General chugging on idle

[levemircento]

ok, done the head gasket and head

the cam is worn/or need the shims doing

when driving the car feels ok, but its chugging like mad at idle, this, and the fact than in just 15 miles of driving, its used a shed load of fuel, a tad less than a 1/4 of a tank

I took the airbox off to check the connections to the injector unit, I did this with it running to see if anything made a difference, the throttle position sensor didnt make any difference when unplugged and plugged back in, neither did the connector [intake temp?] when undone and put back in, the plug at the top/back of the spi unit made it die when undone.

I also pulled the vac pipe off the map sensor, not much difference, and not much with its connector undone either

I didnt disturb any other connectors anywhere.

any ideas?

 

[rallycinq]

Was the cam making the noise before the head job?

Cheers

D

 

[levemircento]

Was the cam making the noise before the head job?

Cheers

D

I dont know, as the head is new to the car & came with the cam on it already, so I just left it on during the rebuild of the top end

My original cam was as smooth as anything, I am getting the tools to measure the shims etc tonight, I will probably put my original cam on it and shim as needed.

its not the cam noise I am bothered about, its the chugging at idle

I made sure the timing marks were all properly lined up when putting the belt on, and turned it a couple of revolutions to double check.

 

[fingers99]

Chugging?

The fuel consumption suggests MAP to me. Is the pipe clear and intact?

Did you skim the "new" head?

 

[levemircento]

As far as I know the pipe is clear - in fact it must be, cos when I pulled it off the map sensor with engine ticking over, you could hear the vacuum and feel it too if you put your finger over it, the rubber connector pipe at inlet end is ok too.

Head had already been skimmed not long before I bought it, a mechanic friend of mine checked it over with some measuring equipment to check it for flatness, he said it be ok to put straight on

 

[levemircento]

Chugging?

The fuel consumption suggests MAP to me. Is the pipe clear and intact?

Yeah, chugging - quite hard to explain in words, basically the idle is as rough as anything, and lower than what it would be normally which doesnt help. its up and down but not what is sometimes described as "hunting" ie, revving up by itself then slowing down, then revving up again and so on.

see!! its bloody hard to describe!!

Would an 899 map sensor work on the 1108?

 

[fingers99]

Would an 899 map sensor work on the 1108?

Pretty sure it's the same part. Check in ePer?

Hunting idle is another MAP sign.

 

[levemircento]

As the map was disconnected from the vac pipe for just over a week, could that have made it fail?

 

[rallycinq]

As the map was disconnected from the vac pipe for just over a week, could that have made it fail?

Highly unlikely.

If you have a noise from the cam, and the head was skimmed, is there a possibility that the cam has been out and the shims not put back in the right position. If you have a couple of noisy (loose) ones, then you could have a couple of tight ones not allowing the valves to close properly.

Cheers

D

 

[fingers99]

Probably makes sense to sort the shims out before chasing after other symptoms.

 

[levemircento]

I understand what you are saying

Think I need to have a look at the clearances first, everything electronic was working beforehand afterall.

If the shims are too thin [for example] then the valves wont open as much, could that be a factor to explain my idle speed?


as an aside, I havent touched the lambda, and didnt use any substance anywhere that might of found its way down the exhaust pipe, and everything in that dept was ok just before I took the head off.

 

[rallycinq]

If the shims are too thin [for example] then the valves wont open as much, could that be a factor to explain my idle speed?

.

Other way round. If the clearance is not enough on the base circle, the valve doesn't fully shut so you get odd pulses in the induction system, and a lack of compression.

Cheers

D

 

[levemircento]

After I finished putting everything back together, I found I had a spare 13mm bolt, and I traced this to the back of the inlet manifold where it holds a bracket for alternator etc wiring

now, does this threaded hole go straight ino the inlet? or is it blind?

I replaced the bolt, and it seems to idle a little better, but its nowhere near as good as it was with my old head.

