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[up2ng]

OK I need a lil' help

1998 catera/omega mv6 cant rev to save it's life !
I changed the Valve gaskets last year around this time and ever since then there has been a problem with accelerating, that gets worse as the ambient temperature goes down. Now that NY temps are 10 degrees f the car wont move, The car always struggles to get up even slight hills but is undriveable now.

As of late my legs have become temporarily useful as mams on a bovine so I have had to 'outsource' my auto repairs and this is what we found.
Fuel pump and filter - Fine/new
Ignition                   - Fine
MAF                        - Fine

Sensors seem fine except for the occasional p0171 and p0174
The mechanic says it seems like an air issue but he can't find it (not many people here are intimate with these cars) but I just wanted to get any ideas that you guys might be able to throw my way.

Thanks

[Techno]

Valve gaskets?  :-?

Do you mean valve stem seals, valve seats of may be rocker cover gaskets?

[up2ng]

valve cover gaskets = rocker cover gaskets

oops

rockers here are panels under the doors

[Kevin Wood]

P0171 and P0174 indicate lean condition detected by Lambda sensor. Is it possible that there's an air leak into the induction / exhaust systems?

Does the engine idle smoothly and at a sensible speed?

When under load does the engine still run smoothly but lacking power or is it misfiring with added throttle or just bogging down?

How was the MAF and Ignition system tested? Does the car drive remotely OK with the MAF completely disconnected?

Does this model have EGR and secondary air? Might be worth blocking these temporarily just in case they have gone leaky although I would expect the greatest issues to be at idle and reducing with load.

A couple of other things: Is it possible that the cats have become blocked and are restricting the exhaust? Ditto the exhaust back box. The wadding material can break free inside the box and block the tail pipes.

Kevin

[up2ng]

P0171 and P0174 indicate lean condition detected by Lambda sensor. Is it possible that there's an air leak into the induction / exhaust systems ?

I believe that is possible that I didn't put back together perfectly

Does the engine idle smoothly and at a sensible speed?

600 rpm, every once in awhile the rpm will fluctuate about 75-100 rpm. It doesn't happen often

When under load does the engine still run smoothly but lacking power or is it misfiring with added throttle or just bogging down?

The engine runs smoothly until anything over 25% load (as per OBD connected to my Computer) or about 2000-2500 rpm. The colder the outside temp is the lower the rpm threshold is, about 3000-3200 during the summer and 1600-2200 yesterday.

the engine just acts as if the gas was turned off, if i let off the pedal it's fine again. OBD shows the O2 sensors going from normal operation to 0 when it cuts out.



How was the MAF and Ignition system tested? Does the car drive remotely OK with the MAF completely disconnected?

MAF is fine Ignition too. The strange thing is I see no difference when i disconnect it

Does this model have EGR and secondary air? Might be worth blocking these temporarily just in case they have gone leaky although I would expect the greatest issues to be at idle and reducing with load.


I know it has an air pump but i am not sure of EGR

Could the vacuum lines for the air intake being in the wrong places  ?

long winded but hopefully helpful, thanks alot

[up2ng]

nothing at all ?

i had high hopes of a magical fix

[v6venom]

maybe worth checking the exhaust system isnt blocked in any way ?? have a real good check over of the cat if it has 1??

[vauxhallomega]

hi, with problems like this its a case of checking every thing you have undone making sure its all put back correctly ,, so easy to miss the obious , make a stethascope out of a bit of hose run the engine and listen around all joints for a hissing indicating an air leak, ceeck exaust is not blocked ,, but i would be looking for an air leak, or pipe connected wrongly ricky

[Marks DTM Calib]

My Thoughts

MAF .....
Fuel pressure regulator vac connection is off
Vac leak
Any other fault codes?
Cam timing

[up2ng]

there are no other codes

the vacuum line for the fuel pressure regulator had snapped and i replaced it with thin rubber hose, might that be the problem ?

What happens if the FPR gets no vacuum ?

[vauxhallomega]

if the valve gets no vac it will cut the fuel supply, using thin hose will cause the hose to collapse cutting the vacuum

[Marks DTM Calib]

if the valve gets no vac it will cut the fuel supply, using thin hose will cause the hose to collapse cutting the vacuum

Correct.....you need hose capable of withstanding a vaccum