Running very poorly when warm...

woboyto · Post by **woboyto** » Mon Feb 05, 2007 10:20 pm

I just got a 1978 Campmobile. It runs good when the engine is cold but once it gets warm it starts missing and sputtering horribly. There is pretty much no power. I have the manual by John Muir which has given me a few ideas.

1) the engine is too hot (maybe because the van was rear-ended and the engine compartment isn't sealed? Some other malfunction in air cooling system?)

2)lack of fuel (dirty fuel filter? bad pump? there don't seem to be any leaks. I also dont know why the fuel system would suddenly fail when it gets warm.)

Any help for this newbie would be a lot of help.

raygreenwood · Post by **raygreenwood** » Tue Feb 06, 2007 8:33 am

Which engine? Is it fuel injected (I am assuming its is). Let us know a few basics and what you have and have not done. If its injected, there are a whole range of possibilities....mostly different than if it has carbs. Ray

woboyto · Post by **woboyto** » Tue Feb 06, 2007 10:39 am

Yes it is fuel injected. I have installed new spark plug wires, points, condenser, spark plugs, checked the points dwell, and timing. The guy that sold it to me might have replaced the air intake controller but it doesn't look brand new.

raygreenwood · Post by **raygreenwood** » Tue Feb 06, 2007 10:51 am

First thing. Check every hose and vacuum connection. This includes: injector seals, runner boots, vacuum can on dizzy, valve cover gaskets, oil breather gasket, intake gasket, the o-ring between TB and plenum and all hoses.
Next you need to see hwat you fuel pressure is. You need to check at idle and with teh vacuum hose from teh fuel pressure regulator disconnected.
Also...did it run normally before the tune-up? What plugs wires and brand of parts did you use? What about the cap and rotor? What brand of points and ehat is your timing set at?
The fuel injection is very sensitive to vacuum leaks. This includes teh boot between the TB and the air metering unit. It must be crack free and clamped.
Also...while you are trouble shooting, check the ohms on the cylinder head temp sensor and match to the book.

The symptoms you are having are assignable to everything from poor connections of the fuel injection wiring to vacuum leaks to fuel pressure. Let us know what you find and we can help you. Ray

woboyto · Post by **woboyto** » Tue Feb 06, 2007 11:15 am

Thanks.....but whats a TB....It was running the same before the "tune up" and
the timing is set to 7.5 btdc. I don't really know what brand the points, and spark plug wires are. The spark plugs are autolite, and i haven't replaced the cap and rotor. Ill start to do what i can...THANK YOU!!!

woboyto · Post by **woboyto** » Tue Feb 06, 2007 11:31 am

Man some of this stuff is hard to check and i have no clue where it is....you wanna take a vacation to San Diego?

It was 72 degrees and sunny yesterday and im sure this fog will burn off soon today.

This may seem stupid but does the air filter affect the system? I dont have one of those. And also there is a tube on the air intake box(toward the front of the car) that points up and has nothing attached. I bet the problem would be very obvious to a trained eye.

woboyto · Post by **woboyto** » Tue Feb 06, 2007 12:37 pm

As I am reading more from how to keep your volkswagen alive im starting to think it might be the cold start thermostat or jet. I am still reading to find out where all the important hoses and vacuum hoses are. I have found that the tube running to the firewall from the intake air distributor (Im guessing it is the kick-down vacuum tube for the auto-transmission-DAMN all automatics) is loose. When the engine is running i can definitely hear a hissing sound like a vacuum leak. I cant tell where it is coming from yet.

Also the alternator is not working. I'm trying to give you all the info i have.

MedicTed · Post by **MedicTed** » Tue Feb 06, 2007 3:09 pm

A vacuum leak is an intake leak. It will cause it to run lean. While in cold start mode, then fuel mixture is enriched so it is compensating for the leak. Fix the leak.

regis101 · Post by **regis101** » Tue Feb 06, 2007 8:19 pm

But how long after starting do the symptoms appear. Immediatley after cold start? 20 minutes? 30 minutes? Need more info from you.

Easy check is the cheap-ass rubber elbow at the Aux Air valve. major vacuum leak.

Also crawl under and grab ahold of the fuel pump. Should be warmish. not hot to the touch.

Remove the gas cap to maybe release pressure (vacuum actually) due to clogged tank venting.

Read up. Especially the Bently. My public Library even has one

raygreenwood · Post by **raygreenwood** » Wed Feb 07, 2007 7:35 am

Yes, learn a few of the terms. We can help you with all of this. My suggestion also....is to put the Muir book on the shelf. It has some useful cross reference material for part #'s but little else of use on fuel injected vehicles. Ray

woboyto · Post by **woboyto** » Wed Feb 07, 2007 3:32 pm

i think i figured it out.

I found the tube that was leaking and diconnected and plugged it so it stopped the majority of the leak. It ran much better. However my brakes were much weaker so i am assuming that the tube i disconnected was a brake booster vacuum tube.

Thanks a bunch everyone. This site is awesome.

regis101 · Post by **regis101** » Wed Feb 07, 2007 6:51 pm

Nope. Not good enuff. Get back here.

What tube? The ~1/2" diameter hose/tube from the left side of the center plenum? You mean the rubber thingy that has three tubes/hoses into it? That was cracked? Or was it the rubber thingy that connects (the) tube to the center plenum?

Peace, Regis
78 campr
89 325is
98 328i

woboyto · Post by **woboyto** » Tue Feb 13, 2007 5:16 pm

yes it is that tube. I dont know that the rubber thing with three tubes/hoses attached has a crack. Its running much better now that I fixed the leak in the brake booster tube. The leak was in the directional valve thingy.

raygreenwood · Post by **raygreenwood** » Wed Feb 14, 2007 8:02 am

Yep, that is a common problem. You need to check very carefully for vacuum leaks. I always tell people that if you yourself have not replaced any given rubber componet....assume that it is a potential leak. Zero vacuum leaks are allowed. Ray