Car jerky and lumpy in the wet when starting from cold...plus strange sound

[matth76 1]

Hi

Has anyone else find their car really lumpy and noticeably jerky when it is cold and wet for the first five minutes? Initially when I set off from cold the oil temp screen is blank with a couple of lines for the first 5 minutes. I find the “jerkyness” disappears as soon as the oil temperature on the trip computer starts showing a number. After that it is fine. I assume it is the Mass Air Flow sensor taking time to start working. Today I was testing pressing the accelerator pedal during this “jerky” period and I could hear a brief and faint very quick clunking / knock noise underneath the car …for a fraction of a second – it did it a couple of times each time I tested flooring the accelerator briefly. I’ve noticed it before when I accelerate briefly when the engine is cold and in this state when the engine is very cold. It doesn’t happen often at all – normally when it is wet and cold (like today) – I’ve only noticed it when I have had to accelerate fast out of a junction or roundabout after leaving the house on way to work. Does everyone else experience the same kind of jerkyness and has anyone else ever experienced the faint knocking sound? What could the sound be? The car is absolutely fine once the temp starts showing a number. I’m not overly worried as I assume it is the maf sensor. I find in warm whether when the car is cold it is very slightly jerky but no where near to the same extent … but I always try to stay off the power anyway for the first ten to fifteen minutes in any journey to let it warm up.

Cheers for any info.

Matt

[shail 0]

As its getting wet these days this sort of behavior can happen due to damp in the HT/Spark side of things. Check that the HT leads are connected firmly into the coil pack/distributor. Also check for cracks in the coil pack housing.

Ive got a hair line crack in the coil pack which makes the car judder slightly when damp.

As the engine gets hot, the damp evaporates and car starts to behave itself.

[matth76 1]

Thanks for your reply... it's very odd that the slight juddery behaviour disappeard exactly as soon as a number appeard on the temp gage...which was still very cold at only 52 degrees...but it was totally smooth all of a sudden... both this morning and evening. The spark plugs are deep inside the top of the engine (very unusual) and seem to be very hard to actually see... Where in the engine is the coil pack located? Will new leads fix this problem...or do I need new spark plugs as well? How easy are leads to fit to the spark plugs... (I don't have any special tools to remove spark plugs!) as I think its going to be tough for me to get to even the top of the spark plugs to remove the leads... I assume they would simply "un-clip" from the top of the spark plugs and the same for the ones that go to the coil pack (is this the same as the distributor?)

[shail 0]

To remove the HT leads from the top of the spark plugs you need a special tool, or else you will knacker your HT leads trying to pull them out. The Golf came with the tool - Do you have a plastic tube like thing attached to the bonnet stay? If you have then thats the tool, if not you can buy them seperatly. Note: If you are fortunate enough to still have the tool, remember its plastic and will melt if used on a hot engine.

The coil pack is bolted to the RHS of the engine (it has all the HT leads going into it). The pack about 6" x 4" and is black. However, you may not have a coilpack and have a distributor instead (depending on age of car). If you have a coilpack wait until it misbehaves and check for sparks coming from the coil pack. If you can see sparks arcing from the pack onto the outside of an HT lead, you probaly have a cracked casing which you can temporarily fix by slapping some silicone grease over the crack (make sure you've taken the key out the ignition).

If its a distributor - these can sometines need taking off and cleaning. Again, take key out of the ignition.

You could get some new leads, but these are expensive. If you can get the leads out, inspect each one. Im quite sure that VW sell each HT lead seperatly incase you have one knackered lead.

Also, by the time the oild gets to 52 deg, the water temp will be a lot higher - just check the water temp gauge.

[Buzzark 0]

The oil temp is merely a co-incidence, nothing actually happens as a result of it coming into a displayable range.

It's just a sign that the engine is warming up.

As the others have said, it does sound like damp.

Most garages can test HT leads, the kit isn't that expensive.

Wear rubber gloves when working around HT leads, coils, dizzies and coil packs. Had a jolt from one once, it is NOT pleasant! You can end up very dead if unlucky.

Hot wire MAF sensors (meter actually) are good to go in about 2-3 seconds. They don't require a warm up period.

[petervr6 0]

thats what that fat bit on the bonnet stay is i was woundering why that bit was bigger.lol

[matth76 1]

MY car's a 1997 ...does that mean it has a coilpack? What could the strange sound be that I mentioned? It's a strange faint knock and only happens for a fraction of a second - it is as though I have gone over something in the car - it happens when it is very cold as described above when I press the accelerater to the floor (which I don't try to do when it's cold). It's not something really bad like my car running lean and "pinking"?? My car runs really smooth when it has warmed up though.

[Buzzark 0]

The knock could be anything, bit difficult without seeing the car. Hard enough when you've got it in front of you.

It COULD be something as daft as the exhaust just touching the body when cold - don't forget they move a bit as they heat up. Cold might put it right next to the bodywork. I've seen this on 3-4 cars of different makes over the years.

It's unlikely to be pinking when running cold as it's probably on choke at that point.