L67 S/C Motor Struggles On Cold Start.

[Immortality]

I'd be looking at the IAC stepper motor as well, each time the car started it resets the idle, if the TB is all gunked up it will cause trouble. While you have it apart you may as well clean the MAF.

Fitting a pod filter will alter the tune a little but the PCM is self learning and will adjust. IF the pod filter isn't enclosed than I would HIGHLY recommend that you do fit an enclosed pod filter. I recommend the MACE CAI.

Tuning it won't solve the problem but cost a lot of coin for a full dyno tune.

 

[jackcurrie]

Gave it a good clean, along with the TB. Neither were all that gunky, but definitely had a bit of buildup (not enough to interfere though, imo). I'll wait a few hours for the car to cool down, and then we'll see how it goes.

 

[MACE]

Vacuum leak due to popped off vac line or perished lines. Definitely not uncommon with these engines.

 

[jackcurrie]

Vacuum leak due to popped off vac line or perished lines. Definitely not uncommon with these engines.

Definitely wasn't fixed by the cleaning. Any idea where the vacuum leak is likely to be? Haven't seen any obvious leaks anywhere.

 

[Nut Kracker]

Light an incense stick and wave it around the vacuum hoses while the engine is running.
If there are any leaks, the smoke will get sucked in the leak.

 

[Immortality]

Holistic engine healing :hmmm:

 

[Immortality]

I would have thought an vacuum leak would possibly increase the idle ( i guess more so on a MAP based tune, MAF I guess....) ?

Does the engine use any coolant? what is the fuel consumption like? How old are the plugs and leads?

What i'm leading to is engine cylinder contamination after engine shut down, either fuel (leaking injector) or coolant ( old intake manifold gaskets = common problem) which can cause a miss-fire when starting the engine. Tired ignition system components can cause similar problems (plugs/leads and even old ignition coils). A dirty/sticking PCV can also cause cylinder contamination if it's allowing excess oil to be sucked into the engine cylinders.

Is the engine noisy/tapppety on first start up? A sticky lifter can cause issues, once the oil pressure comes up as well as the oil temp the lifter will clear and function properly. Try new oil/ filter and maybe some nulon lifter free

 

[jackcurrie]

The engine isn't noisy or any different to usual driving, except obviously the shudder every now and then as it struggles. I'm gonna ask my first amateur question... Where exactly are all the vacuum hoses on my L67? Can't say I've ever touch a vacuum on any car I've ever owned either, so if you can point out where I should blow the smoke, that'd be handy!

 

[Immortality]

A slight miss won't nearly cause the engine to stall. If the problem is that bad it might be an ignition coil causing 2 cylinders to miss. Have a good look at the coils, look for cracks in the casings.

I'd also pull all the plugs and see if they all look the same.

 

[jackcurrie]

I might have found my problem. Does anyone know which vacuum it is that is literally connected directly under the pulley, on the block. Like 2inches or so down from the pulley. There is absolutely no hose connected, and the previous owner has half-assed some tape onto it, not really sealing it at all.