230ge Engine stutter misfire Jetronic

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Jdring
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Looking for some details of the fuel and ignition side of a 230GE which starts well and runs smooth but has a regular stutter and misfire when on the road.  The stutter prevents the G progressing to a comfortable cruising speed.

There are a lot of good forum threads on here pointing towards: the Bosch K Jetronic injection "is all about fuel pressure and vacuum pipe airleaks."

Some of the electronics have been renewed (distributor), and there is a new/replacement metal petrol tank and pump. 

But the pump is running continuously.  And on another 230 the pump runs for a few seconds and stops (up to pressure?).  So why is this replacement pump continuing...maybe never getting up to pressure?  how is that detected?  

I found a good generic description of the K Jetronic system (attached), and see that pumps have a pressure relief valve in it that opens and releases fuel back into the inlet side when pressure reaches a high level.  But there should be a switch somewhere to activate the fuel pump relay...how is that working?

And then there is a petrol 'accumulator' which is a device that smooths out the fuel delivery and has a spring and plunger in it to maintain steady pressue to the Jetronic when the pump stops. #130GBP plus for such a little thing.

Maybe the pump is struggling to get fuel flow from the tank due to a blockage?  Or through the Accumulator.  But the engine runs smooth until you get on the road and then in each gear there is the stuttering, faltering behaviour.

Any ideas?

Oh... this G is harder to start when warm.  That apparently points to the Accumulator?

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JASONGDS
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Re: 230ge Engine stutter misfire Jetronic

Generally these things are caused by renewing  other parts and upsetting something accidentally,  was the distributor renewed same time as the fuel tank? Have you double checked all the vacuum pipes for cracks etc? 

gav.helme
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Re: 230ge Engine stutter misfire Jetronic

Could also be a failed temp sender or dribbling 5th warm up injector 

Could possibly be not shutting off the cold start properly and over fueling when warm ? 

Jdring
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Re: 230ge Engine stutter misfire Jetronic

So the warm-start issue is often linked to a failed fuel line accumulator, but the stuck/dripping warm up regulator cause is one to check also.

But the main issue is the stutter, or misfire.

We noticed the (new) fuel pump doesn't switch off.  It's supposed to run, pressure the pipeline and cut off.  I know the pumps have a relief valve that lets excess pressure fuel back to the inlet, but then its supposed to stop.  But how would the fuel pump relay know the fuel is at pressure and cut the voltage?  Is there a pressure switch somewhere?

The pump is definitely running though, so checking the flow would be a good thing to do.  It will happily rev when stationary and hold without misfire at 3-4k rpm... so fuel delivery can't be that bad.  Why the misfire when underway.

I'm going to try to look at the wiring diagrams.

Jdring
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Re: 230ge Engine stutter misfire Jetronic

Update.  One garage looked at it, fiddled with something and made it impossible to start.  Handed it back worse. Muppets.  Once running the stutter is still there, but more intermittent.  Running rich but mechanically seems fine and quite smooth and will hold 70mph ok (5 speed manual)

So, G delivered to Bosch Service Centre for a good look at the K-Jetronic.  Likely replace the fuel pump which never stops (suggests it never really gets the fuel line pressurised).  Maybe replace the fuel accumulator which smooths the pressure and holds it with a non-return valve.   Check the vaccum lines and replace the 230GE breather pipe which connects the rocker cover to the airbox (15cm long - anyone know the part number?).  These always split and crack up with the heat.

The garage won't need it, but I found the following good service guide for those wanting to sort it themselves!

https://tasteslikepetrol.net/2020/02/bosch-k-jetronic-basics/

Jdring
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Re: 230ge Engine stutter misfire Jetronic
Further. Bosch expert garage replaced fuel pump relay, rewired fuel pump which was bypassing it(!) and re-connected the electronic control unit of the eK-Tronic injection. Replaced a high pressure fuel delivery line and tuned it up. Still a slight stutter. Replaced the (newish) spark plugs which were oiled up because the engine was running far too rich before - stutter gone. Engine running sweet. But - still not a good starter. Especially when warmed up. I asked 3 garages to replace the fuel Accumulator which keeps good fuel pressure to the Jetronic and none did. Take a look at the state of it, above the new fuel filter. So... New accumulator coming and let's see.
Jdring
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Re: 230ge Engine stutter misfire Jetronic

Final (for now)

A new Bosch Fuel Accumulator took a couple of weeks from Germany (Autodoc) and was about 170GBP.

