96 850 10V NA rough running

Post by **scot850** » 03 Jun 2023, 02:03

I have just replaced the water pump on this car as it had a bearing failure. The car was running seemingly ok otherwise, but I can't be sure as I did not have it running long enough and I was not looking at anything else other than the knock.

I have replaced the water pump and the knocking has disappeared, but it still sounds loud, but I recall my 93 850 20V could be fairly loud mainly due to the injectors.

I think it may be misfiring slightly but I have no way other than old school methods to check it. There do not appear to be any check lights on the dash, and the normal ones come on at start up but they all go out.

When you rev the engine and let it drop back to idle, if seems to have a slight hesitation before returning to a steady state around 950 rpm.

It looks like the car has fairly recent new Bougicord plug wires, distributor cap, plugs and rotor from what I have been told. What I don't know yet is if this was all fitted trying to identify a rough running condition. I will find out later today when the owner comes around.

I refitted the original timing belt and marked the heck out of it to make sure it returned to where it was before removal. I have rechecked it and the marks still appear to be spot on. I will recheck to be sure as the crank mark is always hard to see.

I can do all the stuff like fuel pressure check (I think the pump may be noisy) and the fuel filter looks like it came off the Titanic.

I can also check the spark plugs, distributor cap, rotor arm and plug gaps. Compressions can also be checked for cylinder and valve issues and I can borescope the cylinders and valves as well.

Do these symptoms sound familiar to anyone? Car has 464,000km on it.

I am of the opinion, if the car was fine before, recheck your work, but I don't know if it was. Other than the timing and recharging the battery I have not touched anything else other than the serpentine belt removal and the timing belt removal and the new water pump and TB refitted. Cams were locked and all timing marks are spot on. No electrical connections were disturbed other than the coolant level connector.

Last thing, the coolant is not burped yet and must be about a liter low.

Thanks,

Neil.

Post by **abscate** » 03 Jun 2023, 03:45

Pull that cap and rotor off and check it for dirty brass, first.

Remember it’s a 10 V so it might not “ sound like” a P80 we are used to.

Post by **scot850** » 03 Jun 2023, 07:42

My parents had a 96 10V in Scotland and it had a really sweet motor, and was smooth like most NA's are. That stumble or slight misfire when you rev the engine and it comes back to idle is not normal.

Neil.

454cid · Post by **454cid** » 03 Jun 2023, 10:40

It may need an Italian tune up, if it's been sitting for a long time. I'd look at the ignition too, of course.

I also thought my engine was a bit noisy, when I got my 850.... I assumed injectors, since they're right there.

Post by **P80GLT** » 03 Jun 2023, 14:59

10V engines are quiet

454cid · Post by **454cid** » 03 Jun 2023, 17:23

Post by **scot850** » 03 Jun 2023, 19:49

P80GLT I agree on the NA motors, usually turbine smooth.

Talked to the owner today and his mum and there is a certain amount of family attachment to the car. The young man has been repairing some stuff, but things like fixing the odometer overwhelmed him. I have offered to mentor him so he can tackle it himself.

Decided to start looking at some of the stuff on the engine not being as smooth as I would expect.

Pulled the plugs. #1-3 were a little dirty but genuine Volvo 3 prong plugs. Cleaned them, the plug holes and the plug connectors. All was good until #4. Could not get the plug socket over it. Could not see any flats for the socket to grip too. Realized that there looked like something was over the plug. Got 2nd opinion from Abscate. Concluded the 'mechanic' who fitted the last set of plugs had lost the rubber cup insert in his sparkplug socket and had jammed it down over the plug using the plug lead end. There was also some engine oil in the well as the oil filler cap gasket was leaking and the seal for #4 was not good.

Bit the bullet and forced a sharp straight pick between the porcelain and the rubber. As it had been on there for while it had gone hard. Thankfully the pick split it on one side to allow retrieval. Naturally I immediately dropped it into the next plug well over the plug. Good grief!!

Wasted a good hour on identifying and removing the one plug. The installer presumably could not get the plug cap on so had tried to force it on splaying the brass sleeve that goes over the plug end. It would not stay in place. Cleaned the oil out and removed the end cap of the plug lead to give better access to the plug connector. Bent the end to give it a better grip. With a bit of luck this may be part of the misfire.

With limited time, also found the hood latch was seized with rust. Cleaned and now back to operating condition. Progress, but new issue. Leak from the top of the tank if you fill it fully...........!

Should add, started the car for the owner and it was running much better, but still a slight misfire. Will check it tomorrow for more hidden delights!!

Neil.

Neil.