the ECU and screw it open can i see if something is wrong??

and there is a strange sound (metal)at erratic idle and when accelerate 3500-4000rpm on road. not when standing still and give 3500 or up rpm. could it be worn cam (62000 miles)and could this give the problems??

HOPE NOT!!

[wedg1e]

mhardy said:

dickymint said: Sound to me suspiciously like the ignition module on distributor. can you explane ?? Also, ian said maybe ECU resoldering . If i take the ECU and screw it open can i see if something is wrong?? and there is a strange sound (metal)at erratic idle and when accelerate 3500-4000rpm on road. not when standing still and give 3500 or up rpm. could it be worn cam (62000 miles)and could this give the problems?? HOPE NOT!!

On the side of the distributor is a small item (amplifier) that fires the ignition coil. This can be defective but still work... if that makes sense!

The ECUs were built by hand, not machine, and the quality of the soldering depends on how good the person was that built your ECU. Now after more than 10 years with heat, cold, vibration, sometimes the solder joints of the circuit board components will break down and give strange symptoms. If you know what a good or bad solder joint looks like, maybe you can find a problem. If you are not experienced in electronics you may miss the defect (can be VERY hard to see).

The camshaft may be worn if it is the original one and has done 62000 miles. Also it could be a sticking hydraulic follower that you can hear making noises. It is easy to strip the fuel injection and inlet manifold to take a look at the cam - again, you have to know what to look for.

Ian

[bobble350]

I had this once, hunting at idle, hesitation when opening the taps. Turned out to be sticking tappet(s). Changed the oil to that thin fully synthetic stuff and the problem vanished within 4 miles and never returned.

[mhardy]

This week i will try to change the ECU with a good running car and also will try bobble350's advise!thanks for that bobble and also ian.

bobble350 said:

I had this once, hunting at idle, hesitation when opening the taps. Turned out to be sticking tappet(s). Changed the oil to that thin fully synthetic stuff and the problem vanished within 4 miles and never returned.

anybody else tried this also??

What do you think wich oil i need ??

Thanks from sunny holland (without diving wedge)

[mhardy]

Time to update my problems.!!!!!!!!!!!

Hang on a scope, ignition looks perfect
Fluce engine and new oil + filter (castrol magnetix 10w40)
Compression test 13bar all 8 o.k.
New fuel pressure regulator
Co 0,8% at idle

but still have that plopping engine at all rev's.

waiting for changing the ECU with a good running car and will try measure throttlepot this weekend (sorry ian and danny can't give you answer if it improves)

A mechanic measure a high HC (600) and High O2 (4-7%)
Wich means un burnt fuel comming out exhaust.(smell)

Still have the stange symthome "after long drive run's perfect".........

Hope for ECU or Throttlepot but ??????????????????

5 days to go and then we make the trip too UK, must bring the wedge with me


Hope to see you guys
and or


Matthijs

[wedg1e]

Hi Matthijs:
I will now be camping at Wastwater the same weekend you are over in the Lakes! Hope to see you about the place. At the moment I'm not sure if I'll be taking the 390; if you see a silver wedge that will probably be me...

Hope you get the car fixed...

Ian

[dickymint]

Still sounds suspiciously like the ignition module on distributor to me!

[danny hoffman]

Maybe you have a dribbling fuel injector