Once fitted - it starts cold and warm, within a very acceptable couple of cranks.  The idle rpm cold is lowish and it increases when warm, which I think will be a bit of KJet adjustment (its normally the reverse of that).

The advice on here was absolutely right - fuel pressure is key with this injection system. Including vacuum leaks.  The service guide posted above is excellent, and its good to have a Bosch Service centre that knows the system for overall tuning and making if leaner and efficient.

Needs a week of road test to confirm, but looking good.

JASONGDS
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Re: 230ge Engine stutter misfire Jetronic

That's good news,  also thank you for reporting back, too many of these posts ( not just on here) don't tell us what the solution was

Jdring
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Re: 230ge Engine stutter misfire Jetronic

Next step... not worthy of a fresh post... the idle is too high when warm.  1500-1800rpm.

When cold, the engine starts well and idles quite low, about 1000rpm and it gradually increases as it warms up.

Having learnt a lot about how KEJetronic is all working, and the importance of fuel pressure (control and high pressure), and the need to eliminate vacuum leaks...  I think there is a vacuum leaks somewhere or its the Idle Control Valve (ICV) on the side of the Air Flow meter.  Because there is bugger all else you can 'adjust'.  The only screw you can tweak is the 3mm allen key on the top of the Air Flow meter itself which stiffens or loosens the free play on the air sensor plate, which is what controls the idle mixture (only).  My free play is about 2-3mm which is spot on.

So there is extra air getting in somewhere and tricking the 'ECU'.  Yes the 230GE does have an ECU of sorts, just not a silicon chip type one.

So I am going to locate, test and clean the ICV.  Probably it is gummed up and not free moving any more (its an electro controlled gate/valve). If it is free, then there is a idle control module somewhere that delivers voltage to it.  Hopefully not that.

Jdring
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Re: 230ge Engine stutter misfire Jetronic

I located the ICV.  It's behind the fuel Meter body, down and under the cast intake manifold.  Its not that easy to get to.  It has a electrical connector which is easy to get to and a 12volt supply across those terminals should allow you to hear the operation while insitu and maybe even free it up a bit if gummed up.

But I didn't get that far because I found a air leak/gap in crank case breather pipe to the airbox, and when resolved it seems that the idle is now being correctly managed. A proper run is needed to confirm.

It still smells a bit petrol rich if I am honest, but fuel consumptions is better that other 230s.  If it is rich, it has to do with the KJet Control Pressure too.  This is the pressure that regulates how much fuel is passed to the injectors. The Fuel Pressure Regulator, on the front of the Metering unit, is something to look to there and is easy to get to.  There is a diaphram in there which may deteriorate.  I've not looked at that yet as all is running well again.

The CO2 idle control screw should only affect the idle mixture and is set right as far as I can tell (a couple of mm of free travel).

Jdring
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Re: 230ge Engine stutter misfire Jetronic

Back from the Bosch garage after a tune/adjustment.

The idle control valve is somehow adjustable (i cant see where) and the warm idle is now a nice 1 to 1.1k which is nice for an older engine.

But a stutter has re-appeared.  Just on acceleration and in top gear at cruise. Last time, replacing plugs cleared it.  I cant see if it is leaner now, why they might be oiling up, but maybe I need to have it tweaked back richer again! 

Or as the HydroCarbon readout is still quite high (fuel), it could be poor injectors and time to replace those and seals.  Anyone have experience of symptoms of worn injectors?  It seems quite straight forward to replace.  And its only 4 cylinders.