Can our engines develop morning sickness? |
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Can our engines develop morning sickness? |
andreic |
Oct 16 2018, 09:42 AM
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#1
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
My 1972 914 1.7L suffers from what I call "morning sickness" -- the first time I start the car on any given day it runs like crap for the first 10-15 minutes. Skipping, won't rev up above 1000 rpm, very low idle, stumbles frequently, sometimes backfires. Also makes some strange noise around 2000 rpm, like a very loud rattle, especially when letting off the throttle.
After 10 minutes all is good, running well for the rest of the day. The compressions, which I have only checked with the engine hot, are uniformly 120-125 PSI. I come from an aviation background, and aircooled airplane engines are known to have this kind of morning sickness at around 1000-1200 hours since overhaul. The cause is carbon deposits in the valve guides, which make the valves stick when the engine is cold. After warming up, the guides expand from the heat, and the valves do not stick any more. The solution is reaming the guides, which can be done with the cylinders in place (for airplane engines). Is this something that can happen to our type IV's? Could this explain the problems I am having? What is the cure, short of taking the engine out and sending the heads to a shop? Thanks all. |
Rand |
Oct 16 2018, 01:46 PM
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#2
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Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
Exhaust leak in my experience is a little popping, not a rattle. Rattling is mechanical. Valve train like, or a piston slap or something.
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andreic |
Oct 16 2018, 04:45 PM
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#3
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
All vacuum lines were recently replaced, so I doubt there are vacuum leaks.
The problem repeats itself very consistently, so I would put the probability of a loose connector or a half-way broken wire to be fairly low. What would valvetrain noise sound like? And could that go away after a few minutes? Moreover, would it make sense to try to do a compression test with the engine cold, to see if a valve sticks? I have adjusted the valves recently, but I was thinking of double checking the gaps again in a few days when I find some time. The D-Jet is not going anywhere. I've had a carb setup before, and my clothes smelled awful every time after driving the car. My kids would hug me and say "you have that car smell". Exhaust leak in my experience is a little popping, not a rattle. Rattling is mechanical. Valve train like, or a piston slap or something. |
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