'97 C250TD Lack of power

[aka$h]

I went to see a c250 td today. THe main problem was the lack of power. May be this is becuase im used to driving the e300td, but it felt like there was no turbo.
From memory the turbo kicks in around 2000rpm, and the engine is not too responsive before that. On this car, its like your just waiting for the boost, but you dont get any.

What could the possible problems be?

 

[Dieselman]

Turbo wastegate modulator, MAP sensor, boost air leak.

Not a lot else on a 250td.

 

[aka$h]

Thanks Dieselman,
There is a droning sound from the engine bay too, would that suggest a leak?

 

[hobbsy]

If you've got an air leak it won't be a drone it will be more of a whoosh, rushing or air type sound.

If you go back again to look at it try listening with the windows down or through a tunnel or somewhere with walls to reflect more sound at you.

It should come on decent boost somewhere about 2k rpm.

 

[hobbsy]

Also if the turbo is knackered it often sounds like a police sirens spinning up (but in the distance a bit) this probably isn't the only way a turbo can fail though so just because you don't hear this doesn't mean the turbo isn't knackered.

Any smoke?

 

[hobbsy]

Also its dead easy to check the connection to the MAF as it *could* have popped off. If you look on the inlet manifold (big black plastic thing with 10 smaller pipes going into the engine on the right hand side as you look at it).

On the cylinderical part where all the smaller pipes come from look at the end nearest you - there is a little nipple which the MAF feed attaches to.

It will run without this but the fuelling with me out (and could account for the poor performance).

 

[Dieselman]

I think you mean the MAP sensor, not MAF sensor. There is no MAF on a 250turbo.

 

[hobbsy]

Yes I did mean the MAP (oops!)

 

[compress ignite]

Alda,Overboost,Fuel Enrich,Etc.

All these systems are dependent on there being no "Black Goo" or "Soot" clogging or impeding the vacuum air flow.
The EGR and the PVC type vent hose (from the top of the valve cover) are
Notorious for clogging one or more of the components in these systems...
and then no Boost/or fuel enrichment.
You would not believe how far the "Black Goo" can travel into the intake
system!

 

[garymac]

I had a similar problem with my C250. I was getting no turbo and it was running like a sack of muck. Traced the problem to a very thin vacuum pipe next to the duo valve. the pipe had simply come off. When reattached the car was running as good as ever.

 

[tuikku]

I had a similar problem with my C250. I was getting no turbo and it was running like a sack of muck. Traced the problem to a very thin vacuum pipe next to the duo valve. the pipe had simply come off. When reattached the car was running as good as ever.

Leaking could be anywhere in the vacuum system, and influence is about the same.
Vacuum system consumes many items in car.
Turbo, EGR......

Pressure converters adjusts the amount of vacuum.
Turbo and EGR both have their own pressure converter.

 

[poisas]

same problem with my E250diesel-turbo, nothing was wrong as everywhere everybody was talking, housing was OK, i have bypassed egr valve with vacuum, map sensor was working OK, but just few days ago, my friend told 1 thing, and that change everything to this car...
he was working in car repair service, and there was 1 car he was wandering, that on the intake temp sensor it had extra resistor,
some kind like modding tunning etc.. he told me to plug out the sensor, and put a resistance to the plug. AUTODATA tels that in C250D-turbo IAT senosor is inverse, and for 20C has resistance ~6000ohm, so for the test i have put 10kOhm resistance to the plug, and left IAT alone in the intake.
Before i check the IAT with multimeter, it was working ok in the room i had about 5950ohm in ~20C, But i notice that all sensor was wet in oil. So after i put a 10kohm instead of the sensor, and went for the test drive, i could not stop driving it was so amazingly improoved accelerator became so sensitive, i realy could feel and hear every time every gearr that turbo starts to spool up from 1500 and reaching 2000rpm and you have this whooomp. I even couldn' beleve that the car can perfome that good. I give to drive it to my father, and he confirm that its perfoming very good.
So but this is just 10kOhm for test. Dieselman you told me that IAT has no meaning ) but i found out that it has A LOT OF MEANING to richen the fuel and advance the timing. Peaople call it IAT Mod, or sensor mod, they modificate outputs for the iat map and cht sensors. to fine tune the engine.
So the question is what is wrong with this iat sensor ? How many liters of oil i have in the intercooler that it is capable to come up to the intake from the bootom. Is that oil affecting perfomance of intercooler so badly ? Is that oil on the IAT makes iat take more heat from intake air input ?

 

[Vlad]

Just had a 300TD that was very limp wristed in the acceleration department....turbo was spinning up but not a lot of action. Turned out it needed a Turbo wastegate modulator which improved things significantly, but my Indi also found that the Intercooler had a small hole in it and a % of the boost was being lost through that.......that repair will have to wait until things get worse.

