1.9 8v Compressions And Misfire

[kenp 3]

Hi,

 

My girlfirend's Pug has started misfiring of late. I've done all the usual tests and plugs, leads, cap etc seem fine.

Have replaced all recently anyway.

 

It appears to be missing on #2.

 

Ran a compression test today and these are the results (cold and dry)

 

1: 190

2: 140 (but took longer to come up than the others)

3: 145

4: 155

 

After running a wet test on #2 it went to over 200.

 

Although #2 is the lowest I was surprised at the other results - for a good engine I'd expect around 180 across the board - does anybody else agree with that as I can't find compression figures in the Haynes manual?

 

So to me it seems that #1 is fine but all the other pots are down. The engine in the car was "supposed" to have had new liners and pistons fairly recently but given we had to have the bottom end done (it supposedly had a new crank) recently I'm taking that with a pinch of salt.

 

Can someone confirm the worst and recommend a decent engine builder local to me (South Hampshire)?

[Stonesie 0]

i can 99% confirm the worst going on what you have said (sorry man) but another thing you can try is to put a spoon full of oil down each plug hole, spin it on the starter a couple of times but not for too long, then repeat the compression test.... if its a bad ring seal the results will now be about normal or maby a touch high because the oil is makeing a good temporary seal (this probably works better on upright engines though)

[DamirGTI 342]

Hi !

 

Just one thing have you check the injectors ? my engine starts to misfire badly (like running on 3 cylinders..) when one injector has gone/broke (after ultrasonic cleaning ) I've then fit one spare injector and was fine again no more misfiring and engine works as normal again on all 4 cylinders .

Check also the injector connectors if they are firm tight without corrosion etc. ...

 

As for CR measurements if it's freshly rebuilt engine maybe it needs some more time to let loose - for the rings to bed in properly ... what i mean is that you can't expect good CR build up if it's freshly rebuilt it needs some time of running-in before the first accurate CR measurement test

 

Also ignition amp. can cause very bad misfire worth to check !

 

Cheers !

Damir

[kenp 3]

Cheers for the replies chaps.

 

I did try a wet test on #2 and it went to over 200.

 

What I do find odd is that I would have expected #2 to be significantly down on all the others to show a misfire due to compression loss. So in the event it's strange that #1 is up at 190 but all the others are fairly consistent (although down). I do fear the worst though.

 

The engine has done at least 8k IIRC since it was alledgedly rebuilt so I think I can discount bedding-in issues now.

 

Am I correct in thinking that liners / pistons can be changed with the engine in-situ with the head and sump off?

 

I am going to swap the injector on #2 anyway just to discount that and see if I can get the car running better in the short term. Long term though the discrepancies with the compressions needs looking at.

Edited September 11, 2007 by kenp

[ashley peddle 3]

i have a rebuilt bottom end you can have for £not very much. its done 1500 miles - and was run in properly

 

drop me a pm if you are interested

 

ash

[kenp 3]

Thanks mate but as we've already had the crank done I'll stick with ours unless it turns out to be something really nasty!

[kenp 3]

Update:

 

Swapped the injector with no improvement. There doesn't seem to be anything else external left to check so looking increasingly likely that it's an internal problem

 

Mr Haynes suggests that it is possible to replace pistons and liners in-situ (I've done 4 engine swaps recently and I'm just not in the mood - or have the time - to do anymore) - can anyone confirm or deny that this can be done?

 

Lastly, again due to lack of time (and motivation tbh!) I want to farm the work out, and want to use someone who knows Pugs well rather than just the local garage - I know there are one or two fairly local but would like some recommendations - can anyone oblige (PM if you prefer)?

 

Cheers in advance!

Edited September 15, 2007 by kenp

[Richie-Van-GTi 71 2 Cars]

yes they can be swapped in situ. Try the spoon of oil in all pots and check for even results for me 2,3,4 look in the ball park with 1 being too high as though the oil ring has gone or the liner is scored and the bore is self filling with oil already. Yes 180 across the board is nice but a lot comes down to battery and starter strengths, cam timing, throttle position etc.

[kenp 3]

I'm about to get a leak down test done to try and further isolate the problem - if my worst fears are realised and it points to a problem with the liners / rings roughly how much am I looking at to get new liners etc fitted with the engine in situ?

[CaptainK 11]

Mr Haynes suggests that it is possible to replace pistons and liners in-situ (I've done 4 engine swaps recently and I'm just not in the mood - or have the time - to do anymore) - can anyone confirm or deny that this can be done?

Yup, my local garage did my piston rings and liners and much more with the engine still in the car during its mini rebuild.

[kenp 3]

[update] Had a leak down test last week and problem appears to head or gasket related. Going to have the head off shortly but now more hopefull that it's not a bore / ring problem...

 

Watch this space

Edited October 15, 2007 by kenp