No worries, thanks for the advice and help!

The 02 sensor is a Bosch unit, buy it cheap buy it twice after all!

So I looked at the throttle position sensor reading at idle and it read 0 and climbed as expected when throttle was applied. I'll run some checks on it again.

I just took the car for a drive to see whether the sensor change made any impact to different throttle positions. It's now undriveable - almost feels like it's running on 3 cylinders and lots of misfiring and popping on overrun. This is a new symptom as before the car would do this but only occasionally.

Looked into Throttle position sensor and it is non adjustable and does not require initial setting.

In a way if it keeps getting worse it should help find the cause.

minimayhem said:

No worries, thanks for the advice and help!

The 02 sensor is a Bosch unit, buy it cheap buy it twice after all!

So I looked at the throttle position sensor reading at idle and it read 0 and climbed as expected when throttle was applied. I'll run some checks on it again.

I just took the car for a drive to see whether the sensor change made any impact to different throttle positions. It's now undriveable - almost feels like it's running on 3 cylinders and lots of misfiring and popping on overrun. This is a new symptom as before the car would do this but only occasionally.

Click to expand...

Misfiring and popping on overrun can be a sign of an air leak into the exhaust system.
Odd that this is worse after replacing a finger tight o2 sensor .

Maybe pull the spark plugs and look to see if any one looks different to the others?

I'm wondering if this is actually an ignition issue.

Back when we had carburettors, many times people would go for the carb as a first resort whenever there were running issues, yet carburettors wear very slowly and do not go out of adjustment. (My mother, when she was running a parts department at a small Vauxhall dealer used to sell several carburettors a month, to Viva owners who had tinkered the carb to death. The Viva had a very cheap ignition system that would wear and give all sorts of issues, but everyone attacked the carb first.)

Have there been any checks on the general condition of the engine - compression checks, coolant condition?
Has there been any overheat issues, any coolant loss.
How old are the spark plugs? Are they fitted properly? Are the plug leads, (if applicable) in good condition and fitting well? Are the coils working properly?

Air leaks can also cause issues. Intake leaks can be located by gently spraying something flammable onto joints, carb cleaner or WD40 are favourites, but carb cleaner not good on hot areas. Any that gets sucked in changes the idle speed. On the exhaust side, water can show any leaks out.

Yeah it's strange the problem is worse after changing the 02 sensor, I might swap back in the old one and see whether that makes any difference. In all honesty I didn't check today how the car behaved at different throttle positions, so the misfiring this severe could have been present the entire time. It's strange it's suddenly got so bad though.

Compression wise all are ok, apart from slightly low compression on cylinder 3. The plugs and coils are new, fitted last week. I haven't tested them but DTR mentioned they had.

Other than that the coolant is a year old, and the system doesn't leak. Thermostat is less than a year old, IACV and the throttle body has been cleaned. Intake is about a year old too. This is the first time the car has given me trouble, over the past 3 years it's been fine and as far as I know from the previous owner, they had no issues either.

Initially I thought the problem was a vacuum leak too, and took it into DTR with the request they hunt out other leaks and see if that will fix the issue. They mentioned they found 2 small leaks which were fixed by replacing the hoses and clips. The reason they came back with a suggested diagnosis of ECU issues is because they weren't able to accurately find the leak - and they found that the running issue occasionally went away. I saw that a bit today too, but not for long, 2 minutes tops. Oddly enough when I drove the car home, it ran absolutely fine!!! That was 5 days ago now, and today is the first time the engine has been ran since then.

I've got the coolant sensor being delivered on Wednesday, and can grab a propane blow torch to check for vacuum leaks around the inlet manifold on Monday.

What keeps coming to mind is the ECU not going into closed loop on idle, just can't figure out why that is. The service manual has loads of details about default behaviours on each sensor in the event of a failure, so the car should go into closed loop on idle even if one of them died.

The 02 sensor is detecting a lean mixture but in open loop the car defaults to set air/fuel tables to try to get an optimum AFR. Covering the intake shows that the communication between the 02 sensor and ECU is working and that it'd able to manage the AfR because it idles out fine and 02 voltage goes up/down as the car moves from rich to lean over and over. I guess if the car is remains in open loop that could cause the bad running when driving. Although this does feel like a bit of a rabbi hole...