 

[Dieselman]

Dieselman you told me that IAT has no meaning ) but i found out that it has A LOT OF MEANING to richen the fuel and advance the timing.

Did I.?
As far as altering the timing, no chance, it's mechanical advance.

The IAT is there to reduce maximum fuelling as the air temp rises due to boost.

What's your EGT now.?

 

[tuikku]

The IAT is there to reduce maximum fuelling as the air temp rises due to boost.

....Dieselman is right, as so many times.
IAT rises very easily.
MB stock coolers are very poor.

 

[poisas]

Did I.?
As far as altering the timing, no chance, it's mechanical advance.

The IAT is there to reduce maximum fuelling as the air temp rises due to boost.

What's your EGT now.?

i cant understand what is EGT IAT purpose on engine is one thing.
But my guesses are that i have very very lean a/f mixture,
i have done IAT mod with pot, buy adding extra resistance in to IAT's output, and instead of 5kohm i got 10kohm , this makes ECU think that air in the intake is lower ~ 15C = more oxigen, engine need more fuel to keep with A/F. And its so noticable how fast the engine starts to pick up RPM.
and this change everything on the car, simple 10kohm pot for 1eur makes this car fly how it can bee ?
this is from "sensor mod.doc" I suppose in my car ECU is "not so smart" to change the timing :? In my fathers Audi in service they fine tune the timing just with a computer no mechanical ajustments they make
They use pot with paralel with IAT, so it makes engine think that air is hotter for lean out.

IAT

The IAT is less sensitive to cold start issues. You can add more temp to this signal than you can to the CTS. Just keep in mind that you are not only lowering your lean-out limits, you are also retarding your ignition timing. If you put a timing light on the engine as you adjust IAT values, you won’t see the timing change. The timing changes under load. Hotter air is more prone to detonation. This is why the ECU retards the timing.

If you are tuning on the hottest day of the year, you may find out just how high of a signal you can generate before setting codes. Typically it is in the 240* F range. If you are tuning in the middle of February, then you can offset the signal from your base cold reading and things will be fine for now. Come June or August, this setting may be high enough to trip codes. Allow for this when tuning.


possible map sensor failuer. Today i was measured outputs from map sensor, 3 wires +5V Grnd and output value for ECU. At idle it was 1.48V same as with only ignition ON, o was trying to WOT or "push the bottom" but the voltage stays still or some tomes goes for 1.55V, i realy can feel the vacuum and the pressure in intake. Tommorow dammit now its tommorow i gona blow with something to see if it changes his voltage ( i dont think its frequency based,.... am i right? ) I dam so would like to spend 100eur for that sensor if its bad but i need to proove that its bad
So i can say that no ignitiion ajustments are made but ecu realy gives much more diesel what i found is here:
Diesels fuel is designed to be a high pressure ignition by compression fuel. Running lean on a Diesel engine simply means that you are not making the engines full potential for torque.

Running rich means too much fuel and not enough air and in a Diesel engine this simply means wasted fuel and lower economy with higher emissions.

In both cases neither examples of fueling will hurt a Diesel engine in any way.
So i wonder than, when diesel/air is too rich, should i have "black diesel smoke" ? because i got it when WOT with 2gear with ~15kOhm in the IAT output


So Today i was checkt the map sensor for how it reacts to boost/vacuum. With my mouth i was able to: Vacuum- voltage is dropping, 0.8V Pressure - voltage is raising to 1.8V it like it is working, but while vacuum it is dropping.. But anyway ecu is measurint the difference between 1.5V and output

 

[poisas]

I found this post, describes my car 99% now i only need to get map sensor and test it then
http://www.fordscorpio.co.uk/replacemap.htm

I mean its nasty that mers is having reduced boost when standing still, so i wonder what is this thing that telss the carr that it is moving ? where is that damn sensor i want to "make it think" that car is driving even if its stands

 

[poisas]

how can i measure EGT [SIZE=-1]Exhaust-gas temperature?
and one more thing i have noticed, now when i have addet pot and set on 2.5kohm resistance (+orginal iat) and now what i have is more power on low rpm range 650-2000, but i noticed that turbo boost over 2000rpm is not always so powerfull , boost some times is with much less power, and it can be heard by ear, in the evenings, when i have driven from work to homw, i can hear clearly how the turbo starts to boost at 1500, and you have a very strong umph after 2000rpm, but in the morning when i was driving to work, i had almost no noticable "umph". what i was thinking now, that i would like to install boost gauge, how much this procedure could coust in such crazy enonomical state ? ?
[/SIZE]

 

[poisas]

Turbo wastegate modulator, MAP sensor, boost air leak.

Not a lot else on a 250td.

i found there can be several more things CAN be in 250td, its cloged tank filter and tank, cloged cattalyst, very little retarded timing is droping low rpm power slightly. Those are worth to check