'91 300E Hot Engine Restart and cold engine NOISY start

Two things:

In the morning, when I start my car, it starts up VERY noisily....with a rumbling, loud fluttering sound coming from the engine. Strangely, after about 1-2 minutes, it goes away as suddenly as it started, leaving the nice, quiet purr of the classic gasoline V-6 engine that 300E's are famous for. Does anyone have any idea what that sound is? It almost sounds as if the throttle is stuck in the open position until the engine warms up.

Then, the second problem is when the car is hot, after being driven around for a while and then turned off. When starting the car up again within a one hour window of being driven, the car takes two turns to start. The first cranking appears to start the car. The RPM revs up, so I let go of the starter. But instantly, after the car revs up, it dies. So, I have to crank the starter again, and this time without any delay, it starts right up. Any idea what this is?

Thanks!

Les

[Gilly]

leaving the nice, quiet purr of the classic gasoline V-6 engine that 300E's are famous for.

That sir, is an inline 6 cylinder engine, not a V6.

Problem 1 MAY be the air pump operating. It's belt driven, mounted over near the alternator. I can't tell you if there is a problem with your s or not (if the noise is normal or not) but the air pump runs on cold starts.

Problem 2, could be lots of things: worn plugs, incorrect plugs, carbon on the valves, a leaky fuel injector or two, bad gas or low octane gas, coolant temp sensor.......
Could also be valve stem seals, although the "false start" with valve stem seals are usually upon cold start.

Gilly

Ok, you're right. I'm a novice but I had a funny feeling that saying it's a V6 was not right....

Anyway. the air pump? Does that mean that it should not be operating the way it is? That noisy? Like I said, it goes away right away, but is kind of embarassing as I drive out of my driveway in the morning.

As for item 2, I have already replaced the cylinder head, valve stems, valve cover gasket, new spark plugs, radiator, cooling system sensors and a variety of other items (radiator, for one). Could it not be the ignition wire set/harness?

Thanks again,

Les

[Gilly]

The air pump MAY be operating normally or it may be worn out or on it's way out (seizing or something) or possibly there is a problem with the air pump plumbing (rubber hose came off, or a problem with the divert valve). I'm not there to hear it, so I can't tell you if it sounds normal. It's not usually the kind of noise that causes embarassment though, so probably there is a problem.
It will operate for about the first 2 minutes after a cold start. A few minutes after that it may kick in for about 2 or 3 seconds as the compuer completes a test of the systems.
Look for a rubber hose over by the air pump that's not connected to anything. The air pump again is above the alternator, has a metal shield behind it, and you'll see the hose coming off of it, about the size of a heater hose. As a test you could locate the connector for the air pump clutch, over near the coolant tank (pressure tank) and disconnect it to see if the noise is gone on cold starts, but I would discourage leaving it disconnected as a permanant fix.

Why the new cylinder head?
The valve stems are part of the valves, so unless you also installed new valves (?) you didn't replace the valve stems. What is the history of the head you installed? Are you sure the valve stem SEALS were replaced? Possibly someone rebuilt the head and misinstalled the seals, there are seperate intake and exhaust seals, and they could have been misinstalled on one or all of the cylinders. Also if it is a used head that was simply installed, it could still have the old seals, and/or worn valve guides.
I wouldn't really think of the plug wires as a cause for this problem, no. Possibly wrong plugs, what did you install for plugs and what gap?

Gilly

Well, I guess if it's normal, that's good. It has gotten a little more quiet since I repaired a hole in the muffler that was caused by rust. It definitely goes away as if it's just trying to warm up. It seems to be tied to the cold engine only, because as long as I drive it again within 4-5 hours, it doesn't make the noise at startup.

As for the cylinder head, I had a crack in it and oil was leaking very badly from it to the tune of a quart a week. But, allegedly, they replaced it with a reconditioned head, which contained new valve stems and the like. The car drives very well now, and does not overheat at all.

I didn't mention that my HVAC blower just died this weekend! That's my first priority to fix that. I checked the fuse, and it seems to be ok. It's a single piece of metal, so I can't imagine anything is wrong with it. We'll see....

Thanks again for your advice.

Les

[ED C.]

I have a similiar but not exactly the same problem with my 88TE. At a cold start up (w/ no throttle) it fires right away but runs very rough for 3-4 seconds then smooths right out. On a hot start w/o touching the throttle it fires right up then dies. If I depress the throttle slightly it will fire and run no problem.

I have replaced the plugs (copper core bosch), Dist. Cap, wires, fuel filter & check valve. I am considering replacing all the injectors (original), but don't like just thowing parts at a problem without isolating it. Is there a way to check if an injector is leaking down? Should I be able to see this by examining the plugs prior to the first cold start of the day? Whenever I have replaced the plugs they have all looked very clean.

Any ideas would be appreciated.

Thanks

EJC

Well, as for my blower problem, it turned out to need a new blower motor and regulator. Fixed at a local non-dealer auto repair shop. Ran about $800, but included new fan squirrel cage as well. Probably could have saved a little on that.