W124 idles at 3,000rpm

[franksm]

Hi folks

Have got my 230CE back together after some cylinder-head-off work. Also replaced the overvoltage-protection relay (OVP) as the ABS system was showing its indicator in the recent past. The new OVP is a "working" second-hand relay, but dry-tests with a multimeter show it works fine.

With the OVP fitted, starting engine, idle speed is immediately 3,000rpm

Without the OVP fitted, it idles as normal at about 550rpm (albeit with ABS indicator lit, and poor start when cold).

Am pretty sure I have not upset wiring to the idle-air valve etc, but will have to double-check.

Have read that a failure mode of the idle-valve is high-rpm idle - eg. no +12v getting to the valve. However if the idle-valve is at fault with the OVP fitted, would it not also cause problems with the OVP removed from the system ?

Any ideas appreciated. Car is a '92 230CE with KE-jetronic injection on M102.982 engine

Thanks
Frank

 

[television]

Too late tonight,see who else answers, or will come back to it tomorrow

 

[franksm]

LOL

Anyway, let me just say that the decoke has given the car a new lease of life - feels stronger, more powerful and smoother than ever. I also fixed some leaks in the exhaust manifold, so it purrs like a kitten now. Nice, easy engine to work on too - whoever in MB designed the way the bonnet opens totally vertically deserves a medal

 

[television]

LOL

- whoever in MB designed the way the bonnet opens totally vertically deserves a medal

you mean that your head is still in on piece, thats good

 

[franksm]

Hi folks & Television

You's had forgotten about me

So, I have been driving the car without the OVP relay plugged in these past few weeks, shame on me, and only today got time to do some diagnostics. Having said that, the car is going great albeit without ABS, and is still getting between 23mpg and 28mpg around town.

Here's where I'm at:

- OVP not installed, idle-air-control-valve & everything hooked up ---> car idles and runs nicely, but cold start is a bit poor; ABS doesn't engage

- OVP installed, idle-air-control-valve & everything hooked up ---> car runs and starts nicely, ABS is engaged & error-free, but car idles at 1500 to 2000 rpm

- OVP installed, idle-air-control-valve NOT hooked up ---> car runs and starts perfectly, ABS is error-free, idle is spot-on (700rpm or so).

So, does it look like idle-air-control-valve is the problem ? The pink & blue wire has a healthy 14v when the car is idling, the red and white wire is -ve. Is that normal ? The valve looks to be plumbed into the intake manifold, drawing air from the cam-cover piping, and it all looks fine.

Thanks

Frank

 

[franksm]

Is it possible to take the air-valve apart for cleaning ? Since it's plumbed to the oily air taken from the cam-cover, it's possible that it's gunged up with coke or whatever ?

 

[television]

Are we talking about the rotary air valve and yours is the 4 pin type

resistance wise it should measure 12 ohms between pins I and 2, and the same for 3and 4

 

[franksm]

Are we talking about the rotary air valve and yours is the 4 pin type

resistance wise it should measure 12 ohms between pins I and 2, and the same for 3and 4

It has a round body, and is held in a rubber bung between #3 and #4 inlet tract on the inlet manifold. There are only two wires on the connector though (I didn't check to see if the connector has two spare/unused pins).

 

[television]

It has a round body, and is held in a rubber bung between #3 and #4 inlet tract on the inlet manifold. There are only two wires on the connector though (I didn't check to see if the connector has two spare/unused pins).

If yours is the 2 wire rotary valve, if you put 12 volt across it it should buzz

 

[franksm]

Just run a test - 12v on the pink/blue wire, and -ve on the red/white does make it buzz.

I traced the pink/blue back through the OVP and onto pin#1 of the KE controller. All good.

And I traced the red/whiteback to pin#3 on the KE and that's good too. Am at a loss - are there "proper" diagnostics in this model of W124 that a MB specialist would be able to query ? Am wondering if I damaged a sensor while previously working on the engine.

My KE is "KE0027", part# 006 545 7932 [07]

To recap - with the ISCV unplugged, the engine runs absolutely fine, although is a bit lumpy when starting for the first 20 seconds.

Thanks for the advice so far !

Frank

 

[JIZZSTER]

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