Poorly Zetec

[josephmoore]

Right, engine is a 1992 Zetec 1.8L with a Raceline head, 2.0L cams and Weber DCOE 40s. Had a pretty serious misfire last summer which I thought might be electrics related. Tried plugs, leads and coilpack - all fine, had no impact on the lumpy running. Definitely not burning fuel in one cylinder as it's lumpy as anything and the exhaust does smell of unburnt petrol.

Pretty much nothing happened last autumn/winter as a combination of getting married (as awesome as it was) and persistent storms for the past 4 months hasn't left much time or cash for playing with cars.

If it doesn't seem to be ignition then that leaves valves or rings. Just done a compression test using a cheapo tester. Ok, it's not gonna win any prizes for accuracy but it should be a guide as to any obvious problems. Results with a cold engine:
- cyl 1: 80psi
- cyl 2: 62.5psi
- cyl 3: 80psi
- cyl 4: 70psi

After dribbling a little oil into cylinder 2 it got up to 70psi. This isn't looking great, is it?

Interestingly some folks say that an engine should be making about 200psi, whereas there seem to be plenty of people reporting results around 80psi for healthy engines. I'm primarily concerned about consistency across the cylinders - is that right?

[stylussprinter]

Consistancy -- yes Not sure what reasonable pressures ought to be but my (many yonks ago ) Ford Anglia standard without mod's was 160 psi across all four , so it would appear at least that rings are in poor condition , if not general overall wear . No idea of the mileage on your engine though or rather the mileage on it before Alec put it in the Stylus. I would have thought that , say , up to 60,000 miles would be nothing for a modern engine though.
If it were me I'd bite the bullet and strip it to see then rebuild.

[josephmoore]

Thanks Rob, that's what I was thinking would be the outcome at this stage. Decent head and shiny bits do nothing to guarantee that the bottom end didn't come straight out of an old Escort that had been flogged all its life and has just about had enough.

I'll have a chat to the guys at the car club and see if there's a Zetec knowledgeable garage nearby as I've never poked inside an engine before and there's really no room for me to play around with it in the garage here, but it'd be good if I could peer over their shoulders as a learning exercise. Best start saving those pennies!

I guess at least if it is the bottom end (which is stock as far as I can tell) then there are plenty of options for rebuilding or sticking the shiny bits on a new block. I've heard the 1.8L head swaps onto the 2.0L block with no problems other than a change in compression ratio which can be solved with a thicker head gasket.

Time to get some professional eyes to look at it in case I'm being a numpty.

[stylussprinter]

Alec would have put ARP rod bolts in I'm pretty sure , being an RAF engineer Bottom end won't have given those symptoms though , much more likely the top.

[CMA]

Before you go stripping it did you do the compression test with the throttle wide open?

Compression 20% lower than the others would not stop the fuel from burning, it would jut burn very poorly.

I had lumpy running on mine and it turned out one of the ignition drivers in the ECU had gone pop. This was simply diagnosed by removing a plug and connecting it to each point on the coil pack and earthing it to the bloc with some insulated pliers. On 1 & 3 I got a good spark. 2 & 4 gave me no spark. So tested the coil pack plug and one of the feeds wasn't switching to earth when cranking the engine.

[josephmoore]

Shan't be doing anything hastily, don't worry.

Throttle was closed - google proved inconclusive about whether WOT was necessary. Will perhaps give it another try tomorrow with it open. Air can still get in, as it's as if it were idling. It's the fact it went up from 62.5 to 70 with a drop of oil which had me concerned.

Did swap the coilpack out for another from a breaker so unless I got unlucky that's fine too. Did try pulling the leads one by one and listening for a change but it's so rough anyway it was hard to tell. Probably need some more experienced ears than I have.

Edit - just remembered one of the guys at the club took a quick look when it started playing up last year, pulled the leads and suggested it was cylinder 2 which was the culprit.

[CMA]

All the values will go up with a drop of oil. Do all 4 as a comparison and they will all rise a little. With the throttle wide open it will be a higher compression so any problems will have a bigger difference and be more noticeable.

