I recently bought a 999cc Polo for our daughter. On cold starts the engine hunts immediately, then settles to a smooth fast idle after 20 to 30 seconds. The engine runs well and once warm, generally restarts ok.
However, if the engine is stalled, or if switched off before reaching full temperature it is difficult to restart. Flooring the throttle and cranking for 20 seconds generally works, although not great for the cat. It appears to be overfuelling.
A couple of days ago, I switched it off after running for about 3 minutes and no amount of coaxing has brought it to life since. There is a strong smell of petrol, the plugs are drenched and spinning the engine on the starter with plugs out (and warming the plugs on the gas hob)didn't get it going.
This engine has a multipoint fuel injection system, but no obvious hot-wire air flow sensor. Neither is there a water heated auto-choke like old Polos. The air filter is clean & dry, but there is some oil residue in the venturi throat, so it might have been overfilled with oil by a previous owner. Might there be oil in the inlet manifold tubes? Would this be enough to restrict its breathing to this extent, bearing in mind the inlet manifold loops downwards?
Can anyone offer some advice?
With thanks - John
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you say multipoint injection?i thought they were single point?
suggest you start car without touching pedals and see how it pans out,a lot of single point cars are a bit of a pain in cold weather as it was first generation cat and injection system .
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John
Try changing the coolant temperature sensor. It's a very common problem on these and often causes just this fault.
You might need to know what colour band is fitted to yours when buying a replacement.
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I experianced similr problem. Mine was head gasket. Suggest you disconect the ignition and crank the engine briefly. Remove the plugs and check for water on electrodes.
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I experianced similr problem. Mine was head gasket. Suggest you disconect the ignition and crank the engine briefly. Remove the plugs and check for water on electrodes.
Wouldn't think it would run well when warm if this was the prob ?
If it is single or multi point injection, applying any throttle during starting at any time will cause problems.
The coolant temp sensor is a good bet.
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Many thanks oldman, Screwloose, DavidT & Roly93 for your replies. I've just come in from an afternoon under the bonnet - and I've had it running!
Firstly its definitely a multipoint, but lacks the number of sensors you'd find on our mk4 Golf. Yes I would normally start it without touching the throttle - I only resorted to this when I had problems.
Secondly the plugs were wet with fuel not water thankfully!
Today it fired once before flooding again (no pedals touched). I dried the plugs & tried again but the injectors were putting buckets of petrol in. I disconnected the electrical connections to the 4 injectors, dried the plugs, spun the engine to disperse some of the fuel & put the plugs & leads back. It started & ran on the fuel already in the engine for a second or so. I reconnected the injectors & it promptly flooded! A repeat performance got it going & it ran rather unevenly at 2,500 rpm. It warmed up & settled into a normal idle, but each time the throttle was blipped it would rev to about 2,000 rpm and take 10 seconds to return to idle.
On the road the engine refused to run below 1,500 rpm (didn't cut or misfire - just wouldn't idle) and at times idled at 2,000 rpm. Otherwise it pulled well. Once the engine was up to full temperature, I could stop the car & take my feet off the pedals and after about 10 seconds the engine would slow down gradually to an uneven idle at about 1,000 to 1,100 rpm.
Next I pulled off the coolant temp sender connection and the engine promptly idled just below 800 rpm. A quick road test showed the expected prompt return to normal idle when the throttle was released. Back at home I switched off & it restarted readily.
It looks like a new sensor is the next step though the proof of the pudding will have to wait until Monday!
Many thanks - John
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Did changing the sensor improve/correct things? Had exactly the same problem on my daughter's Polo, changed the sensor, now it runs perfectly. Fingers crossed.
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