Can our engines develop morning sickness? |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Can our engines develop morning sickness? |
andreic |
Oct 16 2018, 09:42 AM
Post
#1
|
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. |
JawjaPorsche |
Oct 16 2018, 10:03 AM
Post
#2
|
Advanced Member Group: Members Posts: 3,463 Joined: 23-July 11 From: Clayton, Georgia Member No.: 13,351 Region Association: South East States |
Temperature head sensor?
|
Mark Henry |
Oct 16 2018, 10:13 AM
Post
#3
|
that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Likely an ignition and/or moisture issue.
|
TheCabinetmaker |
Oct 16 2018, 01:02 PM
Post
#4
|
I drive my car everyday Group: Members Posts: 8,300 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
Did i miss the induction type?
|
TheCabinetmaker |
Oct 16 2018, 01:03 PM
Post
#5
|
I drive my car everyday Group: Members Posts: 8,300 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
Hydraulic lifters?
|
Rand |
Oct 16 2018, 01:24 PM
Post
#6
|
Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
Carbs. Flame me if you want, but that is carb behavior.
|
injunmort |
Oct 16 2018, 01:25 PM
Post
#7
|
Senior Member Group: Members Posts: 1,024 Joined: 12-April 10 From: sugarloaf ny Member No.: 11,604 Region Association: North East States |
theres the answer.
|
andreic |
Oct 16 2018, 01:28 PM
Post
#8
|
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. |
Rand |
Oct 16 2018, 01:43 PM
Post
#9
|
Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
This is getting interesting. Not typical with FI.
Keep the ideas coming so we can solve this. |
thelogo |
Oct 16 2018, 01:44 PM
Post
#10
|
Senior Member Group: Retired Members Posts: 1,510 Joined: 6-April 10 Member No.: 11,572 Region Association: None |
(IMG:style_emoticons/default/hissyfit.gif)
My guess as my car used to do the same thing is something d,jet related and is technically impossible to 100% for sure diagnosis That doesn't mean it cant be. Fixed ,just not for sure . I'll be honest , i dont like carbs in regards to drivability , the worst Unless your near a racetrack or airfield But at least carbs dont have gremlins in em , what you see is what you get Djet repair list : a wegeee board , a witchdoctor, a bottle of whiskey, a crystal ball and a magic 8 ball . See where im going with this. I wouldn't be suprised if the symptoms your describing have been the precursor to engine fires for some of us . So be careful |
Rand |
Oct 16 2018, 01:46 PM
Post
#11
|
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.
|
Rand |
Oct 16 2018, 01:53 PM
Post
#12
|
Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
QUOTE But at least carbs dont have gremlins in em , what you see is what you get Djet repair list : a wegeee board , a witchdoctor, a bottle of whiskey, a crystal ball and a magic 8 ball . See where im going with this. Please don't fall for that. Carbs have as many gremlins as FI. If you thing you need a wee-gee board to fix something it only exposes that you don't understand it. If you think carbs are superior to FI, you need to go back to your witch doctor. If you have djet, there are resources to help you work through it methodically without turning to voodoo. Oof. |
Chi-town |
Oct 16 2018, 02:18 PM
Post
#13
|
Senior Member Group: Members Posts: 850 Joined: 31-August 18 From: Disneyland Member No.: 22,446 Region Association: Southern California |
Sounds like you have a vacuum leak. A very small one may expand and close up as the engine gets warm.
|
914_teener |
Oct 16 2018, 03:02 PM
Post
#14
|
914 Guru Group: Members Posts: 5,193 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
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. Check all your electrical connections including your wiring harness. This is what it COULD be: You have a broken wire somewhere, perhaps in the harness. When the wire or connection is cold, the connection is intermittent. Once the engine warms up, the miracle of molecules and electrons expands the copper wire so that the connection resistance is less. In short: Get a new harness and stop chasing your tail. |
914_teener |
Oct 16 2018, 03:11 PM
Post
#15
|
914 Guru Group: Members Posts: 5,193 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
(IMG:style_emoticons/default/hissyfit.gif) My guess as my car used to do the same thing is something d,jet related and is technically impossible to 100% for sure diagnosis That doesn't mean it cant be. Fixed ,just not for sure . I'll be honest , i dont like carbs in regards to drivability , the worst Unless your near a racetrack or airfield But at least carbs dont have gremlins in em , what you see is what you get Djet repair list : a wegeee board , a witchdoctor, a bottle of whiskey, a crystal ball and a magic 8 ball . See where im going with this. I wouldn't be suprised if the symptoms your describing have been the precursor to engine fires for some of us . So be careful No, an I don't see how this is helpful to the OP. |
mepstein |
Oct 16 2018, 03:13 PM
Post
#16
|
914-6 GT in waiting Group: Members Posts: 19,219 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region |
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. Check all your electrical connections including your wiring harness. This is what it COULD be: You have a broken wire somewhere, perhaps in the harness. When the wire or connection is cold, the connection is intermittent. Once the engine warms up, the miracle of molecules and electrons expands the copper wire so that the connection resistance is less. In short: Get a new harness and stop chasing your tail. Or try a different harness and see if it makes a difference. My non mechanical self swapped engine harnesses in about an hour. Usually you can pick up one for $50-100 and if it works, you have a core with plugs for the rebuild while the car still runs. |
76-914 |
Oct 16 2018, 03:53 PM
Post
#17
|
Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,483 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California |
delete, wrong thread
|
andreic |
Oct 16 2018, 04:45 PM
Post
#18
|
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. |
Mark Henry |
Oct 16 2018, 06:20 PM
Post
#19
|
that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
T4 valves don't stick, unless you're running old gas that's turned to varnish.
My money is still on ignition, what you describe sounds like it's not firing on one cylinder. Get a temp laser gun, point at each pipe, see if one is cold. T4 get really unbalanced, sounds like shit and way down on power with a dead cylinder. But... this could also be a dead/dieing injector. (IMG:style_emoticons/default/huh.gif) Isn't chasing gremlins fun? (IMG:style_emoticons/default/biggrin.gif) |
Lo-Fi Version | Time is now: 18th April 2024 - 05:47 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |