My missus had to put her car on the road two weeks ago (MOT/tax) and there's something wrong with it - when it warms up, the car loses power, and under load it's on-off-on-off. Basically, cutting out in the middle of junction, trying to stall all the time. You can cruise at 60mph as the car isn't under load, but getting up hills and pulling out is a nightmare, and dangerous.

I've so far replaced:

* spark plugs,
* HT leads,
* distributor cap and rotor,
* all earth cables,
* coolant temperature sensor,
* throttle body,
* idle control valve,
* throttle stepper motor (TPS),
* all injectors and harness,

The engine was replaced in December for a new one, I even changed the belt, pump and idle pulley, and it's barely run in on it's MLS head gasket. There's no overheating, no mayo or water usage, and then I redid the timing again last week to make sure it was OK. To put it another way, the engine's 100% fine, it's the bits around it that aren't working.

I've yet to check the wiring loom and the lambda sensor (which are near enough welded onto the manifold).

Does anyone have any ideas? Not having the best year for cars so far and she's knackered without the motor.

Try running off battery only, in case alternator sending out some nasties.

Try adding some more earth's to the engine to the body

They suffer from bad earth problems

I'll tell you now bud its HGF, this was the biggest down fall for this engine. Stuy mac can go in to great detail about why but for now i'll list a few


Rubber positioning dowles so the head travels,
thermostat in the wrong place so the coolant is always wrong,
It was made on the cheap,

and a few more. There is a new head gasket you can buy that does help but thb its not worth it.

Mattlfc also knows alot about this too.

He already has the MLS headgasket Andy, and if he has done the oil rail, it will be solid as a rock (the N-Series which MG have sold in the TF since 2007, is basically the K-Series with the MLS HG, uprated manifold gasket and oil rail, and tuned to new emission regs, hence the 143/160 no longer being available).

Id be guessing at electrical problems, try what DD and Robbo say first, I have to admit ive not come across anything like this before, have you asked over at .org mate? Ive heard of something similar on one or two L-Series engines, and the first one was a fried ECU thanks to a jump start, and the second one, iirc, was an earthing problem. Not heard of an N-Series HG failing either, as yet (theres always a first), though I have heard of uprated HG's fail, its very very rare - provided the jobs been done properly and no corners have been cut (its easy to think just skip the oil rail, they did that on Rhys's TF160 twice, and I kept saying do the oil rail, and the third time the eventually did it, and he had no probs lol).

The HG itself doesnt just blow randomly, there is always a root cause of it, and its 90% of the time, due to coolant loss around the manifold gasket, and with a tiny coolant capacity, the engine doesnt stand much of a chance. Believe it or not, run any engine without coolant for long, and it will eventually blow a HG, and that includes Honda's lol. Theres vids on YouTube of K'ers running continuously at 7500rpm for stupid amounts of time, without any problem... it does occasionally occur on the original HG due to the engine being fully alloy and different parts expanding at different rates (heat), and if you don't achieve ORT before flooring it, it can go, but the MLS was introduced to remove this flaw, by expanding with the engine as required. But HGF itself, is usually due to water loss.

Well that sorts that one then cheers mat, Is it a possible MAF sensor prob?

Always wondered why all thermostats don't have the "leaky bypass hole" - must be a terrible shock to engines when the thermostat first opens, engine running at near enough full temperature then a blast of ambient water gets shoved up its passages - it would crack me up

I have seen a few recommends to drill a hole when a thermostat doesn't have one.

Come to think of it, it could well be Andy. My brains blank atm, but try unplugging it, if that cures it, its the MAF. If it is, you can get a Pierburg MAF to replace it. The sensor wire inside the MAF can be cleaned as well, though it doesnt always work.

Strange thing with the K'er is, on the 75 and 45, they have Coolant Overheating lights, but they don't work on the K'er... lol.

As much as I love the K, gimme an L or T anyday! though a VVC K in an F/TF... there is no comparison!

If it where the HG there would also be other symptoms - water system pressure, oil in water etc etc....

Surely it must be a sensor if it only does it when warm - lambda comes to mind, but I doubt that would increase the fueling enough to cut out at junctions, and the lambda only works on cruise, so under load wether it works or not, there shouldnt be an issue. As for the MAF - pretty sure that would also show its problem hot or cold....

Maybe fuel pump? Ok under no load, but cant keep up with demand, though that would be an issue hot or cold

David, your not exactly novice at working at cars, and if it has you baffled, Im sure it will have most people on here too. Might need some more in depth investigation - like you mentioned above, see if you can get it code read and take it from there

You can read the fault codes yourself, don't know exactly what car this is in but

THIS might help

Yeah Matt, the engine is solid, it's upgraded and the head is new - I'm pretty 100% that engines that haven't overheated and have had the multi layer gasket and oil rail are no longer susceptible to HGF. You can buy low-coolant sensors and the coolant bottles from Rimmers.
Where is the MAF? I believe I can't find it anywhere! Only the VVC and some later MPi's had a MAP sensor as well.

It's also got the new thermostat splitter that doesn't thermoshock the engine.

The earthing cables have all been replaced!

DD, I never knew you could do the paperclip thing on the diag plug with these, thanks for that!

Got to love wiki team work, try looking around the air intake for the maf bud!

how old is it? might be worth blasting down ill do a diagnostic scan & view live data?

Good old gilly to the rescue

It's a P-reg, I think it's OBD compliant as well ... ? Knowing Rover you probably need some kit from the 1940's.
I'll try anything, it's pissing me right off, I'll come down if you don't mind, if I'm not killed by a truck in the middle of a junction en route.

Oh, early K-series have a MAP sensor in the ECU (connected by a pipe from the inlet) and no AFM sensor.

Car finally spluttered to a final stop today! No chance of getting it started, so called the AA.
The bloke checked it over, and replaced the rotor arm for a new one. It started on the button and revved nearly A1! It was the ROTOR ARM!
I bought a new one of these, but just shows new ones can be faulty.

Exactly.