ok an odd one this and long winded so bear with me....

i bought a much cheapo felicia mpi for the missus to run around in, it needed some work but now its all ok etc.

the engine has a massive hesitation from 2500 rpm and it is really gutless and crap on fuel too.

now having worked on these since they were new i should be able to fix it especially having several motors at work to swap bits from

so i did some data logging and found that the knock sensor was pulling the timing back from 2500 onwards and recording a lot of det.

anyway nothing i have changed has altered it i have swapped ecu , throttle body, map sensor engine wiring loom, lambda ,crank sensor,coilpack,injectors,fuel pump, crank sensor..

basically if its bolted to the engine i have swapped it

now i did a compression test and got 190psi on every cylinder which seems excessive as most only get 150 or so, so i notice the head has been off and maybe skimmed too much??? so remove head and lower compression by using my miling machine to mill the chambers out a bit (well i got a bit carried away so a lot really)..

still no change.. so i got thinking about the possibility of it having been fitted with one of those faulty timing sprockets on the timing chain??? removed crank pulley and oil pump drive and marked the chain between the dots and counted 12 pins and the crankl dot is correct too..

soo everything i have seen regarding incorrect cam timing has the same symptoms as i have (the exh mani gows a bit too lol) but the cam "appears" to be right.. i am thinking that maybe there were also some cranks or camshafts made to match the "incorrect" timing sprockets and that fitting the normal one has altered it.. (no idea if it has ever had a chain replaced tho)..

any suggestions. i did think about setting tdc with a dial gage and measuring the lift on cyl 4 valves compared to another 136 to see if there was any differance.........

its annoying me properly now and i hate working on my own cars lol...

throw me some ideas folks :wonder:

I don't see a link between a compression test done between compression and power stokes, and cam timing, unless the mis-timing means that the intake valves close on BDC rather than part-way up the compression stroke?

hi ken..

ok well neither did I until i googled retarded cam timing and it apparently has the effect of increasing the cylinder filling... only on single cam motors.. even after removing quite a bit of material from inside the combustion chamber the compressing reading was the same (tester is correct i have checked with several cars)..

defo an odd one tho

it definitely sounds like the cam is retarded too much... if you turn it so number 1 piston is at tdc, you should get equal amounts of lift on both valves on cylinder 4, so you will need 2 dial guages

Edited 29 January, 201016 yr by TeflonTom

Link [pun intended!] below may help.

http://briskoda.net/forums/topic/131845-idle-power-problem-14-mpi/page__p__1666051__hl__daverapid%20fabia%20timing%20chain__fromsearch__1entry1666051

That thread Dave has linked to seems pretty conclusive - have a look and report back!!

ok yes i know about the incorrectly marked sprockets, mine is the right one as i took the crank pulley off and checked it, also checked that there were 12 pins between the marks (with the timing cover still fitted) and there are. thats why i wondered if perhaps some of the cranks were wrong or maybe they were made to match the "different" sprocket..

cheers dave tho

either way i am certain the problem i have is something to do with cam timing but everything looks right. when i am able i think i will start by measuring the lift on various valves at tdc and go from there..

i did think about removing the key from the crank and advancing/retarding it and running without the key just to try it as in my opinion the key itself does not take up driving forces only for setting up, the torque on the crank bolt should be sufficient to drive the cam... any thoughts??

I think put a DTI on there and measure where the maximum opening of the inlet valve on cylinder 1 is (having, of course, found TDC accurately, you can probably simulate a stop bar by welding something about 20mm long (and smooth-ended) to a spark plug and screwing that in, and being very careful turning the engine over by hand to find either side of TDC with a degree wheel on, half way between will be true TDC) - having had one of the incorrectly-made sprockets used in a build I was doing, it was the only way I was 100% that the cam timing was right. You can do the same for the valve opening to get the true centre-of-lobe figure by measuring either side of it at a given lift (about .5mm off of the maximum seems to work well), so you get a really accurate setting of the max lift time.