1973 W114 280ce m110.981 Spluttering at full load

Hi All

First of all, i am gaining a great deal of knowledge so far from this great resource but i can't say i am any sort of expert yet. I struggle to find people local to me to diagnose Djet issues so i am attempting myself .I am no mechanic, but an enthusiastic amateur who will have a go at most things if i have clear instruction

I have had my w114 for 8 years, recently it was in storage for a few years. It has recently started to splutter/miss under full load and i'm trying a few of the obvious things i can test myself.

It had electronic ignition to replace the points a few years ago, along with new HT leads, distributor cap and rotor arm. New air and fuel filter along with full service.
New fuel lines, along with new injector seals.

I have just replaced the original vacuum hose to the MAP as it was perished. I think this made an improvement , but did not solve the issue. 

I have tested the following :

MAP sensor holds vacuum (15)
Fuel pressure is 2 bar and holds once engine turned off. measured at the cold start injector 
TPS has 20 clicks
i have sprayed brake cleaner round all the possible places there could be a vacuum leak with no increase in engine speed.

There is a known issue of a stuck Aux air valve which i have temporarily blocked off the air pipe to until i can refurb the AAV. My understanding is that this simply closes when warm and is for cold starts and does not interact with the djet in any way. 

Could the spluttering be a symptom of  the throttle position sensor being broken/dirty . is this something i should maybe check next ?

Should i get a longer length of fuel hose and check the fuel pressure whilst driving under load ?

I appreciate that ther's a lot more testing i could do, but if anyone has any pointers that would be great. Or it might be better to wait until i can demonstrate in a  video hopewfully in the next few days.

Many Thanks

Avi

 

Hi Avi,

I am not sure what I shall advice you. Sputtering is not really precise. Try to drive with Throttle Switch disconnected and try to measure vacuum pressure via T-connector on MPS.

Another possibility is that your low tyre pressure cánd chassis close to floor has somewhere closed a fuel line.

Well but ignition distributor can well be another source of problems. Even with Pertronix original rpm and vacuum change of timing must work.

Thankyou. I did manage to get this short video. Specifically when the gearbox does a downshift it's almost like the rev limiter comes in

Hi Avi,

there is only one mistake I see on this video: Steering wheel is on wrong side

If you have problems with rev limitation, check your ignition distributor finger.

Thanks Volker. the spluttering i reference is at 7 seconds. The Rotor arm (finger?) is relatively new. and i can;t see any signs of issue. 

 

Hi Lance,

but it could well be your trouble as it is supposed to shortcut ignition at 6650 rpm. If spring adjustment does not work properly it can be any rpm. Try to isolate the tongue on left side and drive again.