I decided to clean the engine bay of my MY95 1.6GL on Sunday, using CD2 from Halfords that seems to have been used with good results by a fair few Scoobynetters. I had a 20 mile drive straight after the cleaning, heart in mouth when I started up but it was fine and drove with no problem at all.

On Monday night it started up fine again and drove 5 miles without trouble. A couple of hours later I started a 20 mile drive, during the last mile the car would idle at 2200rpm, at the end of my journey after several minutes of idling it slowly came down to the usual ~700rpm idle.
Another few hours later it started fine and ran as usual for a cold engine start. It ran fine for 5 miles but then started stuttering badly (misfiring?) when accelerating under load between 2000-3000rpm and with a very lumpy and hunting idle of around the usual 700rpm, above 3000rpm it seemed normal. I had to complete another 10 miles and it kept up the same stuttering all the way. I then switched off for around an hour. The cooler engine started as normal but immediately had a very lumpy idle and was stuttering badly while I was manouvering out of the drive I was parked in. After a couple of minutes of driving it was fine, no stuttering and only a slightly rough idle exhaust note with no hunting, I made it the 10 miles home like that. I've left it switched off since then, currently the bonnet is up and the sun is out!

Any ideas what I've done? Where water has got to, or what the solvent has done? What do I need to do to fix it?

Other factors that could have an influence:
I had the standard exhaust replaced with a custom stainless with a centre decat a few weeks ago, no odd running since.
I filled up with Sainsburys SUL instead of the usual Optimax, that's now down to the last quater of a tank after ~250miles of running fine.

Any advice would be much appreciated.

Cheers,

Ben

 

Hope isn't mass air flow but takes my vote!
JIM

 

Try disconnecting the MAF when it is playing up.. if it idles okay then likely to be MAF sensor, as Jim says.

JGM

 

Thanks for the replies.
I had the MAF well clingfilmed up while I was hosing down. I'll give disconnecting it a try though. If it needs replacing where is my best bet? Not cheap things as I remember .

The bonnet is open and the sun shining so if there's any moisture left in there hopefully that will help. Just unplugged the leads to the plugs and had a couple of drops of water come out with one of them. Will leave it a couple of hours and give it a run, possibly ending up at the garage depending on how it goes. Reckon my local independant (who employs ex Subaru main dealer mechanic) who usually services it would get it sorted? Or does it need to go to Subaru to use the select monitor?

At least my engine's clean to be worked on

Ben

 

Just been to fill her up. Started ok and idled relatively well for a minute or so, a slightly erratic idle getting worse and needing a throttle blip to keep it running now and again. Tried disconnecting the MAF as JGM suggested and the engine stopped almost instantly. Wouldn't start again with the MAF disconnected. With it plugged back in it started with the erratic idle again and I drove off with it stuttering quite badly under acceleration for half a mile or so. After that I was on a dual carriageway at a steady 55-60mph with it behaving fine. Still a bit lumpy as I went back into a 30 limit 3 miles later but much better than at the start of the journey, was idling fairly smoothly when pulling into Shell after a mile of the 30 limit.

Here's the interesting bit. The tank was very low, lower than I expected from the gauge and experience (I work out my MPG after every tank so have a good feel for what it should get). Got 46L of Optimax into the tank (which is only 50L on a GL). Worked out at 29MPG and I rarely get below 30, though I suppose in fairness I have been having a few spirited runs now I have the exhaust to enjoy.

It ran very nearly perfectly for the 6 miles back from the petrol station, no stuttering and a much smoother idle (perhaps as smooth as before the problems, it's hard to tell seen as I'm not quite used to the new exhaust note yet).
So now I don't know if it was crap at the bottom of my tank causing the problems, or the ECU being used to Optimax and not liking the SUL (though it has been fine on SUL before, have even run it on NUL and it was only a little less smooth). Or it could still be the MAF or the moisture. I have a MY98 (registered November 98, S reg) 2.0GL that I could borrow a MAF from to test that, would it be the same? Will have to wait a couple of days before I can have a look for myself.

Will try another run tomorrow to see if a full tank of Optimax really was all that's required.

Cheers,

Ben

 

Ben

I'd do an ECU reset.
This often shows up an problems or helps after bad fuel.

WW

 

HAD SAME PROB ON MY97 IMPREZA TURBO, TRY REMOVING IGNITION LEADS AND DRYING AS MINE HAD WATER IN AND CAUSED A MISSFIRE AND ENGINE LIGHT OT COME ON. ITS BEEN OK SINCE I DRIED THE LEADS OFF

 

Have just been for another 15 minute run from cold and it ran faultlessly throughout on the fresh Optimax. Will try to take it out for a longer run tomorrow and get it completely warmed through, see if its ok then. Thinking it must have been the fuel though. Wonder if I should now have it drained to get rid of the 4L of crap at the bottom of my tank. May try an ECU reset like you say WW, seems to be completely happy now though so perhaps its not necessary.
Cheers for all the advice folks.
Ben

 

what do u mean, the crap at the bottom of the tank??

your fuel line should take its feed from the bottom of the tank not the top???

otherwise you would run out of fuel after 5 mins

 

try removing plug leads and check for moisture . common problem!

