Lumpy running

johnblitz · Post by **johnblitz** » Mon Jun 05, 2006 20:41

Help!

car has just had a B service and had the valve clearances sorted (as well as cam cover gasket replaced etc.etc) however is now running very lumpily (is that a word?), uptill now its always been very smooth symptoms are:
Difficult to start when cold
Difficult to start when hot
At idle (6-800 rpm) feels like i'm inside a badly balanced washing machine until the cooling fan cuts in and then once the temp has gone down it just vibrates a bit (but more than previously)
hesitation when accelerating
general lumpiness
misfiring at low revs

I realise that this could be symptomatic of a whole lot of things but what can I easily test before I have to resort to the local lotus dealer?The garage warned of a possibility of burnt valve/low compression in one cylinder but........

any help/advice would be appreciated

Cheers

John

Steve C · Post by **Steve C** » Mon Jun 05, 2006 21:27

Try a compression test? What made the garage come to the conclusion of a possible burnt valve? Had the clearance dropped to 0?

600-800 sounds quite slow for tickover, mine is around 900 ..

bash · Post by **bash** » Tue Jun 06, 2006 09:19

I can tell you that when mine burnt a valve that it had similar lumpy low speed running that dissapeared at 3500+rpm. The best way to check is, as mentioned, to do a compression test. But befor taking the head off I would check that the valve clearances are not too tight cos if one is then it may hold the valve open slightly and give similar symptoms. Also, when I had sorted mine out I had to rebalance the carbs cos that gave a very lumpy tickover too. Check all the possibilities before committing to have the head off, which isnt a difficult job if you do it yourself, but it is a very expensive job for somebody else to do. As an Aside, I had to regrind in all of my valves. It seemed to indicate that the valves were softer than the seats and that the valves were recessing into the seat area, possibly cos of unleaded petrol, even tho i always use superunleaded ( another name of which is 'rip the driver off fuel'.)

GavinTaylor · Post by **GavinTaylor** » Tue Jun 06, 2006 11:52

Ummm . . . hang on a second, here.
The car has just had a B service and was running smoothly prior to this.

Did I miss something?
Is a lumpy idle a standard post B service item?
The garage warning sounds like they stuffed something up and they either don't know how to put it right, or they smell a "customer".
It may be time to have a very serious conversation with the garage.

amarshall · Post by **amarshall** » Tue Jun 06, 2006 13:26

Threads elsewhere seem to suggest that a faulty rev. limiter can cause some of the problems described ?

steven popay · Post by **steven popay** » Wed Jun 07, 2006 22:43

you could check the cam timing it may be a tooth out, if they have sorted out clearences then they would have hade the cam belt off

johnblitz · Post by **johnblitz** » Thu Jun 08, 2006 20:57

New Info:

Taken all the plugs out - plug into cylinder no 1 (nearest the front) is very coked up - I've done less than 150 miles since the service. All other plugs are OK

Misfires predominanly when starting from cold

Choke cable is free running so choke is not permanently on.

Feels like its going to stall pulling away at less than 2000 rpm

Doesn't pick up very well when cold (kind of disconcering when pulling out into a main road in the mornin)

garage did the following:

Reset the valve clearences (they were down at 1.5 mm)
Removed and resealed the cam covers - they were both leaking
'B' service
MOT

I've noticed that the top cam cover gasket is fibre - I was under the impression that they were supposed to be gasket paste - is this correct?
BTW the plug in cylinder 4 was under 10mm of oil as well - fixed I dont think so.

Thoughts that occur to me are:

- iffy HT leads
- they retuned the carbs to get it to pass the MOT and I'm running lean?
- iff distributor
- loss of compression on cylinder 1 - this is the nightmare scenario - they want to charge a grand to fix it! 'customer' indeed.

I'm thinking of taking it to a specialist carb tuning place - any thoughts on whether this would be a good idea or anything else I should be checking?

Cheers again

John

GavinTaylor · Post by **GavinTaylor** » Fri Jun 09, 2006 14:28

John,
At the risk of sounding repetitive, I'm concerned that you say:

. . . uptill now its always been very smooth.

