Idle trouble when cold - 1.8 16V 1990

[shaunje 10]

Hi people, I have recently bought myself an H-reg 1.8 16v and since this morning I have been having idle issues with it.

 

This morning I came out ready to leave, I turned the key and it took a bit of persuasion with the accellerator to get the car to start. It then would not idle at all unless I applied pressure to the accelerator pedal. Once the car has warmed up (closer to operating temp) there has been no problem at all, and is able to be turned off and started again with no problem - this only happens when it is cold.

 

Has anybody experienced this, and is anyone able to shed a bit of light on a possible problem? I'm not sure if there is some kind of air by-pass valve type thing that may not be functioning correctly, and I've also heard that a coolant temp. sensor could throw it out of line?

 

 

 

While I'm posting, it seems to be disgusting on fuel, and has murdered £110 since thursday last week in fuel under careful driving conditions (I'm a student and it's been snowy). I understand with the engine size, the age of the vehicle and the K-Jet injection it's going to be a wee bit thirsty, but I was'nt expecting it to be quite this bad! It also smells a bit petroly when I start it. I am thinking a fuel filter change might do it some good? Other than that, I'm not sure if there is something not quite right? The engine tends to 'pink' slightly under heavy acceleration above 3500RPM too.

 

Hopefully someone can shed some light on something:scratch:... Cheers, Shaun! :)

[davidwort 0]

there's a few potential suspects, the thermotimeswitch on the side of the head (large sensor) may be old and giving an incorrect voltage, this would affect the cold start valve (the 5th injector that squirts horizontally into the inlet manifold)

It could also be the cold start injector itself or the idle stabalisation valve (ISV) the cylindrical metal unit on the right hand end of the head with an elec. connector and breather pipes in/out of it. The isv may not be operating correctly when very cold (it's an electromagnet so will weaken with age) and so the air bleed into the inlet is incorrect, causing stalling/lumpy, bouncing idle.

[shaunje 10]

Nice one, i'll have a look through what you've described and see if I can find anything. Cheers!

[shaunje 10]

Anybody else had any trouble?

[Corradochris16v 10]

The owner before me told me he had this problem and changed the idle control valve and various sensors but it turnd out to be the fifth injector also mine smells of petrol as does my mates 16v mk2golf I always thought it must be due to the age of the engine but itwould be nice if there was a cure to stop the smell am sure they wernt like that from the factory.

Hope you get it sorted.

[shaunje 10]

also mine smells of petrol as does my mates 16v mk2golf I always thought it must be due to the age of the engine but itwould be nice if there was a cure to stop the smell am sure they wernt like that from the factory.

Hope you get it sorted.

 

I'm talking to the point where people are coming over and telling me it stinks of fuel :/. I have got on the floor to look for leaks a couple of times now lol

[Corradochris16v 10]

Yeah that don't sound right have you checked the lines and the tank? You might have a small leak which is also causing the idle problems?

[tony_ack 0]

Could be a long, long list of things unfortunately!

 

Let's work through this logically...

Thermotime switch richens the mixture by firing the 5th injector for the first few seconds of cranking, if the engine is cold, and then switches off. This could be causing the car to struggle to start, but shouldn't be causing rough idle beyond a the first few seconds.

 

WUR problems could be causing problems during warm-up, and could also cause poor running when warm. I don't think this is the issue, but it's worth testing it to make sure. Undo the plug and check the resistance across the terminals on the WUR - I can't remember the exact values but I think it should be somewhere between 22 and 28 ohms?

 

5th injector leaking/stuck open could be causing problems, and make it a little tricky to start, and cause bad running. This could also manifest itself when warm though, and if your 5th injector was leaking, then you'd expect it to run rich when warm, but it sounds like yours is running lean if it's pinking at 3500rpm. It could be though that someone has adjusted the CO/idle/timing to adapt the car to run with the problem.

 

Timing/CO/idle - may be worth getting these checked after you've checked everything else. A healthy k-jet system shouldn't be pinking at 3500rpm. Set idle to about 1000rpm, CO to 2.0% and timing to 6 deg BTDC at idle when the engine is warm. If this works out okay, you may be able to advance it a little to 8 deg BTDC if you run it on super.

 

Air leaks - I'd check all the vac piping for perishing and leaks. It's not expensive from WV, so may be worth replacing. I don't think this on its own would cause the cold start problem, but it could be making things worse and the cause of your lean running

 

Wiring between thermotime, temp senders and ISV - This is pretty frail on cars that are over 20 years old, so check for any breaks in the wires, frays or bad connections. Also try swapping the the wires on the three temp senders on the side of the head - they're all the same rating, so you may be able to isolate a duff sender.

 

Condensation in dizzy cap - not seen this much, but could explain your difficulty starting. It's also prone to leaking oil into the cap through one of the shaft oil seals on the dizzy.

 

Fuel leak - this could introduce air into the lines when the engine is off, so it would struggle to start initially while the pressure builds. Shouldn't take long though.

 

There's probably more to check but that should get you started.

 

---------- Post added at 7:15 PM ---------- Previous post was at 7:11 PM ----------

 

Forgot to mention - for the air leaks, don't just check the thin vac pipes, but also the intake boot and the breathers. I had an air leak where the rubber had perished between the folds in the intake boot and was letting in air!

[shaunje 10]

That's brilliant Tony! Thanks!

[Wild-Animal 0]

I would be very suspect of the injectors, mine was hard to start when cold, but fine once warm. The injectors were leaking, I only found this out once i replaced them.

 

Now the other problem I encountered was, i had adjusted the fuel/air ratio level fuel mixture. Now I got it set up at the MOT. The car was pinking all over the place after the M.O.T, I was looking at everything testing, replacing parts.

 

Anyway I gave up took it to a specialist and found out the car was running far to lean.

 

You could try pulling an injector out and check their condition, as soon as I pulled one out I knew straight away they were past their best just by looking at one. But if the previous owner has been tinkering around, then I would be suspect of the fuel/air ratio it may have been adjusted to try and compensate for the running of the car.

[tony_ack 0]

You can test the injectors by pulling them out (while still attached to the lines), and placing them in clear containers. First of all leave them overnight and see whether they're leaking - they shouldn't drip at all if working properly.

 

Next, remove the air intake boot, disconnect the coil (for safety), bridge the fuel pump relay and turn the ignition on. Push the flap on the metering head down and the injectors should spray. Check you've got a nice clean conical spray pattern and that they're all firing equal amounts.

 

Also check the seals on the injectors - actually may be worth replacing them. There are two per injector, one at the top and one at the bottom. The inserts are bakelite and can crack, so you may need to replace these too. The seals/seats could be another source of vac leaks.