I'm trying to eliminate throttle hesitation immediately after press. Happens hot or cold. When in neutral the the engine bogs/sputters briefly then revs. When driving there is no felt acceleration then the car picks up speed. It feels like an accelerator pump with a torn diaphragm or obstruction to those familiar with carburetors. Car runs has not been on the road in years, while I'm sorting out a host of issues. Nearly there... I think!
I have replaced:
the first fuel regulator, was leaking. checked the pressure, now within specs.
the fuel pump (dead) and filter
checked the throttle voltage for dead spots while opening, none seen on an oscilloscope recording.
checked the vacuum tube to the ecu for obstructions, none.
rebuilt and balanced injectors, new hoses (LEAKING!!!)

Can you think of anything I've missed?

 

OK,

The Full Load Fuel Valve, and/or the micro switch, they are connected so either will richen things when needed, is NOT working.

1) The Blue./White valve is located somewhere near the 5A Inlet Tarck. This a vac to keep the contacts OPEN, and as vac drops (you hit the gas) the contacts lose, teh ECU richens things about 10++%, and a way you go.

2) The Micro switch is on the REAR of the throttle capstan, and st switched into operation by a built in "cam" in that capstan.

1 & 2 are 2 wire items, and the wires are paralleled, so either /or item will give the enrichment needed.

Next, the timing is too far advanced, not common, but just saying.

The Mechanical advance of the distributor is seized, VERY COMMON.

The setting of the TPS, has been done without the spacer fitted to the idle stop of the capstan.

The throttle bodies are contaminated with Jaguar Black Goo.

Lots more things in the Sticky, "Worksheet..........." at the top, as well as the "HE tune up" Sticky.

If nothing new, ask and I will drin more and think more, simple.

 

The black goo....together with mis-adjusted throttle linkages and/or worn throttle bushings, was my first thought.

Cheers
DD

 

In addition, I would also check what happens to the fuel pressure when you open the throttle. Also i would eliminate the A bank FPR which make pressure testing far easier.
I would change the filter as a precaution, even though it is new, and blow out the fuel line to the engine. I spent months chasing this exact problem on a Range Rover once, and it turned out to be a duff brand new filter.

 

I checked to ensure the distributor was not seized then did an Italian tune up. Not gone, but noticeably improved.
In the mean time the brake light switch stopped working. So I opened it up, cleaned it out, filed everything flat, and put it back together. I have brake lights again.

 

check the throttle position sensor. It should have a gradual increase in voltage when plugged in, key on. I'm not sure what the starting range or finishing range should be but it is usually .5v to 4.5v start to finish. If it is not a gradual increase from start to finish, you found a problem.

 

best to use an older, cheaper analog multimeter for this test, you know the kind with a needle, rather than the more common digital meters. As soon as you see the needle hesitate, or drop, you know there’s a problem. The digital might skip this over.

 

I think it should be, at start, key on, not started, .32 to .36...?

 

Is the voltage to these switches supposed to be 12 volts? 5 volts? Mine is 3.7v which I'm sure isn't right.
More stellar repair work by jaguar of Troy Michigan.

 

Memory??, 12V.

I dont have a V12 anymore, so cannot check for sure.

Greg will check his car, kindly, for us when he wakes up.

 

Sorry to blunder in im on mobile phone, is this a car with o2 sensors?

Bog and near stall condition will result from ruined non functional o2 sensors. My car would practically stall on a green light then catch and go -- shop said the o2s were original (gasp) new heated sensors have great response time much improved throttle mpg etc. No more boat gas smell at idle.

 

I think this is right because I used to use the 12v as a source when I use a timing light. I also noticed my turn signals don't work which is on the same fuse as the enrichment power, I believe.

 

Hmm. Thanks for the info about this Grant... I never knew what this was. I had assumed (and you know what they say) that this blue set up had to do with the blower (which I removed) and controlled the air being blown into the manifold, or sumpthin... Currently, this gizmo is in a bag in the boot... Plugs are still there,,,... Should I bother with it?

 

In my opinion you should. It is probably the first indication for heavy throttle enrichment to the ECU, because it is MAP based and the MAP drops quickly with a quick, large throttle opening. It enriches before the switch on the throttle.

 

The enrichment switches are not fused.

However, the kick down switch, which is on the throttle cable right next to the throttle capstan, is fused with the signals and brake light.

The enrichment switch (mounted on the capstan) and the kick down switch are often confused as they look alike and are mounted near each other

Cheers
DD

 

Thanks Jeff... I will take some readings off the leads, take a look at it, and maybe hook it back up... If vacuum driven I guess I will have to figure out accessing another port on the rear of the A side. About the vac. Some ports are a little bigger than others. Does it matter which sized port? Does the rate and amount of vacuum in that instant make such a difference?

And, which area would I find the wiring info in the ED? In which category?

 

These and this, I guess... 25.1 in the 1990 ED...
Call me an old timer if ya want, but I never hit my throttle so hard, ever. Fear of sumpthin breaking loooose! Haha

 

thanks Doug. This is not good as that goes to the new transmission.

 

Easily done I suppose.

The wires for that Blue/White, AND the Capstan Micro Switch are probably tucked down near the heater tap.

The Blue.White will change fuel mixture on light load even, It is Vac reliant to keep the contacts OPEN, and as the vac drops to a predetermined value, the contacts close, and away she goes, without stumbles etc.
The Capstan Switch does EXACTLY the same, but at "about" 2/3 throttle opening.
This all protects the engine from LEAN MIXTURE in any given scenario.

SIMPLE.

That Blue/White is adjustable, see the PDF attached. I spent HOURS driving around with my 1/2 leg to get MY driving style recorded, as far as vac readings went. Then did teh same with Spouse driving. I then adjusted that Blue/White to where I wanted it for OUR driving. That really did change the whole performance of that engine.
I also did NOT run a trans kickdown switch. I cannot get FULL throttle, same leg issues, and Spouse is way too short to even think of that. Sooooo, a compact adjustable Vac Modulator in the transmission, MUCH driving and adjusting, and whoopee, another SO SIMPLE fix.

 

For the purposes of the enrichment switch, no, I wouldn't think so.

The vacuum switch actuates at [something like] 3" of vacuum...which is pretty low. It's not a situation where instantaneous vacuum response is needed

Cheers
DD