if you had bad lambda, engine light would be on

i would measure compression before doing anything else

It doesn't seem to have a check engine light but there aren't any errors stored. Also, compression has been measured and it was OK.

what about timing? changed anything recently

flisko said:

if you had bad lambda, engine light would be on

Click to expand...

not necessarily, it will throw a code if the sensor has completely failed and ecu is receiving no signal from it or if the value its sending is wildly out of expected range, they can give a false reading and not throw a code as well.

Well, for me from what the OP has said, it sounds like an ignition issue to me, maybe a faulty coil pack or HT lead(s).

Actual figues the sensors are giving can be misleading as if something is wrong and then thu the engine is not running right then the ecu will be trying to compensate for that. e.g. if the lambda is saying its running lean it will increase injector duration to try make it not run lean. Everything has a knock on effect and just noting one or two sensor are not saying what you expect doesn't mean at all that there is something wrong with them particular sensors.... You say it doesn't run on all cylinders sometimes, so this points towards an ignition fault.

mhm, how to test for bad lambda if no lights are on? mes?

could bad lambda prevent car from running normally when cold? problem with one of my puntos

Mmmm, depends what you mean by when cold....

On startup from cold no it won't be the lambda, its running in open loop on cold startup and basically completely ignoring the lambda and running rich on purpose using set parameters rather than reacting to the lambda.

The car runs open loop also when under hard acceleration and also under engine braking conditions as clearly there is no fuel at all being injected then.

They a running in closed loop basically when idling and up past a certain temperature, not sure what exact temp but for sake of fault finding i would suggest ignoring lambda problems right upto normal operating temps. Then its also using it during partial load conditions, so like cruising along at constant speed.

So a faulty lambda will usually result in car not idling properly once warmed up and/or lumpy running under partial load, but would still startup fine from cold and also go ok if you go flat out.

Try remember also that its only a narrowband style sensor and so it doesn't know how lean or rich the burn is only that its lean or rich or not. What the ECU will see from it is it just rapidly switching from 1v to 0v and back again and reacting to it - this all clearly happens so fast you don't notice its doing anything. Unlike a wideband which can tell an ECU how rich or lean its running, the ECU on these cars cannot do anything with this signal as its a wider range of voltages, that would just throw a code.

Poor running when cold only, first thing i would check i think is the temp sensors, check resistance at certain temps, there is some figures in haynes what they should be. But it might be telling the ECU its warm when its not so its not rich enough when cold. I guess you could look at the temp in MES when the car is cold and see what figure its giving too, fire it up and keep eye on that signal and see if it goes up as you would expect (depending on exact car you may have a seperate fan switch or may not, if you do you can see what temp the coolant temp sensors says when the fan kicks in, should be around 96°C on a fire engine - some use ecu to switch the fan though and in this case that wouldn't work.)

didnt think of temp sensor, i checked for vacum leaks and cant feel any, but its only noticeably hesitating when you put your foot down hard, like stuttering for few mins, once warmed up, its fine, also consumption is fine

yea i found out its drinking antifreeze along with misfire when cold, so its probably hg