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Registered User
Join Date: May 2020
Posts: 1
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Basics
Have the chassis and fuel injection ground points been checked?
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Registered
Join Date: Feb 2002
Location: Victoria BC Canaada
Posts: 47
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Read a few pages and thought I might have one way to narrow your search...
Have you got an IR thermometer gun? I know you've measured the mixture leaving the engine, but that's the "raw" output form the engine. The computer might not be dropping the mixture and it's something else causing the mixture level to decrease. Measure the exhaust temperatures on each cylinder at idle when the fault is occurring. If all ports are consistent in temp then you know the issue is system wide. If one or more ports are much lower than the others, then you can focus on those cylinders specifically. Like what could be common to them, fuel rail/ground/???. That $19 tool has helped me solve lots of rough running engine problems before! Works the same for an engine that's off idle too. Run the engine at speed "lumpy" for a while, so the exhaust temperatures can adjust. Kill the engine, pull over and read the exhaust port temps and look again for one really high or really low. Hope that helps Wayne! You're WAY farther ahead on your 914-6 than me. Still have to get my 3.6 mounted and 915 flipped. -JR-
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James Renfrew 75 Porsche 914 78 Porsche 928 Last edited by jrenfrew; 05-27-2020 at 03:55 PM.. |
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Join Date: Nov 2017
Location: Houston, TX
Posts: 870
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Triple-valve constapulator bonding nipple is either blocked or invariable, consider re-regulating both sides.
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Ivan
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1985 911 with original 501 761 miles...807 506 km "The difference between genius and stupidity is that, genius has its limits". Albert Einstein. |
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Registered
Join Date: May 2007
Location: Van Alstyne, Texas
Posts: 24
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Its an OXYGEN sensor...
An O2 sensor measures residual O2, not fuel mix, the correlation is only valid with no misfires. An ignition misfire shows up as a lean mix. Fix your ignition? Small exhaust leaks can also provide interesting 02 readings. Also... fuel going super rich and causing misfires will also read super lean on the o2... if it doesn't burn it isn't using oxygen, so it reads lean even with fuel pouring out the tailpipe. check your injection pw and flows. check fuel pressure. What else changes at same time and what drives the change in behavior? temp sensors bad? Last edited by piledriver; 05-28-2020 at 06:05 AM.. Reason: clarification. |
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Registered User
Join Date: May 2020
Posts: 1
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Definitely try the temp sensor - I had a similar issue years ago on a 3.2
You could also confirm this by the following as well.
Look up the resistance spec for the temp sensor when the engine is warm. Run the engine until it gets warm (when it starts to act up). Check the resistance on the sensor. To confirm this is the issue, unplug the temp sensor and put equivalent resistors between the two slots in the wiring harness. Start it up. If it runs well when warm, you have your solution. Curt Morgan |
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Registered User
Join Date: May 2020
Posts: 1
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Distributor 3.2
Dr. Bartlett can tell you ,the distributor will cause problems as the clearance of the rotor to cap . this is caused by ware in the shaft because of the design .the ware
drops the cap to rotor clearance .As the spark can not flow Undesired Operation will mask as fuel injection problem. Frequency over load . Had one 3.2 in VW. bus with this problem Shaft on this had 7mm end play. installed good used .05 clearance. engine ran perfect. the 914 is hard to get to the distributor make a hole in fire wall for service. Dr bartlett sign off. |
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After going through all the posts here, including the beautiful description of Wayne's feelings for his 914 (post #254, yes some wine helps to write nice stories), which took me two full days and nights I became aware something has not been mentioned.
