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[jmariog]

I found on my battery that the terminal clamps  had actually stretched and although you could tighten them they weren't particularly tight on the posts,

[Ocracoke]

I'd also go for a earth wire check as well. Mine was broken internally and if you hit the right pothole, it'd die altogether.

[454_1.1_55_2004]

As G said, you should take a closer look at MAP sensor.
There are quite a few things that can lead to a defectuous MAP sensor: bad gas, age, bad cleaning, dammaged tip .....
Because it's an old car, you should change it (small chances that this sensor was changed before....) and, maybe, this will fix your problem (changing mine has fixed the same problem as yours).
It's not an expensive part, but a new one will make a difference.
Also, a MAP sensor that is not working properely could be a factor for your high fuel consumption.

[the_wirewalker]

You are probably right, there's no need saving on map sensor money. I will order a new one and change it, it is maintanance anyhow. So next jobs are:

• Changing battery to a new Banner 45Ah
• Changing MAP sensor with a new one

Will let you know of the results..
Thank you guys!

[the_wirewalker]

Status update: Changed the battery with a good quality Banner Power Bull
No luck at all, still rough idling and higher fuel consumption.
All my hopes are focused in the MAP sensor...

[454_1.1_55_2004]

Also you can do a compression test on all cylinders (just to be sure).

[CrazyG]

Agreed....clean or change the MAP sensor, and do a compression test.

[mr singh]

there are a couple of things that can cause a poor idle. too much air (an air leak of some kind), too little air (blocked air filter), poor spark, failing O2 sensors.

personally id do a full service, replace the oil with oil from mercedes, i had an issue where my SB3 would burn oil after having the head rebuilt but since i used oil from my local mercedes dealer, the oil consumption has reduced (i still need to recheck the oil level but its not burning as much as when i used castrol or petronas oils which conformed to MB225.9 standards), replace the air filter and replace the spark plugs and inspect the old plugs. spark plugs are generally a decent way of telling how your engine is running. in fact just buy all the parts from the dealer, rather than using non genuine service parts.

failing O2 sensors could be sending the wrong or incorrect signal which are JUST within the set tolerances in the mapping, back to the PCM. the pre cat O2 sensor is the one that reads what is coming out of the engine and the post cat sensor does the fuel adjustments, if either are playing up but within the set parameters, there is a possibility that you could have a poor idle.

a big enough air leak will make the engine run like a bag of spanners, log a code and bring the EML on, but if the air leak is small enough, it may not be enough to log a 'bank 1 running lean' code. easiest way to find a possible air leak is to spray brake cleaner on the induction pipes, but do it in stages and not on every pipe at once, and dont be shy with spraying the pipe work, a good drenching will work better than a 5-7 second squirt.

also depending on how it was driven by the previous owner, a good thrashing with premium petrol might also do it some good. i know when i had my 1st 1.1, it defiantly ran better by the time i sold it than when i bought it, that's partly down to the fact that it was always run on shell v-power (or the equivalent) and because i did 60,000 miles in 5 years and it was properly used on several long distance trips (one of them was a trip to south germany with 2 passengers and a boot full of luggage) and a 50-60 mile commute to work daily.

[the_wirewalker]

I wouldn't say that it can possibly run lean, because it pulls really hard and even after 2 months of ownership, I am still impressed when hitting the gas pedal. The only issue would be it running rich or something like that. My new genuine MAP sensor has just arrived and I will post after I change it. Moreover, I noticed that when the engine is running, the voltage is all over the place, fluctuating from 14.1 to 15.1 volts at idle. Can this be an alternator issue too? @mr singh, what fuel consumption did you get at highway usually in your 1.1?
Moreover, it could be a post cat o2 sensor, I will test it tomorrow.

[mr singh]

i cant remember what MPG i got with my 1st 1.1 on the highway but i know i would easily get 420 miles out of a tank, and that was with the a/c switched on all the time. i did try and get 500 mile on a tank but fell short by about 5 miles and ran out of fuel.

with my 2nd 1.1 i averaged 41.56 MPG in the 9 months i owned it and the highest i managed was 45.73 MPG

[Bari87]

454 Alternator SetPoint from ECU is: 14,4V
It would never exceed 14,5V (cause of Temperature variation, cold temperature=less resistance = more max alternator output).

So 15V is definitely wrong. For the ECUs it's not Problem, they work between 11-16V. But your Battery will be grilled.

Conventional wet Battery=14,4V
Lifepo4 Battery=14,4V
AGM=14,8V

Only Optima YT/BT could handle: 13,8-15,1V

As for fuel as i said: Greek fuel is 30% fuel, 20% dirt and sand and 50% water. If the manipulated fuel dispenser shows that you have got '10L' fuel, then you can be glad if its '9L' in real inside. Better known as: Apateones.

So everything fine with that consumation.
Just need to handle the crap idle.

[the_wirewalker]

Latest update on the new forfour's condition:
- Cleaned fuel injectors (they seemed clean enough), no change. But I noticed the that the injectors' o-rings are quite "tired" and somehow cut in places. I will replace them as soon as possible.
- Changed old alternator with a used one (in very good condition), together with the belt. No change at all.
- Changed rear shocks and front wishbone bearings. The car's performance on the road was greatly improved. The suspension now feels way more comfortable on bumps and bends.
- Polished both the headlights and plastic roof. The roof I would say that improved by 50%, but is not perfect, still I can see little cracks like tree branches inside the plastic. Headlight illumination has not improved at all, aesthetically they do look way more fresh.
- I bought both new o2 sensors but did not install them, since I am now 100%  satisfied with the car's fuel consumption.

So, finally, the only issue I still have is the erratic idling. I found out that the issue is 100% electrical, since I can notice it, only when I use some electric device, hence:
Example 1: When I am idling at 800 rpm and I turn on the rear window heater, both the car's voltage and rpm drop instantly from 800 to 750 and from 14.4 to 13.9 and return back in a second.
Example 2: When I am idling at 800 rpm and I run on hazards, the idling of the car starts to decrease and increase in the same tempo as the hazards go. The car's rpm follow in the same order.

Moreover, this is not an issue of the speedometer, since I can here the engine going up and down into rpm when using the hazards. Finally, when I start the car cold (1.300 - 1500 rpm), I cannot reproduce neither of the above two examples.

Any ideas?
Thank you forfourers...

[cecil]

Why don’t you clean the chassis earths and possibly replace the battery to chassis lead with a thicker one.

[CrazyG]

I definitely agree with cecil's suggestions on the chassis & battery earth leads.

[the_wirewalker]

I will trust your recommendations guys. Just ordered the upgrade earth leads from smartmods. Will let you know as soon as they arrive.
Will like to underline here again that I am very impressed from the car and I wish I have bought it earlier. Although having 200k kilometers on the clock, it really feels very solid! Third gear on a slope and it pulls very hard!  With Michelin pilot sport 3 tires, it is almost impossible to go out of a bend. My previous car (Vauxhall Corsa) was understeering heavily when pushed too hard, this does not, no matter what.