I would try a 30 mile run: preferably on fast roads. Ensure you rev it to 5,000 rpm (in lower gears) and keep at 4-5000rpm for at least 25 minutes.
this way if you have carbon deposits, they should burn away..(but ensure the engine is warm and oil and water levels are Ok before you do it).
Also try using Shell or Texaco fuel: as HJ says they do make a difference...
madf
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Hi, and thanks for the reply.
I usually use asda fuels, but filled up with shell this morning, so maybe I?ll continue to use shell for now. Really, I am too mechanically sympathetic to attempt driving like this, however, as my car has only 4 speeds, 70mph is achieved at 4000rpm anyway, and in some day to day driving situations, the engine is spinning quite fast. For this week, I'll drive the car harder than normal and if after a week, the car still idles 'erratically' then ill book it in. The garage have repaired lumpy idle before so should be able to do it again.
Thanks very much for the info.
Roberson
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Hi once again.
I can now safely say that the distributor was to blame for the poor starting when hot.
Yesterday, however, brought an entirely new problem. During a long journey yesterday, the car began to jerk when driving on small throttle openings. Thinking nothing of it, I continued, but nearing journeys end (and on one other occasion) the car lost power considerably, just as I was pulling into a side road from rest. The power was 'lost' for about 2 seconds, before the car surged, giving rather violent kangaroo hops up the road. About 50 meters later and this time turning to the left, it yet again kangarooed rather violently.
It always seemed to happen when cornering, not even on hard cornering, where the most gentile of turns gave slight 'twitching'.
When the garage fitted the new distributor, they made a bit of a mess of re-fitting the HT leads. (Not enough slack meaning they were pulling on the plug as well as some rather tight coils/bends). Could an ill-fitting HT lead cause such a fuss?
Also, the fuel filter has 50 000 miles on it, could this cause the unsteady idle as described in above entries as well as the above jerking?
Tell me what you think
Roberson
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Also, the fuel filter has 50 000 miles on it, could this cause the unsteady idle as described in above entries as well as the above jerking?
If the fuel filter has done 50,000 miles, then it wouldn't hurt to change it.
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Check the Carb to Manifold Rubberized gasket is not slit and sucking air in. Remove air filter and try to rock the carb when it is running. If it stalls etc then you will see the gasket is slip and requires a new one. Very common fault for the year. Regards Peter
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Hi,
Thanks for those replies. I was looking through past receipts today, and the filter was last changed in 1996, 63500 miles ago, which is over the 60000 recommended change. I was following the same lines as you Dynamic Dave, hence the new one I bought today for a whopping £9.00 (not bad considering its a BOSCH part)
I've heard about this gasket and haven?t checked it yet, so ill do both jobs at once. Could this be the adjustment that the garage made, that no body can seem to fathom out? I'm not very keen on running the car without the filter present, so I?ll have a good look at it and look for cracks and signs of perishing.
Thanks guys
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Are your fuel pipes elderly and perished? Try changing the ones downstream of the filter. They rot on the inside, and little bits of rubber get into the engine giving strange running problems.
If this makes a difference, have a think about the ones upstream as well.
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UPDATE...UPDATE...UPDATE...UPDATE...UPDATE...UPDATE...UPDATE...UPDATE
Hi, thought I?d keep you up to date with developments.
Today, I changed that Fuel filter, as it was really having trouble idling about 3-4 minutes after starting, and wasn't being that responsive, taking about 3-4 seconds to respond to me opening the throttle when the idle speed dropped below 500rpm. And for the fist time in ages, cut out at a roundabout.
When the old one was removed, excess fuel in the filter ran freely from one end and only dribbled from the other. When I let it dribble from either end, the fuel running out was a bit 'sooty' leaving dark grey patches on the wad of tissue. (Oh dear)
I can only assume that fuel pressure was so low, that when the 'choke' effect was shut off by the ECU, it couldn't deliver the leaner mix effectively.
On the test run after changing, it didn't cut out, or idle dead slow. When I returned with the engine hot, I sat with the engine idling and it didn't drop or fluctuate as described above. Driving the car back to the front of the house, I sat with idling again, it wasn't quite as smooth (very very slight wobbling) as before but it still didn't fluctuate, which is what I wanted rid of. It is definitely better that it was, but time will tell. I would imagine that with use, any excessive crud that had accumulated in the system would be filtered out in turn smoothing out the idle. (Any smoother I wont be able to hear or feel the engine so I may be asking for too much)
Roberson
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Everything you mention I had on my XR3i. Start OK. Get warm and wouldnt start. Running up to junctions cut out etc.
Crypton Road test and timing tweaked.
OK for a couple of days and fault back in earnest.
