I have a 88 cabriolet that chugs/misses at normal driving range. it has a new timing belt, plugs and wires. My ladies brother who is a mechanic but does not know enough about vw's to help checked the spark and say its strong and firing ok. I was told that the mass air flow sensors are known to be defective in these cars so i bought a can of MAF cleaner and sprayed all around the sensor and parts but she still chugs.

Could the problem be the oxygen sensor? Looking for any help before i go out and buy one as i see them on Kragen auto parts ranging from 15.00 all the way to 150.00. Also whats the differance between the single wire universal and a 3 wire unit. the 3 wire units seem to be the more expensive ones.

thanks in Advance for any Help!
The Dog!
Woof

 

If your having problems with the computer items, the
check engine light should be on or blinking. If the light
isn't on then you should be having problems with non
computer items. Fuel filters, injectors, etc.

 

No "check engine lights"...Does the car even have one? the dash has very limited "idiot lights"!

The Dog

 

1988 is new enough to have computer controlled
goodies.

 

Ok...with no "check engine light" on could the oxygen sensor be a problem. Im getting fuel, great spark, cleaned the mass air flow sensor.

also does anybody know the differance between a 3 wire oxygen sensor and a single?

The Dog

 

If the 02 sensor was bad the ck engine light would be
on. People jump to quick on the 02 sensor, all it does is
get carbon on it from the exhaust sense it's screwed into
the exhaust, You can use a good injector cleaner or use
mineral spirits or Laquer thinner for a cleaner, add about
1 pint to the gas and drive the interstate for about 50 miles
and it will clean the carbon off the 02 and it will work again,
unless it's broken some way. If you guess and start replacing
computer parts your throwing away money, you have to
have a system to analize the parts before replacing or saying their bad, can't guess at all. All 02 sensors work the
same, when their cold the produce nothing, when their hot
they produce voltage, about 3 volts. This voltage is
read by the computer and it changes the fuel system from
rich mixture to lean mixture, the rich mixture is for cold start
and cold running, the lean mixture is for running after normal
engine warm up. One wire or three wire doesn't matter,
have to use the one the car is built for.
Have you checked the valve adjustment? If they are
too tight that will make the engine run rough.
Also the EGR valve carboned up will cause the same thing.

 

geeze, where to start. First off, unless your car has a digifant 1 or 2 ignition system, and is specifically acar produced for sale in California there will be no check engine light. As for the O2 sensor being the culprit, I don't think so, it would most likely cause your car to get worse fuel mileage. The main difference between the 1 and 3 wire sensor is this, and please bear with me its kinda long winded. The O2 sensor is a catalyst that generates a voltage based on the difference in oxygen content in your exhaust and the ambient air outside your vehicle. In order for it to do this it requires the sensor to be heated up beyond a certain temperature, i don't know what it is off hand so i won't guess, the one wire O2 sensors use the hot exhaust gasses to heat up the sensor where as the 3 wire ones use electricity to do it, which heats it up faster. The voltage created by the sensor is between 0volts and 1volt depending on the difference in oxygen content. The higher the difference, meaning the richer your exhaust gas is the higher the voltage created will be, ideally a car will try to maintain a .5volt reading which creates the best combination of engine performance and low emissions. Your car will have valve shims that are used to adjust the valve clearance, or if its a later model it will have hydraulic lifters, either way if your valve clearance is the problem there will be a very obvious clicking sound coming from the engine. I'm not 100% sure on this one, but my 1990 vw had no egr system, so i don't think yours would have one either. As for the rest, its kinda hard to try to diagnose without actually being at the car to do some tests to. hope this helps.