156 stalling under slow speeds

Hey all

So for a good while now I've noticed what I thought was a typical lambda sensor failure.

What would happen is that as I approached a junction, slowing down to second gear speeds would normally result in the engine cutting out. Second gear would have to be "dropped" in, to effectively jump the car to keep it going. Power was also effected up to 3500rpm where before it would be very slow to gather revs.

This would only occur when at running speeds of 70 degrees and above. Never bellow, it would always run as smooth as a dream until it got to 70.

Fuel consumption wasn't effected as much as I'd thought it would be, but I replaced the sensor today anyways.

But the problem STILL occurs? I haven't reset the ECU yet, but would that really make a difference? (How do I reset the ECU?) The Lambda sensor was coated in residue and looked pretty foul.

The MAF look pretty new though. Is that the only other option to try guys or is there anything else?

Thank you in advance!!

P.S my cars a manual, not a selespeed, and uses a CF 2 engine 2.0l (99)

There's an engine temperature sensor somewhere in the top of the engine, its not the coolant temp sensor, and I think before 70 degrees by this sensor your car ignores the readings from the lambda sensor, and once the engine temp sensor reads over 70 it tells your engine to obey the lambda sensor.

Did you replace it with a universal lambda or a proper one for your car?

Try pulling the cables off your battery and leaving it for 20 minutes. That resets the ECU. Make sure you have all radio codes etc first though.

Thanks Pud

Yeah I bought a universal one from justlambdasensors online. It was a big saving over a Bosch one that would have cost me £90, as this one cost me £53 including P&P. I'm not to fussed about the quality difference for the meantime, as I just needed a quick fix that WORKED.

I'm just resetting the ECU now so I'll let you know how it goes. I'm doing the method I found online of disconnecting the batter for 45 mins, then starting it and running it at idle for 15, and then off for anther 10, and the off for a rag. I'll be dumbfounded though if this isn't the cause of its problems though, as the 70 degree part seemed like a pretty tale tell sign of a faulty lambda.

As I bought the car second hand very recently, with a part service history I don't have much to fall back on it terms of how an Alfa 156 should run and sound like. Is it possible a spark plug could be a failing? As I have no idea how old they are in a car that's done 95k.

Cheers for your quick reply though Pud, thank you

Those universal ones have a bad reputation, or at least my local Alfa specialist seem to think so.

One thing you could check, is to make sure theres no leaks in the exhaust system before the lambda, this would screw up its readings whether it worked or not.

Hmm? Yeah but as far as there failure rate from new is concerned with I doubt they'd be THAT high, otherwise nobody would stock them let alone run a entire website with them? I hope its ok

There doesn't appear to be any other leaks along the manifold or at the joints though which is good.

The ANNOYING thing was, is that my lambda sensor was basically welded into the exhaust and I had to angle grinder it off, to then fit a ring spanner over the top to get enough force to get it off. If I wanted to claim a dead lambda sensor, id have nothing to replace it with! Do'h!

But are you with me in that all the tale tell signs were there of a faulty Lambda sensor? As I would hate to think I wasted my time. I guess I'll try the MAF now on the off chance, but this is bugging me.

Thanks again Pud

I don't think its the MAF mate as it wouldn't make any difference what the temperature was.. But by all means try unplugging the MAF and see if it clears the error up.

It still think it is something to do with the lambda/exhaust, are you sure non of the wires has fallen onto the exhaust and got burnt, or anything like that.

Sure, the universal lambda's aren't terrible, I think its just some of the really cheap eBay £20 ones.

Hmm, good idea, would never have thought to have considered that, especially as the heat shielding cable cover didn't reach all the way. But i used good ol' duct tape to cover the wires up at the lambda end.

Thanks, I'll let you know asap. Going on a test drive now to see if the ECU reset helped.

Ok, weird....

So I check the cabling of the Lambda sensor and its all clean and ok.

The problem is STILL there weirdly enough, making me think either

A: The sensor is faulty
B: There is another problem that is interfering with lambda sensor

What's worse though, is that while I was coming back from my test drive, I noticed along the bypass doing, nearly 100mph, is that the all of sudden; the revs completely dropped (at least on the dial to 0) and my throttle was completely unresponsive. I coasted on, and just as I thought to change down to 4th, the engine became responsive again.

The lights, power steering and everything were still working, but this is a whole new problem that could have very dangerous consequences if I'm driving around country roads (all the time)

I'm going to try running it with the MAF disconnected now.

But as I said before, I have no idea how old the spark plugs are, does anyone think that could be a possible failing point in light of the symptoms I described.

I'm not exactly flush with catch, in fact more so the opposite. But I haven't got the money to go blowing on 8 new sparky's at around £80 unnecessarily.

What about a failing battery? I noticed some weirdness when reconnecting that after I left my stereo plugged in last week draining the battery. After charging over night, I connected it up and tried starting it, and it was DEAD. Wiggled around the positive terminal, and it started ok, but its not like the terminal connection was off, it should of made decent contact, and its not THAT sensitive anyways as it has a large amount of contact area when on? That battery seems fine too on a multimeter :s

I hope I have given somebody out there enough information, please let me know otherwise. Thanks

Ok so I tried disconnecting the MAF sensor, and there was very little difference in the performance of the car, suggesting a faulty MAF. I did disconnect the sensor while the car was running and sent back down the road I just ragged it down. I hope it wouldn't have made a bad difference in the engine being ON while I disconnected the MAF though. The injector light did come on though, so at least it knows. That still wouldn't explain my power loss on the bypass but,

My next question is

Would and engine diagnostic flag up a MAF failure? What other things would it flag up though? Poorly performing spark plugs?