Mechanic then diagnosed arcing from one of the HT plug leads out of the Dissy cap and ID'd through black marks in the seat. New cap fitted. I also bought Magnatec leads and fitted and since then it has run like a sewing machine. No problems.
Appreciate many faults cause the same symptoms but have you done a full check of the leads to see if they are letting you down?
DVD
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Hi,
No, I actually have not checked the HT leads despite the fact that they are the original ones and have 100000 and 11years use on them. But at the end of the day, I have solved the starting problem (the main worry) and haven driven the car once more today, am satisfied that the filter has cured some other faults. I had not realised how poor the throttle response had been in the past, as it used to take a good 5mm to 10mm of throttle opening before it would respond, very unsmoothly.
I think that if I come into any spare money, I?ll invest in some new HT leads, but at the moment I have my eye on a new battery, so some of the money is spoken for.
When I go to work the next time, that will be a bigger test. It was these long runs, which seemed to exaggerate the idle problems.
If I were to test the HT leads, what would be the best way to go about it? I don't really have any form of specification for them, as the Haynes manual doesn?t have the resistance etc.
The engine is about as perfect as it could be really, so I'm probably nit picking
Thanks for that response
Roberson
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If you have the proper VW metal clad plug tops then the risistance is stamped on there from memory it is 5K ohms. The leads themselves are solid so you can measure each lead regardless of length and they should be whatever is on the cap. These resistors are prone ( due to the heat ) of going high resistance and could cause your rough idle. Regards Peter
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Hi Peter D, thanks for that reply,
They are the metal clad ones, so I'll have a look for the resistances on them the next time the car is running rough, IF it runs rough. I take it that the resistances are best taken when 'hot' as this is when the lead will heat up causing high readings.
Thanks once again
Roberson
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Hi, me again,
Just completed a long run, and although the idle was relatively smooth, it was back to its fluctuations. I pulled up to do a parallel park outside the house and as I was reversing in, the revs fell away, as if I had momentarily released the accelerator, before coming back to its correct speed. Doesn't seem to happen on the move, only when riding the clutch, for parking etc. It picks up smoothly and throttle response is otherwise still better than it had been.
Also, letting it idle, it still fluctuates from 800rpm to 400rpm every seven seconds or so, before returning to a steady 800. It will remain at this 800 for about 10 seconds before it fluctuates again.
This only happens after a long fastish run (say motorway). Could the HT leads cause this as I'm starting to run out of ideas?
Any ideas much appreciated
Roberson
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This latest problem - it could be a weak mixture caused by inlet manifold air leak of a connection letting in air somewhere. Engines usually behave differently when cold or at town speeds, than following a long fast run when it is fully warmed up and expansion has taken place.
Have you checked the spark plug colours? Once you return home from a decent hot run, switch off immediately and let it cool down a bit before taking the plugs out to check them. Normally a nice sand colour is OK, possibly paler with today's stricter emmission regulations. If one plug is sooty, or different from the others it may indicate a problem on that cylinder.
It is a bit of guesswork, but my theory would be:
1 - Inlet air leak somewhere, causing the idle to fluctuate up and down.
2 - HT leads may be worn out, possibly breaking down and causing a misfire - this is usually more regular with the engine shaking rather than the rising and falling you described. One way of checking if the HT leads are arcing or shorting out is to look at dusk in the engine bay with it running, you may see sparks arcing from the leads - BUT BE CAREFUL WHEN GOING ANYWHERE NEAR HT LEADS WITH ENGINE RUNNING, LOOK, DON'T TOUCH.
3- Possibly a dodgy valve clearance that closes up when the engine is hot, perhaps one of the valves is slightly burned out and leaking compression. A long shot, only possible to check if you take the head off.
It comes down to replacing the parts in sequence until the problem disappears. As you found with the fuel filter, a slight improvement resulted. New HT leads would do no harm and eliminate this area.
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While I haven't read all of the posts on,I have a sense of deja vu here.
When my wife had her 1992 Polo 1.3 CL coupe,it had a problem not too dissimilar to what has been described above.Mucho head scratching went on,and all sorts of things were suggested as to what may cause the problem of it dying whilst at standstill,and taking ages to start again.
The problem? The distributor was past it's best.New one fitted at a cost of &80,and the problem went away and never came back.
In fact,she has since part ex'd the car,and we still see it and it's still going.
Ken.
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Hi, and thanks for that brilliant response, very thorough.
When the plugs were last changed in October (the problems was present then too, I think) the colour was fine, very dark brown colour and the mechanic saw nothing much wrong with them.