What ECU is it? Have you checked that its actually sending the signal to the coil pack for a spark? That was my problem and took some finding.

Also Zetec plugs are very sensitive and can fail easily, so try swapping them around and seeing if the problem moves.

[MattD]

Broken piston ring ?

[josephmoore]

I'll give it another test tomorrow with WOT and see what the results are.

ECU is Weber Alpha, apparently. Can't say I've rooted around and checked though. Got a multimeter to hand - how did you test it at the coilpack plug?

Spark plugs are brand new - changed them first for the pittance it costs.

Cheers for the help, guys

[CMA]

I have a probe similar to this (but a cheaper version) http://www.ebay.co.uk/itm/Sealey-PP1-Au ... 0733547688

This shows if a wire is live or earth with the colour of the led and a buzz on live (I think). On cranking it shows the 2 side connections of the coil plug flicking between live and earth if they are working correctly. I had one that just stayed at live, showing the ignition driver, or wiring was at fault

[pigeondave]

Stupid question but...
is it a misfire or rough running?
Maybe its the carbs, are they balanced?

After last years tour, 3000 ish miles in 10 days I got back to Dover and the car was running like a pig all the way home to Brighton.

I whipped off the carbs and stripped them down and ran them through the ultrasonic cleaner. Then they were drowned in carb cleaner (careful not to get it in the eye as it stings like fricken hell) once rebuilt and balanced the car ran fine.

Its carbs they're supposed to be temperamental

[josephmoore]

It feels like a misfire to me - lumpy at idle, if it'll idle at all but isn't so bad when you give it some beans. It's always run a little rich just by my nose and last year the car did have to sit for a while. Could be gunked up carbs though my experience with them extends to my first car (Austin Mini) and small outboard engines - so that's not much!

If it helps the problem came on kinda gradually. One weekend it was a bit grumpy when not booting it, then the following weekend after some hard use it refused to idle. Drove it home, keeping the revs up at junctions but it seemed happy enough if I put my foot down.

[kevp]

Hi, my Zetec input.

Think if the carbs are out of balance or jets blocked - the plugs would show this up.

If it was a coil driver, the engine would be really rough as only 2 cylinders would be firing. I had this on mine last week. So had to change the coil drivers.

If the cylinder pressure is bad enough for rough running, I would have thought that either oil would be burnt or the block would become pressurized & blow out of the breather. Does the breather go back into the inlet or a catch tank?

With my experience of Zetecs its usually ignition. I would start off with new plugs & leads 1st.


Good Luck

[spegru]

Could be an inlet manifold air leak?

[josephmoore]

Ok folks - productive lunch time's fettling and testing. Feeling relieved

Redid the compression test with WOT and all plugs out. Results: 165, 155, 165, 155. Bang on the money. Phew. Turns out WOT is very important on a Zetec with DCOEs.

Tried to test the coilpack plug but my cheapo multimeter wasn't really up to the job. I did read ~12v when cranking, it just wasn't fast/accurate enough to record the switching. I would perhaps have expected it to smooth the voltage and read less/more if one wasn't working but both were near enough the same so for now I'm putting that on the back burner.

More googling suggested carb setup as suggested above - there are a few people (usually on bike forums, it seems) who have similar rough running with a blocked jet or improper tuning. I've always thought the Stylus was running a little rich as the exhaust usually smells a little of fuel but it's more so at the moment. Found a rough guide for starting point setup (here: http://www.redlineweber.com/html/Tech/d ... ical_i.htm), tightened until seated the idle mixture screws then backed them off a turn, then set the idle speed screw (only one as it's got a linkage) a little tighter as it wasn't quite right. Runs less badly, but still not great. Will read some more guides on tuning Webers and seek more advice - let's see what happens. I don't want to pull it all apart to clean it if it's just that it's worked itself out of tune.

What RPM do you guys have your idles set at? It seemed happy from about 1200rpm which I guess isn't awful given the engine was cold. Needed just a smidge of throttle to hold it there so I could tighten the idle speed screw a little further.