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What can cause 3 cyl running at start up?

scam75

scam75

Well-known member
Afternoon All

My project S2 cab likes to run on 3 cylinders for a few minutes at cold start-up. After a short while it runs on 4 and seems to pull well. Worst case scenario maybe the HG needing refreshed, however before I start ripping the head off it (oh err!), what else could cause such symptoms? I cleaned up the cap and arm but have so far not inspected the plugs which I believe are at least 9 years old!

Thanks

Stuart
 
You may well be correct Gerry! Plugs next on my to do list, hope it's nothing more sinister!

Stuart
 
I can't be too smug Stuart, I raced two seasons before I took mine out and looked at them. But there as cheap as chips and its an easy thing to kick off with.

I recently had all sorts of misfiring on my Stage IV Mini cooper whilst en-route to somewhere so I stopped and swapped the plugs for the hotter spares I carry, still had a problem and the next town Halfrauds only had cheap crap or multi-point Bosch plugs so I bought the most expensive plugs I'd ever bought (at £22 for 4) but by jove! they are the business! Might get some for the 944.
 
Have always used Bosch Supafour plugs in the 924S's -whenever they are taken out for whatever reason,they always just look like new. Much cheaper at ECP who normally stock them.
 
IMO (besides a HG) the following can also cause a car to start on a cylinder or two less:

1) Tired tappets (they will generally make a noise as well until the oil pressure builds up). I have only really noticed this however on my S2 when I left it for over a month (the tappets sounded as if there was something quite terminal with the engine and it only ran on around 2 1/2 piston until all of the tappets eventually filled up ; On my Escort with a number of short trips, one tappet decided to stick which again resulted in a lost cylinder for over a couple of minutes :/).
2) Leaky injectors: If an injector is leaking it will generally wash/glaze the bore. However, you may get a tell tale sign of blue smoke at startup as the oil for the timebeing becomes almost a makeshift ring (my Stag never did this from hot when the fuel vapourised on the new carb initially ; honest).
3) Tired ignition system. Plugs are cheapest and quickest port of call. If I am honest my Turbo was fine on both NGKs and Bosch plugs. My S2 seemed fine also on whatever went in.
 
Leads perish over years/decades.

Rotor arm and dizzy cap wear/ arc very easily especially if the cap isn't perfectly aligned.

Not massively cheap but I would recommend a new cap/ arm every 40K miles or 5yrs.

Chris
 
Thanks for all the replies gents! I have ordered plugs, once its out the paint shop this week I will pop them in and report back.

There is no blue smoke on start up, no tappet noise, excellent oil pressure and I cleaned the cap and arm when doing the belts. Hopefully ignition related as don't see any signs of HG failure!

Fingers crossed.

Cheers
 
Plugs can make a huge difference. My wifes Hyundai Coupe wouldn't stsrt Sunday evening! Checked plugs, nice colour but gap was huge, corrected them, purrs again. Ordered new shouldbe home when (if) I get home. Snowing in Stockton on Tees!
 
That's why Bosch Supafours are so great-with 4 electrodes ,they never seem to wear at all-they have lasted over 24K miles in Rover Vitesses inc Turbos & only changed for the fun of it-still look like new when removed -even in the 924S's I let them do 20K plus miles.
Note to Mike:-don't neglect your Wife[:D]
 

ORIGINAL: A9XXC

Plugs can make a huge difference. My wifes Hyundai Coupe wouldn't stsrt Sunday evening! Checked plugs, nice colour but gap was huge, corrected them, purrs again. Ordered new shouldbe home when (if) I get home. Snowing in Stockton on Tees!
Click to expand...

have you ordered new plugs or new wife? [:D]

Cheers,
 
something else to consider.
If the car is not used regularly or has had a spell off the road the injectors can get sticky from the laquer residue from fuel additives

Injectors are generally self cleaning but the piston can be sticky when cold.
If you remove each of the injector electrical connectors in turn, when the engine is running cold, it should be easy enough to identify which cylinder is at fault .

Then its just a question of troubleshooting the ht circuit and fuel delivery.
You can use a 9v PP3 battery to flash the injectors 20 times or so ( simulating the ECU pulse ) which will get the injector solenoids moving freely again
 
So back on topic! Have fitted new plugs, checked cap and arm and both seem fine. Car runs and drives great and pulls well. However, when starting from stone cold it is not interested in firing. It turns for about 2 minutes almost without compression, keep cranking and it starts to cough and splutter and threaten life, then about a minute more cranking sees it fire up, possibly 1 or 2 cylinders then 3 then a couple of minutes later we have a sweet running 4. I am at a loss. Starts perfect hot and runs perfect when hot. Could this have anything to do with it being laid up best part of 4 years? I am yet to change the oil however oil pressure is as good as my turbo. I wonder if it could be lifter related and not seeing compression until the oil pressure builds a bit? Maybe a good flush and new oil will help? Not sure. What do you guys think? I get tacho bounce during non start phase and have changed to a known good dme relay.

Help!

Stuart
 


It is difficult to diagnose a fault on a car over the net that you cannot see or test. We only have your description to go on.

From your description it would appear to be due to a temperature and fuel related issue.

A simple test to eliminate a potential over-fuelling problem during cold start would be to remove one of the electrical connectors from one of the injecters.

If the car then starts more easilyon 3 cylinders it would indicate a possible over-fuelling issue due to the cold start system.

If you just do this simple test and report your observations it would give us something concrete to work from



 
Ok will do! I appreciate your advice just never got round to it today so decided just to follow up with adding a bit more to the original issue.

Gave it a good run tonight. 30 miles. Going to roof shop tomorrow. See how it starts in the morning and then follow some of my helpful advice once I get it back. Weekend probably.

Cheers

Stuart
 
ok Stuart fair enough. Just let us have an acknowledgement occasionaly if nothing else. Some of our responses to help requests can involve several hours work pouring through manuals and schematics and typing etc . Its good to have some feedback [;)]

The good news is that there probably isn't anything wrong with any of your components because otherwise your car wouldn't run as well as it does when it is warmed up so please don't be tempted to buy a lot of new stuff for it until you've done some simple tests.#

My feeling is its related to the cold start mechanism so I would be looking at the Engine temperature Sensor and testing that first. Its probably located on the cyl head near the front and looks identical to the coolant sensor in the radiator. It tells the ECU when the engine is cold and needs more fuel .An easy test for this is to squirt a bit of Easy Start in the inlet when starting from cold. If it starts more easily then its 10:1 its not getting sufficient fuel due to a faulty Eng Temp Sensor.
 
Cheers Peanut.

Well good news this morning. After my 30 mile Italian tune up last night it purred into life first turn of the key today and ran sweet as a nut on 4 cylinders. It's away at the roof shop now, new seals, new rear screen and roof align plus they are going to tidy the stitching on the steering wheel which has come away. Fingers crossed it keeps starting properly.

Next job thermostat, although on an S2 it's much easier to access then the turbo!

Stuart
 
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