Funny you should mention the lean mixture as I had forgot to mention one major thing which may answer the first point you wrote. The breather assembly has been causing a major headache since we bought the car 25000 miles ago. Every few months it kept splitting at the Cam cover outlet as it was becoming perished (soft and squidgy, not unlike old chewing gum texture) So to over-come this, we cut the split part off, which over time lead to less and less 'slack' hose. So we cut a 50cm part of the old hose off, and substituted it with better hose from a scrap yard. Not so long ago I had noticed a large hole had appeared at the joint of the new hose and old hose.
This hose is linked to other breather hoses, but is actually very close to the opening in the air filter housing, right next to the injection inlet. Could it be, therefore, that this hole is letting in excess air into throttle body?
This may coincide with why today, it surged a couple of times, usually on very small throttle openings on the overrun.
I'll check the HT leads over on the next available opportunity and may also try to temporarily plug that hole.
Am I on the right lines?
Thanks again
Roberson
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The breather system on this car is importnat and a leak in any pipe will upset the slow running considerably. The pipe that breaths into the air filter if holed or not reconnected if the the filter assembly has been removed will give you hassle as will the small vacuum pipe connection. Regards Peter
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Hi and thanks for that.
Its good that someone can confirm, with some degree of certainty that this could be the problem. I did not know that it was as important on this car as it seems. 2 People have now said that a air leak into the intake system will cause poor slow running. Ill get onto my VW specialist tomorrow and see what price they quote including fitting. I have seen two complete systems available, one for £22 and the other for £33.
Thanks again
Roberson
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UPDATE...UPDATE...UPDATE...UPDATE...UPDATE...UPDATE...UPDATE...UPDATE.
..
Had the breather pipe changed on Monday by my specialist at £38 a go, and after 150 miles, the idle is smoother and the revs dont die away during parallel parking or fluctuate (as much)
But, like I say it does still drop, but NO WHERE NEAR what it used to and OCCASIONALLY goes a bit lumpy. (New HT leads on the list I think)
More important is the vast improvement in performance that I have gained. Its far more 'zippy' now than it has been in months. Throttle responce is even more crisp and quick than ever and hills can be attacked with gusto (speed used to tail off markedly and wide throttle opening wouldn't do much)
But whats with the faster idle speed?
Roberson
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Glad to hear of an improvement. Perhaps the faster idle speed is a result of the air leak being fixed, the engine running more efficiently. If the idle speed was previously set with the leak problem it may have been set to compensate for the problem. Now the problem is fixed and engine running better the setting may be artificially high, just needs turning down a bit from the adjusting screw?
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Hi, and thanks for the reply.
I too think that it is a result of the air leak being fixed. But if only the remedy was that simple :-) The AAU engined Polos have no manual adjustment of the idle speed, and it only seems to do it when the engine is properly warm. I dont know if there is ANY way it can be adjusted as the ECU is really too simple to allow for computer altering.
(by 'fast' I mean 1000-1100 max otherwise it remain at 750 all of the other times)
Roberson
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Okay so it's seven years since the last post on this topic, but I still found it very helpful in finding the cause of my Polo's not starting when hot problem. The car is 17 now and has done 155K. Replacing the distributor has fixed it, I fitted a used Bosch unit with exactly the same number, that came off a MK3 Golf. I did try a new one but that broke half a mile down the road on its test run. The drive peg sheared off! Beware copies made with low grade materials.
I dismantled my old distributor to see what's in it. The electrical bit that causes the problem is the Hall Sender. This is a magnetic sensor that switches on/off as the cut outs in the steel cup rotate through it's field. To dismantle the distributor you need to drive out the split pin that holds the peg assembly in place. Once that is out, it all slides off the spindle. The sender is held by two screws. Why it fails when hot is still a mystery though. I did notice that the fibre washer/spacer in there had broken up and little bits of it were spread around in there.
Oh and ignore your Haynes manual when it says you have to get the engine at TDC before you take the distributor off. The offset peg that drives the rotor spindle will only allow the rotor to be pointing exactly where it was when you took the dizzy off. But you might want to mark the position of the bolts so that the advance adjustment is the same.
Gene
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Don't ignore the haynes manual if you are fitting a new distributor Gene. I tried to fit an after market disi to my 1993 polo and it went on 180 degrees wrong . The problem was that the plastic disc and retaining dowel that slots into the camshaft had been placed on the unit 180 degrees out at the manufacturers . This is easily done when you look at it.
The result of this was that the hall sensor sent electricity to the ecu, there was a spark from the plugs and fuel delivery (which there hadn't been previously with the original disi ) but the enginre wouldn't start because it had been timed up 180 degrees wrong
After much head scratching as to why the car wouldn't start , I took the unit off and compared it with the old unit .This verified the problem .With the locating dowel placed at twelve o'clock the rotor arms pointed in different directions .
So at least compare the new unit with the old one
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