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87 420SEL, starts and only runs a few seconds

18724 Views 41 Replies 9 Participants Last post by  waybomb
87 420SEL, starts and only runs a few seconds - Still need help

Have a 1987 420SEL. 140,000 odometer.

Start the car, rpms come up slow, idles fine, then races and shuts off. If restarted immediately, the process becomes shorter. If a wait of a few minutes, the process may take 45 seconds.

3/4 tank fuel, replaced the fuel filter today, still has same problem. The pumps are running, air filter ok, no wires seem to be off anywhere.

Any ideas on what to check?

Thanks in advance.
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Hey everyone, we unplugged the idle control and it still does the rev and die. If you spray starting fluid it will keep running though.. We jumped the relay and it stayed running. Any Ideas?
Also it runs for about 15 mins at idle then it does the rev and die... When restarted it will rev and die. The longer it sits the longer it will run... I am sooo confused...
Well everyone, we replaced the Idle control valve and the Idle control relay and still doing the same thing..... Anybody have any other Ideas? Could it be the computer itself?
do as mvmiller had suggested in an earlier post and check the air plenium tubes. if you checked the air plenium tubes along the valve covers and under the intake then I suggest you re-check that area again. kind of wiggle the airtubes around very gently and see what happens. use a spray bottle of clean water to do this test. you need to spray a mist of water and not a stream around the connections and the injector holders. the problem you are having is definatly a vac leak somewhere in the system. either by way of the airtubes, injector o-rings and seals, icv tube and all of the formentioned vac lines, the rubber boot under the airflow meter or possibly the 8 rubber o-rings under the intake. look up my thread on this and you will see what we are trying to tell you here. you can change out the ICV, ICR and the ECM and have no change at all if you have a vac leak. by the way. the ECM will have nothing to do with this at all. I had this same issue a few months back, go read my entire thread titled 89 560SEL check engine light on, hard start. there are many pics in that thread that will show you more or less what these air distribution tubes do and how brittle they become after years of use. I also did a search about "high Idle" and found alot of info there so you might want to do some reading in the archives for awhile. good luck.

When it has an idle of 750 when cold I sprayed carb/choke cleaner around all the tubes and by all vac connections and the rpm did not race until the car warmed up..
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