Volvo 164 73' horrendous fuel economy!

yes thats what perplexes me as to why it would get richer as it warms despite the sender appearing to show the correct resitances values. i am yet to try measuring at the ecu what signal i receive.

I have ported and installed a mildy more aggressive camshaft so this would imply more airlfow than the ecu expects at high load full rpm. that is what i was referring to. but i have been told this should not drastically affect d jet and it can cope with a mild change.


Thanks Jorg. yes unfortunately i have been through all that. the timing has been verified as with all of the other things. i had tried the fuel pressure at 31 psi and it did not drastically change fuel economy. so it is operating at 34psi to allow the car to start on a warm start

Thanks Norbert, yes it did oringally come with a MPH speedo which i have converted to KM/H and verified my readings with google maps and they are reasonably close. I estimate around 21L/100km as fairly accurate if i want to conservative on the readings it is 19L but that is still pretty horrendous on 98 octane and for just a 3 Litre. My friends jaguar mk2 with carburetta gets 15L/100km from the 4 litre engine

UPDATE:

I have determined what is causing the mixture to be leaner at cold and richen as it warms up. It is linked to the auxiliary air valve. When it allows more air in the mixture is leaner as it mustn't be adjusting for the extra air at idle. Is this possibly because the map has a diaphragm leak.

i confirmed this by turning up the idle adjustment screw when it was fully warm and with it the mixture will lean out. now i also found that when unplugging the the throttle switch the idle mixture will get slightly richen. i dont believe from reading on here there is a way that throttle switch can be altered to affect idle mixture that would be the MAPs job. This would only leave the MAP as the culprit.

Hi Al,

have you checked your MAP sensor for leaks? If it leaks, it signals fully open throttle to ECU. So it will enrich as much as possible. In cold start that could just be enough and the warmer it gets the more it would then enrich. I would say: Check vacuum.

Hi Volker, yes i have tested it and it is on the edge between determined failed and working with respect to the leak test.

i will post an update if i can locate a known working unit. and hopefully have some positive results

i appreciate all the help i have received from everyone. it has been very useful. i must say im not used to it some places can have some very rude people but everyone here is friendly and very open to helping someone who isn't massively technically inclined

Hi Al,

I keep my fingers crossed that you find a suitable unit. The 015 for P1800E I would have had available. but not for the 160 series. And please do not drop your MAP sensor to the waste bin. Before you do that, send it to me.

@ Volker,

Manifold pressure sensor (MPS) BOSCH 0 280 100 015 equipped in
B 20 E: VOLVO 1800E , 1800ES and 142, 144, 145
B 30 E: VOLVO 164E

www.bosch-classic.com/en/internet/bosch_...__mit_teaser_1.html#

@ Al

Have you ever checked whether the cold start valve is leaking all the time?

Jörg