VW rabbit stumble at stop

[jmarshall024]

Hi all-

I got my 1981 VW rabbit convertible out on the road today for the first time in over 5 years!

Overall is runs pretty good, but my two main complaints - (1) until it has been running for about 5 minutes the car needs some feathering of the gas pedal to keep it running and (2) when at a stop light (while still in drive) the idle gets down low to about 600 RPMs and barely stays running. If it is a long red light I'll put it in neutral and the idle comes up to 1,000 RPMs.

Some things that have been addressed recently or over the years. Years ago I dealt with a rusty gas tank which caused havoc on the fuel injection system. I had the fuel tank, fuel pump, fuel injections, and fuel filter all replaced. There was a vacuum leak at the brake booster, which was causing the car to stall when hitting the brake, so I had that rebuilt. so now I think I found all vacuum leaks because once it is warmed up and in park or neutral it idles solidly at 1,000 RPMs.

The last thing that I've never addressed is the fuel distributor. Perhaps that has got rust in it from the bad gas tank days? Anyone have any other thoughts before I dig into that? Thanks!

[timvw7476]

Bosch used a few different set ups for the airbox/intake snorkel to feed the CIS system on Rabbit/Golf/Jetta.
The distributor is the right place to go, but don't take it apart. It has a few larger air hoses near it with simple press-in fittings. Just changing the element in there, or under there, is enough to tug one loose or partially out of its place. Creating just the leak you describe. I do it all the time on a mid-eighties Golf 1.8. Check those fittings. They are all external. Use decent lighting. They even hide they jammed right into interfering with the inner fender well.
Some models even have a spigot incorporated into the feed tube from the fuel distributor / airbox to the throttle body. It's underneath the feed tube to the throttle body. Look carefully !!! I tug them loose when fitting a new filter element then wonder why it idles like krap. Mine has one spigot that pulls off an electrical solenoid switch. No clamp on it. I guess VW thought engine vacuum holds them on?? They do till I manhandle the assembly putting a filter under it!

[jmarshall024]

Thanks Tim. I took the fuel distributor off the car, but not apart. I took the fuel pin out and cleaned that up because it was sticking.

I reinstalled everything and now no start. I have fuel in the lines with some decent pressure because if I crack one of the connection hoses I get a spray of fuel. I did change the fuel filter at the same time. I'll check around/under the assembly. Maybe I knocked something lose while doing the above.

[timvw7476]

Hope your vacuum routing diagram is still on the underside of the hood. It shows the routing & any T-offs & splits in the vacuum/emissions system....

[jmarshall024]

I re-titled the subject line here. Initially I was struggling with a low idle while stopped at red lights and poor warm up performance.

I changed out the warm up regulator and cleaned the fuel metering rod to help address that. Since then I have a no start problem. I was thinking I messed up something with fuel delivery since that's the system I was working with, but I pulled the cold start injector and confirmed it is spraying fuel. I checked all vacuum hoses to make sure I didn't pull one of those by accident and don't see anything.

Now I'm leaning towards no spark. I pulled a plug wire and cranked the engine - seems like no spark. I checked the fuse panel and the fuses all look good.
There is power to the coil. It seems odd that the coil or distributor would just fail since I didn't really touch anything related to the ignition system. Any thoughts? Any good online reference showing out to test each ignition component?