UK RHD M2.7 348 Running like a B***h at low revs

Of course.... I should have guessed that... I guess I'll never be starring as a contestant on Wheel of Fortune any time soon.......

I'm thinking that particular word is blocked because of the possibility it could be used for bashing women --- which would not be acceptable. But, in the context of describing a car --- why not?

 

Ok, I've now completed all tests on Motronic M2.7 Diagnosis sheet 13 for both sides and nothing seems to be really jumping out. I provided pin 19 on both ECU plugs with direct grounds and that really made no difference, still runs badly, in fact pretty undriveable when revs are under about 2600. Provided the revs are above 2600, and all the way up to redline, she drives sweet as a nut.

Strangely, whilst the engine was cold, on a drive to get a tank of fuel yesterday (and to add some injector cleaner) there were no running problems at all. So the rough running seems to be something that is VERY present when hot and at <2600rpm and not as likely, if at all when cold and/or over 2600rpm.

I'm now at a loss to know what to check but until I unearth the root cause the vehicle is certainly unuseable because around town, i.e. at low revs it's undriveable, chugging and even backfiring occasionally when throttling up in a low rev position. Having carried out so many measurements, admittedly under static conditions, my suspicion is shifting away from sensors. The only codes in both ECU's are 4444 = no error code. It feels like fuelling/FAR but why only at lower rev range?

 

Perhaps one of your temp sensors has failed such that it only reports that the temperature is cold, whether it is cold or hot in reality.

 

Sounds like a candidate for the davehelms gold package!

 

And the crank sensors?????????????

 

Well.... if the operation temperature causes so much difference on behaviour, at least it's a good feedback to help diagnosis...

Personally I have had the experience with faulty ignition coils... and usually they fail when hot... if no extra coils are available to test, try to find some diferent shade on either bank's spark plugs.. and then switch them to confirm..

Other possibility is a sticky IACV valve. When cold it allows extra air to compensate the richer mixture, but if keeps open then, the the mixture gets too lean when the ECM's change the status to normal running temperature (or faulty temp sensor as mentioned before)

 

Update:

I removed both IACV's last evening and they both appear to be functioning correctly. No detectable stiction of the inner valve. Both sit at rest position with the port staying just very slightly open. The inner valves of each IACV have a nice bouncy feel to them as they react against the force of the liner magnets. I pulled one apart just to take a peak, look very clean and no issues in there. I effectively checked the resistances via the break-out box but will check 'direct' resistances of the coil windings this evening.

So I'm back to the drawing board.

 

Well... it could even be a defective ECM....

Can't you at least tell by the feeling if the missfiring is due to fuel or ignition cut-offs? Usually the ignition cut-offs are much more harsher...

Colour of ignition saprk plugs are a good indicator also....

 

It doesn't feel sharp enough to be Ignition, more like fuelling. When the fault is present (at normal operating temp and revs below 2600~2700rpm) and I try to put my foot down to get power back I can hear an occasional mild backfire. All 8 plugs look similar in colour to each other and as they should when referenced against available material. All plug leads and tips read the correct resistance (this not to say one or more isn't breaking down under load, but then wouldn't that/those plugs show it? Also, if a plug lead wouldn't it be worse when I try nailing it? As long as the revs are over 2600~2700 there is no problem at all with how it drives, right to the limiter.

Each banks coolant temp sensor was reading in the correct range when checking against the Fig. in the Workshop manual (Diagnostic sheet test 14 in my copy), with engine at normal operating temp.

I've changed the Ignition modules to new ones (made no diff), I also have a brand new spare pair of coils, so will try them next as they are available.

 

Have you considered going to a roling road diagnosis centre?

They will imediatly find out what is causing that, even under a very light load..

I believe that there are plenty in the UK.

I understand that you do not want to let your baby on stranger's hands for repairs, but this at least would point out the way to wich system is failing and wich components to change....

 

Hiya Dapper

If its a feeling of being too rich or over fueling it could be engine tempature sensor for the engine management telling lies and running too rich and confusing the lambda (oxygen) sensors, dont rule out fuel pressure too high for some reason, I dont know what exactly controls the fuel pressure on your car or sticking injector/s dribbling causing low speed flooding...?

Or is it possible the cam timing could have jumped on a cam during a start up after a long lay up you really need some live data from a diagnostic machine, and have a look at the maff readings etc. Read eobd with a fiat, lancia connector, should work but I believe you have to reverse the two outside wires on our uk cars?

Hope this helps

 

Jerry thanks.

I ruled out the cam timing being physically out, as the car has recently driven without any issue whilst the engine was still cold, and always drives well when the Revs are above 2600~2700, with a hot or cold engine.

To make matters worse, I now have an additional problem, as soon as I switch the ignition to ON (without starting engine) my cooling fans are on full time with a cold engine. So looks like I'll be diagnosing the radiator Temp sensor also next! Dohhh.

 

Could it be the thermostat?

If the cooling fluid does not flow, all temps are wrong on both sides of it... or at least diferente from the temp sensores and fan switchs....

 

Thanks Ricardo, so thermostat is another thing to bear in mind.

I read a thread on here this afternoon from a guy with a 360 who's description of his problem sounded near identical to mine. His problem turned out to be a coil gone bad. With this in mind, as soon as I got home from work I changed my coils for a new pair I already had. I then unplugged the battery for a few minutes, re-connected battery then started her up and let her idle for a good 10 minutes without touching throttle. I unfortunately haven't had time to actually drive her yet but she did seem to idle a little better. Will go for a drive tomorrow when I get home from work, fingers crossed!

