A lad I help now and again with his (80k) 1.4 Polo just sent me this:
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He says it only misfires / brings up the EML under moderate to heavy acceleration and if you back off it runs ok.
He changed the oil / filter a month ago and the air filter a week ago and (FWIW) I helped him change (well, refit the new) the pollen filter yesterday. These were just to give it a basic service, not because of any faults etc.
Before he does anything else (like change the plugs), does anyone know of anything that might give those sort of symptoms on that particular engine / car please?
A lad (hooligan) once asked me to look at a Golf with a similar fault, I asked a friend with more experience about it and he immediately said fuel pressure low, replace fuel pump. As I am naturally conservative i checked fuel pressure and found that it dropped off as the revs rose, clamping the return pipe improved things. So I took out the pump, as I like fixing things I dismantled it and found that there is a filter inside the pump which was clogged. A clean out and rebuild and away it went. I don't know if the Polo is the same as the Golf, but it is quite likely. Try the easy stuff first (plugs). Reading the codes that the EML puts up might help. (I don't remember what they said on the Golf)
IIRC No. 4 is at the farthest end of the fuel rail, I guess it would get the lowest amount of fuel pressure after feeding the first three. I would put new plugs in first or if they look really mint swap them around to see if the fault moves. Back then it would have HT leads and a distributor cap that could also be problematic.
Because if it was a 'known thing' that was nothing to do with the plugs then there can sometimes be more to doing things like changing plugs than one might hope ... like 'they are known to snap off in the head' and then he would be into a whole world of hurt for 'no reason'. [1]
FWIW, he has got some plugs on order and I've also advise he get a torque wrench as 'most people' have no idea what constitutes (say)
15nm. ;-)
He said it was 'much better' this morning so could it (just) be some bad fuel?
Cheers, T i m
[1] I had a very similar thing happen on the Meriva a bit back (I think I posted about it here) and after a couple of trips round the block it cleared up and hasn't re-appeared since. I reset the light with Torque Pro and my phone and I didn't change the plugs or anything. ;-)
Do you mean on the OP's car? I'm pretty sure it would be coil-on-plug.
If the OP valued money over time, and has a code-reader, the first step would be to swap plugs on cylinder 4 to somewhere else, then do the same with the coil.
After that, he could check the fuel rail pressure. If within tolerance, swap the no.4 injector with another.
Finally, those engines are known to burn out exhaust valves, so a compression check would be a worthwhile test.
Ok. He did ask about changing any fuel filters as part of a service and I suggested 'generally no' and the symptoms would (typically) be faltering when traveling at a prolonged high speed?
(as am I, especially when one can do unnecessary work or incur unnecessary cost).
Isn't that likely to some degree or not?
Ok.
And in most cases you have 'little to lose' eh. [1]
Result. ;-) [2]
To good thing was that it *was* re-buildable. So often these days stuff is 'snap together' and breaks when you strip it down (as the plastic gets old / brittle etc).
Ok. And would 80k miles also fit that scenario would you think?
Understood.
P0304. Cylinder 4 misfire.
Cheers, T i m
[1] A mate paid 5 bags for a walk-in twin shower with a glass wall / door less than a year ago. The door hits the floor and he asked me to have a look at it for him. I was concerned about 'what if I break it' and he said 'it's fkd anyway so ...'. ;-)
[2] Ford 2000E (Auto) on our (Dad and me as a boy) way from London to Sth Wales to buy and tow home a small sailing cruiser. On the way down it started faltering up the hills and after replacing several things along the way (plugs, leads, distributor cap, points, rotor, fuel pump and filler cap ...) we found ourselves in a small Welsh garage and someone who had experience of this model and age. We drained most the fuel out and he pulled a filter off the fuel pickup pipe and said 'that's yer problem'. When we asked what the solution was he threw the filter across the workshop and we put it back together and the petrol back in and carried on our journey with no issues. ;-)
1) It's not my car and 2) there is more to this than money or time. It is car owned by a lad you is *very* competent at learning / doing many things (like tablet / phone / console repairs) and it *seeing* if car maintenance is also something he could do and would be interested in (for himself / mates etc).
So, he's looking at me for some basic support / guidance and I'm keen to insure he doesn't rush into doing stuff that he might later regret.
He has on his phone if that counts? I have some USB / Laptop diagnostic solutions that may be better if his phone / BT OBD dongle solution aren't.
Understood ... and something that we have already discussed (and he's ordered the plugs as he was looking to change them in any case (for the experience as much as anything else).
I'm not sure how one would do that and I don't have the kit to help him do so.
That sounds like it is getting a bit deep but I think I understand from here previously that isn't as tricky a job as it might be with a diesel etc.
(I think he's already Googled that) I may have the kit to help him with that so could be done along with the plug change (assuming my compression tester is the right thread etc).
Cheers, T i m
p.s. I re-fitted his pollen filter in return for him swapping a LCD screen on a laptop for me and they both took us about the same time. He asked me to help because he's all new to car maintenance and didn't 'think' to look how it came apart he did so. So I used 'first principals' to work it out myself (as I wasn't there when it came out). ;-)
Again, one often decides if to 'have a look' based on many factors. If it's cheap it's often not worth bothering with, similar if it's not too expensive but very complicated or if a positive outcome is unlikely. If you have someone who needs the car back desperately you might offset the time or cost for speed etc etc.
Because I have more than one of each type of vehicle I generally have the luxury of time to explore the various solutions before committing any money (especially sending good money after bad). Like, I had no issue spending the 200 odd quid to have the Meriva ECU rebuilt I would have been miffed if I'd also replaced the crank position sensor or BCM for 'no reason'.
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