Here is the basics. Over the past month or two she has been spitting out black unburnt fuel after sitting for a few days but ran fine after warmup. Then after a nice long weekend of several trips, and a couple hundred miles of a great weekend of driving the current problem came up. Driving back at night from a couple mile run she would die everytime I came close to idle at a stop or light. I was planning on a full carb rebuild this winter anyway so I pulled the carb and sent out for rebuild. Problems fixed included ruptured choke pulloff, wrong power piston spring,wrong primary metering jets, jetted too rich, float too high, unbalance idle, missing choke seals. Thought the carb was my problem but it is not. She will not run without pumping out lots of unburnt fuel out the tail pipe. Pulled all spark plugs and all looked normal except with carbon deposits. Vacuum seems to be the issue as it is only 5-10ish. Bought a vacuum pump and I am going through all the lines and systems one at a time. Found EGR valve bad. Can this valve be causing all this trouble? It is kind of strange to have been running so good and the problem come on so quick. Advise?

If the EGR valve is stuck open she won't idle. Replacing that would be a good step, and should solve your problem.

This problem comes up often. The best solution is to replace all rubber hoses with new ones. This is not expensive and will either eliminate your problem or help isolate it.

I bought a vacuum pump today and I wish I bought one a long time ago. Easy to use and can quickly test each vacuum section. I plan to go through as many vacuum sections as I can.

|UPDATED|12/21/2003 3:42:32 PM (AZT)|/UPDATED|

There can be a number of causes for low vacuum. Later C3's have many vacuum lines for potential leaks so the previous suggestion to carefully replace them all is a good. It's also not too uncommon for intake manifold gaskets to begin leaking after they age.

Also...the does engine have a bigger duration cam installed? That alone can account for lower engine vacuum. Does your car have cruise control? If the servo or diaphragm is leaking it will cause problems.

Take your time and with your vacuum tester go through all the vacuum systems one at a time and eliminate any potential leaks.

If you pull your vacuum lines the manifold and cap them one at at time you should be able to tell if things improve. Did you change your spark plugs or just clean them? It is posible that you have a fouled plug from before. How old are the plug wire?

The spark plugs were changed less than 1000 miles ago so I just wiped clean, checked gap, and re-installed.

The vacuum had been only 5-10 and completely eratic before fixing the EGR. After fixing EGR, next test vacuum was 10-15 still swinging eratic. Next test vacuum was 10" at 1500rpm and swinging, raised to 2000rpm and she came up to 15 steady. Held there for 30 sec steady. Drop to 1500rpm, stayed at 15", drop to 1000rpm vacuum swings and drops below 10" and stalls.
My vacuum pamphlet points to timing. Guess I'll look there next.

|UPDATED|12/21/2003 3:44:05 PM (AZT)|/UPDATED|

FLA, howd it go? What as the outcome, as I am having similar situation. So far I was able to isolate to manifold gasket, situation got better but still not idle well.

Deffinetly set the timing. make sure you disconnect the vacuum advance first. Is the car hard to start, if the timing doesnt help change the fuel filter (cartridge in the carb)

Well I found my problem. Compression test showed zero on #5. Time for a valve job. I guess I can't complain, the engine has made it 23 years without one. The time of year could have been better. I missed out on some of the best driving weather in Florida.