1970 914/4 resurrection help needed!, Poorly running F.I. 1.7 Options

[daveholiday]

Hello all, this is my first post on the forums, but have been "soaking up" information from here for a bout a year! This is a long post and perhaps a complex problem or multiple problems that I desperately need advice and guidance with. I am going to provide all the info I possibly can but if I leave something out please let me know! I will describe my problem first and then give a detailed history and specs of the car.

The problem:

My car will just not run smoothly across the rev range. I constantly have to give the car throttle inputs just to keep it running. When it does try to idle it is around the 400-500 rpm range. I can also hear pops through the intake if I try to hold the throttle open at a set point (hold the car at a specific rpm). If I am constantly moving/revving the throttle the engine will respond, but in exaggerated revving/deceleration. It also is very low on power when I do attempt to get it out on roads in the neighborhood. It also appears to be running very lean as all 4 of my spark plug tips are white.

Car/Engine specs:

1970 Porsche 914 1.7. The car is still fuel injection. I have most, if not all, of the service/repair records for the car including the bill of sale from when the car was purchased new. The car has the original engine (W004-9961). The car had a rebuild in 1977 that consisted of the installation of a HP camshaft (no description), 96mm big bore kit, lifters, rods, coil, seals etc. In 1980 the car had another major service consisting of: lifters, rings, lapped valves, and camshaft. This camshaft had a Porsche part number that matches the stock part number. The previous owner didn't have anything else major done to the car since the 1980 service. So the best I can tell the engine has a stock crank, cam, heads, F.I., distributor, but does have a 96mm big bore kit installed. The last time the car was running reliably was 1988-1990.

My service history:

-Engine removal for clutch replacement and flywheel resurfacing.
-While the engine was out, I replaced all the seals I could without removing the heads.
-Replaced all vacuum hoses, fuel lines, and clamps
-New F.I. and ignition wire harnesses (Thanks Jeff, they are gorgeous!)
-4 new fuel injectors with seals
-new points, condenser, cap, rotor, wires, plugs (NGK BPR6ES), and timed @ 3500rpm
with some help I was able to hold the engine rpms enough to time it.
- distributor vacuum advance tested and seems to be working
-AAR, CHT(new), manifold air temp sensor, TPS all test good.
-The MPS will hold 10in,hg for 30 minutes before dropping to 9.5 in. primary and secondary resistances are 89 and 349 ohms
-The cylinder compression is 160,160,155,150
- valves set to .006 at TDC for each cylinder
**edit** fuel pressure trigger points cleaned and tested, fuel pressure at 28psi

The bad news is the engine runs as poorly now as it did before I started working on it. I am out of ideas and could use some advice. I have religiously searched for vacuum leaks and have brand new proper metric sized lines. I have even gone as far as to use small spring clamps on the vacuum lines. The only other items that I haven't done extensive testing on is the MPS and the computer. My MPS holds vacuum and sounds like the internals are moving when releasing vacuum, but I don't know of any other tests that I can do without specialized equipment. I haven't stumbled across any references regarding testing the computer as of yet, but I hear it is rare for them to go bad.

Thank you all who have taken time to read this post, and thank you ahead of time for any advice big or small to help me.

Again, if I have left out any info that you think would be pertinent, please let me know and I will be happy to add it.

Thanks again!

Adam

[Chris Pincetich]

Sounds stupid but.....I solved 70% of my D-jet issues with a new battery and good grounds. The ground post above the battery, when inspected, was a pile of old paint and rust in the shape of a bolt. The ground strap at the transaxle had a corrosion layer in between the body and strap. My issues had appeared and worsened during year 6-7 of a new Optima Red Top battery. Replaced battery, then alternator was bad. Replaced alternator. It's been running great with 2-4 days of weekly commuting over the last month.

Good luck (IMG:style_emoticons/default/beerchug.gif)

Oh yeah, I should mention that 8 months ago I had the fuel pump die, but it wasn't the fuel pump, it was the ECU. In the process of diagnosis I went through lots of the D-jet and other electrical connections.

The other 30% fix was replacing the TPS circuit board, which was deeply grooved. Unplugging the TPS allows the engine to run fine at normal throttle, and will diagnose issues related to it (if the issue resolves while it is unplugged, your TPS is a culprit!).
(IMG:style_emoticons/default/driving.gif)

Oh yeah, one more thing, my battery tested bad at the auto parts store even though it had 13V across the terminals. I thank Cap'n Krusty for the advice "even a bad battery can read OK on your voltmeter"