Stalling at cruising speed

My mk1 cabriolet (Pierberg 2e2) is stalling at cruise. I’m a newbie, only a beginner mechanic so trying my hand where I can.

Here’s what she’s had:
New coil, new sparks, leads good, new switch, new fuel pump (last owner), new throttle cable and connections(last owner), new fuel tank and lines (last owner). I adjusted distributor too, so she idles nicely.

She was running great, even drove her from wales to Scotland last summer.

But recently she keeps stalling out at cruise, especially where she needs to work on the slightest incline.

Seems to be starving from fuel or air, so thought about tweaking the mix screw but on research that seems to just influence the idle mix.

So looking for some advice - any ideas and guidance welcome, thanks!
Mark


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Tell us a bit more about the circumstances when it stalls - while changing gear, accelerating, driving uphill, slowing down, coasting, what kind if speeds, etc?

Normally when accelerating/cruising around 40/50+ mph. She drives fine at low speeds (30), its normally when I go to open road and often when there is an incline or if I accelerate harder. It often occurs after she’s up to temperature, so I wondered if that was something to consider too.
Thanks


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Does it completely lose power, or just become jerky and hesitant? When I first got my Scirocco, it would sometimes  become hesitant and jerky at higher speeds. This turned out to be a split in the rubber section of the carb mounting flange.

The carb/air cleaner assembly should be horizontal and feel pretty solid if you try to tilt it from side to side. If it looks lop sided or is able to be easily tilted, that will likely be your problem, part number 026129761E

Does it restart straight away or do you have to leave for a while?

It’s as though there’s not enough fuel getting through. No jerking, no immediate stop, just a slow frustrating loss of power and revs start dipping and just coasts to a stall. Pumping accelerator pedal does nothing.

When restarting, it needs a few attempts with giving it some gas and she eventually starts up again. But then the cycle repeats [emoji3061]

Checked the carb/air placement and flange, all tight. Maybe tweak air mix screw?


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It does sound like a fuel starvation issue, as though the carb float chamber is running out of fuel when higher demand is placed on it. A partial obstruction in the the fuel line or blocked filter on the intake tube at the base of the fuel level sensor assembly or at the carb inlet port. Or a failing fuel pump.

The mixture screw has a negligible effect on mixture except at idle or very slight throttle opening, so is unlikely to have any impact on the problem

poss a failing fuel pump?, remove fuel hose to from pump to carb and cranking over there should be a healthy spurt….

or very much symptoms of muck and rust in the tank via a rotten fuel filler pipe

Even if filler pipe is replaced the tank needs cleaning out. Under rear seat is inspection cover to get at an remove the fuel sender. Remove and look inside with a torch.

Cheers folks, really helpful. I’ll look into these and report back [emoji106]

Might be a wee while to get the work done as have a new-born at home! But I’m itching to get working and get her out in this fine weather, so expect I’ll find the hours


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Had something similar.
Can be fuel filter or vapor separator.
In case you want to know how 2B carb works, see
Volkswagen Audi Group - Carburation II - The 1B and 2B Pierburg Carburettors - Adjustments (1984) - YouTube

May I suggest another possibility, that I personally have seen with a Toyota that my wife drove?

1976 Toyota Corolla Coup SR5.
My wife claimed that the Car wouldn't go over 45 mph.
So I get in and drive it around with no issues 70 mph for about 10-15 minutes.
Then she says a few days later that it won;t go over 20 MPH….Same thing.

Verified her story, get in new plugs, wires, dizzy cap.  Nada.

Remove the Carb, rebuild it, rule out the Fuel pump.
Still the same thing.  Have the carb rebuilt again same thing verify the timing spot on. It always idled great.

Taking the Air cleaner off, and running the car Noticed that when it was choking down, That Fuel was occasionally shooting up out of the Carb.

Disconnected the Muffler (silencer), which looked from the underneath to be Pristine, and only 6 years old was rusted and rotted out.  The top of it had caved in and Plugged the Exhaust or silencers input…Dang.  Funny thing it did the same thing about 4 years later but I caught it quicker.  I had an identical Toyota SR% liftback that burned unleaded gas only no Cat.  Still had the OEM muffler, with never an issue.  Hers that was built 6 months earlier ran on regular gas.

What I have seen on my 92 cabby similar issues but unlike having a blocked tail pipe, I had timing gear shear.
Idled great give it gas, and it would struggle jump time
then jump back in time. I only found it when I decided to replace the timing belt Ruled out everything else (as in going down the rabbit hole.).  I found the timing gear could move about 90 degrees or some times 360.

Needless to say that the Previous Owners Service Person (POS) who replaced the timing belt over torque. the crank bolt (12pt) to over 110 pounds which forced it to the end inside of the crank and bent the tip about 5 degrees.Ruining the crank. Had to Drop the Crank with the seal carriers, out. Took to a machine shop to salvage it… WRONG.  It took them with a 1 inch  pneumatic impact wrench 260 to 300 PSI to remove it. while it didn't shear, it did back out enough for the cam gear to slip over the keeper. Couldn't wrap my head around what I was seeing with a timing light.  Occasionally I  too have crainialrectumitius.

So just so you don't get snookered.

 
Sorry for the bad pic, but it was a 1mP camera.

 

Cheers Kris and Briano - loads to unpack in that post!
I’ll try and put together a diagnosis list, starting from the simplest issues


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