$50 at P-parts if you know the answer

[RazorRacer]

I have a 78SC that has had a problem since I bought it about 6 months ago. I am offering a $50 gift certificate to anyone who knows the solution. There is plenty more information in my previous posts.

Starts great hot or cold.
Idles great and revs great with no load.

Problem - Hesitates under load.
Problem - Heavier loads generate a stronger hesitation.

P-car runs great under load and rpm's greater than 5800.

What is it about the engine being under load between idle and 5800 rpm in 1st, 2nd, 3rd, 4th, or 5th gear that causes the p-car to hesitate?

I am fairly new to car repair, so please don't tell something that I won't be able to do.

[stray15]

Clogged up cat maybe??

Just a guess.

[Bill Douglas]

Good strategy Razor

I'll put my extra serious thinking cap on this time and try again.

Bill '79SC

[Vipergrün]

I'd guess the CD (capacitive discharge) unit. My 79SC did a similar thing, but tended to be only in the higher RPM's. You can test this easily enough by swapping it out with a known good one. My symptoms were almost as if the fuel filter was clogged.

cheers
-Brad
80SC

[john70t]

Weak coil, low fuel pressure? (I know thats two)

[Adam]

Have your fuel injectors flow tested.

Change the fuel filter.

[john70t]

Another thing (but probably not it) often overlooked are injector seals. I changed mine in an 84 Golf and they were hard as a rock. Could lead to an unmetered vacuum leak=lean miss.

[Wayne 962]

Check fuel pressure and vacuum pressure, but it does sound like it could be a cat issue...

-Wayne

[JackT]

Have the warm up regulator tested. My car was missing under load. I replaced fuel injectors, spark plugs and wires, rotor and distributor cap but the car kept missing. Mechanic tested WUR and said if not that then fuel distributor. Fortunately did not have to replace the fuel distributor because by that time I was pretty discouraged. Now it run great, knock on wood.

[Wil Ferch]

Hi:
How about some basic checks.....ignition wires ( check individual resistance), replace if necessary...and partially clogged injectors ( run a few bottles of Techron through).
--Wil Ferch

[bell]

i'm gonna say fuel filter but i'm leaning towards the cat

[stormcrow]

If you had a loss of power across the rpm power band, then I would say it was a clogged cat. But because over 5000 rpm it runs strong I would rule that out.

Could be a weak spark plug that is causing the problem. At high rpm it wouldn't show up as much as at lower rpm. If it was a fuel related problem, the problem would also be there at the higher rpm (blocked filter etc.)especially if it was a fuel flow restriction.

Check your distributor cap - make sure your connections are tight, pull the plugs and see if any are fouled, and check your high tension wires.

Steve

[Sunroof]

Look for cracks in the distributor cap...

Bob

[dickster]

definitely fuel related, imho.

as a ot example i have a sports bike that i recently put a race exhaust system on and it does the same thing severly-below 2.5k. i went to do an overtake the other night ( in second gear i think) , and so with the engine at 2k i opened the throttle right up (no clutch use) and the engine just bogged right down. i kept it there for a few seconds (usually clears itself) and it would not budge (embarassed ). i had to drop down a gear and slip the clutch to get past.

i'm pretty sure the bike just needs a remap for the new exhaust.

my 3.2 does the same thing but not so severly - i just live with it, and use more revs.

yours sounds worse than mine though. i'd give it a thorough service/tune. have you replaced anything?

[pbs911]

The sy7mptoms sound exatly like how my car ran when i leaned out the fuel mixture for my smog test. At a CO level of .5 @950 rpms, out the tail pipe with air pump and no cat, the car idled great and had good top end pick up. However the mid range of the car was gone - not enough fuel.

I would check the fuel mixture ratio?

[Talonz82]

Check your vacumne advance on your distributor, make sure hose's are not crimped, brittle, broken.

You can check this with a timing light also, let me know if you need more info.

Good luck, Peter

[Kevin Stewart]

You may think this is silly, but have you tried the cap and rotor, had this problem before and it was the rotor button, Kevin

[Bob W.]

When ever I am having problems with the CIS system, I always change the fuel filter first, then the starting point of investigating/testing is with a clean filter.

Bob w.

[RazorRacer]

Well now...these are some good suggestions. Thanks.

I have checked the cat. converter and the guts were gone and the screen was hanging into the muffler (see photo). Could the cat. converter still be a source for the problem?

I have changed the fuel filter. I have also changed the fuel pump with the internal check valve.

I have checked the vacuum advance and timing.

Things that I need to check are:

fuel mixture (I will try this tonight).
ignition wires (I will try this weekend).
distributor cap / weak spark (I will try next week).
vacuum / fuel pressure (I need to purchase test unit).
If those don't solve the problem, then I will test:
CD unit, WUR, fuel injectors and fuel injector seals.

I was hoping someone would say definately that the solution to your problem is ... but I guess there's not enough information. If one of the items above solves the problem, I will gladly honor my offer of $50 at P-parts.

Thanks again.

[Pillow]

Maybe the rod in the fuel distributor is sticking.

Once the max air volume is reached at 4800 RPM the final tug probably yanks the air flap down and fully engages the fuel distributor rod.

This seems to be a common problem on VW Rabbits from what I am told.