Idle high when rainy. Drops to 1000 when car comes to a stop

[baggy798]

Originally Posted by SalvadorP

So, the vibration and fluctuation of idle speed might not be related to the high idle when wet. The "rythmic misfire"/idle fluctuation happens all the time. Also the car shakes at 1500-1700 specifically too.

Here is video of the needle at idle, like it is normally, when the air is dry/normal. Do you think it's is a misfire?


If you see the video, you can see and hear the car shake when the needle drops.

That is completely normal dude! Mine behaves exactly the same and I describe that as rock steady.🙃 Here's a video from tonight.

To bypass the idle I blocked off the ports on the intake pipe and manifold that go to it, the valve is still plugged in.

I'm going to say knackered engine mounts are causing the shaking when it dips, as my car can dip much lower than the rpm in your video and not make any 'shaking' noises.

+ YouTube Video

[SalvadorP]

Originally Posted by baggy798

That is completely normal dude! Mine behaves exactly the same and I describe that as rock steady.🙃 Here's a video from tonight.

To bypass the idle I blocked off the ports on the intake pipe and manifold that go to it, the valve is still plugged in.

I'm going to say knackered engine mounts are causing the shaking when it dips, as my car can dip much lower than the rpm in your video and not make any 'shaking' noises.

I think mine is worse than yours though. But do they all behave like this from new or is this an age/mileage thing?

Engine mounts are original so they do probably need change and that's gonna be on eof the first things after i successfully get portuguese the plates.

[baggy798]

Yeah they're like this since new, it's due to the AFR ratio swinging back and forth. Here's some data from my AEM wideband gauge, as you can see it's only a swing of about 50 rpm. Yeah, yours might be moving slightly more but it's got that idle valve doing its own thing on top.

[SalvadorP]

Originally Posted by baggy798

Yeah they're like this since new, it's due to the AFR ratio swinging back and forth. Here's some data from my AEM wideband gauge, as you can see it's only a swing of about 50 rpm. Yeah, yours might be moving slightly more but it's got that idle valve doing its own thing on top.

Alright. Do you think a slightly fauly MAf could have anything to do with this? I'm asking because i did have weird readings when i tested the maf.

[V40onepointeight]

Originally Posted by SalvadorP

Alright. Do you think a slightly fauly MAf could have anything to do with this? I'm asking because i did have weird readings when i tested the maf.

Have you tried disconnecting the MAF to see if there's any difference?

Have you inspected inside the MAF at the little wire sensors to see if they are dirty? A quick careful clean with the specific MAF cleaner can work wonders.

[SalvadorP]

Originally Posted by V40onepointeight

Have you tried disconnecting the MAF to see if there's any difference?

Have you inspected inside the MAF at the little wire sensors to see if they are dirty? A quick careful clean with the specific MAF cleaner can work wonders.

yes, i've disconnected but it is inconclusive. I've cleaned it with proper mad cleaner. Tested it with voltemeter too and got abnormal values.

[V40onepointeight]

Originally Posted by SalvadorP

yes, i've disconnected but it is inconclusive. I've cleaned it with proper mad cleaner. Tested it with voltemeter too and got abnormal values.

So you have at least a partial explanation. Without a known working MAF any further attempts at diagnosis are futile.

[SalvadorP]

Originally Posted by V40onepointeight

So you have at least a partial explanation. Without a known working MAF any further attempts at diagnosis are futile.

It's just that a known working maf costs a lot of money :s

[V40onepointeight]

Originally Posted by SalvadorP

It's just that a known working maf costs a lot of money :s

So you will have to live with the symptoms, the poor running and the high fuel consumption. Today I drove in 240 miles in very cold conditions down from the north of England in my 1996 940 2.3 HPT auto Estate and got just over 33 mpg with the car fully loaded. That's because the car is well maintained and set up.

[SalvadorP]

Originally Posted by V40onepointeight

So you will have to live with the symptoms, the poor running and the high fuel consumption. Today I drove in 240 miles in very cold conditions down from the north of England in my 1996 940 2.3 HPT auto Estate and got just over 33 mpg with the car fully loaded. That's because the car is well maintained and set up.

I have never complained of low mpg and I try to maintain my car the best I can with a knowledge I have and the help of the guys in the forum.
Nor am I against buying a new maf. I just don't want to buy a maf and then still have the problem. And maybe down the line realise it was a pin size hole on a hose afterall. One thing is to load the parts cannon with 50€ projectiles... If it's not that, well, you now have a brand new part. Another is to load it with a 300 to 500 bill. I would rather troubleshoot and replace cheap parts first.