http://www.pixelloft.com/car.mp3

I recorded the sound above to demonstrate the sound my car is making.

Just to recap, this only happens in the morning, and will not repeat itself from cold start untill the next morning so it needs time to cool down and sit for quite some time to develop.

Since the problem started i have changed the map sensor, IAC valve, Coilpacks, New Plugs, rerouted the coolant from the inlet manifold (just in case there was a leak in there).

There is a definate chemical smell (could be fuel) when this clicking/surging happens and it doesn't happen every morning but most mornings.

I have noticed that LONG drives seem to stop it from occuring for up to a week.

When i am only nipping around locally it occurs most mornings.

This is a replacement engine for my old one that blew. The problem started some time after the transplant when i jacked the rear of the car up for 2 days while working on the rear brakes. I initially assumed it was becuase i had ran the car very low on fuel.

A brake problem couldn't cause the engine to do this could it?

Any insight as to what to do next would be much appreciated.

 

i doubt that a brake problem could cause the engine noise... do u feel movement when sound is being made? does the sound seem to get worse & worse?

im thinking maybe its the bearings on crankshaft main journals... maybe its starting to wear causing it to pulsate like it does when u first start, and it stops as soon as enough oil is there for the crank to ride on.

jus my 2 cents.

 

Hey thanks for the advice. The engine i have in there has only covered 6k miles so i'm guessing it it unlikely that the bearings have worn, but i shall check that out.

The engine clicking does cause the engine to buck a bit.

I had assumed to this point that it is the engine switching from lean to rich... hence the petrol smell and the revving/ surging was the engine management system trying to balance it all out.

Does this make any sense.

 

The hunting sound is caused by a vac leak in port on the side of the intake manifold. or atleast it was on my motor when I had the same issue.

 

Thanks Stratocaster.

And did it sound similar to the mp3 ive uploaded of mine.

What did you do to fix it?

Since this started, I replaced the brass colored valve thing on the intake manifold at the back which is part of the VAC system I think (please excuse my ignorance). How did you check for the leak and would you suggest i should replace the whole vac system which bolts onto the inlet manifold. I have a spare intake manifold here that i am slowly stealing parts from.

Thanks for your help!

Nick

 

shot a few pictures of the intake manifold. Show the hoses if you can.

For me, I just needed to replace the broken hose I had that was leaking. if you take a can of starter fluid, you should be able to spary some next to each vac line in turn. one of them will take the fuel into the motor and you should hear the RPMs change their pattern. That is the hose you need to fix.

The hose on my was the one on the manifold next to the TB, that points to the ground.

 

It's possible the coolant bypass is also causing the idle hunt, or you've got a vacuum leak somewhere.

With the engine idling block the large port inside the thottle body, with the throttle closed.

If the engine still runs you've got a vacuum leak.

 

Thanks, both of you for your help.

Following your advice, this morning i checked all of the vaccum lines. They all seemed good, but i replaced them just to be sure.

I then removed the throttle body which I had removed, cleaned and polished some weeks before the problem started.

I compared it to a TB which hadn't been cleaned and you could see daylight round the edge when in the closed position. Obviously when i cleaned away all of the gunk that had accumulated, and with the factory seal (whatever they use) warn away to the brass. Could this be enough of a leak to cause the vacuum pressure to drop?

I replaced the TB anyway, I reset the ecu and it started up fine (although it clicked a few times and the air pump came on for some time and it almost stalled whenever i blipped the throttle and the revs came down too far. After warming up, this seemed to disappear.

I will see what happens over the next few days and continue hunting for vaccum leaks using starter fluid as suggested by you.

Thanks for your help, ill keep this updated.

 

Wouldn't this condition last regardless of when and how long he has run the engine? The vacuum issue should persist at all times. His idle is only affected from a cold start after the engine is fully cool...

 

Nicholas, given the fact the the idle is only affected from a fully cold start, and that the issue does not happen after you restart the car after it has been driven (warmed up) you may have a problem with the air pump or one of your oxygen sensors (it may be going bad or it may simply been knocked loose, which may have happened during the jacking of the car for the brake work).

I think there is a problem with either one of your sensors, or with the proper airflow into / out of your engine.

Here's a pretty picture referencing the airflow into the engine. Have you checked the PCV valve? The hose from the air pump?



You might also consider inspecting those sensors that apply from this list:
How Stuff Works