Technical 1.6 rough running - HELP

[thespark2001]

Hi there,

Sorry I have been mis-informing you cylinder 3 is not missing its not firing, using a auto range meter with a range bar on idle and at D81 connector on volts connected to positive the range bar bounces on cylinder 1-2-4 so conclusion is that there is no voltage pulse on cylinder 3 the cable has been checked from ECU to plug and tested OK, could be the ECU or another sensor going mad?
Any thoughts?
Thanks.

 

[thespark2001]

Sorry guys I didnt reply to your questions in the last post but the car has done 55.000 miles, restistance is 16.1 ohms pre cat.

Ta.

 

[Deckchair5]

Fault code number?

Have a look red circle at the ecu in the wiring diag I gave in post 14. If you know there is no problem with continuity (resistance/ open circuit) from the ecu to the injector then i'd look at the actual ecu connector contact with the ecu. An open pin/ poor or intermittent connection there would obviously cause your problem.

You somehow need to find out if the ecu is actually putting out the signal voltage to No.3 and if it is then where is it getting lost?

 

[thespark2001]

Hi, the continuity between the ECU plug and injector is good, when the ignition is on and engine is not running I get a 12v approx voltage to the injector but when running I lose all signal.

I got a jumper wire and flash connected (very quickly) between injector 4 and 3 at the D81 connector and presto she ran lovely and the STFT read 2.3 and the LTFT read -3.9 this lasted for about 5 mins then cylinder number 3 dropped again.

There is no fault codes at all.

Thanks for helping with this, I feel that the fault can not be far away now.

Mark.

 

[Deckchair5]

There should be a constant 12v supply to all the injectors on their respective pin 1 constantly fed from F17 to pin 3 (the larger pin) at the D81 connector coming through wire coloured MB (brown and white). (See above diag). The ECU supplies earth to the injectors in turn through ecu pins 34 35 49 and 50

Where are you reading your voltage?

If you're on the downstream side of the injector then you will see 12v with ignition on and engine stopped and a pull to earth with engine running with injector operating


Try jumpering across from MB input pin 3 on D81 directly to cylinder 3 injector pin 1

 

[Deckchair5]

I got a jumper wire and flash connected (very quickly) between injector 4 and 3 at the D81 connector and presto she ran lovely

Flashed what exactly, the 12v supply MB brown/white or the earth signal to the ecu?

I purchased a fault code scanner and the fault was saying number 3 cylinder missfire after reseting the MIL light the car still runs poor but no MIL light
What was the fault code? P0303?

swapped injector 3 and 4 to see if missfire moved
Do you mean you physically changed the injectors around or just the wiring?

Are you absolutely sure they changed the No3 injector? Won't be the first time a garage said they were going to do something but then didn't do it because, in those familiar words, "it seems to be running all right now" until you're almost home and then duh duh duh duh

 

[thespark2001]

Ok here goes,

All 4 injectors have a constant 12v feed to their respective pin 1 from the D81 connector pin 3.

Im using a autorange multimeter, one end connected to the positive on the battery and back probing the pins 1-2-5-6 on the D81 connector im getting a constant 12v feed with the engine off ignition on. Once the engine is running pins 1-2-6 are pulling to earth but not number 3 this is at D81 still, all wiring has been checked from ECU plug through to injector plugs (all good).

My meaning of flash connecting is: jumpering from pin 5 to 6 on D81 very briefly ( so touch and remove).

I initially had two fault codes P0303 and P0300 but once cleared they have not returned.

I changed the injector on cylinder number 3 for a new one, with no improvement I put original injector from cylinder number 3 into cylinder number 4 and 4 into 3 (new injector now on the bench).

I hope that answers the quiestions.
Mark.

 

[thespark2001]

Deckchair5

sorry error in the following:

Im using a autorange multimeter, one end connected to the positive on the battery and back probing the pins 1-2-5-6 on the D81 connector im getting a constant 12v feed with the engine off ignition on. Once the engine is running pins 1-2-6 are pulling to earth but not number 3, this is at D81 still, all wiring has been checked from ECU plug through to injector plugs (all good).

Sorry I meant pin 5

Thanks

 

[Deckchair5]

That's ok i got the idea
I'd guessed you connected to the negative side of the battery too and not the positive

I'd jumper across the D81 connector (shown in red) to eliminate it as a problem and then you're only left with ecu pin connection 49 (green) and giving that a wiggle test with the engine running

After that it looks like it'll be down to the ecu itself.

Check you have a good earth at the ecu, all sorts of things can happen with a bad earth there

 

[thespark2001]

Thank you, I will try that ASAP.

If it is the ECU is there anyone that you would recommend (ecu doctor - ecu clinic)?

Thanks.