Interestingly on the cooling fans issue, whilst the car was idling and got to temp, the fans were going on and off 'very' regularly, like they couldn't make their mind up! Either a faulty switch providing a intermittent ground or relay sticking. Will get to this at the weekend sometime.

 

I already mentioned ignition coils/modules ....

Regarding the erradic fans, it could indeed be some switch problems.... but could also be thermostat and/or air in the cooling system. Use the bleeders next to the RH hood hinge..

 

Indeed, they could be the gremlim you look for..

 

Thanks Ricardo,

At the time when coils were suggested my car drove bad even when cold on one or two occasions, so on that basis I must admit I kind of shelved the coils idea (although I had changed the ignition modules for new items and tested the Ignition wire resistances). The engine has since behaved itself perfectly when cold, only running rough once up to Temp (with revs below 2600~2700). Then having read about another posters 360 symptoms turning out to be a bad coil, made me think again.

With the new coils on, ECU's reset, fresh fuel with a charge of injector cleaner, it will be interesting to see how she drives later today.

 

Best of luck...

It's a great sensation when one finally gets that weight off the shoulders...

 

May be in my imagination but I would say the engine ran even rougher with the new coils on.

When I got home from the drive I checked the Fault codes for both sides. With the engine 'not' running I got:

1-4 bank code 4122 - cats too hot (strangely I didn't get any panel lamp warning whilst driving?)

5-8 bank code 1121 - RPM sensor.

I then started the engine and got:

1-4 bank code 4122 - cats too hot (residual code?)

5-8 ban code 4444 - no faults

From the above could it be that the 1-4 rpm sensor is faulty such that it isn't producing a fault code (even with a non running engine) but due to whatever fault it has, it causes that bank to run hot, hence the 4122 cats too hot code?

I would normally expect to get code 1121 from 'both' ECU's with a static engine.

 

Well took mine out today running rough just like yours seems to be
car drives great apart from very light throttle openings between 1500- 2800 rpms
and full throttle and if the engine is under any load ( going up hills etc) its fine.

ATM i am putting it down to crappy supermarket fuel so i will do a load more miles at the weekend..

As to your new coils i got some from ebay a while back fitted them to the car and found the same as you it ran worse! sort of felt a bit flat when under load so i sent them back.

Mine is going for its annual in a few weeks so i will let them service it road test it ans say what they see if the problem is still there, i do feel however that mine does run a bit rich i do have de-cat pipes on though!

 

You can check the gap between the rpm sensor and the pulley. I believe it should be 0,6mm (at least the Ferrari dealership chief mechanic said so).

You can also dry the conector and put some contact grease.

A detail I found on mine, when the sump protection was removed, were mice traces... so damaged wires can be a cause.....

 

1-4 bank code 4122 - cats too hot (strangely I didn't get any panel lamp warning whilst driving?)

5-8 bank code 1121 - RPM sensor.


1-4 bank code 4122 - cats too hot (residual code?)

5-8 ban code 4444 - no faults

From the above could it be that the 1-4 rpm sensor is faulty such that it isn't producing a fault code (even with a non running engine) but due to whatever fault it has, it causes that bank to run hot, hence the 4122 cats too hot code?

I would normally expect to get code 1121 from 'both' ECU's with a static engine.[/QUOTE]

By RPM sensor is that refuring to the camshaft sensor, if it is then your timing advance will be all over the place and running on limp home map I should have thought, cant really see how its telling lies but if it was showing the wrong advance it would make that bank run hot as well as setting the wrong ignition timing as the ecu looks at the cam and crank angle together to set firing order and inital timing setting?

If this is the case and with your fault codes I cant see why the engine management light isnt showing

With your intermittant fan operation could you have some kind of earth wiring problem somewhere as all the faults could be linked, Has there been any work done where a earth wire could have been left off or loose?

 

Jeremy,

The RPM/Speed sensor code being reported is I believe referring to one of the crankshaft sensors for the ECU being milked. The sensor also reports TDC position (2 missing teeth on the ring). These sensors are the ones that are the same as for various KIA models and can be had for just £30 a piece ($30 in the US).

I have the car rear jacked up at the moment so will have a 'good long' look at those sensors and their connectors tomorrow. I had to go out tonight but I couldn't resist a very quick look earlier and the connectors/pins looked absolutely fine.

 

Your 5/8 bank ECU should not have cleared the 1121 code from simply starting the engine. The codes only get removed when power is cut to the ECU (or when more than 50 codes are stored it starts dropping the oldest ones).

Assuming you did not disconnect your battery and reset your ECU's before starting the car again, it appears power was cut to your ECU from some other means and cleared the memory. This could be a faulty relay or damage to the ECU wiring loom (for example check that the rubber grommet hasn't worn through in the engine firewall where your ECU wiring runs).

If your ECU is frequently resetting itself from a power out condition while driving that would give you a rough idle from the bank cutting in and out. I haven't read all the reponses in this thread, so you may have already tried (1) swapping relays for the ECU's to see if the "code clearing" moves to the other ECU or (2) swapping ECU's to see if the problem still remains on the same bank.

 

The RPM sensor code follows different rules. You'll always get it when checking codes with the motor off, but you'll never get it with the motor running unless there is an actual RPM sensor error!



*if his codes were cleared via a faulty cable or relay or fuse or via the battery disconnect, then his other error codes would have been cleared instead of remaining