Hope you guys can help
2001 (4200m) 1.6 Marea, suddenly developed poor engine performance
Well maintained, new cambelt a couple of months ago
Seems normal when cold for first few miles
Then severe lack of power (virtually undriveable) usually develops.
Can sometimes performs normally, although now rarely.
Initially no warning light to indicate any problem
Local garage has carried out diagnosis testing
Injectors checked all same resistance (16 ~ 17)
fuel pressure and flow checked OK
Car starts and idles OK
Emmisons are strange very low HC (4 ppm)
Plugs are very clean, if anything lean mixture
All cylinders running at idle
If you can drive through the lower rpm, car will start to pull after 3500rpm
But sometimes it is almost impossible to reach anything approaching this engine speed
I ran it with Lambda disconnected, although runs rough it is significantly better
seems to be lack of fuel, but why?

All inputs welcome

that does sound lean but i couldn't say for sure anything to check but i have seen this fault before on a 1.6 merea and it was never solved literally after changing every sinlge engine sensor and checking every single wire and showing no fault codes

the one i worked on missfired under load and but had little power loss besides when misssing but would cruise ok and it only did it when it was at absolute full running temprature

watching the lambda readings it would wonder up and down near lean and only on the lean side would it show sighns of missing or strugling at idle so a similar thing

you realy need an experienced mechanic to watch the live data on a fiat examiner wile running from cold and driving to pin point the cause

as you have unplugged the lambda and it ran better i'd start with a new one of them howether and check resistanses on temprature sensor

Thanks for you input, I cut the heater wires to the lamda and reconnected, as I had read that the lambda heater circuit could cause poor running by interfering with the lambda signal. Anyway it runs the same as with lambda disconneted, assuming that I have cut the correct wires (both white wires) I now have a warning light continually lit (engine control system failure) this illuminated before I disconnected the lambda, but was not illuminated when being checked by local garage. All emmission data is :
at Idle CO :0.006 HC :4 Lambda :1.102 CO2 :13.75 O2 :2.01
fast idle CO :0.005 HC :5 Lambda :1.205 CO2 :12.58 O2 :3.69

So looks like High O2 and low HC indicating insufficient fuel
What system is controlling the fuelling?
All inputs welcome

disconnect the maf connector and go for a drive with out it, you will have the injector light come on but tell us if it runs any better?

(there are a number of things controlling the fuel, the maf is one of them)

(reconnect the lambda)

Thanks for your input
My understanding is that there is no MAF on this engine it
uses MAP (manifold pressure) engine speed sensor & throttle position sensor to control fuelling, but what one and how to check any of these?

yes you are correct your car runs speed density injection and no maf sensor

now the engine will not run atall without the manifold presure sensor plugged in so you cant do much with that throttle position would not cause the faul it'a not related to mixture greatly and the map sensor overules it

water temprature shouldnt cause lean mix even if it was saying cold when hot

rpm sensor obviously works

so i'd narrow your search down to fuel presure and delivery lambda air leaks into the inlet something as simplke as a leaky servo maybe try blocking that pipe completly and drive it causiously as there will be little to no brakes

and air temp sensor may cause it but i wouldnt have thought to that extent and the end of the day the fueling system is hard to trick it relies heavily on the lambda and the main data it uses map sensing and rpm gives it it's main rought fueling guide

and i would definitely get that error read it may give a clue it is more than likely lambda faults not because of you but generally or a misfire fault if it got lean enough

Thanks for all replies, I will probably get fiat diagnosis carried out and take it from there. I will let you know what happens so that others can use the information

Any fiat experts out there with any additional input
getting desperate. This fault could render a fundamentally
sound car as uneconomical to repair, not a good advert
for Fiat or modern automotive engineering in general.

I think The Sultan has given you enough food for thought for now. Try what he's suggested and maybe look at getting your hands on a known good map sensor.

OK, here we go, fiiat examiner report :-

Parameters
Engine speed 701 rpm
Air temp 55 deg/C
Water temp 95 deg/C
Spark advance 6 deg/ang
Injection time 3182 usec
Engine load 7.75 kg/h
Intake pressure 334 mbar
Lambda sensor Open loop

Errors
PO170 Mixture strength Intermittent system rich
PO299 Mixture strength distribution Present above top limit
PO130 Lambda 1 status above catal Intermiittent S.C. to +Batt.V.
PO443 Evaoration control valve Intermittent open circuit

So looks like I will be replacing the Lambda
Anyone have any comments on the meaning of this stuff
For example should I be doing something about PO443 or is it all
tied in to the Lambda

Had them remove the old Lambda, whick took them 3.5 hrs
fortunately they charged me for 2 hrs total including the Examiner
Still a lot of money to still have a car that doesn't run well
Hope new lambda will fix it will let you know soon
As usual all comments welcome
Thanks

adoks said:

OK, here we go, fiiat examiner report :-

Parameters
Engine speed 701 rpm
Air temp 55 deg/C
Water temp 95 deg/C
Spark advance 6 deg/ang
Injection time 3182 usec
Engine load 7.75 kg/h
Intake pressure 334 mbar
Lambda sensor Open loop

