Difficulty cold starting

[TomG]

Hi all,
My g/fs rev 5 N/A UK spec MR2 has been difficult to start since the weather started getting colder. Have just replaced the battery with a Varta, the engine turns over fine but can take many attempts to start when cold. When I finally started it yesterday the engine was a bit hesitant at about 2000rpm but once warmed up it was fine. Starting the engine when warm is also fine. Idle is stable when hot and cold. Starting with the throttle part open doesn't seem to make any difference. The car did have a K&N filter fitted but I refitted the standard air box yesterday.

I've ordered a set of NGK BKR6EIX as I'm not sure what plugs it currently has in there. Would be nice if they solve it but I suspect they won't!

What are the next things I should be looking at?

Thanks!

[Poker Face]

Coil pack would be my guess, they cracking and suffer in the cold and wet giving you a weak spark.
You can get cheap aftermarket ones but the oem one is meant to be better from what I have read on here same with rotor arm and dizzy cap.

[TomG]

Cheers for the reply, think I know the bit you are talking about. Is it easy to remove?

[Poker Face]

I found it easier to take the bracket that it's mounted on off first as the screws were all corroded. I'm not sure if it is mounted in the same place as it is on a turbo but you can Google that. It would be worth getting some new screws at the same time, I was getting a bad earth to the bracket as well.

Jim

[Mullen]

Coil pack is under the engine bay fuse box.
Unscrew that and push it out of the way to get access to the two screws in the firewall that hold it on.
It's a bit fiddly but not hard.

[mrturbotom]

I'd be looking at a coolant temp sensor and intake temp sensor

[TomG]

I'd be looking at a coolant temp sensor and intake temp sensor

Would these show up fault codes? What will happen if they are disconnected?

I found the air intake temp sensor the other day when re-fitting the airbox, not sure where the CTS is yet. The water temp on the dash is working fine - could the CTS still be faulty?

[Mullen]

CTS is the green sensor round the back/underneath the throttle body.
You'll need a deep 19mm socket to get at it.
They're £14 ish from Camskill - I replaced mine recently and the old one crumbled to dust as it came out, so might be worth replacing it regardless just to be sure.

[TomG]

CTS is the green sensor round the back/underneath the throttle body.
You'll need a deep 19mm socket to get at it.
They're £14 ish from Camskill - I replaced mine recently and the old one crumbled to dust as it came out, so might be worth replacing it regardless just to be sure.

Cheers. Was your coolant temperature gauge on the dash normal before the replacement?

Any tips for replacing it and minimising coolant loss? Is there a rubber seal round it to replace at the same time?

[Mullen]

The green sensor isn't the dash one, that's the black one next to it.
The green CTS is for the ECU.
Provided you don't mess about you don't lose any coolant swapping it over, or a couple of drips at worst.
The new one will have a washer with it & that's all you need.

[TomG]

Thanks, looks like the temp sensor would be a good place to start then as they are quite cheap.

Would the CTS or coil pack cause any other symptoms than cold starting problems?

[TomG]

Yesterday the car was down on power after a cold start - would this point at one part in particular being faulty?

I will inspect the ignition coil at the weekend.