M104 HFM hesitates cold when revving up. Open air filter.

[hismajestics]

The engine starts fine with smooth idle. When touching the gas pedal it does not respond. When warmed up everything works fine.

Can an open air filter disturb the HFM-system? I needed to make the change due to lack of space for the original in my swap to W114 Coupe.

/johannes

 

[carat 3.6]

Not having an air filter wont upset the engine management, have you driven it on the road yet?

 

[hismajestics]

Not having an air filter wont upset the engine management, have you driven it on the road yet?

I've been driving it, yes. It appears to be really quick and fast.

I put in new sparks plugs, Bosch F8 DC4, but the problem when cold is still there, hmm...

What about the exhaust, does it play a role? It's a 2,5" free flowing with the Y-pipe some 60 cm more in front (closer to manifolds) than in original. Any thoughts?

/johannes

 

[carat 3.6]

That fit's in there beautifully, I think I need a w114 now.

I don't think it would be the exhaust as it runs fine when hot. What shape is the engine loom in? or more specifically the wiring to the throttle body and ignition coils.

Have you tried running it with the air mass sensor unplugged?

 

[219]

That's a very neat looking conversion .

 

[hismajestics]

That fit's in there beautifully, I think I need a w114 now.

I don't think it would be the exhaust as it runs fine when hot. What shape is the engine loom in? or more specifically the wiring to the throttle body and ignition coils.

Hehe, thanks...

Engine loom to coils etc. is rewired, throttle body is not. Engine idles and runs smoothly and revs easily when warm. No cut outs or similar symptoms as with a bad throttle body wiring.

 

[grober]

Symptoms would indicate the mixture is not being enriched enough when cold. There will be an initial short lived enrichment [ timed] on starting but this will only last seconds after that it will be mixture enrichment - by increased length of injector pulse ? This will be controlled by the engine ECU influenced primarily by the engine coolant sensor and the air intake temperature sensor. I would suggest testing / replacing those first. The other thing to possibly test would be the composition of the exhaust gases when cold and hot. You should see an enrichment followed by a leaning off as the engine warms up. As a reference point you could do the same measurement on a similar engine you know is working correctly.

 

[hismajestics]

Symptoms would indicate the mixture is not being enriched enough when cold. There will be an initial short lived enrichment [ timed] on starting but this will only last seconds after that it will be mixture enrichment - by increased length of injector pulse ? This will be controlled by the engine ECU influenced primarily by the engine coolant sensor and the air intake temperature sensor. I would suggest testing / replacing those first. The other thing to possibly test would be the composition of the exhaust gases when cold and hot. You should see an enrichment followed by a leaning off as the engine warms up. As a reference point you could do the same measurement on a similar engine you know is working correctly.

Many thanks, grober.

Where is air intake temp sensor located? The engine coolant sensor is by the thermostat, I guess.

/johannes

 

[grober]

Many thanks, grober.

Where is air intake temp sensor located? The engine coolant sensor is by the thermostat, I guess.

/johannes

The air intake temperature sensor is usually somewhere on the plastic intake pipework.

Distinguish between the temperature sensor for the injection system and the one for the temperature gauge.

http://www.w124performance.com/service/w124CD1/Program/Engine/LHIS/07.4-0015.pdf

AND
07 Mechanical/Electronic Injection - M104


Other completely different possibility is a faulty OVP relay which feeds the fast idle control and the ECU which leads all manner of weird faults.

 

[hismajestics]

The air intake temperature sensor is usually somewhere on the plastic intake pipework.

Distinguish between the temperature sensor for the injection system and the one for the temperature gauge.

http://www.w124performance.com/service/w124CD1/Program/Engine/LHIS/07.4-0015.pdf

AND
07 Mechanical/Electronic Injection - M104


Other completely different possibility is a faulty OVP relay which feeds the fast idle control and the ECU which leads all manner of weird faults.

Thanks again, grober.

I'll start with air intake temp sensor. Mine is the same as in the pic attached.

/johannes

 

[hismajestics]

Ok, started to change the air intake temp sensor. I think there was some improvement in throttle in those immediate seconds after a cold start (+20 C). It takes a minute or so to get full response on the throttle.

After that I put in a new coolant temp sensor and the feeling is the idle is a bit lower.

