ECU problems

[sean]

Hi all,

I have had problems with my "check engine" light coming on. I did the self diagnosis on the ECU and it tells me that the oxygen sensor is at fault (fault 13 in the manual). Problem is, I didn't think I had an oxygen sensor. Anyone know where to find it? I can't see one anywhere and to my knowledge the NZ cars never came out with it. Any help please

Simon

[GTi_Clubby]

yeah mines doing the same.. check engine light... havnt gotn that far to test ecu yet, but hmm, wait and see if anyone knows? :?:

[evilernie]

Isn't this the MAF?

[BassAddict]

I thought it was Lamda sensor (sometimes referred to as O2 sensor) - this would usually be in the exhaust system somewhere.
Rich

[fbm-spec]

If the O2 ( lambda) sensor is missing, that is certainly why the EM light is coming on. The lamda (o2_) sensor is usually located between the exhaust manifold and the cat or first silencer box. If you are using the standard manifold it should be there, or it will be rather noisey without it :roll:
The ECU is looking for a feedback signal from the lambda sensor, if it is not there the ECU uses a default fuel / ignition map which will give reduced power / economy.

Hope this helps

FBM-SPEC
chris

[sean]

Very interesting Chris,

Yes, I am using the standard manifold and pipe to where the first silencer fitted. There is definately no senor there. And yes your right, it would be rather nosiy without these parts.

What I find most interesting is your comment about reduced power and economy. The power does seem down a bit on what I think it should be and the economy is definately suffering. It has been like this since I got the car on the road so I don't have anything to compare it to. Seems to be using about 8 litres of petrol per 100km on long runs.

Maybe my donor car had a new ECU fitted as some stage, one that was designed to run a oxygen sensor. If so, is there anything I could do about this?

Simon

[BassAddict]

If you can find a wiring diagram it should give you the details for connecting up the O2 / lambda sensor - you can then fit it either in the existing thread in the manifold / downpipe, or drill a new hole and tap a suitable thread ( I think its usually 18mm diameter with 1.5 pitch).
If I'm thinking straight after a few ales ( :) ), the sensor basically determines the air/fuel ratio from the exhaust gasses and adjusts the fuel accordingly - think its called closed-loop mode - yup, just found this :
http://www.fuelairspark.com/Information/Support/C-ComHelp/v1-00/closedloop.htm
Hope this helps,
Rich

[GTiMini]

Simon

Is your engine from a MK1 or MK2? Most MK1's in this part of the world didn't have an Oxygen sensor fitted.

From my experience with these conversions the CEL (Check Engine Light) is usually as a result of part of the Suzuki wiring harness missing or not connected. Especially if it was all working before being taken from the donor vehicle.

Have a look at redlinegti.com there is a MK1 Workshop manual there.
http://www.redlinegti.com/manuals/redlinegti.com_MK1(SA413).Manual.zip
There is also a MK2 one there somewhere too.

[sean]

It is all New Zealand new MK1. There is no provision for an O2 sensor and I have since been told that one was never fitted to this model.

What I have also been told is that there should be a link in the ECU wiring loom somewhere to default the O2 sensor circut. The person who told me this is in the process of scanning the relevent part of the service manual so I should be able to sought the problem.

Unfortunately the system wasn't fully tested before being removed from the donor car as the air flow sensor was missing and consequently the CEL was staying on.

Thanks for the link to the service manual, I'll have a look.

It's just a matter of time, I'll get it soughted.

What sought of fuel economy can I expect?

[GTiMini]

With a stock GTi engine in a Mini you should expect 45-50mpg cruising. Around town a little less maybe 35-40Mpg. At least thats what I was getting. 8)

[sean]

I'm not getting that.

It's using about 8 litres per 100km which equates to about 35 miles to the UK gallon (4.5 litres).

There must be a problem somewhere. It has new spark plugs and filters and the timing is as per the manufactures specs.

[GTiMini]

Off the top of my head could be one of 2 things.

Firstly, I'd check the AFR's (Air Fuel Ratios) and see if its rich anywhere.

