General High fuel consumption and lambda sensor

[Currymunster]

Trying to fix my daughter's 1.2 8v 2004 Punto.
Hesitate at 3300revs and won't go higher. Fuel consumption down to about 22mpg.
Pulled code using multiecu scan for the post cat sensor. Changed it and it seemed okay. Long journey of 200 miles to university and engine light on and bad running again.
I drove all the way over and hooked up the computer. Same code. So I bought a new ngk sensor. Last one was a known good one which was only hours old.
This time I removed the pre cat sensor and fitted the new one there as the original was a generic cut and shut one. Codes gone. Test drive and still okay. Live data appeared okay.
Came home.
Now it's hesitating again and using too much fuel. No engine light this time.....
So I thought I'd but a catalytic converter tester to and check that.
Am I checking the right thing.....
Anyone got any ideas.....
It also kangaroo jumps when you lift of the throttle.
I thought that might separate issue like an engine mount or induction leak?
Thanks
James

 

[judderbar]

long shot but is your exhaust blocked?

 

[Currymunster]

long shot but is your exhaust blocked?

If it was completely blocked surely it wouldn't start??
I've ordered a backpressure cat tester so that will help.
I'm also just about to make a smoke tester to check for an induction leak. I'm guessing this might actually be the fault causing the O2 sensor code for being too rich. Due to the fuel situation in going to Gloucester at the moment to look at it. But it did need doing soon as she using twice as much fuel!

 

[judderbar]

I was meaning to say maybe the exhaust is partially blocked and the engine power is being used to drive the exhaust thru a restriction.

If it was totally blocked the car would probably start then quickly stop

I suppose though if the exhaust was partially blocked you would notice the car warms up very quickly and the radiator fan is going all of the time when you stop the car.

 

[Stelios punto sporting 00]

Hey there. Mine is doing the almost the same thing. I measured O2 sensor and it is fluctuating like crazy. I suspect that it is a bad earth point connection. If you manage to find out let us know.

 

[lukasrn82]

Buy new MAP sensor it will fix the problem. MAP sensor regulate fuel consumption!

 

[jackwhoo]

Buy new MAP sensor it will fix the problem. MAP sensor regulate fuel consumption!

The ecu uses the map sensor and engine rpm sensor to calculate the quantity of air entering the engine.

 

[lukasrn82]

The ecu uses the map sensor and engine rpm sensor to calculate the quantity of air entering the engine.

On my punto 1.2 8v LPG normal fuel consumption was 9l/100 km and spark plugs were milky white.
Map sensor died or was bad, increase fuel consumption to 15l/100km LPG and car didn't have power even using so much fuel.
And spark plugs were black!
I've changed new map sensor and fuel consumption back to normal.
Even with bad valve clearance car wont consume much fuel if map sensor is good.

 

[Mike1alike]

Also, maybe the spark plugs need replacement.

 

[Currymunster]

Just been up to Gloucester today to look at my daughter's car. Smoke tested the inlet manifold and exhaust...no leaks. Also pressure tested the cat and that is fine. Noticed the breather pipe had no clip where it joins the under side of the breather. This is connected to the inlet manifold so could cause as an induction leak. I've put pipe clips on now and cleared the fault codes. See how it goes. If the fault still persists I'll get the MAP changed.
Thanks

 

[Currymunster]

Also, maybe the spark plugs need replacement.

Had a full service two months ago.

 

[Mike1alike]

James, check the timing to be correctly aligned. It's possible that the belt had jumped 1 or 2 teeth.

 

[Mike1alike]

And what's the reading on the MAP (intake manifold pressure/intake air temperature)?

 

[Currymunster]

James, check the timing to be correctly aligned. It's possible that the belt had jumped 1 or 2 teeth.

Already checked the timing and is perfect..?

 

[Currymunster]

And what's the reading on the MAP (intake manifold pressure/intake air temperature)?

I didn't check the forum until I got home. I had not thought of the map sensor so I have not checked the live data.
I'm old school so these sensors are a new thing in my book but I am learning.
Unfortunately the car and my daughter are a 4 hour drive away so I'm not going back any time soon.
It does sound as though the manifold absolute pressure sensor could be the culprit though.
Like I said. I'm sure she'll let me when the engine light comes on again.
Thanks guys
Watch this space
I will update

 

[Mike1alike]

Had a full service two months ago.

Check the leads to be correctley connected, not crossed between, to the spark plugs.

 

[Currymunster]

Check the leads to be correctley connected, not crossed between, to the spark plugs.

Leads order is correct. I checked them when I put two new coil packs on. Besides. Would that cause an O2 code?

 

[Currymunster]

Engine light came back on. I'll have to get a MAP sensor and try that....

 

[Mike1alike]

Check what error is stored on the ECU.

 

[Currymunster]

Check what error is stored on the ECU.

I can't as the car is 4 hours away as my daughter is at University. The last few times it has been 02 sensors or catalyst. Running rich.
As I've said before, I've changed the 02 sensors and did a compression test of the cat. All good.
Smoke tested exhaust and inlet manifold with no leaks.
HT leads are in order and it had a full service with all filters, new oil and new NGK spark plugs. Plus both coil packs are new.
As suggested before an I looking at MAP now?