VS Caprice 5 litre. sluggish, struggles to climb in revs.

[Caprice_5.0]

Hey Guys,

I own a 97' VS Caprice Series 2 5 litre. Have had it for over a year now.

For a v8 I have always thought it was a slow piece of crap compared to my previous cars. (Stock HR31 Skyline Turbo and a supercharged VT Berlina.)

It takes off alright but once it rev's past around 3000 rpm it's power seems to peak and after that it just makes a whole lot of noise and my speed stays constant until it changes gears then the power sort of kicks back in. Next gear, it does the same thing.

Been searching around the net with similar symptoms and it could be a number of things. I thought maybe slipping auto trans but i thought a slipping auto trans would also slip in to other gears uncontrollably too, which mine doesn't.

The car does have HORRIBLE exhaust leaks after the cat. Im talking 5+ holes through out the piping. The car sounds like a dirty ass tractor. There is also a manifold leak on the drivers side near were the manifold bolts to the block which is making a really loud ticking noise. Thinking the gasket is rooted. Not sure what the condition of the cat is like since i couldn't unbolt the bastard because the nuts are seized on. Could be blocked, not sure.

So I am thinking since my exhaust is full of all these leaks that it's messing with my back pressure so the motor can't move the gasses effectively at high rpm? Or the leak at the manifold is messing with the oxygen sensor making the car think its running lean therefore adding too much fuel? Or the cat is that blocked it just chokes the car? Sometimes on hotter days when it's trying to rev past 3000 rpm, i hear little backfires. (running rich?) The fuel consumption is stupidly high too. Babying it everywhere i get around 17L/100km. Short drives around on weekends it's around 20L/100km... my supercharged VT use to get around 12L/100km and i flogged that car.

The motor apparently had a rebuild 60,000km ago from a company called GEM engineering or something (got books). The odo just clicked over 200,000km. Last service was at 187,000km. I know, i know. It really needs a service too. Maybe something like a simple service could fix it. IE: leads, plugs, fuel filter, oil filter etc.

Checked for error codes but came up clean, code 12 was all i got.

So basically I know these motors have balls but my car is a slug. Something ain't right at all. Hoping you guys could help me out. I know i could take it to a mechanic and have him tell me he has to replace a thousand things but I just dont have the money to do that. I am not super mechanically minded, but i know a little bit. Hoping you guys could maybe help pinpoint the problem. Any advice is welcome really. Need to get this car running right.

Thanks in advance!

[Scrubmonk]

The leaking manifold gasket will be causing a lot of the problem which is compounded by the holes in the exhaust. After combustion the exhaust gases continue to burn up in the manifold, and at valve overlap this combustion draws fresh oxygen through the intake. If your exhaust manifold is leaking, it is drawing the air through the leak and not through the intake, making a big difference to performance and economy.
The holey exhaust wouldn't be helping with a smooth flow of exhaust gases. I think you would be amazed at what a good exhaust can achieve.
However I would be first doing a compression test as well to make sure that there is nothing more sinister wrong with the engine before spending money on an exhaust. Although if it was rebuild 60K ago, it still should be pretty good.

[hako]

Seems strange that it was overhauled at such a low mileage - V8's are usually good for 450,000km. A blocked cat is a possibility especially seeing as it's probable that the old motor was burning lots of oil (which blocks the cat)....although to contradict this a blocked cat usually gets worse over a few months and you say yours has been much the same for 12 months.
I'd throw a complete new exhaust on it - I'm a tight-ass so I'd get a complete one from a wreck as you can sometimes get a fairly new complete system very cheap. If that doesn't improve things then it a process of elimination - fuel filter, air filter, ignition module, coil etc etc.

[Decicrate]

First thing that I would do is check the distributor for damage and then to see if it has been fitted correctly.

A lot of people get this horribly wrong, they either have way to much timing or way to little, or the dizzy hasn't been aligned properly so the reference angle is out.




Edit Remember the timing should be 10deg advanced with the diagnostic pins bridged.