Hi all, I have a 89 VW Fox, 4 speed, that suddenly wont idle. When I take my foot off the gas the motor usually cuts off. When it runs, its very rough. If I give it a little more gas it smooths out. What is some possible causes? Thanks for your help.
kevin
vacuum leak possibly large intake boot cracked
lol They hid that adjusting screw from you huh! SHAME on them!! Some of them might have had an anti-tamper plug on them. I have not seen one of those plugs in soo many years I might even be mistaken.
That idle adjusting screw should be on the throttle body just like the Rabbits except easier to see IIRC. Jim you do very well with the answers! I would call you a GURU! :-)
Now the OP could have other issues such as the engine is running too rich, or the secondary throttle plate is stuck open or ????
One thing I have done on other cars like my Toyota and a Sunbird was clean the throttle body where the butterfly valve is. PCV fumes and oil gunk that all up. I haven't seen that issue on those older VWs as they seem to vent in a better way. Now my TDI is another story.
Back to Dave's original air leaks idea. I use unlit propane to find vacuum leaks. Aim at likely areas to see if the idle bumps up. Some use carb cleaner but I am afraid of goofing up paint with that stuff.
That is funny that they were c>lol
Common in cars pushing 2 decades are rotting vacuum hoses. My 88 has a bunch of vacuum hoses. Start with about 10 ft of .25" vacuum hose and replace all that size. Then, buy to size the larger ID vacuum hoses and replace. Don't forget the charcoal canister hose. Careful, some fittings are plastic, can be easily cut or broken.
Temp sensor may be defective causing the vehicle to run on the rich side. Possibly, preventing normal idle, rough running, aid with gas pedal for more air to allow it to run.
Another similar looking sensor that controls warm-up period may be stuck, not timing out. Thermo-time switch its called.
"Brain box", actually a bridge resistive network, has no data processer, may be defective. Located under glove box.
Any defective/kinked wiring associated with the 2 sensors mentioned and the "brain box" can cause similar results. Check the Bentley on how to troubleshoot.
That sounds like a good idea. I had to replace plastic T-fittings on my Scirocco because the carb cleaner a mechanic used dissolved them.
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