OT - 1998 VW Polo 1.6 stalling/temperature issues

[Etwenty1 45]

have you checked the TPS ? reset the timing?

[gjm 3258]

have you checked the TPS ? reset the timing?

Not looked at TPS yet. Timing may not be quite spot-on, but it's less than 1 degree out.

Worryingly, VW are on record as saying that it may be necessary to replace the ECU to resolve some issues such as these. Not that there was a recall or anything like that, of course...

[Etwenty1 45]

I tried to school up on these while fixing my sisters one, luckily for me a new throttle body fixed a cold stalling issue. Its still not feeling quite 100% but runs ok.

I see (read on the googlenet) a "throttle body alignment" is recommended if you have cleaned/removed the throttle body.

Will be following with interest to see how you get on.

[2052NV 43]

im guessing there may be a idle adaption you do with the tester, im sure qualitat would know

[gjm 3258]

I keep being told the problems we are having aren't related to the throttle body.

I've changed the vacuum pipes, the coil, the plugs (why are spark plugs so expensive here? $30 each from Repco or SCA, or £1.48 - say $3 - in the UK!), air filter, and the dizzy cap. The rotor arm is a Bosch and hasn't been replaced because the one I received had a too small bore to fit, but the Bosch one looks pretty good. The changes I've made all seemed to make a small difference, but haven't really resolved anything.

So, I've checked the leads. The leads to the spark plugs are all ~5.7kΩ; the coil lead is about 2.2kΩ. Without a detailed manual I can't verify if these are correct. (These figures are a simple measurement taken with a multimeter on a 20kΩ range and the leads off the car.)

Most troubling is that the car has become harder to start in the mornings. It turns over fast enough, but then fires on 1, perhaps 2 cylinders. Sometimes I can coax it into bringing the other cylinders to life, sometimes it stalls. Before starting the engine I can hear the fuel pump running, but it doesn't seem to matter whether I let the pump run 'til it cuts out (3 seconds or so) before starting, or just go for it.

Once warmed through the engine will normally now idle albeit at lower revs (about 600rpm) than is correct. Occasionally, it will stall, as it did entering the roundabout at Taupiri, in traffic, yesterday morning. Fortunately a slick out of gear, ignition off, ignition on process saw the engine fire and run immediately, but it's hardly ideal especially when navigating a roundabout with a sudden loss of power steering. Good job it's not a heavy car.

Also, the hesitation is becoming more prevalent. Cruising at 90-100km/h the engine seems to purr very nicely, except that every once in a while it feels as though it cuts out for a split second. I can't tell - don't know how to tell - if this is due to a fuel or electrical issue. Hence replacement of the coil and my checking the leads.

The only thing I can see that I'm not happy about is the emulsion in the crankcase breather pipe that connects to the air filter box. There's no other signs of any sort of problem - no drop in coolant, no discolouration of the oil, no emulsion on inside of the rocker cover or underside of the oil filler cap.

It doesn't appear to be using silly amounts of fuel: economy is around 14km per litre, or 7 litres per 100km. That's most of 40mpg in English, which is quite acceptable.

I've not checked the timing but will do so. Kinda need to get a timing light first.

So, despite assertions to the contrary, I'm probably back to pulling the throttle body off the car; it has been removed before at some point, as evidenced by mismatched bolts used to secure it. 3 Allen socket head bolts, and one crosshead. There should be a ring gasket on the base which should be replaced, so I'll source one of those first.

If that doesn't improve things, there could be a very cheap, sort-of-running, Polo on the market.

If anyone has any suggestions for what to try in order to fix it, please say!

[elmarco 56]

Cutting out at running speed sounds fuel related to me (had similar cutouts in our Golf which was the fuel pump & got progressively worse until it was downright dangerous). Is it getting fuel to all cylinders at cold start? Have you pulled the plugs when its hard starting? Are they wet?

[gjm 3258]

Fuel-related problems do seem most likely. This isn't like a miss, where one cylinder drops out - it is more like everything briefly stops. It actually feels a little like a 2-stroke engine just before it 'nips up'.

I'll have a look in the morning - take the coil out of the circuit, turn the engine over and pull the plugs.

Seems to start OK when it's warmed up, though.

[gjm 3258]

Done a bit more investigating. The only really positive thing to be said though is that every little thing I do, seems to improve things just a little bit.