 

Fair comment Micky, that was a bit dippy of me! Well the crap would be more concentrated when low on fuel then. Or is it just a case of once its through its through?

It has been fine on short (under 10 mile) journeys on the Optimax for 70 miles or so. But today I've done a 110 mile journey and after it was really warmed through I got the original problem of the idle being far faster than normal. Usually it only lasts a minute or two, but later in the journey it was all of the time when idling, including off the throttle for a gear change. After a few minutes of idling it will slowly come down to around 900rpm. On the whole it seems to be running fine though, no stuttering as before, no lumpy running. I was wondering if it wasn't pulling as hard as normal today though I was reluctant to give it any beans in case there is a problem. It was fully laden with 4 up and a load of clobber on board which obviously affects the 1.6 a fair bit in any case.

Also the exhaust seems to be popping much more than usual, when lifting off the throttle and when changing down. Would that be overfueling? And would that further indicate a failed MAF? Going to try the ECU reset now.

Any advice? Time to visit ScoobyClinic or a Subaru dealer?

Cheers,

Ben

 

I suspect the rough running was water in somewhere it shouldn't have been and not crap in the fuel tank.. leave it and see how it continues to run would be what I would do.

JGM

 

....sorry to poke my nose in where there are obviously other far more Knowledgeable noses, but i too had similar experience after cleaning engine.
I gave all the leads (ignition and otherwise) a good dousing in WD40........did the trick for me, defo sounds like moisture somewhere, i would start there......also ecu reset gets my vote.

 

Is it not odd for water somewhere to be upping the idle speed though? I understand it would cause lumpy running as I had before, but now it runs as smooth as usual, just with this intermittent higher idle speed.

eek, your nose is most welcome . Tried some WD40 this morning before another 110 mile drive and it seems to have improved. The idle is still sometimes faster than usual, but now at a peak of 1100rpm where I would expect 700rpm for the hot engine.

Are the suppressors built into the leads or on the plugs? My dad reckons if they're built in they're prone to give trouble.

You guys sure about doing an ECU reset? If it thinks there's a problem and it's idling fast to compensate, surely it's not a good plan to make it forget about the problem...?
Would it be best to use the 'proper' reset method with the connectors under the dash and holding half throttle business (I've got instructions printed out somewhere) so I'd get the error code flashes afterwards, or would disconnecting the battery for a bit do the trick. Never done it before and I'm having trouble finding the connectors, any advice?

Cheers for the ongoing help folks, much appreciated.

Ben

 

Suggest you get it looked at ASAP. If you have a MAF or Lambda problem you are treading on "thin ice".

Surely better safe than sorry ?

 

I took your advice Russell and took it to the local independant garage today. There they weren't certain what was going on but reckoned on the idle air control valve being the probable culprit, or the throttle position sensor being a possibility.

Since then I've managed to do the ECU diagnostic (but not reset) by connecting the two little black connectors and switching ignition to on. I'm getting error readouts from the CEL of 14, 15, 16, 17, 24 and 31 .
They are, Fuel Injectors 1, 2, 3, 4; Air Control Valve or Circuit; and Throttle Position Sensor or Circuit.

What do I do now?! Why on Earth did I clean the engine?! How can so many things be wrong and yet its runs faultlessly sometimes?

So who do I call or what do I buy?

Ben

 

If it was my car I would do a reset and then see what codes persisted.

However as it's your car, I would suggest a trip to a specialist.

Cue someone who knows what they are on about ................ !

PS If you do have a dicky MAF, it wont necessarily show on a diagnostic, and the ECU may have been compensating for the fault. However, after a reset, you could make things worse, as the ECU will no longer be compensating for it. In other words, don't blame me if you do a reset and your engine goes bang.

 

Many thanks for the advice Russell. Nice disclaimer . The auto electrician was confident it wouldnt be the MAF so I think I'm pretty safe.
I'm got a similar thread running on Impreza Sport and they all think I should WD40 the connectors to sensors and reset the ECU, so that's what I'll try in the morning.

Cheers,

Ben (Jamp on ISN)

 

Some WD40 and an ECU reset seem to have done the trick! Another diagnostic check after reconnecting the battery (and getting deafened by the alarm!) gave the all clear code from the CEL. Then after a gentle run of 6 miles or so with perfect running, I switched off and another diagnostic gave the all clear.

I'll still keep a close eye on in with regular diagnostic checks for a while.

Many thanks for your advice on it guys.

Cheers,

Ben