Valve guides shot within 3000kms - due to overfuelling? - Alfa Romeo Forum
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(Post Link) post #1 of 6 Old 28-07-10 Thread Starter
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Valve guides shot within 3000kms - due to overfuelling?

My Phase 1 2.0 Twinspark started pushing out oil through the exhaust in the form of a cloud of smoke (especially when under power). But she was starting well (hot or cold), idled beautifully and pulled as strongly as ever.

The engine was rebuilt from top to bottom, by a rebuilder with impeccable track record and using modern equipment. New pistons (still standard size), valves, valve guides, the whole tutti. Valve guides come from Italy - name sound like mereilli - and is used by other Alfa specialists as well.

After this, the car drove, idled, started and sounded exactly as it did during the previous nine years of my ownership. Fuel consumption was as before, between 10kms/liter (28 mpg) and 12kms/liter (33mpg). Problem was only that I was again noticing smoke shortly after about 1000kms - oil consumption was however not excessive. I returned the car to the workshop owner, who took the vehicle to the engine rebuilders and to an Alfa specialist. Verdict: The engine needed some "running in". Even the fuel was suspected of possibly being contaminated. So I drove the car for 3000kms/2000 miles, until I could take it no more. By now the oil level has dropped from being at the maximum mark after the rebuilt to about the minimum mark on the dipstick. Eventually the top was removed in the presence of various role players, including a representative of the retail motor industry body.

All pistons had the same dark colour, with a slightly "cleaner" area towards the rear of the car (inlet side?)

But: The valve guides, especially those of all the exhaust valves were so worn, some people claimed that this was the worst they have seen in many years of working on engines. Miracle that no valves were dropped. Overfueling was cited as the cause of this wear, and the rebuilders claimed that it was not their fault. Fortunately my relationship with my local garage owner goes back about 18 years, and he offered to fix the engine at his cost. (The rebuilders will "donate" their labour as their contribution.) I accept that I will have to pay any costs to cure the overfuelling problem.

I am a lay person when it comes to overfuelling. I have gone through nine years of invoices and emissions were tested on a few occasions during the 50000kms I added. I reiterate - the car showed no signs of overfuelling, except for the wear. I will have the emissions tested as soon as the engine has been assembled again.

a) Is it possible for the engine management system, myself and various mechanics never to have noticed any symptoms of overfuelling?
b) How reliably can injectors be tested, and is there merit in the ultrasonic(?) cleaning of injectors?
c) Did all the Alfa 2.0 twinspark engines use the same Lambda-sensor?

Any help/advice to prevent a recurrance would be appreciated.
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I probably don't know enough to comment with certainty, but it sounds a bit fishy to me... Lack of lubrication, wrong/miss-fitted guides, grinding compound not cleaned up etc might be more likely...

a) An emissions test would be the best test, but a noticeable lack of fuel economy would be the first sign.
b) Dunno, sorry!
c) I think so... later engines had 3 though.


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Well I wonder if this is my problem, too. My recent post "Up in Smoke" told of my Phase 1 spluttering into life one morning a month ago, but smoke was puthering out of the oil filler as well. My engine had supposed to have been reconditioned by a well known Alfa specialist (the cylinder head looks shiny new)

Not quite sure what you mean by "overfuelling". Running too rich?
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In answer to c)

no they do not..and even vary across similar engine models in different CF1 engined 145/6's have a different lambda sensor to a CF1 engined Spider.....

ask me how I know!

Why would over fuelling cause excess valve guide wear? Would not any excess unburnt fuel take the path of least resistance and scavenge out the exhaust ports?..or are they suggesting it forces it's way up the valve stem, and replaces the lubricating oil and causes excess wear?
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BUT the stem seal is exactly that - a seal at the stem end ie camlobe end of the valve. The valve guide is below the stem seal so no oil goes down there onto valve stem towards valve head. It is simply a very close fit guide for the valve to slide up and down - no lubrication is provided by oilflow. They are usually self lubricating type of metal (phosphor bronze?)
Overfuelling? It would have to be serious overfuel to have any unburnt/non vaporised fuel left in cylinder that made its way up valve guide.
Sound to me like your being BSed to be frank.
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(Post Link) post #6 of 6 Old 29-07-10 Thread Starter
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Thanks for the comments, information and advice

I understand by overfuelling that the engine is running too rich. I see on the forum (in a thread on fault codes for six cylinder engines) that running a too rich mixture is also listed as a possible fault code. I do not know whether the ECU in my phase 1 would be so clever thou.

I am waiting for the injectors (that have seen 170 000kms of service since new) to be returned to me, and intend to have them tested by an independent specialist. According to internet-wisdom is not only the correct spray pattern important, but a wrong angle can also lead to wear. But still I would have expected damage to the heads of the valves, rather than the sleeves.

Thing is I need to find the cause of this, before ruining the third head/top in a short time.
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3000kms , due , guides , overfuelling , shot , valve

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