M112 320 Vacuum / Secondary Air injection / EGR fault

[mbzclk]

Hi

Wondering if anyone has any experience with a poor idle. Not a misfire but more of what appears to be an idle leak.

I’ve tried both of the EGR switch over valves that are quick and easy to swap to no avail.

I’ve not tried the EGR value itself on the rear of the engine.

No fault codes at all. Not sure what to look for with live values. Seems to go bad idle after the secondary air pump turns on and it doesn’t always occur right away.

Doesn’t appear to be a misfire or coil pack.

There was a split hose from the bottom of the manifold so used a pipe repair kit and think it’s ok.

MAF bracket was previously broken so letting in unmetered air but now resolved.

Any other ideas? Car is of low value so am loathe to spend lots of diagnosis.

Can’t see any other split / disconnected hoses. Would be good to get to connected to something that could detect a leak like a smoke machine of sorts?

 

[AnthonyUK]

If the MAF bracket was broken, is the air filter fitting well?

 

[mbzclk]

Yeah the air box clips on well. But even with that not fitted I wouldn’t expect to see the wonky idle.

I’ll try get a video

 

[mbzclk]

air or vacuum leak else an EGR related fault. I think there has been a perished hose or two under there. So could be that again. Just can’t see any other hoses that are perished now.

 

[mbzclk]

Link to video

trim.D8226495-0614-46A6-BA3A-E3074BE7D885.MOV - VEED - Online Video Editor - Video Editing Made Simple

www.veed.io

Secondary air pump and it’s fine, once that finishes it’s cycle that’s when it becomes notable.

Another video below from inside with some blips of throttle… video is a bit quiet so need the speakers turned up!

trim.692FA090-6AFD-48A5-9AF1-0ED45869B1A9.MOV

trim.692FA090-6AFD-48A5-9AF1-0ED45869B1A9.MOV

embed.api.video

Replaced both of the below items with another known working ones. Made no difference.



The pipe from the manifold (as shown below) that was split I used a straight and some silicone pipe to join when I disconnect it from the valve it does make a hiss as if it’s releasing vacuum it’s held. It could be there is another split in this pipe further down but I can’t see it and then I wouldn’t expect the his when disconnected.

YouTube videos explain how to replace the pipe, it’s a manifold out, open up, replace and reseal job so hopefully not! Hopefully the pipe repair should suffice. Thinking to swap EGR next or buy a kit with all hoses and swap them all over.



As discussed here: https://mbworld.org/forums/clk-class-w208/175568-brake-booster-hose-check-valve.html

At this rate I considered swapping the engine, it was £100 for an engine on eBay last week but now sold.

I was going to disconnect the EGR at the rear and give that a go but struggled to get the connector off after the car had been run as it was so hot.

Not sure what I should be looking at with regards to LIVE data, the EML isn’t lit (only when I disconnected the valves as above, no codes stored or pending either)

 

[mbzclk]

Am wondering if it could be a dodgy ancillary - hmmm if I get the belt off I’ll struggle getting it back on right. Lol

EDIT, actually could be time to replace the EGR valve I think