Secondly, if the engine has a few miles on it I'd decoke it. My daily driver is a WRX STi and it was getting 250k's to tank and running poorly. I had a dyno decoke done and it gained 26Kw in power and now I'm getting 450K's to a tank of fuel. :D

[sean]

Is the AFR adjustable throughout the range or is it just the idle mixture that's easily adjusted?

What is a dyno decoke? I thought the engine had to be stripped and the carbon deposits cleaned from the combustion chambers, tops of pistons and ports.

[GTiMini]

Checking the AFR's will lead you to check other things. If its rich everywhere there could be a problem with the intake, MAF or filter or injectors. Its a check to make sure everything is working right.

The local STi guys have a "Dyno Decoke" service to remove the carbon deposits without stripping the engine. Its really neat and here's how it works as explained to me.

They get the engine up to temp on the dyno and do a power reading. Mine was 186Kw. Then they tee into a fuel line so they can put injector cleaner into the mix and cover up the radiator and get everything really hot but not overly. Then they take a vacum hose off and inject engine cleaner into the intake at such a rate that it slows the engine down but not so much it causes hydraulic lock in the cylinders. The engine slows and almost stalls as the mixture is difficult to burn. They shutdown and let it soak for 3 hours. Then start it up again and let it run hot under load for 15 minutes or so while injecting more cleaner into it. Then run it at high load and high speed until all the exhaust smoke clears.

Finally they do another dyno power run and mine showed 212Kw after the whole process. WooHoo and it was noticable!! These engines are supposed to be 206Kw standard and all mine has is a straight through muffler fitted (to get that BOB BOB BOB boxer sound) so that was a good result. Cost was $300 so it wasn't cheap but the best money for HP gain I've ever spent.

[sean]

Well bugger me, things have come a long way since I worked as an apprentice mechanic in the early 80's. What an awesome process and cheap horse power too.

Unfortunately this service is not available in the remote location I live. The nearest dyno is 2 hours away and I doubt very much that they have even heard of such a process.

I might be able to get hold of a protable gas analyser and if so i'll check the mixtures on the road.

[GTiMini]

One of the best investments I've ever made was a Wide Band O2 sensor and meter. I have it mounted permanently to the dash so I always know what my AFR's are. And I need to because I'm always messing with the engine. :twisted:

[sean]

Did you fit this to your STi or mini? Maybe I should look at fitting one to mine.

What are you doing about fuel management on the mini now that it needs more go juce or will the standard ECU cope?

[GTiMini]

The Wide Band is fitted to the mini. I don't mess with the STi I need that as my daily driver.

On the mini I still run the standard ECU. But I have a lot of control over it. The original programme is still in there but I can adjust overall AFR's using an adjustable fuel pressure regulator and I have designed, built and installed my own sensor benders that give me control over WOT mixtures. Sort of along the lines of an APEXI SAFC but put together out of parts of an old transistor radio. While it works and the WB02 tells me that, I'm happy and the engine is happy.

[sean]

Update on my ECU and fuel consumption problems.

I downloaded and printed off the entire service manual for the MK1 GTI. A very useful document that I would recommend to anyone wanting to know anything and every thing about their GTI.

I went down to Dick Smiths and purchased a trusty $16 multi meter ( best money ever spent) and carried out all the checks on the injection and ignition systems as per the book. There was nothing wrong with anything.

I then checked the fuel pressure and found that it was running at the maximum allowable (when your foot is hard up it), even with the vacuum hose connected to regulator.

Just before rushing off to order a new fuel pressure regulator and tried blowing through the vacuum hose. It was blocked.

After jambing a piece of wire up it I discovered that some idiot had plugged the hose with a short piece of aluminium round bar. Obviously when some servicing was done by the previous owner of the donor car.

I put it back together and now the fuel pressure is within limits, the engine runs better at low to medium throttle and the fuel consumption has improved by about 6 miles to the gallon. It was also burning a bit of oil but has now stopped completely. I put this down to bore wash from the over rich mixture. It's amazing what a difference of 7.5 psi fuel pressure can make.

My next mission is to fit an O2 sensor which will stop the "check engine" light coming on and should further increase the fuel ecomony and emmisions.