 

[Deckchair5]

I can't say for certain it IS the ECU on the information you've given, I just can't think of anything else it might be. Check the ECU earth though

Draw Fiat techs e.g T1 NumanR and Dannyboy's attention to this thread and see if they have any suggestions

If it is the ECU is there anyone that you would recommend (ecu doctor - ecu clinic)?


I don't know what this guy's game is but you don't get that kind of 100% feedback through being a waste of space

http://cgi.ebay.co.uk/Brand-New-Fiat-Alfa-Ecu-Units_W0QQitemZ220305948753QQcmdZViewItem?hash=item220305948753&_trksid=p3286.c0.m14&_trkparms=72%3A1299%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

 

[Dave-G]

re: 1.6 fault codes

will post back with result thanks

It's a pity he didn't post back because I've got exactly the same problem.
My sons 2003 1.6 stilo is clearly running on less than 4 cylinders & my code reader has brought up P0303, P0300 and P0460.
I replaced the 4 spark plugs which made no difference & then after removing the codes & mil light I swapped cylinder 3 coil, with cylinder 2 coil.
I started the engine & after a few minutes the light came back on, flashing and with an alarm going off, as before.
I then checked the codes & it read P0302, but also still had P0303.
Obviously there is a problem with no-3 coil but why when I replaced it with no-2 did no-3 also show a problem?
I had definitely removed the codes before swapping coils, so it wasn't showing an old code.
Any help gratefully received.

 

[Deckchair5]

re: 1.6 fault codes

Well P0460 is more often caused a weak battery at start up and nothing more

P0300 is multiple misfire warning which you had to start with so it's not unheard of for two ignition coils to be cracking up at the same time as they seem to have a "life".

I had 3 coils go in one week once.

So change the definitely bad coil, give it 3 clear engine starts and see where you are. Reset the ecu by clearing the fault codes as your fuel trims will be way off by now

ALWAYS carry a spare coil or two in the boot

 

[Dave-G]

Re: 1.6 fault codes

Thanks deckchair, the car seems to have had two faults on no-3 cylinder.
Coil 3 was knackered, whatever spark plug I put it on that cylinder triggered the light & came up as faulty.
I got a new (Champion) coil, replaced no-3 & the car ran a lot better but not perfect.
I'm still getting the light coming on showing no-3 as faulty even though it has the new coil.
The car runs better but it is shunting / kangarooing along, it now feels like a misfire rather than the running on 3 cylinders that we had before.
Any ideas what else could be causing no-3 to missfire, apart from plugs & the coil?
Cheers.

 

[Deckchair5]

Re: 1.6 fault codes

Well, as you're finding the OBD is pretty smart and can point the finger exactly to the cylinder that didn't produce power and it's not just the ignition although that's the easiest to go for first.

What plugs and plug gaps have you put in there?

Easiest solution is to scope the ignition coil then you'd be able to eliminate the ignition electrics side. I appreciate you may not have a scope but a good garage electrician could save a lot of time

Next might be the injector but don't just replace it, again, scoping it is a quicker and cheaper solution than just guessing . There's another very similar thread here with "thespark" who has a misfiring cylinder 3. Take a look there

Of course there's other really ghastly things like head gasket and valves and piston rings but let's not go there

 

[Dave-G]

Re: 1.6 fault codes

I put in ordinary NGK plugs, gapped at 0.8mm.
The jerking effect from the misfire is almost none existent at low speeds & when the engine is cold. Once the engine warms up though it gets worse especially over 2,000-rpm. The tick over is slightly erratic, dropping below 800 then moving back up to a steady 800, over & over again. The engine revs ok when the car is stationary, but the misfire can be felt as I said over about 2,000 rpm.
Would I be better off taking it to an auto electrician or a Fiat dealer, which the city I live in no longer has.

 

[T14086]

Sometimes you get to the point where parts subsitution has to be included in the diagnosis procedure.

If you were my customer and after having read through what you have done I would have to check the ECU for the sake of eliminating it at least. I would do this by using a donor ECU.

 

[spudalud08]

dont know how to start a thread so adding to this one same sort of problem!!! stilo 1.6 52

my car cut out and would not start! the car has been tested its missing on 3 they changed the coil over but still misses with different coil on 3 been told there 90% sure its the ecu they said the coil can spike the ecu if its faulty do i take the chance and get a new ecu or pay for further testing ? money i cant aford the car over heated 3 weeks before the problem but they say its not the head gasket! can any on say 100% ecu fault

 

[Argonought]

dont know how to start a thread so adding to this one same sort of problem!!! stilo 1.6 52

You did good.............and welcome

 

[Deckchair5]

Dave g

Personally my 1.6 is much happier with 0.9mm plug gap and threw tantrums with 0.8mm but I wouldn't think that's your main problem.

This isn't an engine that's just had a cambelt change by any chance? Slightly lumpy and rythmically dropping tickover and misfire at higher rpms sounds familiar that's all

Tickover ought to be as smooth a silk and around 750rpm with aircon off