Fuel injectors clogged or bad contact in electric plugs ?!

I see with mes there are three possible hitachi ecus fitted to barcetta.
Do you know which one you have?
If so please tell and I will look to see which parameters are available to view.

Reason behind question is it is important to select the correct version of car ecu in mes.
If only one out of the three mes options communicates with ecu then you know you have the correct option.
If more than one mes option communicates with ecu you have to identify ecu in car and only use mes option for the ecu you have.

When posting data about maf readings please post it g/s or kg/hr whichever mes reports,as the voltage reading from maf means nothing to me, I don't have the built in look up table like the ecu (-:

I have been puzzling as why partially covering air inlet makes a difference and have a theory . Will think about it some more.

Please pull plugs and post pics of the firing ends and a pic of the old o2 sensor end the is in exhaust flow.

Don't bother swapping old o2 back in take readings from new o2 sensor.

jackwhoo said:

Reason behind question is it is important to select the correct version of car ecu in mes.
If only one out of the three mes options communicates with ecu then you know you have the correct option.
If more than one mes option communicates with ecu you have to identify ecu in car and only use mes option for the ecu you have.

Click to expand...

Search devices will get MES to scan the vehicle

Then you know what it has communicated with


Personally .. I think putting the old lambda probe in could be worth 10 minutes

May highlight something

Good thinking using scan function.

Yes to comparing o2 sensor signals, possibly get readings from new one that is in there first ( could already have been done)

Jack

varesecrazy said:

Search devices will get MES to scan the vehicle

Then you know what it has communicated with


Personally .. I think putting the old lambda probe in could be worth 10 minutes

May highlight something

Click to expand...

PM sent to you Charlie

Way back Charlie posted about hand over air inlet reducing air being drawn in to engine. This got me thinking


why partially covering air inlet causes barcetta to go closed loop.

Or rather enables car to go closed loop.

My theory is engine could be running wildly lean , infact so lean the ecu has increased injector in time to it's maximum programmed enrichment limit but still does not see o2 sensor signal switching to a high voltage , so cannot go into closed loop.

Partially blocking air inlet just reduces incoming air enough that mixture is rich enough to send o2 sensor signal high which then enable ecu to start timing the injector pulse time and so enter closed loop.

Some steps to take .

Locate fuel pressure regulator, usually on fuel rail. On pressure regulator there should be a vacuum pipe and a fuel return to tank pipe.

Examine the vacuum pipe for splits / holes.
Connect a vacuum gauge tee between the manifold connection for the pressure regulator (gunson lo gauge is cheap but it works) and the pressure regulator. Start car and post vacuum reading at idle.

Check the brake servo vacuum hose and where it connects to inlet manifold.
With engine running is there a hissing noise inside car near brake servo?

What happened with the crankcase breather system / pcv system when gsr induction fitted?

I wouldn't be at all surprised if there is a holed/split disconnected hose.

Oil filler cap on and seal good?

Dipstick in fully?

You could temporarily fit a clear plastic fuel filter in the return fuel line from pressure reg to fuel tank. You should see fuel returning to the fuel tank, if not then the fuel pump is not supplying sufficient pressure and or volume.

Is there a Schrader valve on fuel rail?
If there is there is a very easy way to check fuel reg opening pressure.

The nuclear option is a smoke machine oooh yeaaa

I know some of this should have been covered by dtr correctly but never assume.

Reading through this thread and feeling your pain.....

I have the same engine revision I think...plastic inlet manifold, with Hitachi ECU bolted to it, and MAF incorporated into the throttle body.

I too would not be considering the ECU yet, as there are far more likely (and cheaper) things that could be wrong.

I've noticed one thing on my engine, it is running perfectly hot and cold, but if I pull off the main intake hose to the throttle body, it runs fine on fast idle when cold, but gets more and more uneven as the engine temperature rises and revs drop towards normal idle. You can hear the icv trying to maintain idle, but it can cut out. If I put the hose back on it's perfectly smooth again. So despite there being not sensors upstream of the tb, it is doing something....perhaps smoothing the airflow/pressure into the throttle body & MAF

Not sure this helps with your problem, but thought you should know on my engine the idle is irratic unless that hose is on.

