Ronin-951

Mileage is still a bit low at 27 mpg IF you were trying, mid 30's on a flat Road using Cruise is where I'm at stock and with Tire Pressure to 34psi. Solder at the Plug wont hurt the O2 Sensor, just cut out and Crimp if there's room, or open up the Cable and inch short [O2 side] of the Solder joint and add a Crimp. The idea is to get Reference Air from someplace where Exhaust Gases are not present, like the upper Engine Bay.

BoostBuggy

Wow I've never heard on anyone getting mid 30's mpg. that's pretty impressive.

I checked the O2 and it was not soldered. The shop used a male/female style (not a porsche oe type) connector and crimped the wires into the connector.

I'm picking up a new DME Temp Sensor this afternoon and will install it. I'll see what that does....

Ronin-951

The pain is not worth the cost, when you have one of the best Road Cars of all time, keeping it in check is torture, thus the CC, - willpower vs foot control is a bad bet!

BoostBuggy

Is this the DME Temp Sensor (circled)



Assuming it is, mine seems to have a single wire going to it but the replacement part that arrived yesterday has a rectangular 2 wire connector. Did I get the wrong part or did Porsche make a change early in the 86 MY run?

Tom M'Guinn

That's the sensor that controls the turbo aux pump, not the dme temp sensor. Look under the front part of the intake manifold and you'll see the actual dme temp sensor -- with a connector similar to the ones on the fuel injector (not the one with two separate spade connectors). A cheap multimeter from radio shack can test those and other sensors. If you need a tutorial on doing the tests, lots of folks here can help.

Ronin-951

Your pic reminds me of another problematic area, I don't know the Porsche word for it, but it's the Screw in the Throttle Body accessed by the port on the upper far right of your pic. Some call it the 'Pilot', some 'Air Bleed', some 'Idle Mixture', but it does tend to loosen up once the Seal Plug is gone. It should be set to 1 and 3/4 turns off the bottom seat, and add a little goopenpucky to the threads to keep it there. Not a big Fuel waster, more a rough idle thing, but every little bit helps.

BoostBuggy

Well, finally got the DME temp sensor replaced. Here is a photo of it's placement

(as there didn't seem to be any here)

It will be interesting to see if it's replacement has any effect on the rich condition/crappy fuel mileage. I made a drive down to LA last week and running with the cruise set at 80 on the I-5 my mpg avg was about 20. Even at 80 one would expect better mileage than that. I will be heading down to Laguna Seca for the Historics later this week so that will be a good trip to see if the mileage improves.

There was also another sensor looking piece a few inches behind this sensor however it had 2 spade connectors on it. anyone know which sensor that is?

Tom M'Guinn

Spade connector sensor is for dash gauge.

Did you test the one you removed?

Dave W.

Did you check the continuity of the wires from the sensor plug to the DME plug? It's not uncommon for the wiring to become brittle with age and cause a short or break. Check out the pinouts here;
http://www.the944.com/connector.htm

Ronin-951

ok, now we know that your not working on a 'pristine' 2.5, and just a quick glance at the goop squeezing out of the Water Pump say's 'hack', - Porsche say's that's a dry gasket, most of us backyard type's still use a 'little' Sealer, but gob's on the outside mean gob's on the inside too, which will break off and plug passage's in the radiator and cooler. Anyway, bottom line is that the Engine has not been pampered, and a fairly good chance the Injector's are stock and have a spray pattern similar to a Garden Hose. You can fight the good battle's all night long, but without the Injectors at 100%, all will be for naught. 25 years has taken it toll on EVERY part, and now I doubt you will find just one cause to the Fuel Mileage problems. Guess really the starting place is with a baseline Compression/Leakdown Test, -because the inside may match the outside.

BoostBuggy

Never suggested it was a "pristine" example... :-) Yeah it's been ridden hard and put away wet (as they say) but it'a been a very reliable DD for me since I purchased it in late 09.

I wouldn't doubt there some "messes" internally and such. And one of the seals/O rings at the turbo has developed a leak also. So I'm in the process of figuring out what all the parts I will need so when I pull the intake manifold to get to the turbo et al I have everything and can replace all with new. Albeit that will not include the wiring harness and frankly that thing even scares me! :-)

Not so concerned about compression as it pulls REALLY stock for a stock engine and the head was rebuilt about 5k before I purchased it some 60k miles ago.

Nonetheless thx to all here for the helpful suggestions and tips...

BoostBuggy

Update: This has been an ongoing issue. Last weekend I replaced all the vacuum lines with new (LR silicone.) In that process learned there was a line (the line going from the J Boot to the cycling valve) that was left open when the Dual Port WG was installed. Also it seems the vacuum lines on the WG to the MBC were also mis-plumbed. And to add to this, in pulling the fuel rail I saw that the injectors looked horrible with two having small pieces of the orange bakelite material near the tip broken and missing. And finally the car has been running a little on the cool side (water temp rarely gets above the first hash mark [about 1/3 of the total gauge travel]) which I understand could also be contributing to the rich condition.

FWIW have been checking mileage following the vacuum line install and on a trip to/from Sacramento (cruise set at approx. 77-78 mph) the best mileage was 21.2 and checked it again today with more in-town driving and mileage was 18.57) I also smell fuel from time to time upon exiting the car after being turned off.

So picking a new used set of injectors this wknd, have new injector seals ready and a new thermostat and seals ready. Other items on the list to check/repair/replace are the J Boot, TPS, injector and various sensors wiring harness. I figure sooner or later (hopefully sooner) this thing will be running correctly once again.

As always, any thoughts/suggestions are always welcomed and admittedly I'm not exactyly the world's most talented automotive diagnostician or mechanic by any stretch of the imagination! :-)

Michael

URG8RB8

I have a mint set of stock injectors and I am close by, let me know if you want to try. I also have a mint set of 55# witch hunter B&B injectors with resistors.

URG8RB8

I also have a complete Scivision setup that would make your car really nice with the proper exhaust and turbo. I ran it for over a year with zero issues. I got it from Darwin.

BoostBuggy

URG8RB8, PM sent