Hi All,

I have been searching all over but I couldn't find a thread on the following subject (on this type of engine at least).

My impreza estate is a non-turbo 2.0 RS 2006 reg and it has been converted to dual LPG some 60k miles ago. I owned it for less than a year and replaced myself the oil/ and filter and air filters. It always had a slightly rough idle but I always thought it was the boxer engine.

3 weeks ago CEL went on and I booked the car in for a check. The mechanics said there was no code other than a misfire and although I told them that from online readings it could have been the MAF or lambda sensors they did not listen to me at all. The engine has been running on petrol since CEL went on btw. Mechanics did a compression test ("up to scratch" were his words), air leak test (fine), camshaft timing check (fine) and replaced the camshaft sensor. As they said the fault was mechanic and not electronic I decided to get the car back and check myself (£450 spent already).

On the way home the engine dropped rpms when lifting the gas pedal and it idled so low that it stalled 3 times on the way home. Engine sounds fine when accelerating so, as it was due, I replaced the oil/ with filter. After few checks I used the OBDC as CEL came back on and it showed:
P0102
Number 10 mass airflow low

P0113
Temperature sensor high
Circuit 1


So I bought a CRC MAF cleaner and gave it a good clean yesterday. Now the idle has changed slightly but it is still rough and unpredictable (goes very low when not accelerating).

I would need some help in locating both a good reliable Scooby mechanic in the Liverpool area (since the ones I know have no idea of boxer engines) and the MAF sensor (AFH70M-59A 5Y03 22680 AA360). I did check with dealers but have not got back to me and some other part reseller required me to send the "faulty" part before they send the good one (or required me to bulk buy!)...

I would really appreciate some help on this and I promise I'd be back to add the follow up in case it works.

PS: LPG is fine as compression test didn't find a recession valve, but it simply amplify any problem present on petrol (my understanding)...

thanks in advance

 

Did they do a leak down test? I'd be incline to go somewhere else and get someone who's familiar with Impreza engines to do a leak down test paying special attention to the exhaust valve seating. It does rather sound like you might have issues in that area, especially I the idle is shaky? And also knowing what LPG can do!

 

No mention of plugs ever being changed?

 

The mechanics said they did a air leak test which was ok, I would like to replace the MAF as it was flagged on last CEL.

Sorry, post was so long that I forgot to mention that spark plugs have been checked (and are less than 20k miles old) and they tested the HT leads (put on spare ones to see if it changed anything)....

I was under the impression that LPG can cause valve recession, warping exhaust valves, but this should have been picked up on compression test shouldn't it?

I'd like to buy a new maf sensor but I can't find a place that would sell it straight. I basically want a new one while keeping the old one (in case i'd be able to test them)...

thanks!

 

might be worthwhile checking the idle control valve and make sure the throttle body isnt too gummed up as both these can give errattic idle. Its always a good idea to clean them anyway as it all helps with the health of the engine generally

 

I thought that the "gummed" was supposed to be left there and not cleaned. Or better saying that the grease was meant to be there so if cleaned out needs to be replaced...
I have seen quite a number of forum posts and there are different opinion on the throttle body...

I found a good manual so will see what I can do on my own (far from being expert) and order a new maf sensor as it came up on CEL code.

If someone knows a good reliable mechanic/ garage in the Liverpool area I still would appreciate :-)

 

a quick update, last weekend I replaced the MAF sensor and the engine runs a little better. It is still perfectly fine at high rpm but now it doesn't just drop to almost zero and it's not all over the place. It seems levelling itself at ~700 rpm when warm. So this is good.

However it still stutters a little as the rpm goes down (as if it struggle). Checked again the air pressure and it seems fine, sprayed some wd40 in the throttle and this seems to ever so slightly change. It think it's safe to assume that TB needs some cleaning as low idle runs a lot richer than higher rpm...

Also will try and take it for a ride with some cleaner in the tank, does anyone know of independent garage with knowledge about scoobys in the Liverpool/ Wirral area please? I don't want to take to the dealers as I haven't won the lottery yet (still hope thou :-)

 

Depending on where in Liverpool you are W.M.S racing are about 1hr from you, near Chester/flintshire.

https://www.scoobynet.com/member.php?u=126902

 

thanks for that tip, I'll get the engine driveable then will get in touch with them.... checked the tb and it's charcoal black inside, so will clean that first and might take the part apart to do the job.

I was looking for part numbers in case I needed ordering a new tb gasket (more likely than not) and I found this http://opposedforces.com/parts/impreza/ (maybe can be of help to others)

 

another follow up:
last weekend I managed to partially disconnect the throttle body (couldn't get the coolant hoses out, so I left them attached) and I cleaned it inside/out with a tb cleaner. it was absolutely charcoal black and now you can see the metal. I replaced the tb gasket and also cleaned that surface; doing this allowed to fully clean the little canal that leads to boost sensor...

now the car is absolutely driveable as it doesn't stall anymore when off the accelerator. so I guess doing this and MAF sorted that issue. Which is good :-)

I now noticed that the engine is still shaking a lot (more than before) but I also spotted the drive belt (alternator/ power steering) as it needs replacing: it's really thin and it might cause drag that can in turns cause excessive shaking from what I understand. but this would be another thread I suppose....

Ps: my model didn't have a IACV and the tb valve is controlled electronically so the whole tb is one part....

Hope it can help others too :-)