Badly Over-fuelling Mi16

[Stu 18]

Right, my Mi is overfuelling terribly, its contaminated the oil its that bad! I did a search, and so far ive done the following:

 

1: Checked all of the wiring and belled it back to the ECU with everything where it should be.

2: ECU has all feeds and earths in the right place.

3: TPS gives correct reading with throttle closed, part open and WOT.

4: CAS gives the correct voltage while cranking, havent checked it whilst running.

5: Temp sender resistance is in the right range, but i figure this doesnt matter at this point as the car is cold.

6: AFM: Ive checked the resistances with the flap closed and are within spec, at WOT they are within the range, there is a slight fluctation along the track (i.e. it drops a few ohms as it moves up then carries on at a steady pace), but nothing i would have thought would lead to the massive overfuelling problem.

 

Is there anything there that ive missed? anything obvious ive overlooked? The only thing im unsure of is the idle mixture screw on the AFM, or the gear inside, i understand that rotating this alters the air/fuel ratio? Is there anyway of resetting both of these to a 'factory' setting to get it in the ballpark?

 

The guy i bought the car off said he'd tried to get it to idle properly and had messed with the AFM, im wondering now if something drastic has been done to it.

 

Answers on a postcard peeps, im getting desperate. Like chucking it all away and getting a set of 45's desperate...

[Stu 18]

Forgot to mention, it overfuels that badly that when you shut it off it wont restart, yet if you unplug all the injectors it'll fire up and run cleanly for a few seconds then stop. If the injectors are then reconnected it starts, and the cycle repeats..

[paul205mi16 4]

Hi.

I have just got rid of the exact same symtoms that you describe..

Mine is a alloy block 1991 Mi16 running Mi16 3row management non CAT.

 

Have u checked the spark plugs m8? I bought a new set and one was'nt firing as strongly as the other three.

(strange!This made it sometimes run on three cylinders,very rough!!)

Regarding the Ht leads....

I had to cut the end bit off the rubber on the new HT Leads I bought, They was not cliping on the spark plugs properly and would pop off leaving a slight gap between the terminal on the HT lead & the plug.

When I took the car for the MOT I found the emissions to be more than double the normal Co, I left the MOT station & I got another tuner to hook it up to their gas analiser and turn the AFM screw anticlockwise (I think!) to get the emisions down. So far the car seems much much better and is due the restest tomorrow.. It no longor smells of fuel and seems to rev and start fine.

I also bought a new ECU temp sensor from Peugeot, for peace of mind, think it was about £20.00 ish..I belive it is used for cold starts and tells the ECU to double the fuel mixture when cold.

Hope you sort it m8.

Paul

Edited November 9, 2007 by paul205mi16

[j_turnell 134 3 Cars]

Is the allen key wound right in on the afm?

[paul205mi16 4]

Don't think the Mi's have a allen key TBH.

[Stu 18]

I dont think there is an alley key, there is a slotted brass screw in the top which i assume is for the idle co setting, its this im wondering about, has anyone tested the resistance on the pot on a good running engine so i can compare?

 

Hi.

I have just got rid of the exact same symtoms that you describe..

Mine is a alloy block 1991 Mi16 running Mi16 3row management non CAT.

 

Have u checked the spark plugs m8? I bought a new set and one was'nt firing as strongly as the other three.

(strange!This made it sometimes run on three cylinders,very rough!!)

Regarding the Ht leads....

I had to cut the end bit off the rubber on the new HT Leads I bought, They was not cliping on the spark plugs properly and would pop off leaving a slight gap between the terminal on the HT lead & the plug.

When I took the car for the MOT I found the emissions to be more than double the normal Co, I left the MOT station & I got another tuner to hook it up to their gas analiser and turn the AFM screw anticlockwise (I think!) to get the emisions down. So far the car seems much much better and is due the restest tomorrow.. It no longor smells of fuel and seems to rev and start fine.

I also bought a new ECU temp sensor from Peugeot, for peace of mind, think it was about £20.00 ish..I belive it is used for cold starts and tells the ECU to double the fuel mixture when cold.

Hope you sort it m8.

Paul

 

 

 

Cheers for that bud, but he plugs are new, leads are all good and the dizzy cap and rotor arm isnt that old.

 

Im wondering if it might be worth getting hold of another AFM and swapping it just to test, anybody got one in the West Midlands for sale?

Edited November 9, 2007 by stu da rude

[pug309twin40s 1]

have you fitted a new ECU temp sensor?

 

mine was knackered on my 8v engine even though resistance was fine.

[Stu 18]

I havent, would this make a vast difference even with the engine in its cold state?

[Anthony 1,000]

Slightly far-field suggestion, but whip the dizzy-cap off and have a look at the condition of it.

