Got my 72', 1.7FI out of the shop after having the top end done.


The car ran well for a day or so, then started to miss at higher revs.


It ran rather poorly and lacked torque and was'nt "revvy" now at any rpm. I took the car in for 500 mile valve lashing, got the car back and the "power" was good again. BLAH,Blah,blah.........

It seems when the car is hot, perhaps, the "spark" diminishes....

I once needed new dizzy bearings for my 75' 914, is that perhaps what my problem with this car is?

The Az Toy Run would be allot "funner" with full power!

sounds like muffler bearings instead

what kind of ignition setup do you have?

(coil, points or electronic??)

Stock FI, D-jet sound right?

TIA

yes, that sounds correct...but inside your distributor you will either have mechanical points (contact breaker) or an electrical device, (magnetic or optical)

check out this site:

Brad Anders most excellent D-Jet information web site

he has some tables and troubleshooting info...

I have breaker type- points-

I'd ditch the points and go with an electronic setup (pertronix, crane, etc...). If it starts out okay cold, and then loses power after warm-up they might have the valve/rocker gap too tight.....just a thought.

Hi check your trigger points smooth movement (lube) clean points and lube cam lobe. Then the FI harness for grounds and mine had a couple terminals ready to rot off the end of the green copper wire. I removed every plastic plug from the harness to inspect the crimp connection where I found the green copper wire corrosion. One terminal fell off when I opened the insulator clamp of the terminal. Every terminal has 2 clamps one for the insulation and other for the copper connection. I cut the casing off the harness to inspect the insulation for cracks or stiffness. Then used spiral wrap from raido shack and heat shrink tubing from another eletronics supply.........Oh yea I found alot of loose connections on the ECU connection. The ECU plug has terminals you can slide a feeler gauge into to feel the difference of each terminals grip on the ECU then pinch the terminal tighther as nessary. Mine had loose ECU terminals on both 12v supply's and the ground and on trigger points all thoes C clamp looking terminals. My intermintent miss took awhile to find sometimes ran 3 days fine and other days it would come and go in one ride. It got so bad I would park it a week out of anger and thats hard to do with a street legal 914. Good luck mine drove me crazy. I agree with the pointless ign. I cant feel any play in the distrubitor but my timing light jumps all over the mark. I think the perlux ? pointless ign will help that. Good luck my miss about drove me crazy. Did alot of reading on this board and alot of procedures like soldering the rivets in the relay board. That one didnt help but it was a process of elemination. Sorry bout the long post hope it helps.

Thanks, DJsRepS

Slap a timing light on the engine and warm it up. Check the timing marks for jumping, blurring more than 1/2" etc....thats what bad dizzy bearing looks like. You can also pop off the cap and see how much slop side to side the dizzy has. Should be fairly tight.
Geoff

Special K,

Thanks for your reply.

It seem to be a spark thing,IMHO

Comes and goes, when driving at revs you can feel it snap on (miss) and snap off (clean up).

Me gut says spark.

then I would start checking and cleaning all the grounds...tranny strap, battery neg, FI grounds block on engine etc....
Geoff

A miss at high revs could also indicate misadjusted dwell. Check the connection to the head temp sensor also. And yes of course, the grounds

My car behaved like that when I got it but it wasn't a worn distributor just one that needed to be cleaned. I took it apart, lubricated it, and added a Pertronix and driveability improved 100%.

The Pertronics fixed it right up, did it?

Yes, a ground check is in order.

The problem is not dizzy bearings, too repeatable after further testing ( Bad dizzy bearings are much more "excentric" ( greater swings in timing?).

This problem seems to be heat related- happens when the engine is good and warm.

What does the head temp sensor do? dwell adjustment?

To drive the car, the "miss" seems consistant with a "flaky" electrical connection, ie. in corners sometimes it will suddenly clean up and there is a certain "on" - "off" feel to the power going in and out.

I will first check the grounds, then go thru and clean every FI electrical connection I can find.

Thanks for the feedback to all

When you had the engine worked on---do u still have the aluminum pushrods?? if not the valve clearance specs will change---that sounds far too like too close of a clearence.

The head temp sensor is a part of the system that is a requirement for it to work. It's the wire coming out of the engine tin above and right of the # 3 spark plug.

Dwell is the amount of degrees the points are open (for spark). An essential for proper tuneing.

vsg914,

Does the head temp sensor (thru the d-jet I suppose) vary dwell?

No. Do you have a djet system? 2.0? 1.7?

1.7 1972 d-jet, l-jet, it all the same thing.

stock FI...

All the same thing? Who the hell told ya that?

My idea of humor, could not remember which the car has...

Sorry, my humor often does not always translate right to text.

It almost has to be a Djet the Ljet has a big ugly box before the ugly airfilter, the air flow sensor. Also my stock 1972 1.7 has Djet. I doupt it was an factory option, lets see Ljet or Djet ??? Take the cap off lay it to the side, pull the green point's wire off the coil, 10mm wrench loosen timing clamp, pop off adv vac hoses, and trigger pts wire, spin dist all d way left, 13mm nut on block remove, pull the dist then trigger points then advance plate clean clean clean then lube then ohm with meter. Mine had rust stains on dist cam lobes and one of the trigger points had gummy feeling movment had to lube the piviot. The dist can only go back one way offset slot. But you will need a timing light. Always set your points/dwell before the timing light. Do the points up grade apx $80. Im doing mine asap$$$ as my timing mark jumps around setting tring to set the timing.