Engine revs

[jensencars]

Hi,
Been helped here before and appreciate your assistance thanks,
Now have a new issue with my rover 3.5 engine running fuel injection with the flapper system,
Went out today car was running fine but just suddenly decided to cut out, typically on the narrowest section of a country lane!!!!!!!
Anyway it eventually re started but did this a further 3times before I got back home probably taking around 2/3 minutes each time before re starting funny thing is I then had it ticking over / reving in the drive but it would not cut out only thing I noticed was if you blip the throttle and let go the idle virtually dies and then picks back up or it will just stop, re started ok, anyone had anything like this? Everything engine/ fuel wise is new or recon although I know this doesn’t mean it’s not faulty ( the flapper box went to a reputable company 3 times before they got it right) timing is set about 5-6 degrees before not quite sure where to look now it would be better off if it stopped and stayed stopped but not in the country lanes lol!

[adam quantrill]

1. Loose connections - get it idling and go around all the ECU connections and sensors and wiggle the connectors, don't forget the resistor pack.

2. Coolant Temp Sensor - can fail intermittently (but you will usually get black sooty exhaust).

3. Ignition amplifier - especially in this heat - can go intermittent.

[Pumpkin123]

Just a thought, but with regard to the engine dyeing after you blip the throttle, I had a similar thing recently, it would normally stall whilst reversing which was slightly tedious, no matter what I set tick over speed too. When I attached a fuel pressure gauge and blipped the throttle you could see the fuel pressure increase as you increase throttle but then dropped really low briefly when you released throttle before settling back to normal pressure.
I discovered throttle potentiometer was wound right down, fuel pressure on regulator had been adjusted about 12psi high and the grub screw which controls the throttle butterfly vane was adjusted so the vane went passed the closed position when you released throttle.
Set all this lot up and car ran loads better not surprisingly and one of the perks was the revs dropping low/stalling issue went away. I'm guessing the revs dying was due to running lean at tick over, probably throttle pot and FPR working against each other possibly.

As for cutting out on country lanes, sounds electrical to me as Adam says above assuming it cuts out whilst driving and not just on tick over.

[ElvisWedgeman]

You probably have an air leak. Not easy to find but it’s there somewhere.

Tony.TCB.

[colin mee]

I second that tony.sounds like a air leak

[Sardonicus]

No way an air leak you have something failing fuel pump relay ign module etc, next time it happens listen for the fuel pump priming when you put the ign in the on position should run for a few seconds then stop, also watch the tacho needle during cranking but non start situation does it flicker or move ? you really need to check to see if this is no spark or no fuel causing breakdown before going forward so basic checks under bonnet will be necessary when fault occurs you may need to work fairly fast however if its intermittent

[adam quantrill]

Air leak a possibility, get it on idle and spray around the pipes and joints with WD40 (or the cheap stuff from the pound shop), if the engine revs rise then you are getting warm. Also check the longish hose from the AFM for splits, easier done by taking one end off and flexing it around.

[jensencars]

Have been out to the garage tonight checked all engine electrical plugs all ok, coil wires and afm hose which is new all ok , I did however notice that the cts is the plastic nut type although it’s new I read in another post that these are not desirable, also noticed a bit of the metal fuel hoses (approx 3 inches is exposed near the exhaust manifold so need to get a extra piece of heat wrap/ insulation to put around them. Maybe my imagination but the ignition coil didn’t seem as hot tonight but admittedly I have not been out in it. I struggle to get out the garage much in the week and I have to work away this coming weekend but will carry on doing little checks as I get time will report back!! Annoying thing is it will idle quite happily in the garage.

Oh and in answer to one question yes it did just cut out whilst driving along a straight road at approx 30 mph trouble is in these lanes around here you can’t really start checking things it’s more a case of try to get it out of the way..

[adam quantrill]

The fuel pipes are under high pressure so no chance of vapourisation if that is what you're thinking.

Get out there with some spray then and check for leaks, and yes those plasticy CTS's can be a bit iffy, get the LR one.

[Sardonicus]

2/3 minutes to re-start clearly NOT an air leak

[ElvisWedgeman]

It’s possible you may have a combination of two faults, air leak being one of them. The development of a secondary fault such as ignition amp or ETS has highlighted the primary fault causing the confusion. Investigation needed.

Tony.TCB.

[mrzigazaga]

This is an interesting post, I have the exact same thing, mine has cut out completely at 60 mph and then instantly bump started itself...a bit disconcerting to say the least..Its only happened twice in 3 months, however I get the stalling from cold, especially if I drive it a tad over zealous whilst its warming up, this has stopped since i drive it like Miss Daisy until the thermostat has opened fully.

Have to agree, definitely NOT an air leak or the revs would increase...not decrease..the comment as regards to the fuel pressure is interesting ...Ill have to check mine to see if the pressure gauge does the same thing...

[adam quantrill]

When I had cutting out I had some chafed wires from the throttle pot intermittently grounding on the throttle bracket - which is in a funny place on the 400SX. Another one wot eluded Mr. Priddle....

[jensencars]

Ok
Tonight on idle in the garage sprayed wd on all the plenum hoses etc no difference in idle, checked throttle pot there is a little bit of cable exposure on green wire just where it’s moulded into the pot but not touching anything, did a check on pot and got 312mv my book says 325 + - 25mv as I recall so well in there also got a smooth sweep up to 3.9 volt at open throttle, it seemed to idle very well today for some reason or is it just in my head!! but still only just recovers before stalling
New metal type Cts ordered, checked vacuum at distributor take off on manifold (for my curiosity more than anything) it’s pulling approx 8” of vacuum on tick-over
I also have a co tester it’s old but a good guide and it’s running at 1.3 % on idle is this to lean? I know I can go to 3.5% for mot

Edited by jensencars on Tuesday 2nd July 19:25

[SEvans]

I don't know much about the rover V8 but it seems you need some practical ideas to try and diagnose the fault. As it's only happening when you are driving is there any way of rigging up a fuel pressure gauge that you can observe whilst driving? If that drops off then you could rig up a bulb to the contacts of the fuel pump to see if it's dropping a 12v feed to the pump whilst driving. Cheers Steve

[adam quantrill]

Is one of your symptoms that it stalls or tries to (revs dip) after you take your foot off the gas?

In which case check the throttle butterfly gap and set to specification (when throttle closed), check the linkage always returns to the throttle stop when blipped.