Here's the background...

When I bought the 914 it had a single Weber progressive carb, was well tuned by the PO's mechanic, and the car drove great. I got a box of all the original fuel injection parts + some extras when I bought the car.

I dropped the engine to clean the engine, engine bay, and re-install the FI system (including all emissions gear -- EGR valve, decel valve, canister, etc). Also put in new injectors, plug, wires, oil filler gaskets, air filter, points, condenser, cap, rotor. All new fuel lines and vacuum hoses. Tuned the dwell to specs, set timing, adjusted idle, etc.

I ran the car through emissions on the weekend and it passed with flying colours.

Here's the problem, when I punch the accelerator pedal it "stumbles" (misses?) and only when I ease off the gas does it run smoothly. I have to gently increase the RPMs to avoid the stumbling. It seems more pronounced in first and second gear, but I'll have to check into that some more. I was preoccupied with the sticky brakes and grinding shifts to get a real feel for the exact conditions when it occurs. Those are to be addressed soon.

I plan to go through the L-jet troubleshooting I've found here and on the web, but want some advice from the experience L-jet folks who have been through this similar problem.

valves and timing/dwell
check them again.
Check fuel pressure with a gauge, adjust to proper settings.
I just had the pump kinda die....wierd...put out 15 psi...no more...
Could also be a failing AFR...

Rich

I didn't mention: new fuel pump and filter.

Fuel pressure is good, and I don't think it's adjustable (the regulator doesn't have an adjustment screw).

I did adjust the valves prior to reinstalling the engine and double-checked them when back in the car. I'll go through the procedure again to make sure I didn't do it wrong.

Check the fuel pressure.
Its a rising rate regulator...and its 35 years old.

Rich

The regulator's job is to keep the pressure in the fuel system to a constant 28 psi. It does this with a spring-loaded diaphragm that controls a valve. The valve, when opened by excessive pressure in the fuel lines, uncovers a fuel line that returns excess fuel to the fuel tank.

The vacuum connection is there to help reduce emissions during deceleration. During deceleration, the vacuum connection serves to open the fuel return valve wider, which reduces pressure in the system and prevents excess hydrocarbon emissions due to less fuel being injected as a result of the lower pressure in the system.

This is a very nicely designed device in that it provides for an automatic self-adjusting pressure regulator and emissions control device all rolled into one. The simplicity of the design also contributes to its reliability; the fuel pressure regulator rarely, if ever, goes bad. There's just not much to go wrong with it.

Unfortunately, it's not particularly tuneable either. With Bosch's older FI system, D-Jetronic, the fuel pressure regulator was adjustable. The L-Jetronic pressure regulator is not.

Throttle Switch..

This switch does nothing more than tell the ECU to enrich the fuel/air mixture (more fuel) when the engine is at full throttle.

The switch can be tested. Measure the resistance between the two switch terminals. With the throttle closed it should be infinite ohms. Then open the throttle all the way, you will see the cam close the switch and hear the click, at which point the resistance reading should drop to near zero ohms. If the switch doesn't quite make it, it can be adjusted where it mounts for proper functioning.

Good call on the TPS, I don't think I checked that yet.

I think I have a spare fuel regulator in my box of parts so I'll swap it out to see if there is an improvement. Can you explain how the regulator functions under high acceleration?

i don't have anything concrete to add but i wonder if a faulty distributor vacuum advance would cause such a problem. so i'm asking the question: what are the symptoms of a faulty dizzy vacuum advance?

Vacuum advance just gets the advance plates to move to the advance position a bit faster than without it....so, if you unplug the vacuum, it will still advance all the way using the wieghts and springs.

If the vacuum advance hose or the diaphram leaks...its just a simple vacuum leak which makes the car run lean and erratic.

Rich

According to my Haynes manual (page 51), on L-Jet cars, fuel pressure should be 35 psi. So which is it? My car is set to 35 psi.

so is mine....

Rich

I removed the TPS to clean it and this is what I found:

Click to view attachment

It doesn't look like what I was expecting per the Pelican tech article: http://www.pelicanparts.com/techarticles/9...brate_17-18.jpg

The part number on it is correct (022 906 111D) but to me it doesn't look adjustable. I'll clean up the contact and see how that goes.

I cant see the pic...to fuzzy
Its an on/off switch that adds fuel at WOT (where your problem is...right..???)
Rich

Yeah just flips common to one terminal or the other (WOT and idle). The contacts look alright no worn circuit traces like the other types.

So the Pelican Parts adjustment guide is wrong, doesn't apply to 1.8L L-Jet.

Not sure what you are talking about with the PP article...could be the Djet TPS....

Your issue was a WOT issue, yes???
It may be this part that will help fix the problem.

If you can play with positioning it may eliminate the stumble you are having....
Based upon the logic from the other TPS swithes you probably need to get it set just right at Idle...then WOT will happen at the right time.

Rich

The PP article says the adjustment procedure applies to 1.8L but it doesn't since the 1.8L L-Jet TPS is a three connector and doesn't have provision for adjusting CW and CCW. Plus the terminal designations in that article are incorrect. It must be for 1.7L D-jet only. I deferred to the shop manual on this one.



The only adjustment I could figure out was to carefully bend the contact tabs so that the circuits close at the right time. I put it all back together and checked terminals 3 & 18 at the CPU connector, the circuit closes at WOT as it should. A test drive will tell me if this is the fix.

Before that I have to sort out my pedal cluster issue.