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. |
andreic |
Oct 16 2018, 01:28 PM
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#2
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
It is a D-Jet system. I have checked several times the CHT sensor and it seems to be good - showed 2.5 kOhms at 65 degrees. The connector is good on the CHT side; the other end was loose, but I replaced it (at the harness) and nothing changed.
I have gone through the whole ignition system with a fine-toothed comb: two different coils were tried out; new points, rotor, cap, wires, and spark plugs. I tested the injection trigger points and they seemed good. The only thing I did not change yet is the condenser, and I don't see how it could consistently work well when warm and not when cold. But stranger things have happened... The engine is original (so no hydraulic lifters) for all I know. What puzzles me the most is the weird rattle when cold. It could be a poorly sealing exhaust port, but I was wondering if it could be a rocker hitting against a sticky valve. |
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