VW Polo Carburetor Problem - wallregg
H reg VW Polo 1L

While I was driving this evening, about 10 minutes after starting the engine, I noticed that the accelerator had become 'sluggish'. The engine started to run a bit rough with the power varying slightly. Stopped the car and listened to the engine at idle, which was smooth and sounded perfectly normal. When I revved the engine the RPM climbed smoothly to the expected speed, then dropped back again and then stalled. The moment I released the accelerator the engine ran smoothly again at idle.

Started driving again and the engine cut out a few times when accelerating in 1st and 2nd gears, so lots of acceleration needed. Also noticed an intermittent popping or banging noise from the exhaust when driving when the engine was just above idle. Couldn't replicate the noise when stationary (despite rocking etc. the car so am reasonably certain it's not the exhaust banging against the underside).

About 2 weeks ago it had an MoT where it failed on emissions but was corrected by (I think) adjusting the carburettor. Its run fine since then though (about 150 miles).

Anyone have any ideas?!?
VW Polo Carburetor Problem - wallregg
I'm having problems with my Mk2 Polo and I think it has something to do with the carburetor. When driving yesterday, after about 10 minutes, the throttle became sluggish and I had to depress it further than normal to accelerate. Engine is fine at idle (sounds and feels normal), but when I depress the throttle to increase RPM the engine speeds up as expected, then slows down and cuts out. If I take my foot off the throttle the engine returns to normal. Eventually got home, but not without some random pops or bangs from the exhaust when the engine was a little above idle, and lots of over revving when changing up a gear to keep the thing moving.

Had a look at the carburetor just now and the throttle value/plate appears to be fully open it idle. If I accelerate, the valve doesn't move but if I move it to a more closed position with my finger then the engine continues to run happily at the higher RPM. Releasing it, so that it fully opens by itself, causes the RPM to drop and engine to cut out unless I take my foot off the throttle.

Is this the normal operation of the value, indicating that something else is at fault, or do I need a new carburetor?

Many thanks in advance!

Rick

{moved post to earlier question asked on same subject - DD}
VW Polo Carburetor Problem - Drew20
Is this the pierburg carb? not sure what carbs polos had.

I am guessing that the valve that you were adjusting by hand was the choke flap. THe choke flap should be fully open (as you describe) when the engine is warm and almost fully closed on a cold start (and somewhere in between open and closed as the car warms up)

so more info is required. Did you experience problems when the engine was hot/ cold?

It sounds like a fueling issue, either running rich or lean. The choke flap being partially shut makes the engine run richer, which is necessary for cold running. So by pushing is closed you were making the engine run richer.

so it may be that you're garage overly leaned your idle mixture? but id this is the case I would expect the main problems to be when the engine was idling, not ar part throttle?

hope this helps a bit. Really need to know what carb it is, if its a pierburg 2E3 then I can probs help a bit
VW Polo Carburetor Problem - wallregg
Many thanks for replying. Absolutely no idea what carb it is, sorry! I presume its the standard Mk2 Polo one if such a thing exists.

Thinking about it, I suspect that I was adjusting the choke flap since it is the first part of the carb the incomming air gets to after the air filter.

The problem occurs regardless of temperature. When I first noticed it the engine was hot (radiator fan running) and this morning it was cold. Same symptoms both times. No problems running at idle either.

Its done three journeys of 40 miles each since the MoT so while I'd love to blame the garage I don't think I can!
VW Polo Carburetor Problem - rebel
Sounds like a partially blocked main jet to me.

If it's done a lot of work, a strip / clean / rebuild would be the way to go.
Preferably using new gaskets, diaphragms etc if still available?

DC
VW Polo Carburetor Problem - wallregg
Thanks DC, it's all beginning to make sense now. I presume that at high RPM it's running too lean because the main jet is partially or fully blocked which is why closing the choke valve improves running. At idle, the separate idle jet (am I right here?!) is fine and delivers the right amount of fuel. Accelerating happens because a third jet(?) temporarily squirts additional fuel in to provide a faster response.

I guess that, for an H-reg car with 114000 miles on the clock, it probably has done a bit of work by now! The fuel filter isn't looking too great either so I'll be changing that (can't be helping matters).

I'm reasonably mechanically minded and generally not afraid to take things apart. Is dismantling a carb something that can easily be done at home?
VW Polo Carburetor Problem - wallregg
Took the air filter housing off the top of the carb this morning and, yes, it is a Pierburg carb. Not sure what type of Pierburg, although its got "Made in West Germany" on so I'm assuming it's the original since the car was made in 1990.

Temporarily solved the problem by fixing a piece of wire over the choke valve to keep it in its 'cold engine' position (turns out that the engine operates normally when completely cold and the choke valve is nearly closed). Not the most economical way of driving I know but it'll get me to a garage if that's the way things go!

Could anyone advise me on how I'd go about cleaning the carb's fuel jets, or even removing it from the engine? It has got to be relatively simple, hasn't it?! (finger's crossed).
VW Polo Carburetor Problem - Kevz
i've had a simmilar problem on my 1.3 golf, the fault was with the springs in the choke housing, or it could be the plastic cam on the choke, this is that i'm assuming you have a simmikar 2E3 pie burger carb, if you wana take the carb oiff there 4 nuts in the bottom of the intake manifold, and disconnect any pipes or connections before removal, to take to top part of the carb the's philips screws on the top that takes it off and there you can clean you jet, let me know how you get on!
email me:kevin_jones87@msn.com
 

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