Surging and Backfiring PT 2
 

The shop put in new plug wires and test drove the car when cold they said no problems. When I picked it up he showed me the distributor cap and the rotor had cut a nice grove into one of the posts. My guess is that it wasn't seated right. Last time I remember having the cap off was about a year and a half ago. Car idles great now, but I picked it up right after they test drove it and on the way home I noticed it began to show the same symptoms. It was less than before but damn. I called the shop they said to bring it back in. I was so looking forward to solving this problem. I need the car so I am going to keep it for the weekend and take it back in on Monday. If I want to start checking fuel system would you start with the fuel pump pressure and work toward the injectors or start with the injector pattern then check pressure at each injector?

Well no responses humm.

I promissed someone I would share info so here is an update. Went to the shop on late Friday. the owner meet me up front and had one of the mechanic's pull the car in and recheck the mixture. I didnt realize:

That CIS runs rich and the purpose of the WUR is to lean out the mixture. I assumed that WUR richened the mixture.

That pressure regulator is an electronic soleniod. There is no vacum line.

That fuel distributor has a pressure adjustment.

He has been doing this for years and one other thing I realized is that I know very little about CIS. Well the result is that I will bring it in hot Monday morning and they are going to test system pressure and control pressure at the same time. Then check pressure regulator let it cool down and retest. Car seems to be running better the longer I drive it. The only thing I did was to add some fuel treatment (ZMAX), but I would be greatly surprized if that has much to do with it (repairs dont come in a bottle). I am going to by a book on CIS and try to improve my knowledge. I also have to get a factory manual. Haynes is good but there is not enough detail.

"Not all 924's have fuel problems. Only the ones that still run." Britwrench 2003

Water?
 

If you put in a fuel treatment, and it ran better, could you have water in your tank?

anything is possible but I doubt it I run fuel treatment every 3000 miles.

Its a 924 or I could help you more.
 

I haven't had much experience with the 924's. I almost bought one with a snapped timing belt (early engine) for $500, but decided to leave it.