Can Anyone one help with Rough Running?

[Ian C70T5]

Hi

MY Wife's 1998 V70 2.5 petrol has a few issues. It's had a full service and new cambelt, but seems to show the same issues that it had before it went it. They said it was just in need for the service that it ran rough, but I didnt really believe that.

Before the Service it would run and sound a little rough, but in the wet or damp air it would be hard to start and idle. Pressing throttle made it stall and sound rough when trying to restart.

After Service, it starts ok, sometimes is a little harder than others. It idles like a tractor in the cold mornings. When the "auto-choke" kicks in it sounds better, but you can almost hear it missing beats on the idle.

It is using more petrol than normal and generally feels rough.

Do you think its a MAF sensor? It's done 130k

[Ian C70T5]

Having swapped the MAF sensor for another one with the same engine it still does the same thing. Obviously it is not this.

Can anyone shed any light?

[timbo_1975]

My money would be on combinations of (as they say at the curry house) Rotor Arm, dis cap and HT leads. If they are still original, then its time for a change.

Use geunine Bougiecord replacements from Rufe or PFV.

tim.

[Alan M]

Are you sure the parts were actually changed at the garage? Its worth doing a basic service of serviceable parts yourself as it is an easy job to do. People on here will be able to advise on the jobs when you do the work.

[flyingbrick]

My money would be on combinations of (as they say at the curry house) Rotor Arm, dis cap and HT leads. If they are still original, then its time for a change.

Use geunine Bougiecord replacements from Rufe or PFV.

tim.

I agree...
With all the sensors about I think people forget about (old school parts) cap rotor & leads...........
Changed mine not so long ago and stopped the rough running from cold...

[Ian C70T5]

Hi all

I swapped the Dissy cap, rotor arm, leads and still same issue..

really stumpted now, runs rough still, its at its worst with a cold start.

[Ian C70T5]

Anyone else got any ideas.. It sounds terrible on cold start and seems to also run a little lumpy (enough to notice it)

Its very strange

[Babybadger]

First make sure they are standard spark plugs, it may be just a duff one, known before, Just a long shot, but how about the injectors might be slightly clogged? That would make it lumpy at startup.

[jdavis]

bit of a long shot but has timing been double checked?

[Ian C70T5]

Another issue noticed.

If you pull away from 20mph in 4th or 5th obviously it is slow, but there is also usually a big bang backfire at the same time as I push the throttle down.

[Terminator]

It does sound 'timing' related and possibly a worn distributor.

[flyingbrick]

Another issue noticed.

If you pull away from 20mph in 4th or 5th obviously it is slow, but there is also usually a big bang backfire at the same time as I push the throttle down.

Sounds like the belt might be a tooth out.......

[Ian C70T5]

hmm, could it be related to fuel pressure?

If I try and start it when the car has next to NO fuel (in red) in it, its a bugger to start cold. It chuggs away and if i go to the back of the car I can smell the fuel pouring out of the exhaust in the fumes. Fill the car up and it generally runs slightly better (still misses slightly).

I am worried that if i keep driving it, its gonna break. But I dont want to give it to a garage to charge a fortune to "troubleshoot" it.

[5seaterT5x2]

presumably this is similar to t5s etc? is there no where to get the fault codes read?

[Babybadger]

It sounds like the fuel filter may need changing as well

[Babybadger]

Hi all

I swapped the Dissy cap, rotor arm, leads and still same issue..

really stumpted now, runs rough still, its at its worst with a cold start.

What about spark plugs? Genuine Volvo ones only, don't mess around......

[Ian C70T5]

What about spark plugs? Genuine Volvo ones only, don't mess around......


Thank, changed them too.

[Taff - t5]

What were the plugs like when you changed them?

[Ian C70T5]

dunno, was done by garage to be honest.

[Ian C70T5]

Could it be an O2 sensor in the exhaust? Would this cause the overfuelling.

I'm confident its not the timing, it was happening dramatically worse before it had a service and cam belt change. it never used to start at all on a wet day, it used to overfuel and flood itself.

It does run slightly worse in a wet day.

[LeeT5]

Hi Ian.

From what you've said so far it's almost certainly not the timing because you said it was running rough BEFORE it went into be serviced. You've changed all the obvious things that will cause a missfire/rough running ie plugs, leads, cap, rotor arm. You have also changed the MAF meter so it can't be that.

Without seeing the car i can tell you it won't be the fuel filter because if it were blocked then it wouldn't run at all. Also it won't be fuel pump because unless your getting 3-5 amps at the fuel pump fuse the car will never start! Less than 3 amps and the pump is open circuit or the fuel tank is empty, more than 5 and your pump is seized. Either way the car will not start unless it falls within 3-5 amps.

Therefore you need to start at the beginning my friend. Forget what the garage has done, start with the Crankshaft sensor. Make sure it falls within the limits of resistance or this will give you major running problems. You say the car runs slightly better once the car has warmed up and the ECU retards the amount of time the fuel injectors are open for.....therefore your problem is almost certainly fuel / ignition related. Have the fault codes read (if any) and then you should look at following wiring lumes making sure that no exposed wires are chaffing on the gearbox/engine. Undo and clean all your engine earths using a wire brush and some WD40...don't forget to tighten them back up, you'll be suprised at what a difference that can make.

Check or replace all your vac hoses (the little elbows are a common culprit) change anything that is suspect.

Disconnect the battery and then disconnect the ECU plug and make sure there is no corrosion present. Reconnect and then reconnect battery. Have your car tested for a possible headgasket leak. This can be done electronically using an oscilloscope or the old fashioned way using a pressure tester. The smallest hole will give you running problems and once the engine warms up, metal expands and the hole closes up! Seen it many times on various cars.

Other than that...it's off to a good garage that has a mechanic that knows these cars ie a Volvo specialist. Plenty here as you already know, depends where you are in the country and how far your prepaired to travel.

The best advice i can give you thou for now is DO NOT drive the car...you will cause irrepairable damage to the exhaust system, mainly the catalyst and both O2 sensors!

Good luck and hope my comments help.

[Ian C70T5]

Cheers mate, I'll have a look.