Removed the throttle body. Price for the sealing washer/o-ring? $22. OEM part in Europe is the equivalent of $4... Shipping kills any advantage, of course.

Carefully cleaned the bottom part of the throttle body, ensuring I didn't get cleaner on the plastic parts on the side of the throttle body. Replace.

Warmed the engine, removed the plugs, checked compression. 1, 2, 4 are all 150-155; 3 is around 145-150. Not enough difference to cause a problem.

I've managed to get things to the point where the engine does now tickover when warm, albeit at around 550-600rpm. Way down on what it should be, and not good enough to tickover when cold.

Unfortunately, at the moment, chief suspect is an ISV (Idle stabilisation valve) issue. I think this is under the secure plastic cover on the side of the throttle body, and I can't find anything anywhere about checking or repairing it. Throttle body replacement is too expensive to be considered.

'Cured' the starting problem after experimentation. A tiny bit of throttle when starting means it again starts first time. (But apparently this will throw an error code - throttle while starting.) Stalling can be avoided by left foot braking while retaining that tiny bit of throttle, although this is typically no longer required. Adjusting the throttle cable isn't really an option as the adjustment available is too coarse and the engine will 'tickover' at 1200rpm+.

Theoretically the ISV can be reset by turning the ignition key to position 3 (lights showing on dash) and leaving it there for between 15 seconds and 3 minutes, depending on the source of info. Tried that, of course, but it has made no difference.

The occasional hesitation when driving (constant speed, etc) is still there. I think this is probably unrelated to the low tickover/poor starting issues. I'll check the fuel pump relay, and maybe investigate replacing the in-tank fuel pump. ($240+ here, equivalent of <<$100 in Europe so that part will be imported if I go ahead.)

When running, it's great! Economy is good, engine is smooth and revs freely, gear changes are sweet.

Oh - all four plugs get wet when starting, so there is fuel getting through. Start and run the engine for a few seconds and the plugs are black; pull the plugs after a reasonable run and they are an appropriate grey colour. Possibly just on the hot side of OK, but nothing to be concerned about.

The starting thing is odd. The engine turns over fast enough, but just doesn't fire on all four cylinders - it sounds like it starts on 2, then a third cuts in, and then the 4th at which point everything is smooth and lovely. I've not replaced the leads... Maybe that would also help? I was going to try an alternative set but the only spares I have won't fit. I'll also check the voltage at the battery while turning the engine over.

[vtgts300kw 90]

Do you have a workshop manual for the Polo? Or you doing things through experience on other cars?

I've been looking online for one and can't find anything. And the Yanks never got this model, so there is an absence of good online "tutorials".

[gjm 3258]

I'm using a combination of 30 years experience working on cars and info gleaned from internet research. There is a .pdf of the VW Polo Haynes manual around, but it's not great. Pages are in the wrong order, and reproduction quality is OK rather than good. There's a manual referring to the older cars, but they didn't (I don't think) get the multi-point injection.

It's a fairly basic engine which somehow seems to have been poorly implemented. The problems I'm having are less severe than some described on various forums, but many agree it is the throttle body (design) that causes problems. VW are no help - typical dealer response is to replace, replace, replace, rather than diagnose correctly and fix.

Of course, the car is now 16 years old, but the issues we're having now are described as being fairly commonplace even 10 years ago. Take that with a pinch of salt - VW produced hundreds of thousands of these cars and variants or derivatives, and reports of a few dozen problems could be giving a false perspective.

[vtgts300kw 90]

I'm using a combination of 30 years experience working on cars and info gleaned from internet research. There is a .pdf of the VW Polo Haynes manual around, but it's not great. Pages are in the wrong order, and reproduction quality is OK rather than good. There's a manual referring to the older cars, but they didn't (I don't think) get the multi-point injection.

It's a fairly basic engine which somehow seems to have been poorly implemented. The problems I'm having are less severe than some described on various forums, but many agree it is the throttle body (design) that causes problems. VW are no help - typical dealer response is to replace, replace, replace, rather than diagnose correctly and fix.

Of course, the car is now 16 years old, but the issues we're having now are described as being fairly commonplace even 10 years ago. Take that with a pinch of salt - VW produced hundreds of thousands of these cars and variants or derivatives, and reports of a few dozen problems could be giving a false perspective.

Ours has been pretty good considering, nothing terribly major, most things have just been due to it's age. It leaks oil like a sieve, but it's easier to just top it up when needed.