When I swapped my 914-1.8 LJet for a 3.0 911 SC engine, I took out the charcoal filter. When starting the 3.0L engine it ran quite well during a short while, but after that it ran very badly and often stopped running at all. After some days I had to take gas and a lot of air escaped from the tank when taking off the tap. At first I thought it was due to the warm weather here in Catalunya at that summerday but also wondered me if I had ever seen this before. After some searching I discovered that the breather hose to the (removed) charcoal filter was obstructed. The high pressure in the gas tank seemed to be the cause of this and of the erratic running of the engine disapeared instantaneously. So I suggest to have a look at this. Now I am in the process of mounting an identic 3.2L engine my 914. Thanks to this thread I learned a lot. I like very much the elbow of the air filter and will have a look to order this. For the moment my K&N filter is mounted straightforward to the AFM. Therefore it slightly hits the trunk lid. I also came across the brake-out board which is very interesting for analyzing electrical problems on this engine. Last thing: Unfortunately the shipping costs for orders at Pelicanparts to Europe are unforbiddingly high (apart from customs taxes). For any tiny thing the bill easely raises to $40 only for shipping. Isn't there a better, more economical way? Greetings, Gerber |
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Registered User
Join Date: May 2020
Posts: 2
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Wayne,
If you will replace the cylinder head temp sensor , your problem may be solved. This component fixed a similar problem that I encountered. i believe their was an update for this sensor from two prong to three. Get the one that matches your engine. If the three prong is the only one available , you will have to wire in the three prong plug to your existing harness to match the three prong sensor . Hope this info will bring you the solution you are after! Easy Ed |
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Author of "101 Projects"
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Thanks everyone for the input - I've been very busy with family / personal stuff, but I will post an update soon...
-Wayne
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports |
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Registered User
Join Date: Jan 2015
Posts: 5
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Hi Wayne,
If the fuel outlet fitting is too close to the return line fitting, it could cause a turbulence in your fuel supply. The 3.2L engine will need more fuel volume than the four cylinder engine. Hope that helps. Bill L. |
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Author of "101 Projects"
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Yup, Steve W. lent me one of his loaner ECUs for testing (along with a host of other stuff to test with), and the two ECUs behaved exactly the same. That was a big help, as so many odd things can go wrong with an ECU.
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports |
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You hinted at something there, I think the O2 sensor is correctly reading, which means that there's something wrong with the engine left/right. More on that soon. The fuel pressures, injectors, etc. have all been checked. Quote:
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-Wayne
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports |
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Author of "101 Projects"
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Okay, Sunday May 31 update. Did the following:
- Replaced all fuel lines with new ones (except for the center tunnel). - Installed new fuel tank - New spark plugs (third set - they are only $1.50 each my cost, so why not?) - Cleaned up the engine compartment - Installed new air flow meter from the 964 Singer take off - Re-plumbed the air filter and pipe - Cleaned up the battery terminals - Cleaned up the intake and some of the carbon build-up in the cylinders - Changed out the oil filter (added some anti-friction zinc additives) - Had the injectors cleaned and tested (again) - one came back as "CLOSED", but now are functional Started the car up. Conclusion - it runs better, but still has issues. It's not misfiring per se, but the idle is lopey and not smooth. Same as before, where it starts and runs fine at 1,200 for about two minutes and then settles down into an irregular idle. Also, plugging in the O2 sensor makes the mixture go lean (again) - this has not changed. If you read the previous posts, I determined that the engine was seeing 1-3 run rich, which was then (presumably) resulting in it leaning out the whole motor. This behavior does not seem to have changed. Exhaust temps seem to have improved and are uniform. I have measurements and photos of these. My thoughts at this point? I think there is some type of underlying issue with the engine. Indeed, all of this crap running at idle has gummed up the cylinders with carbon (one can see it with the intake off), and I will be runing a bunch of Techron and Seafoam through the system as I take it out for an "Italian Tuneup". Perhaps that will assist. It's possible that there were previous problems (documented on the previous threads and fixed, things like ignition wires, cylinder head temp sensors, and AFM issues) that caused a rich running condition that gummed up the cylinders. No engine likes to really just idle for long periods of time, which is what this has been doing as I've been working on it. So, I plan to take it out on the highway to beat the snot out of it and get it proper and warm (with the Techron running through it too). We'll have to see how that works. In general, at this point, it's easy to over think things... -Wayne