The D-Jet equipped cars are nice but you gotta do them one step at a time and in the correct order .
# 1 : (ALWAYS
) is to do a valve adjust as they're always tight on every car I touch and this upsets the intake manifold pressure , that makes the M.A.P. sensor go wonky and can ruin it too .
Then the ignition timing and advance , often no one has ever pulled the rotor off the dizzy and dribbled a bit of engine oil in there so the advance mechanism sticks... gently turn the rotor and see that it moves and snaps right back . NO side play in the dizzy shaft is permissable ! . just a few drops of oil will do the trick , do this every couple months .
Then begin looking at the various vacuum hoses on the intake manifold , any leaks no matter how minor will upset the D-Jet .
The injector seals a very easy to change , two per injector and they're the same as old VW so cheap anywhere . they make vacuum leaks too .
Do the spark plugs have .035" gap ? never
trust the pre gapping from the factory as the parts haus guys toss the boxes 'round .
Lastly , the T.P.S. is often dirty and this makes surging , usually very jerky in nature . get a spare one from the junkyard , take it apart and _polish_ the contacts untill glossy , NEVER use sand paper or steel wool ! .
You can also use a $5.00 oil pressure gauge connected to the cold start injector's hose to ensure the fuel pressure is 32# dead nuts and doesn't drop when you goose the throttle ~ if it drops , change the fuel filter (it's next to the fuel pump by the fuel tank and costs about $32.00) , clean the in tank screen and try again , the fuel pressure is adjustable but if it won't come up -or- the pump squeaks , it's dead , new $$ !! good used , very cheap , easy to clean before use by running Diesel fuel through it , polarity _reversed_ .
Running thid car out of fuel will kill the fuel pump in short order .
I hope this helps , D-Jet books are available new @ Auto Books for $30.00 and well worth the $ . used should be less , maybe Amazon.com ? .
You should easily be able to tweak it to 0.2 % CO and under 300 PPM HC , then your fuel milage should be better .
I'm in the market for a W-114 Coupe here in La-La Land..
Originally Posted by D_R_Payne
I'm still working on sorting out my new purchase, however i'm at a stumbling block.
The fuel consumption was in the single figures with low power, and the CO% was 11%. I was frightened enough to send it to a merc specialist to solve this. They replaced the inlet manifold gasket and injector rubbers. And the result? 0.3%CO and same power. It starts easier from cold and drives a bit smother, but now misfires a little while driving for a couple of seconds and then is fine again! Ive had a look at a d-jet fault finding guide, but am still not any further! ideas?
The rest of the car is slowly getting there, only have to locate the source of a leak accumulating in the front footwells, but i'll get there! Thanks in advance for all the suggestions!