‘88 480ES only runs fine without MAP

[musicoptimizer]

Hello,

I own a 1988 480ES since January this year.

When I bough the car it run with some issues. Power was low and the car would cut out in traffic.

I replaced the MAP, coil, leads, plugs, but it didn’t make much of a difference.

In June the car had a breakdown in traffic and after that it would idle fine, but had absolutely no power. It would cut out when you engage first gear.

Today I disconnected the vacuum hose that goes from the intake manifold to the MAP sensor and I was amazed that the car started to run better than ever and pulling very strongly.


Since I already replaced the sensor, I don’t think that it is the issue.

Does anybody know why this is happening?

Thank you and best regards.

[Alan 480]

Did you blank off the small entry into the manifold when you pulled the pipe to MAP?

If it was an 'idling issue' I'd suspect the idle valve was goosed and so letting air in at the small vent would improve things!!

I know that the small flexible pipe broke on one of mine, (maybe 1700) and it wouldn't run worth anything, died especially when put the foot down!!

so in answer 'nae idea'

BTW what engine is it, I assume a 1700? (not a turbo?)

[musicoptimizer]

Did you blank off the small entry into the manifold when you pulled the pipe to MAP?

If it was an 'idling issue' I'd suspect the idle valve was goosed and so letting air in at the small vent would improve things!!

I know that the small flexible pipe broke on one of mine, (maybe 1700) and it wouldn't run worth anything, died especially when put the foot down!!

so in answer 'nae idea'

BTW what engine is it, I assume a 1700? (not a turbo?)

Hi!
Thank you for you answer,
Yes, I blocked the manifold vacuum nipple.
The car is a 1.7 N/A, not turbo. Engine is B18E.

The car runs fine except at vey low RPM and over 3500RPM. Bellow 2000RPM it hesitates and above 3500RPM looses power (not enough fuel?)

The car also develops a vacuum in the fuel tank, and cuts fuel supply. Once you unscrew the filler cap and releases the vacuum it runs fine again.

Fuel use is very heavy. Before the problem I could average 8L/100Km, but with the MAP vacuum line removed it is now averaging 20L/100Km.

Idling is fine without MAP vacuum line and inconsistent if I put it back.

Could this be a fuel pump issue? Injectors? Tank ventilation?

This car has no catalític converter and the 48L tank.

Thank you and best regards!