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[jonathanh]

ok  so here's the story so far

toyota avensis 4 cly petrol:  running rough: sounds like it is running rich. 

so stored codes are P0172 and P0175 - Bank1 % 2 running rich.  plus misfire codes

so I reset the fault lights....

On restart and after warm up I get

Temp sensor 87dec after about 20 minutes of running

the MAf was giving live data

the fuel trim on bank 1 & 2 is showing 36% and lean

Fuel system status is showing " open loop control - warmup"

I also remember I was getting live data from the O2 sensors around 0.02 and 0.03v

and "ignition timing advance cyl 1 is 25 deg" with "advance shown"

Now I've got to the limit of my knowledge - can anyone on here help me!!!  where do I look next?

I think the ECu is trying to over fuel but don't know why.

any thoughts would be most appreciated

[Welung666]

Can you get live data on the MAF and Air Intake Temp. Sensor?

[jonathanh]

Yes

the air intake temp sensor started at 3 deg and then made it to about 14 - we were running the car in the garage so that seemed right asthe air warmed up

the MAF seemed to respond to engine speed.  Can't remeber exact values but low when engine slow and they did increase....

[Welung666]

Are the 02 sensors changing status once the car has warmed up? Air filter clean and dry? Breathers clean?

[jonathanh]

not sure what i'm looking for on the O2 sensors...

i was getting some changing values on Bank 1 and Bank 2.  what should I be seeing there?

everything is clean and dry - been in garage for 2 weeks.  no idea on breathers: its a toyota!

[Welung666]

02 sensors should change from open to closed (or vise-versa, can never remember which way round) at about the same time the thermostat opens (mid 80's deg C). The fueling trim should change with rev range as they adjust the timing and fueling accordingly. They should be fairly stable once warm and at rest (tickover).

[jonathanh]

I've definitely still got the O2 sensors on open "warm up"  and not closed despite engine temp on 87 deg...

the fuel trim is positive and reading lean at most engine temps and the engine is advanced at all speeds as well

thanks for the help i really appreciate it

[Welung666]

Check the 02 sensor wiring as a first. Also check the zorst for any leaks, this can give erronious 02 readings

[jonathanh]

ok  would this stop the system going into closed mode?  i.e. leaving the O2 sensors in warm up?

many thanks

[Welung666]

It could, dependant on where the leak is. A leak at the manifold end could draw in outside air adding 02 to the fumes making the system over fuel thinking it is still on warm up.

[jonathanh]

really odd.  i cannot find any air leaks or zorst leak. 

the o2 sensors give 0.035 on bank 1 and bank 2 in the exhaust manifold and 0.02 post cat

for some reson there are two sensors pre cat one post?

I'm still totally stumped

[jonathanh]

further update on this conundrum....

O2 sensor wiring seems absolutely fine and there does not seem to be any air leak anywhere or zorst leak.  got me beat... so any suggestions gratefully received

[jonathanh]

UPDATE

so after checking a few things it was definitely running lean.  I unplugged the MAF and it ran better so then plugged the MAF back in.  when it was running poorly the airlow was about 0.2 g/s but after discinnecting and plugging the MAF back in it ran at idle at about 2 g/s

so all is well again but I suspect a dodgy MAF so will be watching for problems to arise again

thanks for the help guys   

[Kevin Wood]

A typical MAF reading at idle when warm would be about 10-15 kg/h. Does sound like the MAF is a possibility.

Kevin

[jonathanh]

thank you.  Yes I do suspect the MAF.  Will keep running it for a while and if problems develop again I know where to look

thanks all for the help

j