 

Massive overfuelling (to the point that there was visable black smoke coming out the exhaust) and the engine flooding when trying to start it was always a tale-tale symptom that the cap had failed on mine (it was an all-too frequent occurance). I've no idea why - all I can assume is the coil was sending some nasty signals back to the ECU because it could discharge through the cap properly. Other symptoms were the ICV doing completely random things with the idle - it would usually stick at 2k rpm or so

 

Mine's the only car that I ever heard of that happening on, and problems with the ECU temp sensor or AFM are definately more likely. Swap them out with known good ones, and see if it cures the problem.

[Stu 18]

Its funny you should say that as the idle has always been erratic, the cap 'looked' fine, but then i dont suppose thats a scientific test.. Ill get hold of a new temp sender and cap methinks then see what it does.

 

My money is in the AFM, im thinking its been buggered about with in the past by someone who has no fookin' idea what they're doing. Much like the rest of the 'conversion'...

[sorr 0]

Double check all you have no leaks in the intake pipes or manifold. I had the same issue and it was due to a badly seated AFM to throttle body pipe as spoted by the eagle eyed Higgy. Well not eagle eyed actually eagle fingered as everything looked spot on from above but not below.

[C_W 3 1 Cars]

Forgot to mention, it overfuels that badly that when you shut it off it wont restart, yet if you unplug all the injectors it'll fire up and run cleanly for a few seconds then stop. If the injectors are then reconnected it starts, and the cycle repeats..

 

Yea that's normal for it to do that and a good way of getting a flooded engine restarted.

 

It sounds too rich to be caused by the mixture screw but try unscrewing it for a while with the engine running to see if helps. It's on the side of the AFM recessed in a hole slightly.

 

What colour are the injectors?

[Stu 18]

yellow i think, what colour should they be? its a 2 row ECU, ML4.1.

 

Whilst it was running i probably turned the 'mixture' screw 4-5 turns, and whilst the engine note sounded marginally better, it still stinks of fuel and wont restart unless the injectors are unplugged. Does this pot have a 'range'? i.e. will so many turns only do so much?

 

Im wondering now if the CTS sender could be a problem, what are the triggers for 'limp home mode'? would a dead CTS sensor do this? is it possible to re-set the ecu (and hence fault codes) and then try to extract them after running it again?

Edited November 9, 2007 by stu da rude

[Hilgie 16 2 Cars]

I think it will be the temp sensor. Or broken wires to it...happens quite often.

[C_W 3 1 Cars]

yellow i think, what colour should they be? its a 2 row ECU, ML4.1.

 

Whilst it was running i probably turned the 'mixture' screw 4-5 turns, and whilst the engine note sounded marginally better, it still stinks of fuel and wont restart unless the injectors are unplugged. Does this pot have a 'range'? i.e. will so many turns only do so much?

 

Just keep unscrewing and see if something changes, it seems to spin freely and never seems to screw full out or in but it uusually does do something, but can't see it being infinite!

[Stu 18]

While the loom was off the car i belled it through to the ECU ok, but i daresay now its back on the car a break could have materialised..

 

Ill get a new sender and check the continuity before i go any further, ive just got a gut feeling the AFM is bejiggered...

[jackherer 543]

The pins can get pushed back inside the plugs on the loom quite easily.

[Stu 18]

Reet, quick update as ive semi-sorted the problem and one thing that annoys me a little with posts on forums is that people dont reply once the problem is sorted!

 

My CTS displayed some very interesting characteristics, i realised that id only ever checked the resistance of the sensor whilst stone cold, after being left overnight, in this state the resistance it gave was in the right range.

 

However, my morbid curiosity got the better of me so i devised an experiment, i got a pan of water on the cooker with a thermometer in, then plopped the sensor in with the multimeter attrached.

 

At 5-6 degrees, it was fine, but as soon as a little bit of heat got into the sensor the resistance values shot through the roof, anything over 25 degrees gave a reading of 18k ohms! No wonder it overfuelled! The ecu must have thought the engine temp was -100! lol!

 

Tried a new sensor and all was well.. Ive got a misfire under load now, so the ignition module is next on my 'to test' list.

 

Thanks for all the help and replies people! *awaits the 'i told you so'*.... :)

[Hilgie 16 2 Cars]

I told you so

[kenan 0]

Which temp sensor was at fault?

 

Is it related to the temp gauge on teh dash?

 

Thanks

[C_W 3 1 Cars]

No, it'll be the two pin coolant temp sensor that's used by the ECU to determine engine temperature (separate to the dashboard temp gauge/sensor).

[kenan 0]

No, it'll be the two pin coolant temp sensor that's used by the ECU to determine engine temperature (separate to the dashboard temp gauge/sensor).

 

Would overfueling cause the engine to run hot?

 

Also where is the sensor located? had a look yesterday and thought it could be near the thermostat?

[Hilgie 16 2 Cars]

Yes, near the thermostat (side of the waterhousing). It is a blue 2 pin connector.

[kyepan 291]

any more joy on this?

[kenan 0]

where can you get this part, is it Peugeot dealer only?