In Reply to: Re: Likely sources for _intermittent_ idle problem posted by demet on August 26, 1999 at 09:42:48:
Although Demet always has good advise, there is no cold start valve on the '88, his car has one, as do all 528e's up to '87. The Motronic is a different unit on the '88 - it directs extra fuel to the main injectors based on engine temp. There is a temp sensor you may want to check.
: You should check out the cold start valve as well as the thermal temp switch. The Bentley has a good procedure for that. Then check out the ICV. One method is to swap it out with a known good one and see what happens. Since I didn't have one lying around I swapped it with a 1/2" inner diameter pipe valve from a local hardware store (about $4), adjusted the idle to 800 via the valve screw and monitored the idle under various driving conditions. Turned out to be very stable. The only problem with this kludge that made me not make it permanent was the cold start operation that required a slightly higher than normal idle for 30 sec or so. Since I concluded that the ICV was faulty I bought a new one and have had a good idle until now.
: 87 528e
: : Recently purchased '88 528e (145k miles) has intermittent hard start and idling problems. It is usually OK with great mileage and decent acceleration, but occasionally (1 time every 2 weeks or so) will be hard to start and will run very rough until warmed up. Sometimes will be OK after 2-3 restarts rather than wait to warm up. Have put in new plugs, rotor, cap, air & fuel filter; 1 tank of Techroline to clean injectors; cleaned ICV with carb cleaner; cleaned fuses.
: : Shouldn't most hard start/idling problems be more consistent (vacuum leaks, bad pressure regulator, bad sensors, etc.)? Or are most of the problems encountered usually intermittent? Any ideas what to look for?
: : Many thanks.