Maybe getting it 100% right is a Tom Cruise job? Thinking that the original E320 ECU just cannot cope with removal of a catalytic converter, EGR pump and an open air filter?

Any educated guesses on this?

/johannes

 

[grober]

Where is your lambda sensor located and has it got a functioning heating element ?

 

[hismajestics]

Where is your lambda sensor located and has it got a functioning heating element ?

Lambda is at the Y-pipe, immediately after the downpipe. It's the original E320 M104 lambda. What do you mean by a heating element??

 

[grober]

Lambda is at the Y-pipe, immediately after the downpipe. It's the original E320 M104 lambda. What do you mean by a heating element??

Most lambda sensors have an electrically powered internal heating element to reach their operating temperature quickly. Before this the injection system will operate in open loop mode[ fixed air/fuel ratio] then after the lambda becomes operational it will operate in closed loop [ =feedback controlled] mode [ variable air/ fuel ratio] except for certain conditions where a fixed air/ fuel ratio may be desirable e.g. full load or acceleration. If the lambda fails to reach operating temperature due to a failed heater or its electrical supply then lambda control [ fine mixture control] may fail to operate. Usually this means the engine will run slightly rich which might be effecting your idle?

 

[rorf]

Wow, not having an air filter is certainly going to mess around with your MAF never mind the longevity of the engine. The MAF will get contaminated

 

[hismajestics]

Ok, started to change the air intake temp sensor. I think there was some improvement in throttle in those immediate seconds after a cold start (+20 C). It takes a minute or so to get full response on the throttle.

After that I put in a new coolant temp sensor and the feeling is the idle is a bit lower.

Maybe getting it 100% right is a Tom Cruise job? Thinking that the original E320 ECU just cannot cope with removal of a catalytic converter, EGR pump and an open air filter?

Now with some 400 km's and a track day of testing the car runs certainly better. No more hesitation. But, still a drop in revs when stopping after steady driving. Happens every time. Some stalling when engine is cold...

I guess I need to live with this as long as the original ECU is there. Would really like to tune it properly but the only option is a standalone. Have been looking at an Ecumaster EMU, but I don't really know...

What would be the benefits (except a proper tune-up) of a standalone in a N/A engine? Is it worth the investment without any other mods?

 

[coupe addict]

On the M104 loom there is usually an 8pin connector tucked under the inlet manifold area joining the front end of the loom to the wiring to the ETA.
This is fallible through loom decomposition, and doubly so if handled frequently, as may be the case here. Symptoms are broadly similar to going quietly mad, as with all loom problems.
A further related possibility is the wiring at the coolant temperature sensor, even if the sensor itself is fine.
Complex problems are, in my experience, rare with the engine management, but weird results from quite minor wiring problems are rather common.

 

[hismajestics]

On the M104 loom there is usually an 8pin connector tucked under the inlet manifold area joining the front end of the loom to the wiring to the ETA.
This is fallible through loom decomposition, and doubly so if handled frequently, as may be the case here. Symptoms are broadly similar to going quietly mad, as with all loom problems.
A further related possibility is the wiring at the coolant temperature sensor, even if the sensor itself is fine.
Complex problems are, in my experience, rare with the engine management, but weird results from quite minor wiring problems are rather common.

Thanks coupe. I suppose you mean the round connector coming from idle/cruise control ECU? That and loom to ETA are not rewired. Everything else is. So, you may be right there, thanks.

/johannes

 

[bolide]

I have a suspicion that an M104 with an aftermarket ECU might end up being brilliant. But I wouldn't underestimate the amount of time it'd take to get it mapped & working well

The car has all the sensors it needs, including two knock sensors, and it has variable cam timing, electronic ignition, MAF, Cat & Lambda. I'm surprised no-one offers a plug-in kit

Nick Froome

 

[carat 3.6]

I have a suspicion that an M104 with an aftermarket ECU might end up being brilliant. But I wouldn't underestimate the amount of time it'd take to get it mapped & working well

The car has all the sensors it needs, including two knock sensors, and it has variable cam timing, electronic ignition, MAF, Cat & Lambda. I'm surprised no-one offers a plug-in kit

Nick Froome

Using a flywheel and crank sensor from the late m111 engines gives you a 60-2 trigger wheel, then it's just the throttle body to sort out. I paid just over 700 for an emerald ecu to run mine, not that expensive when you consider the cost of an m104 loom from the dealer....