Hope you find the issue soon!

Mike

Voko said:

Reading through this thread and feeling your pain.....

I have the same engine revision I think...plastic inlet manifold, with Hitachi ECU bolted to it, and MAF incorporated into the throttle body.

I too would not be considering the ECU yet, as there are far more likely (and cheaper) things that could be wrong.

I've noticed one thing on my engine, it is running perfectly hot and cold, but if I pull off the main intake hose to the throttle body, it runs fine on fast idle when cold, but gets more and more uneven as the engine temperature rises and revs drop towards normal idle. You can hear the icv trying to maintain idle, but it can cut out. If I put the hose back on it's perfectly smooth again. So despite there being not sensors upstream of the tb, it is doing something....perhaps smoothing the airflow/pressure into the throttle body & MAF

Not sure this helps with your problem, but thought you should know on my engine the idle is irratic unless that hose is on.

Hope you find the issue soon!

Mike

Click to expand...

Hi Mike,

Interesting observation.

Do you know how the crank case breather / positive crank ventilation is set up on these engines?

Where does the engine receive clean filtered air from to vent the crankcase fumes into the inlet manifold?

Cheers Jack

Voko said:

I've noticed one thing on my engine, it is running perfectly hot and cold, but if I pull off the main intake hose to the throttle body, it runs fine on fast idle when cold, but gets more and more uneven as the engine temperature rises and revs drop towards normal idle. You can hear the icv trying to maintain idle, but it can cut out. If I put the hose back on it's perfectly smooth again. So despite there being not sensors upstream of the tb, it is doing something....perhaps smoothing the airflow/pressure into the throttle body & MAF

Not sure this helps with your problem, but thought you should know on my engine the idle is irratic unless that hose is on.

Hope you find the issue soon!

Mike

Click to expand...

The intake system is more than just a box with a filter in it. The shape of the box, and the hoses, are important. Often there is a strange-shaped box within the intake system. This is to smooth the airflow as otherwise pulses may cause issues. By removing the intake system, you may have upset the smooth airflow.
Fiat spent a lot of time and money designing the intake system. Removing it to replace it with something a small company has created, having spent a tiny amount on R&D may not give better results. The manufacturer really does know best.

Hi Again,

Well, at the risk of stretching my knowledge of cranckcase breather systems....... this is what I see...... There are no pipes connected to the air intake pipes upstream of the throttle body. There are lots of pipes connected to the throttle body. Inside the throttle body (upstream of the butterfly) there are two holes at 180 degrees to each other one seems to go to a solenoid gubbins (presumably the icv), the other side goes to a pipe connected to the engine cam cover. If I start at the engine cam cover and follow the pipe, it splits into two both at a Y joint before going to the throttle body, one branch I've already mentioned, but one is lower down, presumably the other side of the butterfly. There is also another housing inside the tb, but I think that's just the MAF.

In the attached pictures the pipes that go between the throttle body and the cam cover are the shinier black ones. I think the other is just coolant.

You can just about see one of the ports inside the throttle body in the other pic.

Voko said:

Hi Again,

Well, at the risk of stretching my knowledge of cranckcase breather systems....... this is what I see...... There are no pipes connected to the air intake pipes upstream of the throttle body. There are lots of pipes connected to the throttle body. Inside the throttle body (upstream of the butterfly) there are two holes at 180 degrees to each other one seems to go to a solenoid gubbins (presumably the icv), the other side goes to a pipe connected to the engine cam cover. If I start at the engine cam cover and follow the pipe, it splits into two both at a Y joint before going to the throttle body, one branch I've already mentioned, but one is lower down, presumably the other side of the butterfly. There is also another housing inside the tb, but I think that's just the MAF.

In the attached pictures the pipes that go between the throttle body and the cam cover are the shinier black ones. I think the other is just coolant.

You can just about see one of the ports inside the throttle body in the other pic.

Click to expand...

Thank you so so much (-:

Yep you have got all of the crankcase breather items in photo.

I am pretty sure the pipe connected intake side of butterfly valve is connected to a tubular valve that screws into throttle body.

crankcase fumes exit rocker cover ,
At idle , high intake vacuum. valve allows a small amount of air through drawing crank case fumes but bypassing throttle plate.