New setup installed with the new pipe and air filter: ![]() Front fuel tank compartment with the tank removed: ![]() Cylinders 1-3, pretty much cleaned up nicely: ![]() Another shot of the air cleaner setup now: ![]() New fuel tank! ![]() Tank with all of the stuff that needs to bolt on to it: ![]() Looking fairly torn apart: ![]() WTF?!? This fell out of the bottom of the bag that the tank came in. It looked like a brochure for some new tanks, and I was tossing it out when I actually decided to read it. So, then I had to don my "Chernobyl" suit and go buy some carb cleaner (Berryman 12 Chemtool), and spend a few hours cleaning out the inside of a "new" tank! I called my supplier on this, as I had never heard of this, and he had never heard of it either! Go figure. Just keep that in mind in case you buy a new tank! ![]() Good stuff, Warren loved this stuff: ![]() Cleaning in the inside of the tank. Gloves, mask, goggles, etc - it's like I'm going to the grocery store! ![]()
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports Last edited by Wayne 962; 05-31-2020 at 12:38 PM.. |
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Author of "101 Projects"
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More photos:
Here's what the Air Flow Meter mixture screw looks like when you drill out the plug: ![]() Another shot of the air cleaner setup: ![]() New gaskets and spacers. They are relatively cheap, so one should probably replace them if they are old: ![]() Cleaning up the engine bay: ![]() Remember to remove the paper towels! ![]() Installed the new lines and the wire harnesses: ![]() Cripes, I forgot to label the speed / rpm sensor and they are both 3-prong plugs, so one can mix them up. The wires will hint to you at which one goes where, but I had to double-check with the ECU connector just to make sure: ![]() Smoke tested the whole thing when reinstalled - found a few spots that I quickly tightened up: ![]() Another photo of the smoke test. I put a screwdriver inside the air flow meter to prop the flapper valve open. Important to put a reminder note on the top so you don't forget! ![]()
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports Last edited by Wayne 962; 05-31-2020 at 12:42 PM.. |
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Author of "101 Projects"
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Even more photos:
This boot is $10 or so to replace. Make sure that you leave one side loose, then mount down the intake and then tighten, otherwise you'll pre-stress the boot. ![]() Ignition wires are now properly sorted: ![]() Filter inside the injectors - they all looked fairly okay: ![]() More ignition wire routing: ![]() Injectors were re-tested and came back with one "CLOSED". That seems bad, and may be a sign that all need to be replaced with new injectors. I think if my problem persists, then I will replace all the injectors. Having one completely closed is odd / bad. ![]() I came up with a clever idea to attach different colored zip ties to each one to keep track of them: ![]() I made sure to label that in the sheet: ![]() Here's what the AFM plug looks like when you remove it: ![]() Newish 964 AFM. Doesn't look "messed with": ![]() Other side of the AFM plug: ![]()
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports Last edited by Wayne 962; 05-31-2020 at 12:47 PM.. |
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Author of "101 Projects"
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Engine bay, jumper the DME relay to power the pump and check for leaks: ![]() Fuel lines underneath, temporarily zip tied for now (I use red zip ties to indicate things that are "temporary only". ![]() Front fuel pump setup: ![]() IR temps:, cylinders 1-6: ![]() ![]() ![]() ![]() ![]() ![]()
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports Last edited by Wayne 962; 05-31-2020 at 12:54 PM.. |
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Author of "101 Projects"
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Videos:
First startup. Running better, but not perfect. With the O2 sensor plugged in it doesn't run as well as without it plugged in. I think there's still something off left/right on the engine: Again, same thing but car is warm and I hooked up the LM-1 O2 measurement tool: -Wayne
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Wayne R. Dempsey, Founder, Pelican Parts Inc., and Author of: 101 Projects for Your BMW 3-Series • 101 Projects for Your Porsche 911 • How to Rebuild & Modify Porsche 911 Engines • 101 Projects for Your Porsche Boxster & Cayman • 101 Projects for Your Porsche 996 / 997 • SPEED READ: Porsche 911 Check out our new site: Dempsey Motorsports Last edited by Wayne 962; 05-31-2020 at 01:02 PM.. |
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Functionista
Join Date: Jul 2011
Location: CO
Posts: 7,717
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One thing I recall from Bosch training.... if you mount the AFM in any other position but dead straight horizontal there will be running issues that are hard to solve. Not saying that’s wholly your issue here but I’d mount it correctly to rule out variables.
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Jeff 74 911, #3 I do not disbelieve in anything. I start from the premise that everything is true until proved false. Everything is possible. |
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Functionista
Join Date: Jul 2011
Location: CO
Posts: 7,717
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Clarification: the one pictured above is inverted and needs to be flipped....
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Jeff 74 911, #3 I do not disbelieve in anything. I start from the premise that everything is true until proved false. Everything is possible. |
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