Errors
PO170 Mixture strength Intermittent system rich
PO299 Mixture strength distribution Present above top limit
PO130 Lambda 1 status above catal Intermiittent S.C. to +Batt.V.
PO443 Evaoration control valve Intermittent open circuit

So looks like I will be replacing the Lambda
Anyone have any comments on the meaning of this stuff
For example should I be doing something about PO443 or is it all
tied in to the Lambda

Had them remove the old Lambda, whick took them 3.5 hrs
fortunately they charged me for 2 hrs total including the Examiner
Still a lot of money to still have a car that doesn't run well
Hope new lambda will fix it will let you know soon
As usual all comments welcome
Thanks

Click to expand...

PO130 - Change the Lambda but before you do first solve PO443 and see if it clears it.

PO443 - Best thing to do is check all vacuum lines from the fuel tank to the evaporative charcoal canister by the fuel tank and to the purge valve located at the engine. This could cause a vacuum and reduce fuel flow significantly. Also some fuel caps can cause this error to come up, make sure the cap is working properly.

Thanks for this infomation, I am not sure where these parts are, but
I will try and find them and check, what am I checking for, particularly in the
case of the purge valve. If I remove the fuel cap completely would this test
the system (ie cap off = no problem, then fuel evaporative system is causing
a fuel supply problem. many thanks

Did Fiat reset the error codes after they read the errors and gave you a print out?

adoks said:

If I remove the fuel cap completely would this test
the system (ie cap off = no problem, then fuel evaporative system is causing
a fuel supply problem. many thanks

Click to expand...

Yes try it, but the fault can be electrical. Could be a loose connector or similar. The purge valve is operated by engine vacuum. It is located behind the right-hand front wing. To gain access to the charcoal canister, remove the right-hand front wheel, support the car on axle stands. Remove the retaining screws and fasteners and remove the wheelarch liner to gain access to the canister. Make sure to label the canister hoses when removing. Check for splits in the vacuum pipe and other pipes. The purge valve is mounted on a bracket next to the charcoal canister. Listen for any odd noises. One common problem with this system is that the purge valve goes bad and engine vacuum draws fuel directly into the intake system. This enriches the fuel mixture and will foul the spark plugs. Most charcoal canisters have a filter that should be replaced periodically, however this is the first case i've heard of it on a Marea.

Read this....

LINK

looks like a lambda fault then not sure about the short circuit to battery positive fault on the lambda that may just be a mistaken error more evidence pointing towards lambda failure

OK, I replaced the lambda sensor today, car seems to be running normally. Other error codes probably caused by me disconnecting sensors when I was trying to figure out what was wrong. This fault should have been diagnosed by my local garage, they said that the lambda was switching. Thanks for everyones contribution, hope the information in this thread helps others. Looks like a faulty lambda can make the engine under fuel rather than the more typical over fueling failure mode. Still have an engine warning light, I am reluctant to pay any one to reset this will disconnecting the battery reset this warning lamp?

adoks said:

OK, I replaced the lambda sensor today, car seems to be running normally. Other error codes probably caused by me disconnecting sensors when I was trying to figure out what was wrong. This fault should have been diagnosed by my local garage, they said that the lambda was switching. Thanks for everyones contribution, hope the information in this thread helps others. Looks like a faulty lambda can make the engine under fuel rather than the more typical over fueling failure mode. Still have an engine warning light, I am reluctant to pay any one to reset this will disconnecting the battery reset this warning lamp?

Click to expand...

Glad to hear its sorted, however disconnecting the battery will not erase the error codes and distinguish the engine light. A local electrician can do it for £20. Fiat will prob want £50-£90.

JoskeJTD said:

Yes try it, but the fault can be electrical. Could be a loose connector or similar. The purge valve is operated by engine vacuum. It is located behind the right-hand front wing. To gain access to the charcoal canister, remove the right-hand front wheel, support the car on axle stands. Remove the retaining screws and fasteners and remove the wheelarch liner to gain access to the canister. Make sure to label the canister hoses when removing. Check for splits in the vacuum pipe and other pipes. The purge valve is mounted on a bracket next to the charcoal canister. Listen for any odd noises. One common problem with this system is that the purge valve goes bad and engine vacuum draws fuel directly into the intake system. This enriches the fuel mixture and will foul the spark plugs. Most charcoal canisters have a filter that should be replaced periodically, however this is the first case i've heard of it on a Marea.

Read this....

LINK

Click to expand...

a simple diagnosis of this is to simply blok it at the in;let manifold it should run without it as it only opens the valve under certain situations also your on the right lines with the filter ontop of the canister to alow fresh air into it can become blocked and draw from the tank but would only periodicaly suck fuel not lal the time unless under exceptional circumstances the valve was leaking and the filter was blocked

Anyone know which OBD fault code reader which will work with Fiats protocol and reset my engine check light?