[Etwenty1 45]

have a look at : http://www.clubpolo.co.uk/forum/index.php?showtopic=109802

edited link to idle and timing DIY

Edited July 15, 2014 by etwenty1

[gjm 3258]

have a look at : http://www.clubpolo.co.uk/forum/index.php?showtopic=109802

edited link to idle and timing DIY

Thanks Chris.

I have seen that, but (to be honest) not followed it through.

Is the ISV is where the thread says it is, I have been looking in the wrong place. I also have no idea how to get to it! Up in the air would probably help but isn't readily possible.

The weekend is coming. Perhaps I'll write off another day in pursuit of a car that runs properly.

[gjm 3258]

The hesitation at highway speeds seems to only happen when the engine is warmed through.

[gjm 3258]

Replaced the fuel filter. It's running a little bit better. Again. Hardly surprising - pouring fuel from the 'input' side of the filter showed it to be quite dirty, and while the filter appeared to still be doing it's job, it could well be original. (It's not a lot of fun to change, despite appearing to be a straightforward task.)

The idle thing is getting more tricky. I tried following the instructions on the link above, but there are one or two issues. Like... Just where is the base idle control screw on this car? I had the throttle body off again, and there is nothing obvious. Absolutely no adjustment, other than on the throttle cable. There is a plastic cover on one side which while it has torx-head bolts through it, also has peened over plastic plugs locating it. Obviously not designed to be a service item. (The throttle body is by VDO.)

OK. ISV next, then.

I really want to get back to working on the Mercedes! And there is just the teensiest possibility that the BMW count in the driveway could double. To two. I'm a-plannin' an' a-schemin' ways to make that work.

Edited July 26, 2014 by gjm

[gjm 3258]

I had a really good look for the ISV at the weekend. I think it is under the inlet manifold, making it a nightmare to get to from above or below. I've got as far as possibly being able to touch it - I don't really want to remove the inlet manifold.

I took the plastic cover off the side of the throttle body too:

_

There is no sign of any method of adjusting idle, base or otherwise, on this TB. I think there is a motor in the side of the throttle body which is designed to rotate the large beige cog to open the throttle at idle or when cold. The first picture shows a connector (secured by two torx screws) above the throat: this takes a moulded 4 (or 6) pin plug, and I'd expect receives an input from the ISV via an ECU. There's no easy way to disassemble the gearing on the side of the TB as the silver cam-shaped piece on the top is peened to the shaft.

Still runs well when I put it back together, so I've not broken anything irrepairably (yet).

So that's as far as I've got with the tickover issue.

The hesitation while driving... Could this be due to a vacuum building up in the fuel tank? I need to pay more attention when driving to see if that's the case. Full tank/half tank, and so on. It certainly only seems to happen after driving for a while, which (I'm guessing) may have allowed a vacuum to build up.

[87HSM 0]

Did you resolve this issue? I bought one of these for my daughter, did the cam belt and other maintenance items and have been having exactly the same issues.

We are in Wellington and she is up in Palmerston North at Massey. I am off up there this weekend with a replacement throttle body to see if that cures the problem.

This has to be the most unreliable car I have ever owned and the most difficult to diagnose. My local auto electrician can't find anything wrong with it and every time we take it to him it runs fine. Next day..... Last time I was there he had another one with the same problem. The bugger is that other than this it is a great little car for her.

Cheers

Martin

[gjm 3258]

Check the fuel filter - this is an easy swap and could help.

If not, it could be the in-tank fuel pump. These have 'history'.

[benpaul12 62]

Checked the fuel pump and relay switch? I had the same year, same engine Polo for awhile (before I got rid of the unreliable f**ker), had stalling and cutting out issues for awhile until it reached cutting out every 100 metres...

[gjm 3258]

Ours very rarely cut out, but fuel starvation (pump) turned out to be the main issue.

After a few 0000kms, throttle body cleaning, fuel filter replacement and so on all improved things, but didn't address the underlying issue.

Great car now! (Although having fixed it, we sold it...)

[87HSM 0]

Thanks for the suggestions.

I retreived the car from Palmy this morning and apart from a slow idle (450) it ran ok to Wellington. I replaced the throttle body with another one and now idling at about 650. My auto electrician is still adamant it is the hall sensor in the distributor so I might swap that out too as I have a spare. I will get a fuel filter this afternoon too as that can't hurt.

I have swapped the fuel pump relay for another one so I suppose by process of elimination I will get there eventually.