Issues with the idle in wet conditions

Technical Area Engine, Transmission, Exhaust etc
2

Hi everyone,

I wasn’t sure whether to post this under electrics category or engine, but I’m more inclined to believe it’s the first one.
So, here’s a huge plea for help from a newbie.

I’ve had my Mk2 for a good couple of months. Since I’ve had her, I’ve swapped full exhaust, engine temp sensor, MAF, HT leads, ISC valve and as of past few days added the EGR delete.
Spark plugs and battery were changed not long ago before I got her too. Alternator has been checked in the past 2 months and is in good nick.

I am yet to have her up and running properly, and I’m running out of ideas.

I have an issue with the idle on the start, when the air (and the car) is damp or when it’s raining. It’s hovering around the 400 mark at best and takes a lot of effort to get her going. The engine shakes quite significantly. In the meantime I can get a good amount of white smoke coming out of the exhaust.
After a solid few minutes of revving her up and driving, she’s running perfectly fine, as if nothing’s wrong. Until it does happen though, there’s a significant lack of power. The revs go up to 4000 if I press the gas pedal to the floor, but my max speed will stay at no more than 20-25mph, if that. When I press the clutch, the revs drop to no more than 400 while shaking, even cutting off completely the other day. Also, there’s plenty of misfiring going on.

Same happens when I go to a car wash, hence why I believe it’s to do with electrics and a leak/short somewhere, and possibly somewhere fairly accessible (although I looked multiple times and still came back with no reasonable ideas)? 

My next go-to was coil pack and o2 sensor, but quite honestly I feel like I’m wandering in the dark.

I will be very grateful for any clues, because I’m driving myself crazy with this thing now .

3

Have you replaced the spark plugs and checked for damp in the plug recesses.

 

Ignore me, i’ve just re-read your post.

4

If your spending that sort of money on parts to make it right, why not take it to a MX5 specialist and get them to find the fault instead of feeling around in the dark.

This will save you a lot of money as adding bit by but in the hope that that will fix it is wasting your time and money. As your first post it does not say were you are in the country, add this to your reply and someone will recommend a good local garage to you to sort the problem so you can enjoy your car.

John

5

Could well be a coil pack issue, especially if it’s an earlier MKII.

6

John, sorry - located in Birmingham. So far any smaller jobs were done between myself and a friend and bigger ones (exhaust) were done in a garage due to lack of proper workspace. 

I’ll probably check over the coilpack with a multimeter and depending on the result think of handing it over for someone else for a fix. This moisture issue only became apparent fairly recently, after we’ve eliminated few other things.

I think nearest specialist is in Nuneaton unless anyone knows of anyone closer? 

7

Check and clean all your earth straps

8

Thank you Hilux, will do!

9

I presume that you have sprayed a moisture repellent such as WD40 over the plugs and coil packs.

Have you removed the plugs to check their condition and security of connections?

Have you also checked the ECU for signs of damp?