Low Pressure or High Pressure?

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Brian S

Brian S

Well-Known Member
Posts
2,886
Location
Braintree, Essex
Hi All

I have been getting poor fuel consumption and I am convinced, reduced power and have been looking up things to try next weekend to help.

I will be cleaning the Plenium chamber and want to check the timing.

The trouble is when I find the settings there are 2 different settings for Low compression or High compression engines.

How do I know what engine mine is?

Its an M Reg, 3.9 EFi Auto discovery.

It should have a Catalyst but I have removed them.

I hope you can help me. :)
 
be aware if you have an exhaust like a drag racer it will mess lambda sensors up.
air flow meter faults will also mess fueling up
 
I think you will find the compression ratio is stamped on the left hand side of the engine block (or the right when facing the engine - just in front of plug No.1) at the front together with the engine number.

However, I suspect it will be 9.35:1. You say it's M reg? Assuming it is a 14CUX hotwire injection system here's some info.

According to RRC workshop manual, engines after 1993 (therefore cat) Timing is supposed to be 5 Degrees +/- 1 Degree butu if inn the unlikely event you have low compression engine (8.13:1) with cats it should be 6 Degrees +/- 1 Degree or if low compression non-cat then 2 Degrees +/- 1 Degree. ( All relate to BTDC, dynamic at 800 RPM, vacuum disconnected).
 
Hi.

The Lamba sensors have both been put back.

When I say Decat pipe, the origional CATS were blocked and useless so I had them cut out and straight pipe welded in there place, so all the sensors and everything remains.

I have not changed any resisters, will this make a difference?

All I noticed when I got rid of the rattly blocked CATS was a small increase in power, but I dont think it still right

I know its a big heavy brick of a vehicle, but I went for the V8 as I thought it would be a bit more civalised to drive.

If I drive for economy it seems to struggle getting up to even town speeds, if I floor the pedal it goes, but I would describe the performance as adequate, especialy with the fuel I'll be using up.

I'm getting 250 miles from an £80 tank if I drive like a snail, but well under 200 miles if I drive normally.
 
If you still have the Oxy sensors in place then you need to leave the Cat spec tune resistor in place.Sounds like it needs a good tune up and check over - its never going to be F1 quick but it should not be a slug.
 
Thats exacly my thoughts. :)

I have normal cars for power, but I expect it to perform more like a 1.6 escort than a 500 cc fiat.

If I want to take it easy it should pull away nicely, otherwise they would never have sold a V8 and just done the diesel.

Its the reason I went for the V8 in the first place. :)
 
I brought a set of CATS from ebay and fitted it for the test, but my manifold is a bit old and the joint never joined properly and it was tappety as hell, so rather that put back the cat pipe, I fitted the old decat and kept the CATS for the next MOT. ;)
 
I run it through the MOT without cats and the emmissions were off the scale.

This is another reason I suspect rich runing through timing or other faults. :)
 
G-man said:
if you are in the uk and not running autogas any petrol powered car post '93 is required to have a catalytic converter, unless it is a kitcar


M i believe is 1995/1996
Click to expand...

I have a 1995 Astra fitted with an engine from a 1991 car. I dont run a cat in that and the tester sets the test up on the engine age.
 
i have a 1990 3.9 engine in mine for mot testing! lol, car is a 1994 softdash!
i would start with the basics gen cap rotor arm and leads and plugs
check the dissy is not seized and the bob weights are free also the timing is correct to reset the co as it is technicaly still a closed loop emissions set up vehicle remove the air flow meter plug and connect a ohm meter to the outer pins on the afm it should read 300 ohms resistance which = 1.0% co pre cat with the cats it should be 0% co% leave at that setting and that is the co set correctly do not adjust if ok as the ecu controls it by the lambdas.
it would also be worth having the ecu fault read as it could be the afm at fault.
 
Cheers Cougese39.

I will do those checks.

I got home in the light the other day and had a bit of quality time with the Landy.

Fixed a couple of bits I've been meaning to do.

I took off the large pipe from AFM to Throttle body and it all looks clean, the hoses conected were unclogged, so moved on to the timing.

I have not got a timing light at home but thought I would have a look for the marks, but I can see any timing marks anywhere?
 
I try to avoid these comments, by looking around, searching and generally poking around the car, they are not too helpfull to me although I undertand some new folks come on asking the same old questions.

I searched 'Timing Marks v8 Discovery' and got 2 old posts, that did not help. I tried Timing Marks, and 3 pages came up and the only close post was this

http://www.landyzone.co.uk/lz/f8/v8i-timing-74505.html

As you can see it does not quite answer my question. I cannot see any posts, or pointers when I look down at the bottom pully. Its a bit tight down there with the fan and rad so close to the engine, Do I need to remove anything? look from a certain angle? look somewhere else altogether? or does the 3.9 EFI engine never require manual timing because the ECU takes care of it.

I know my Vauxhall engine with it ECU cannot be timed as the distribuor fits on a fixed point directly onto the end of the camshaft, but I can see the plate holding the Landy's Dizzy inplace like the type you can loosen to adjust, And the Haynes bok of lies also mentions checking the timing every 25000 miles, only it does not show where the marks are clearly.

I hope this makes sense. :)
 
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