Thread: V8i Idling Issue

Hi There,

I have a 1998 D1 that has sticky valves.

I bought the car for a bargain not realising this was the case. The test drive and the mechanic that checked the car didn't pick it up. I only noticed the day I picked it up and drove it down the freeway. It felt like it needed a wheel balance (I could feel the vibrations through the steering wheel!)

The next day I filled up with fuel (ultimate 98) and had the tires balanced. All sorted.

It wasn't till nearly a year later I did a 1400KM trip in it using regular unleaded (after only using U98) that the "problem" resurfaced. At around 80kph the issue would develop until i backed off the throttle or floored it and it would eventually smooth out.

I tried all the things listed in this thread to no avail. Finally I began to suspect sticky valves. I learnt how to drive around the problem by modulating the throttle but eventually decided to seek advice to fix it.

Here's what I found out. The Rover 3.9 doesn't like to be driven like a grandma - especially on regular fuels. You have got to give your engine a good rev under load. MOST IMPORTANTLY, using a fuel such as Ultimate 98 is a cleaner fuel and has a higher level of detergents in it to keep your engine cleaner. I ran Ultimate 98 in the car for a tank of fuel flooring it all the time and it actually to reduced the sticking valve severity. On-going Ultimate 98 usage saw the sticking valves become barely noticable.

I have also read that the synthetic oils possibly contribute more than mineral based oils to the valve carbon deposits. But I am not 100% confirmed on this yet. I use a Mobil Semi Synthetic 10W 40 and it seems to be working well.

So, I have sticky valves but are just waiting till I can be motivated to get the heads off and fix it properly, but have found a work around to get me by in the mean time.

One last thing I also tried which I think made a difference was running a fuel additive called "Valve Saver Fluid" by Flash Lube. It is a lead replacement Upper Cylinder Lubricant. http://www.flashlube.com/en/valvesaverfluid/index.html I used one bottle over several tanks of fuel and it definitely improved the reduction of the sticking valves.

Sorry about the essay, and please comment if I am making no sense

F U Z

F U Z, that sounds awfully like crossed wires to me.

To me the 80kph wobble would suggest worn steering swivel bearings with insufficient pre-load, not sticky valves.

Also, in general, synthetic oils are LESS likely to cause carbon build up and sludge than mineral oils. I'd be most interested to see what you are reading.

However, proof will be found when the heads come off.

Originally Posted by eddie_V8i

I just bought a brand new Air Mass Flow Meter (5AM MAF like mine) on ebay from the UK for $133.10 (postage is 1included in that price) so lets hope that after that, and a set of new leads and plugs etc, i can start to enjoy the disco rather than scratching my head as to why its running like a demented dog with three legs

lol

ps, is $133.10 a good price for a brand new 5AM MAF meter?

I also have a 94 Disco V8 auto
Im very intrested what happens when u fit the new MAF.
I have duel fuel, runs great on LPG and generally ok on petrol.
However, occasionally if i start it on petrol, it doe's exactly as you describe, idle is higher than usual and when you try to rev it wont rev up properly, like you said only to around 1500-2000 rpm
But most of the time it's perfectly normal,
Ive been leaning toward the MAF playing up

Originally Posted by MacMan

F U Z, that sounds awfully like crossed wires to me.

To me the 80kph wobble would suggest worn steering swivel bearings with insufficient pre-load, not sticky valves.

Also, in general, synthetic oils are LESS likely to cause carbon build up and sludge than mineral oils. I'd be most interested to see what you are reading.

However, proof will be found when the heads come off.

Just to clarify, the engine running poorly with the exhaust valves not seating properly resulted in the engine shaking to the point you could feel it throught the car as a shake and could be mistaken for a poorly balanced front wheel.

I'll try track down the article for the oil...