Griffith Poor Running

[Gizze]

Hi All,
My 1992 4.3 Griffith is not well......under acceleration it's smooth, but at constant speed or on the over run it's awful. So much so that when decelerating I now find myself dipping the clutch to avoid the issue. I'm told that this model was never that good in this respect, something that I believe is called drive line shunt, however over time this is becoming increasingly bad.
One garage I took the car to stated it was camshaft wear, my car's done 70k miles, and they said the low oil pressure is probably also indicative of this. If this is the case getting it fixed won't be cheap. Any other potential causes that anyone has had experience of before I take the plunge??

[5.0ltr]

My 500 did this once fortunately on way to service. It would accelerate fine but lift off would misfire and die, on or off it seemed. Anyway analysis at garage showed throttle pot error, reset and has been fine for 6 yrs now. Not saying it is your issue of course just my 2 p worth.

[Milky400]

Has you taken it to a specialist? If you're on the original cam shaft, agree it could be suspect. But not sure it causes these symptoms

[blitzracing]

Shunting is normally something related to the mixture or possibly ignition leading to a poor burn. The camshaft may well be worn, but your specialist needs to check the sensor readings and any possible fault codes the ECU has logged before you throw £1000 worth of camshaft at it. I assume this is a precat motor (?)- and in this case the ECU diagnostics are limited as there is no lambda fuelling feed back, so the ECU cant log a range of fault codes, but basic sensor data can be checked. There seems to be a number of AFM failures recently, that will throw the fuelling out, and may be just due to the increasing age of these components. Its also worth checking the ignition components are in good shape as a matter of course.

Edited by blitzracing on Sunday 3rd August 09:41

[leerdam23]

Have the symptoms just started, or have they been getting gradually worse over the last few thousand miles.?

Have you had it on a rolling road?

I would investigate the low oil pressure first, failing oil pump will be a big bill, so make sure it is either the sensor or gauge lying, or if a mechanical pressure gauge confirms low oil pressure find the problem and fix it.

Carefull who you trust too, always get a second opinion

[Gizze]

Hi,
Many thanks for the replies, yes it was the 'specialist' who diagnosed a worn camshaft. However it's not been on a rolling road, and the camshaft itself hasn't actually been inspected.
The problem has gradually got worse over the last year, but I do very few miles so it's probably been in the last say 1500-2500 or so miles.
Agree the low oil pressure is probably first priority though. I've already changed the sender in case that wasn't as it should be.
Just don't want to embark on a huge amount of expenditure if I have to live with the shunting, and because it's got worse gradually I'm struggling to remember how good/bad it used to be......

[domV8]

Just to rule it out - double check your driveshaft doesn't have any play/loose bolts.

Prior to moving to Emerald, I used to have a problem with "shunting" - this caused the bolts holding the driveshaft to slacken off, and this loose connection then magnified and exacerbated the shunting horribly (as the driveshaft would bang back and forth within the play allowed by the slack)...

Creates a self-perpetuating issue (shunting loosens bolts - loose bolts increase shunting), and the shunting symptoms get worse and worse.

Worth 5 mins of your time checking..?


Dom

[stevesprint]

Gizze
How are you getting on with your shunting?

Gizze said:

I'm told that this model was never that good in this respect

It's more of an issue with the 500's as Precat's have more flexibility with the emissions. Precat's also have the add advantage the low down fuelling can be adjust with the co trim screw on the AFM.

Gizze said:

Hi,
Just don't want to embark on a huge amount of expenditure if I have to live with the shunting

No you don't have to live with shunting, I also have a 430 Precat with very similar mileage and I cured my shunting by sorting out the fuelling as Blitzracing suggests. It also sounds Bob's (5.0ltr) throttle POT error was also causing a fuelling issue.

Therefore before you spend large sums of money it might be worth checking your ignition timing is 10 to 12 degrees (mine's 12) and you have no faulty engine sensors with RoverGauge or ECUMate.

You could also check your co trim screw voltage on the AFM is between 1.0 and 1.5 volts for a standard ECU chip. The higher the voltage the richer and smoother, mine is set to 1.5v. You can check the CO trim voltage in RoverGauge or with a volt meter across the Red/Black and Blue/Red wires on the AFM. If still no joy ask a friend to watch all the sensors outputs in RoverGauge while you drive the car or you could try borrowing a friends ARM.

How low is your oil pressure when cold and hot? More importantly have you noticed a change in pressure? I ask as the pressure on Precat's is low and tends to appear too low as the gauge is only a rough guide, but best get it checked than be sorry.
Good luck, Steve

[Gizze]

Hi,
Sorry for delayed response been on holiday and away from the internet......
Will definitely check the driveshafts and start looking at ignition and fuelling with some measurements on the AFM next week when I have the chance. Never heard of a Rover Gauge so will get googling on this, and thinking about it the air inlet hose from the air flow meter is probably past its best so may not be helping matters.
Oil pressure: probably 5-10 psi at idle (Just below 1000rpm) and no more than 35 psi at 3000-3500rpm.
And great to hear drive line shunt is not necessarily something that has to be lived with http://www.pistonheads.com/gassing/imgs/2.gif