Car shuddners and loses power while driving

jetta
volkswagen

#1

I?ve got a 91 VW Jetta with 353,000 miles on it. For all intent and purposes all I?ve done is replace the oil and oil filer.



99.999% of the time the engine hums along as if it was brand new. But recently its developed a issue where it will suddenly shudder and lose power. I can keep the engine going by giving it more gas, and after a while, say 40 miles, the engine will slowly return to normal and then run fine for several weeks, at which time it starts all over again.



If I turn the car off while it?s having one of its ?episode?, the car will start up fine but once it reaches operating temperature, it will lose power again.



My VW shop keeps treating it as a fuel injector issue, but the other day, I pulled the air filter cover off and discovered the air filter was in the process of disintergrating. At least 1/5 of it was gone!



So my question is, could parts of the air filter have entered in intake manifold and caused the intermittent power loss?


#2

“I pulled the air filter cover off and discovered the air filter was in the process of disintergrating. At least 1/5 of it was gone!”

Has this filter ever been changed? I change mine out every year. It could very well be chunks of air filter blocking up air passages in your intake manifold. Since the car recovers for certain periods, maybe no lasting damage has been done. Clean out what you can and replace that filter.


#3

“For all intent and purposes all I?ve done is replace the oil and oil filer.”

If the car has really accumulated over 300k miles on the odometer with essentially no maintenance, then I am surprised that it runs at all. As BustedKnuckles stated, the first step is to clean out every vestige of the old air filter that you can find in the intake passage, and to install a new air filter. However, there is a very strong probability that the Mass Air Flow sensor (MAF) has been damaged and will need to be replaced.

For good measure, I would also suggest replacing the spark plugs, spark plug wires, the fuel filter, and all fluids, and also run a can of either Sea Foam or Techron through the next full tank of gas. I realize that you may be opposed to maintenance, but if you really expect this car to keep running, these items really need to be done.


#4

OK, maybe I didn?t make myself clear.

The car has reached 353,000 miles because I?ve been meticulous in my maintenance of it.

Being a Nuclear Engineer and former Nuclear Submarine Engineering Officer I am fully aware of how important maintenance is.

The oil and oil filer get change every 3,000 miles, I give it a can of Sea Foam every 12k, replace the spark plugs, wires, rotor and cap every 45k; brakes & gas, and yes, the air filter every 60K, &c, &c.

While it?s my ?beater car?, I depend on it getting me the 90 miles round trip to work and back every day. So it?s been well maintained. Just like my old Ford Fiesta which got me over 500K before it broke in half coming home from work one day. (I buried that car in my yard all those years of good service.)

When I found issue with the Jetta?s air filter, I did break out a vacuum and vacuumed out all particles I could find.

While I had the air filter container out, I reversed the flow of the vacuum to push air past the Mass Air Flow sensor to see if swung open - it did.

Now the car ran perfect today, almost as good as the day I bought it, but that?s the problem! It can run perfectly for days, weeks, or months then out of the blue, and without any warning, it will have what can best be described as an ?epilithic?? fit.

I?ve tried to identify a common precursor, the only thing that seems of importance is that 1) it always seems happens at times when the gas tank is less then a quarter full … (but only 1 out of 20 times when the tank if 1/4 full) yet filling it will not resolve the issue right away.

And the other common issue is if it is going to have a fit, it will only happen after the car warms up. It runs fine until it reaches normal operating temperature. Which makes me think that whatever is causing the problem is not in use, or is being bypassed while the car warms up.

For example, when the car has on those rare occasions ?suffered? its ?issue? for a few days in a row, it always stats up perfect, but once it reaches normal operating temperature, its acts up.

Does this additional information help?

Mike Hillman