And that after the service, you find:

car has just had a B service and had the valve clearances sorted . . . . however is now running very lumpily

And the garage, obviously realising they've muffed something, sheepishly say:

The garage warned of a possibility of burnt valve/low compression in one cylinder but ........

There is something fundamentally wrong with this sequence of events.
Why doen't the car run the same or better than prior to the service, given that they presumably fixed the valve clearences?
It certainly should not run worse.
How can the car "suddenly" show symptoms of a burned valve?
I think you have to ask the garage these questions with a view to an explanation, a fix and/or a refund.

In any event, I'd be checking the valve clearences again. The garage may have left one too tight, in which case the cam may well be holding it open resulting in the fluffy running. If that is the case, you will have symptoms of a burned valve, and in a short space of time will have a real burnt valve. Not trying to be a scare monger, but the garage don't inspire a lot of confidence, from your posts.

Gavin

Steve C · Post by **Steve C** » Fri Jun 09, 2006 14:51

>>Reset the valve clearences (they were down at 1.5 mm)

1.5mm is 60 thou ... widest gap should be 10-12 thou on exhaust (from memory!).

If they meant the closest was at 1.5 thou, that is possible given that the min clearance is 4 thou on inlet (again, all from memory, please check!)...

At 1.5 thou clearance, they may be right in being concerned that the clearance became 0 (or less) as the engine warmed - hence suggesting to be aware of a burnt valve.

Check the clearances soon ... if all in tolerance, carry out a compression test with a warm engine, all plugs removed and throttle held open ...

Let us know how you get on ...

johnblitz · Post by **johnblitz** » Fri Jun 09, 2006 20:29

Gavin,

That's a good point, I was wondering how the symptoms could suddenly occur.....If by fitting too large a shim they can cause the same symptoms, then using my old mate occam (and his razor) - this is the first thing to check (after compression test etc)...
I'll do a compression test tomorrow and let you know the result.
The major problem I have is how to convince the garage not to charge me for the 'investigation' even if they have messed up will they ever admit it (known as the dentist problem)

Thanks

John

robertverhey · Post by **robertverhey** » Fri Jun 09, 2006 23:16

It's very easy when reassembling the cam boxes to have a shim come adrift from its recess and jam itself against the follower. I did it! Result, no compression on that cylinder, and if you're unlucky, a burnt (or bent) valve. I was lucky. Compression test will tell you this. Basically, cylinder needs spark, fuel and compression to do its job. Sounds like one of these is amiss......

Robert

GavinTaylor · Post by **GavinTaylor** » Sat Jun 10, 2006 02:05

johnblitz wrote:I was wondering how the symptoms could suddenly occur.....

Yes, "suddenly" is exactly the point. I would be wanting an answer to this. Watch for the squirming.

If by fitting too large a shim they can cause the same symptoms, then using my old mate occam (and his razor) - this is the first thing to check (after compression test etc)...
I'll do a compression test tomorrow and let you know the result.

At this point we a are guessing at the cause because all we have to go on is a sooty cylinder. It could be something simple like a duff plug, a duff plug lead or just one not pushed on properly. It could be a number of silly things that would fall within the "suddenly happened" catagory. A compression test will tell you a lot, but you should do the basic checks first. A leak down test might be more valuable. As Robert points out, fuel & spark is the basic stuff needed to make it run.
If it's something more radical, like an excessively large shim or something, the responsibility can be sheeted home to the garage much more succesfully.

The major problem I have is how to convince the garage not to charge me for the 'investigation' even if they have messed up will they ever admit it (known as the dentist problem)

Only you can make the judgement on the best approach to the garage. Maybe a reasoned arguement re the "suddenly" point would see them recognise the part they played in the chain of events and lead to them reasonably offering to revisit the issue - at no cost.
Maybe they would respont to threats of legal action or your going higher and making a formal complaint to their affiliated body - I'm guessing here, obviously.
Or maybe it's one of those events that you just write off to experience.

Gavin

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