I checked the valve clearances, on the old head, and the head thats on the car, as follows

Old head with known good cam, shim figure its the stamp on its bottom
no. - gap - shim
1 - 020 - 4.02
2 - 013 - 4.05
3 - 020 - 4.05
4 - 013 - 4.05
5 - 013 - 4.12
6 - 020 - 4.12
7 - 013 - 4.05
8 - 020 - 4.10

car
1 - 013
2 - 008
3 - 018
4 - 013
5 - 010
6 - 014
7 - 011
8 - 020

Gap measurement was the figure on each feeler blade, I hope it means something to you people that know about these things, it means nothing to me!! I am hopeless at maths!! I assume valve no 8 is .020 of 1mm, or is it .20 of 1mm ?? as in 100 would be 1mm? see, told you I have no idea!!!

I think I want to fit my original cam, whats involved now to do that?

Many thanks

I havent measured the shims that are on the car yet, had enough for this week so will go back to it monday

 

[fingers99]

No point in comparing clearances head to head.

You need to use the feeler guage to measure each clearance in turn with the cam lobe at base circle (lobe pointing straight up).

Clearances should be (for "standard" cam) in millimeters.

0.35 to 0.45 (inlet) 0.45 to 0.55 (exhaust) with a cold engine.

If clearance on a valve is OK, leave it well alone. If it's outside tolerances, note down the clearance (say it's 0.2) pop out the shim. Measure the shim. The clearance should be (say) 0.40, so you need a shim 0.20 thinner than the one you have. Find a shim to suit, pop it in, re-check.

You'll probably find that among the shims you have is something to suit (also, most shims are marked). If not. they're around £2.50 each.

The cam is unlikely to be worn and if you swop cams you'll still need to re-shim it, so don't bugger about with that.

Make sure the feeler guages you have are metric!

 

[levemircento]

You need to use the feeler guage to measure each clearance in turn with the cam lobe at base circle (lobe pointing straight up).



Make sure the feeler guages you have are metric!

I did measure with lobes pointing straight up

The gauge is metric, I just need to interpret what the numbers mean as in my post above

 

[fingers99]

The figures you give are wierd. I'm surprised either engine was running.

I recommend re-checking them and even checking the feeler guage against a micrometer.

But, taking the known good cam

1 - 020 - 4.02

020 is probably 0.20 (measure it!)

clearance should be (say) 0.40. Therefore you need a shim 0.20 thinner. 4.02 - 0.20 = 3.82. So a shim 3.77-3.87 will do the job.

The point about not fitting the old cam to the new head is that shims set the clearance for the whole valve train. If the length of an invidual valve is different (and it will be), or the fitted length is different (it will be) then it'll need a different shim to set the clearance.

If I'm a bit pointy on this it's because I grew up with Ducatis, and shimming valve clearances becomes second nature if you have to do it every 1500 miles! Sorry!

 

[levemircento]

Thanks
Thats very helpful

 

[rallycinq]

It does look as though the cam is a bit tight, hence the valves staying slightly open.

Cheers

D

 

[levemircento]

Righto, mucho help needed by those who understand it

Obviously, given the numbers below I need to reshim, I need to know what sizes of shims to get, as I am hopeless at the maths


no. - gap - shim

1 - 0.13 - 4.75
2 - 0.08 - 4.75
3 - 0.18 - 4.75
4 - 0.13 - 4.75
5 - 0.10 - 4.75
6 - 0.14 - 4.75
7 - 0.11 - 4.75
8 - 0.20 - 4.75


Looks like whoever last had the head, or worked on it, thought the same sized shim goes on all 8 valves!!

 

[rallycinq]

OK, so we know we have a problem. I would be tempted to whip the head off and check the valves first, but if you want to go ahead, see what you can make of this.

Another wee pointer, I presume the shims are marked, you haven't checked them, just incase they've been ground.

No 1, exhaust. Lets start with an awkward one.

Should be between .45 and .55. a 4.50 shim will give .38 and 4.25 shim will give .63. Unless you have access to a surface grinder I'd probably go 4.25, bigger is better than smaller.

No 2, Inlet

Should be between .35 and .45. A 4.5 shim will give .33, ignore what I said above, close enough.

No 3, exhaust

Should be between .45 and .55. 4.5 shim

No 4, inlet

Should be between .35 and .45. 4.5 shim

No 5, Inlet

Should be between .35 and .45. 4.5 shim

No 6, exhaust

Should be between .45 and .55. 4.5 shim

No 7, inlet

Should be between .35 and .45. 4.5 shim

No 8, Exhaust

Should be between .45 and .55. 4.5 shim

Cheers

D