If I reset the ECU with a faulty MAF, would the reset be, erm, poorly set?

I would dearly like to know before I start any more spending, as I love my car I really do, its just I'm skint and when times are bad, my Alfa is the only thing that never fails to put a smile on my face!

Hmmm, excellent news! Its fixed

I took the car to for an engine diagnostic today and it turned out the stalling was caused by a misfire on cylinder 4. The misfiring was caused by worn HT leads that were arcing it turns out. WHOOP WHOOP!

SO guys, put that under your belts of experience, as this can mimic a failing lambda sensor symptoms to a tee!

I just wish I'd done this before I cut my Lambda sensor in half and replaced it... do'h! Oh well

Glad its sorted

Couple of suggestions (first one maybe obvious);

- Problems that occur at lower engine speeds and then clear can sometimes be because the engine generates enough suck, power or whatever to overcome the fault eg. badly blocked air or fuel filters and with electrics enough current to drive the device is theres voltage getting lost somewhere. I don't know where the fuel filter is on mine. A pipe leaves the plastic fuel tank top under the back seat and reappears to go straight into the fuel rail - so wheres the filter ? Also how the hell do you check the airbox intake for blockages etc. it's burried in the front wing. A good battery should still be putting out about 12.7-12.8 V minimum about an hour after you last drove it and about 14.4 V when the engine is running. Fluctuating voltage when the engine is running can be a sign of problems. Obvious **** to some but you never know.

- Early on in the continuing fault finding with mine I discoved a broken HT lead. The top of the plug cap is a vertical brass post with a 4 mm metric thread hole drilled through parallel to the ground. The HT lead comes in from the square coil device and terminates in an end which is a short 4 mm stud which screws into the hole in the plug cap. With time this vibrates, corrodes and gets loose. And every time the plug cap is pulled off to get at the plug, the joint gets stressed unless you grab it below the joint eg. with a pair of mole grips. One of mine was so bad the previous owner had drilled a new hole and just shoved the stud in ! This is all hidden by the rubber cap at the joint so you can't see it (**** design all round). You can imagine my glee at 'finding the holy grail' for my jerking Alfa - pothole = HT lead wobbles = car jerks ! After doing a rough arsed solder repair it made no difference at all to the faults (which it might have been masking). And one week later fitting the new set from a breaker which have the joint and plug cap as a one piece in hard black plastic (obviously later improved mod) this made no difference either ... sob.

If you don't want to cut the plastic cap open to check the condition of the joint you could take the leads out (actually easier than it looks as they can only go back one way) and put a meter on each end and give them a good workover to see if the resistance varies from the figure written on the side of the plug cap. Dodgy connections sometimes jump the gap when the revs get high enough to force them.

New genuine MAF and lambda sensor going in to mine shortly. Also fuel consumption has risen dramatically since the spare MAF from the other car was put in. Thus giving a further indicator of possible MAF failure which is good mpg could mean dody MAF as the engine is not getting enough fuel.

Err, okay...

But its all fixed now so I'm all happy.

I got an engine diagnostic £44.99, replacement HT leads £70, a litre of top oil my car strangely burnt £7, and a new break bulb £4.20 all fitted at my local nationwide for £126... Considering they didn't charge me for their broken finger nails and time working on my car, I consider the work they did an absolute BARGAIN and I couldn't be happier with the results. And they ran a diagnostic on the engine afterwards to make sure the work they did cleared up the fault codes.

I just hope the arcing didn't damage the spark plugs or anything else!

Right, one problem over... another one to go

Sorry for the rant, I somehow missed the update that it was fixed.

A pity I never mentioned my dodgy HT lead earlier.

The first paragraph was just the 'poor idle/low speed running' section from the 'fault finding' chapter of a Haynes manual compressed into a few sentences. A lot of people think Haynes manuals are going to be packed with magic fixes specific to their car but in reality the fault finding section is the same chapter re-printed in every manual since the Mk1 Cortina came out (approximately) and just contains non specific pointers to possible faults.

Originally Posted by StevenJW

a litre of top oil my car strangely burnt £7

Its not strange at all, TwinSparks use oil as part of the cooling process, upto a litre every 1000km. You MUST check the oil EVERY week. If you run it not much lower than you must have done to require a 1 litre top up you will need a new engine, guaranteed.

These engines won't put up with low oil like a Honda or Toyota engine will, cylinder 3 is very near the exhaust manifold so not enough oil here and localised overheating will occur, and sooner or later the engine will start to knock.

its amazing how many people ignore their twinspark's oil consumption.

Originally Posted by jug

its amazing how many people ignore their twinspark's oil consumption.

I think they just don't realise some engines burn oil.. A lot of people don't even check these days, more and more people rely on garages to do oil changes instead of doing them at home.

You guys are so negative

I just CHANGED the oil a week and a half before. And I checked for oil leaks and level the day after I did the job, AND the next weekend after

sorrry, i wasnt accusing you of neglecting your oil. i'm only negative about it because i've seen so many people kill their TS by ignoring their oil consumption and assuming "it'll be alright till the next service"

Well knowing the oil consumption figure of a 1 litre every 1000km is to be expected is pretty useful when compared to something run off the mill like a Vectra like we're used to. But please don't be so assuming in future!

1L/1000Km is the worst you should expect, my 155 2.0 TS used to use to go for 6000Km and only burn a litre. Glad to see the coil pack fixed the prob (HT leads are attached to them which is why they cost so much) and to your earlier question... to reset the ECU when the MAF is faulty would just make it relearn the same management algorithm, so it would do exactly the same again.