I have a Jetta 2.0L MK4 and had this problem as well. I believe the engines and ignition system are similar or equivalent. The key word you stated is "damp" weather. So, in damp weather the surfaces of almost everything in the engine compartment has a microscopic coating of water on it. Also, almost every man-made material absorbs some water. So, in damp weather the plug wires and coil pack can have a microscopic film of water and/or will absorb some moisture in their insulating materials. Any micro cracks or internal carbon tracks in the insulation can offer a path of least resistance in this moist environment. This can cause the high voltage to find a partial short-circuit path or a complete short-circuit path to ground before reaching the plugs, hence causing misfiring. The heat of the engine will dry out the moisture and make the problem go away temporarily. So, to troubleshoot the problem do the following: At night and in the dark, and with the car engine just started in damp weather, look for arcing. If arcing is observed you found the problem! It not, let the heat of the engine dry out the ignition system and allow the engine to run smoothly. (Temporarily close the hood to hasten this process) Use a spray water bottle with ordinary tap water (not distilled water) to lightly spray the wires and coil pack so that you can look for arcing. DO NOT TOUCH THE CAR WHILE SPRAYING! Spray in an orderly manner to try to pinpoint the problem. It is possible that you may not see the arcing but the engine may misfire when sprayed. This usually finds an issue with a weaken insulation system. If not, I have seen on this same Jetta a weak coil pack output on 1 of 4 coil outputs causing an intermittent misfiring, more so in damp weather. In this case use an in-line neon plug tester to look at the neon "glow" on each plug wire to see if any of the coil outputs are weaker than the rest. I had to replace the coil pack in this instance and it resolved the problem. I hope this information helps!
SOURCE: Our 1999 blazer seems to have starting issues only
I'd have a free scan at parts store for any trouble codes first , just in case, if no codes come up then I'd consider a new cap & wire set. One of , or the most common problem with hard start in wet/damp weather is plug wires & cap, especially if they haven't been changed that you know of since new.
SOURCE: engine misfires badly after cruising a while at 3k revs,
Try to check the computer box and check if it is working and check the timing belt as well make sure it is properly tune up.
I’m happy to assist further over the phone at https://www.6ya.com/expert/ramy_d9e7ebea3891f482
SOURCE: MY vw diesel Takes forever to start after parking
replace the glow plug relay its faulty.Hope that was helpfull.
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