924s_owner

HI boyz,

still strugling to find whats wrong with my 924s.

symptoms,

- rough idle and hesitation bugging on low rpm's <3100. Sounds like runs on 3 cylinders and gasoline smells. Little burning fuel on exhoust when accelerating hard. huge fuel consumption.

diagnostics ::

checked TPS, AFM, DME box = nothing wrong

ripped all vacuumlines and manifold+tp and reasembled with good sealant. = nothing wrong

checked ingnition in bosch service+ changed all parts to new (rotor, wires plugs) ++ = no help

checked fuel presure and pump performance = still nothing wrong.

all injectors spray when checked starting ...

3rd cylinder has carbon buildup in sparkplug but there is nice spark. All other plugs are really nice.

releasing third cylinder injector wire 'Hayness' style has no effect on idle -> dead injector .... but swapping injectors between 2nd and 3 rd cyl. still reacts same (no change)-> dead wire ... but there is voltage and resistance as specified...

if someone has more test to find whats wrong let me know please !!

thanks in advance,

marko

pikey7

Have you done a compression and/or leakdown test? sounds like you have either valve guide problems, or maybe something a little more serious.......

Is it actually coke buildup in #3, or oil??? (surefire guide or oil ring probs!)

924s_owner

Yep, on compression test my 3 rd. cylinder was prettygood. Leakdown i havent done.

The car runs really good on higher rpms and has the top end as it should. It does start hot and cold and there is ok emission, maybe a bit high HC.

the problem is coming and going depending on engine temperature. Hotter is better.

924s_owner

The buildup is just like in hayness manual example for carbon build up. It actually could not be much closer than it is now...

924s_owner

The problem came suddenly 3 weeks ago during easy driving local countriside. The car was just fine 2 hours but 10 km before home it started vibration and hesitation suddenly.

pikey7

Sounds like you're getting fuel ok, so my guess would be something spark related. How did you check the DME? maybe some timing issue??? Could be an idle valve problem (if you have one......) difficult one for me!

924s_owner

Yep we drove my dme in my friends 944 and it was great.

idle valve is slow.... it is bit dirty as far as i know. i think i need to do something to clean it. BUt i think it should be closed when driving 2800 rpm.s on 5 th gear. maybe it is sticking and stays open.

How the hell could the spark on one plug be wrong and all the others ones are just fine. Cap and rotor sre new and ignition picture is fine.

This hard for me too. I done huge amount of work checking all those things.

SidViscous

If the plug wire is loose you could get bad spark at times. Happened to me on the #1 cylinder.

924s_owner

All plug wires have been asembled many times but i cant find anything wrong from there. ****ing hotwires - wires are guite bad ...

SidViscous

"wires are guite bad" Hunh? if they're hot or bad replace them. But I thought you said you replaced them.

924s_owner

sorry for the bad language there. I men i bought a new set of wires. They are ment for 951 but are just right lenght for 944 /924s. Saying wires are bad i mean the quality of the hotwires compared porche originals. The fit is not perfect in distributor end without some modifications. As said if they advertise set to 951 it should be better fit than what I got for my 29 €.

well wires are new and should work !!

marko

924s_owner

BTW:

Could a faulty injector be giving me an rich mixture so that it would not burn. Can yuo test an injector output by just cranking the engine and measuring what comes out `?

SidViscous

29 euros?

I'd look into a different set. Could be your problem right there. Specially if you have to modify for the dist end.

Wires for a 944 (and 951) are way more exspensive than that.

IceShark

A sticking injector will give you too much fuel. And it will also wash the oil off the cylinder wall and then you are going to have huge problems when you score the wall. But if you switched injectors and the problem didn't follow the #3 injector it must be something else.

I think the way they flow test/match the injectors is to pull them out, put a graduated beaker under it and run it. There is a do-it-yourself description floating around here somewhere.

MHT

here's a possibility, I saw this once a few years ago, a broken outer valve spring, when the engine was cold the oil pressure was high enough to pump up the lifter to the point where the valve would not seat. As the engine warmed up the oil pressure dropped and the valve would close, rev the engine and the miss would begin again, let it idle and the miss would gradually go away. Take the check valve out of your compression gauge, disconnect that fuel injector, run the engine with the compression gauge in place and see if the compression goes away if you rev the engine.

Good luck