Alfa Romeo Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
My Busso GT runs just fine when the engine is cold, but when the engine starts to warm up, the idle gets a little rough. Although it seems like it starts to run better again when the cooling fans kick on. When the engine is warm and you let it idle for a bit, I get the MCSF and flashing check engine light. Both disapear after a bit though. Sometimes they pop up after just a few seconds of idling and sometimes it might take a couple minutes. If I keep the revs up a little (around 1k), nothing shows up. Also it seems just fine anytime it's not idling and there's no unusual noises from the engine bay.

The fault codes read with MES;
P0300 - Ignition failure (generic)
P0301 - Cylinder 1 ignition failures
P0302 - Cylinder 2 ignition failures
P0303 - Cylinder 3 ignition failures

All four codes appear in MES right when the check engine light comes on.

It had a bad intake leak on the rubber bend, but I have replaced it since. That fixed the hesitating when the engine was cold and hanging revs when I let go of the gas pedal. I don't think there was any impact on the idle behaviour though.

I tried to do an ECU reset with MES a couple times but I don't think it worked. Haven't tried the method with disconnecting the battery. I think the ECU should have learned proper values already if this had anything to do with the intake leak.

I took the car to an Alfa specialist this week to have the cam timing checked. The timing was spot on and everything seemed fine. One spark plug wasn't tightened at all when he was taking everything apart. For a moment it seemed like the running issue was gone after he put everything back together and we thought it was a bad connection on the ECU or something. But after the hour long drive back home, the MCSF and check engine light came back when I let the engine idle for a while. I haven't read the fault codes after the service yet.

Spark plugs have been changed about 15.000km ago and the car has full service history. ~186000km on the clock and I bought the car in December. I can't contact the previous owner anymore as he was a car dealer owner and I only had his work number and he retired a few weeks later. He had owned the car for the last 3-ish years and seemingly took a good care of it.

What could be causing the issues at this point?
 

·
Registered
Joined
·
4,885 Posts
It all sounds very confusing. As the problems are most obvious when it is warm I am tempted to suggest the Crank position sensor.

As it is showing ignition faults on the whole rear bank, check the earth point for the rear bank coil packs. It might be worth doing a full compression test too.
 

·
Registered
Joined
·
590 Posts
Is it on the original fuel pump?

Believe it or not I had EXACTLY the same issues with a clients 166 3.0 V6.

It was fine during idling, take it for a test drive, no issues, however, take it for a hours drive and bingo, exact same issues as yours. It was doing this when brought in for a belt change, so during belt change the timing was set perfectly. We also changed plugs, swapped all the front bank coils to rear, insulated any possible cracks in the coil & injector wires. We would then take it for a test drive for 30 min, perfect.

Client then took it for a drive across town and after an hour, misfires on all cylinders on rear bank. The fuel pump was leaking out the crown so it had to be changed, after it was replaced, the issue was resolved.

Not I am not saying this is definitely your issue, but once you have eliminated all else, it should be something to consider.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #4
Pretty sure the fuel pump is original, at least there's nothing in the service book. I guess at least checking the crown should be easy enough just from the service hole.

The check engine light didn't come on today, but the idle still seems pretty rough compared to others on YouTube videos. Again it seems like the idle smooths when the cooling fans kick on.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #5
Today I removed the ECU and sprayed the CRC precision cleaner on the connectors. Also tried the ECU reset because the battery was disconnected anyway. This time it didn't give the MCSF and check engine light a single time when I let it idle for around 15-20 minutes. Neither when I had to sit at traffic lights a few times while driving.

Still the idle sounds pretty rough compared to cold idle, even though there isn't much difference in the engine speed. Upper video is cold idle and lower video is warm idle when the engine temp was about 80 degrees celcius.



Could this possibly be a lambda sensor fault, even though it doesn't give any OBD codes for them?
 

·
Registered
Joined
·
4,336 Posts
Other than the idle and the check light .... does it run well and make good power? Can you get a plot of the manifold lambdas in MES when the MCSF comes on?

How experienced is your specialist with 3.2s? The cam belts have to be timed perfectly to make these engines work, even a barely perceptible wobble in the blocks will cause this.

The cold idle is better because it is richer and the throttle body is cracked open a bit. As soon as you’re above 1k rpm, it’s fine. When the cooling fans come on, the engine is working harder, so idles better.

Did they compression test it when they checked the timing?
 

·
Registered
Joined
·
10 Posts
Discussion Starter #7
Other than the idle and the check light .... does it run well and make good power? Can you get a plot of the manifold lambdas in MES when the MCSF comes on?

How experienced is your specialist with 3.2s? The cam belts have to be timed perfectly to make these engines work, even a barely perceptible wobble in the blocks will cause this.

The cold idle is better because it is richer and the throttle body is cracked open a bit. As soon as you’re above 1k rpm, it’s fine. When the cooling fans come on, the engine is working harder, so idles better.

Did they compression test it when they checked the timing?
It seems to run just fine and definitely makes good power. But then again, I have never before driven a Busso or any v6 for that matter. I'll get a plot of the manifold lambdas some day if the MCSF starts coming on again.

The specialist has been working with Alfas for over 30 years. He has worked on a few 3.2's in the past but they're not too common in here. He has loads of experience with other Bussos and I had another GT owner send me the 3.2 locking blocks because the specialist didn't have any v6 blocks after a garage fire. He is fairly reputable as people around the country take their cars to him for service and restoration. Unfortunately he is more familiar with older Alfas and in the 147/156/166/GT-era there's not much he can do with cases like this.

I don't think he did a compression test because he didn't mention me anything about that. I should be able to do that myself too. What compression reading should I be looking for?
 

·
Registered
Joined
·
4,336 Posts
On a compression test, what you’re looking for is consistency (all gauges will be wrong to an extent). Greater than 180 PSI = OK, but what you’re looking for is 4 cylinders at say 180 and 2 at 130. Rear bank often has head gasket issues as it is more baked than the front. Typically they start to go at 100k miles - you‘ve done a lot more than that.

The only trick with the cam locks is they have to be perfect - I did a 166 3.2 and it idled the same as yours. The rear two cams were fractionally out - when you attempted to wiggle them you could feel movement, but not see it. I reset them, not thinking it would make a difference, and it was all fixed. Look on my GTA thread in the image lounge for what the MES plots looked like.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #9
On a compression test, what you’re looking for is consistency (all gauges will be wrong to an extent). Greater than 180 PSI = OK, but what you’re looking for is 4 cylinders at say 180 and 2 at 130. Rear bank often has head gasket issues as it is more baked than the front. Typically they start to go at 100k miles - you‘ve done a lot more than that.

The only trick with the cam locks is they have to be perfect - I did a 166 3.2 and it idled the same as yours. The rear two cams were fractionally out - when you attempted to wiggle them you could feel movement, but not see it. I reset them, not thinking it would make a difference, and it was all fixed. Look on my GTA thread in the image lounge for what the MES plots looked like.
Around 110k miles in the clock now.

Pretty sure the locks are good. The guy who borrowed them has done the cam change himself with these and has had no issue. And I'm trusting that the specialist did everything right, he has done enough belt changes in his life with the v6's. Don't think the specialist wants to do that again anytime soon, neither do I want to spend money on checking it again.
 
1 - 9 of 9 Posts
Top