90' Cabby, revs up, stumbles, revs up, stumbles, dies.

[CR500Rider]

Howdy gang. I'm about as new to water cooled VWs as you can get. I picked up a 90' Cabriolet (auto) needing a ton of work. The engine ran fine but had a leaking head gasket. The body is straight, the price was right and I was willing to replace the head gasket (and have the head reworked while it's off). Got everything bolted back and when starting the car it revs to somewhere around 3K, drops RPMs to around 800ish, revs back to 3K then back to 800ish until it finally stumbles and dies. It will fire back up and do it all over again. Is there a diagram showing the vacuum hose routing? Any other ideas?

[Briano1234]

www.cabby-info.com.... That sounds like a vacuum leak, but another question is did you re-use the head bolts or new, as the head bolts are one use only.

Check that you have the injectors sealing also as you can spray carb cleaner on the hose connections and where it is leaking you will hear a increase.... I would also suggest that you replace all the cloth covered hoses that are left on your cab....

Lastly check that the Air Intake tube doesn't have a crack or weak spot where the ISV plugs in to it.

[CR500Rider]

Thanks for responding and yes, new head bolts! I'm going to check and replace vacuum lines today. The plastic piece on the dipstick tube and the gas cap are missing. I've got a slight drip on the thermostat housing as well. Those are ordered. I did notice something, my airbox has only one "stud" sticking out to attach (did that make sense?). I moved the airbox while the car was running and it shut off immediately. Fired back up so I'm going to investigate that as well.

[Briano1234]

Thanks for responding and yes, new head bolts! I'm going to check and replace vacuum lines today. The plastic piece on the dipstick tube and the gas cap are missing. I've got a slight drip on the thermostat housing as well. Those are ordered. I did notice something, my airbox has only one "stud" sticking out to attach (did that make sense?). I moved the airbox while the car was running and it shut off immediately. Fired back up so I'm going to investigate that as well.

The gas cap, and the broken oil tube are vacuum leaks. Napa usually has the dip stick funnel buy 2 as a spare is always nice.

[CR500Rider]

Made a little progress on the cabby yesterday. Tightened up and replaced the missing vacuum hose clamps and got the idle to settle down a bit. The idle isn't perfect but it's drivable. Still waiting on the gas cap and dipstick funnel. I also need to order a PVC grommet cause mine is so worn it basically "sits" there. Now to make the gauges work.

[Briano1234]

Napa has the grommet for the valve cover as it too is a vacuum leak, also there is a o-ring on the back of the throttle body that is on a brass screw, count the turns to remove the screw take it to the local hardware store and get a replacement o-ring. (that is of the screw can be wiggles or turned by hand the o-ring is dead.

[CR500Rider]

I have the funnel on order but tried NAPA. They couldn't find it.

[Briano1234]

Oil dip stick funnel

http://napaonline.com/Catalog/CatalogIt ... 0257240212


7 dollar grommet
http://napaonline.com/Catalog/CatalogIt ... 0323785045

3.5 dollar grommet
http://napaonline.com/Catalog/CatalogIt ... 0257240170

Told ya so,,,,, na na na na na na....

[CR500Rider]

I didn't doubt you one bit! Lets just say the NAPA around here is about on par with Autozone. I got the dipstick funnel and PCV valve grommet installed (thanks for the links). Still waiting on the gas cap. I ordered the "hose flange kit" to fix a slight leak and a couple other things that looked like they would eventually leak (plastic cooling connections). The car fires up and drives decently. The rev, stumble, rev, stumble has all but gone away. I'm hoping over the next couple of days I'll be able to pull the throttle body and clean and check that screw/o-ring. Thanks again.