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orthobiz |
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#1
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Senior Member ![]() ![]() ![]() Group: Members Posts: 1,755 Joined: 8-January 07 From: Cadillac, Michigan Member No.: 7,438 Region Association: Upper MidWest ![]() ![]() |
Update: No new engine for me right now, the 1.8 is once again running strong. Thanks everybody for looking at my videos and posting in this thread.
Paul Edit: I added some video of my 1.8 engine's behavior. What you are seeing is about 2 minutes into the engine running from a cold start. I tried to capture a little of the shakiness of the engine as well. Wondering if anybody has a good idea of what's going on as I may want to sell the engine after the swap. 914 1.8 Stalling Original Post: So late last "season" (Porsche weather is May to November here in Michigan), my car stalled between shifts. Started up OK but conked out when warm. So...I discovered a disconnected hose and started a hose renewal project. After replacing every hose, the problem persisted. But along the way I had to replace the AFM as the car backfired and warped the flapping door. Still no success. Replaced the fuel injection seals, oil filler cap seals, still conks out after warm up. Contemplated a new brain and wiring harness and cylinder head temp sensor but have run out of patience. To make a long story short, I've decided to go with a 2.0 and plan on dropping my car off at Brad Mayeur's next weekend. I've always wanted more power anyway. Questions: 1. How much power am I losing by sticking with the stock 1974 exhaust system? 2. What to do with the 1.8? It ran strong before the problems developed, but the car is of unknown mileage. Seems like interest in these engines is, well, underwhelming. Brad said he has more than enough of these engines. 3. I'm sure he could get the 1.8 FI running on the 2.0, I know there are proponents of the L-Jet...Is that something worth pursuing or stick with the D-Jet? Thanks, Paul BTW, I have a pristine orange 1.8 that is staying stock. This is for my red driver! |
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Rob-O |
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Senior Member ![]() ![]() ![]() Group: Members Posts: 1,252 Joined: 5-December 03 From: Mansfield, TX Member No.: 1,419 Region Association: Southwest Region ![]() ![]() |
If you decide to put the L-Jet on the 2.0L, keep the 2.0L intake runners. The 2.0L runners have three holes that attach the runner to the head. The L-Jet 1.8L has 4 holes that attach the runner to the head.
If you look up L-Jet on Google, there is a great document out there that outlines what all the components do, how to check them, troubleshooting section, etc. It was written for the 912 version of L-Jet, but almost all of it applies to the 914. Keep the L-Jet. Instead of just replacing parts, start checking them out. You should be able to narrow down the culprit pretty quickly based on the car dying when warmed up. Since it sounds like it came on abruptly, instead of slowly over a matter of days, weeks, months. I'd say it is a component that failed or is failing versus a vacuum leak. With that in mind, have you checked the AAR (Auxiliary Air Regulator)? I didn't watch your videos, but you have TWO systems at work when the engine is cold. The cold start valve (Whether it turns on or off on start is controlled by the thermo-time switch) and the AAR (has it's own internal heater). The cold start valve injects more fuel into the plenum at cold start. The thermo-time switch detects that the outside air is cold and then (if I understand the theory correctly) the FI brain enables the cold start valve for a matter of time (something like 8 seconds total). The AAR on the other hand will stay open until the engine warms up enough to warm up the heater in the AAR. Once warm, the AAR eventually closes. The air that the AAR receives has been metered by the AFM (but not the TB) and so the amount of fuel will have been metered. But after the engine warms up, if the AAR doesn't close, I believe you'll run into a lean condition that could cause the engine to die. Good news? The AAR can be cleaned fairly easily once you pull it off the engine. More good news? You should be able to check AAR operation fairly easily by pulling the vacuum line from the AAR and capping it off at the plenum. If you do this, I would suggest unplugging the cold start valve as well so the engine isn't getting lots of extra fuel but no extra air at startup. It may make starting the engine a little more difficult initially, but once running you'll be able to identify if the problem lies with the AAR |
orthobiz |
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#3
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Senior Member ![]() ![]() ![]() Group: Members Posts: 1,755 Joined: 8-January 07 From: Cadillac, Michigan Member No.: 7,438 Region Association: Upper MidWest ![]() ![]() |
The air that the AAR receives has been metered by the AFM (but not the TB) and so the amount of fuel will have been metered. But after the engine warms up, if the AAR doesn't close, I believe you'll run into a lean condition that could cause the engine to die. I thought about the AAR but did not check it. The car is taking a trip to Brad's this Friday so I will not do further diagnostics...but I will talk to him about keeping the L-jet. What's a TB? Thanks for the detailed analysis! Paul |
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