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Rover Engine Issues


AndyW

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Hi guys, I need some advice from those more knowledgeable about engines than me. Mine seems to be using a lot of oil and fuel consumption is also terrible.

Superspec with Rover T-series 2.0litre dohc engine, multi-point fuel injection, MEMS 1.6 ECU. The engine has only done 3800 miles so virtually new (although 20 years old).

Last year I had to rebuild the head - had 4 new valve guides fitted (2 inlet, 2 exhaust), and replaced 4 exhaust valves and 7 inlet valves. New gasket set and cambelt used. Everything went back together successfully and I've driven the car over winter but I've got some issues:

- Seems to be using a lot of oil. I've probably topped up with 1.5 litres of oil in the past 800 miles. Every time I check the dipstick it's on Min.
- Starting first time after standing for a couple of weeks, there's a bit of white/blue exhaust smoke that goes after a minute or so. So it's burning a bit of oil.
- There's occasionally some exhaust smoke when driving while warming up, but nothing obvious under normal driving (although it's not easy to see the exhaust from driver's seat).
- When started from cold the engine feels and sounds over choked, and runs a bit rough as though plugs are fouling. It doesn't misfire though and then runs much better when warmed up.
- Fuel consumption over past few months is only 24mpg.
- Changed plugs recently, they were dry grey/black on the tips but oily carbon on the base of the threads.
- Looking through plug holes the tops of #1 and #4 pistons are wet, but middle 2 are dry.
- Compression is good, around 250psi on all 4 cylinders.
- Not losing any oil down side of engine and no drips on floor so I don't think head gasket is a problem. But the top of the head between the cam banks and in the plug wells is wet with oil.
- Had a lot of trouble getting the emissions through the MoT recently. High CO and lambda.

I've used Al Richey's MEMAnalyser software on the ECU which shows no faults and all sensors are working correctly - coolant temp sensor is correctly reporting between 75-100C, and the O2 sensor is in closed loop and outputting 0-0.9v oscillating.

So, it's using a lot of oil, presumably burning it steadily when driving. Where would that oil be coming from? And the fueling is over-rich but as that's all controlled by MEMS I can't see any way to adjust it.

Would these problems be linked? Any ideas what could be wrong? Or checks I can make.

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Forgive me one question, but why did the head need such extensive work last year on such a low mileage engine?

 

If the compression is good then it sounds most likely that valve stem oil seals (or some other part - I'm not savvy with this particular engine) are gone and you're getting oil sucked into the engine on running, and also leaking down in the bores when the engine is sitting. On top of this, the fuelling could well be off - you can't rely on a narrowband to give you any seriously accurate information so rely on the garage report. As to why, given it's a non-mappable system (I presume?) then if all the components are standard, either the MEMS ECU is confused and thinks it should be squirting in more fuel than is necessary, or else some part of the fueling system is knackered - injectors, fuel pressure, etc?

 

I'd be guessing short of the oil issue inside the engine, if the fueling is right off it's probably down to some aspect of the management... sounds like Al Richey is your man there to give you some diagnostic advice on what they system is reporting!

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Leak in the exhaust before the sensor could draw in air.

Thus fooling the ECU into running rich.

 

Oil consumption could be a seperate fault and valve stem seals are a first port of call

Cam cover gasket is a posibliity for the oil between cam banks.

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Forgive me one question, but why did the head need such extensive work last year on such a low mileage engine?

 

Short version of the story... shock absorber rod snapped (suspected previous accident damage) > dropped sump onto road > snapped aux belt > wrapped around crank pulley > seized engine > snapped cambelt > valves hit pistons!!

 

 

given it's a non-mappable system (I presume?) then if all the components are standard, either the MEMS ECU is confused and thinks it should be squirting in more fuel than is necessary, or else some part of the fueling system is knackered - injectors, fuel pressure, etc?

 

 

Yes, the Rover system is non-mappable. The ECU has a fixed map which it self-modifies depending on engine history. The fuel mix is normally adjusted by the ECU changing the injector pulse length. Poor fueling is typically caused by the coolant sensor not working so the engine uses a default rich mix value. But we've verified this isn't the case here. All ECU sensors appear to be working correctly. I guess the injectors could be knackered although they haven't done much work in their lifetime.

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Leak in the exhaust before the sensor could draw in air.

Thus fooling the ECU into running rich.

 

Oil consumption could be a seperate fault and valve stem seals are a first port of call

Cam cover gasket is a posibliity for the oil between cam banks.

 

Yes, I've had an ongoing battle with a leak in the joint between the 4-1 manifold and the pipe to the lambda and cat. However, the O2 sensor only tweaks the fuel mix in response to rich/lean running, so would it have so much effect on the consumption? Al Richey gets 34 mpg compared to my 24 - a huge difference from the exact same engine. So there's obviously something wrong.

 

The cam cover gaskets aren't leaking, but the cam carrier bodies themselves were fitted on Loctite 574 liquid gasket. It's this that seems to be leaking.

 

Valve stem oil seals seem to be the most likely cause of the high oil consumption. However, new seals were fitted when I rebuilt the head, they came in the complete head gasket kit. Two possibilities have been raised - were these the wrong seals (we're unsure if the Rover t-series had different sized seals over its lifetime), or did I not fit them properly!

 

Is the only way of finding out to strip the head down again?

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Fairly small leaks in the exhause can have a big effect.

The lambda sensor is looking for no oxygen in the exhaust so a small leak brings some O2 into the exhaust and hence the lambda sensor.

 

As regards the oil leak you can either live with it or remove the head checking all surfaces are flat.

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I had another go at resealing the exhaust joint last week. Found it was blowing in 2 places. It seems better now so I'll have to see if that improves the consumption. A good run to Stoneleigh this weekend should help.

 

I've been living with the small oil leak on top of the head, that's ok. It's the burning of the oil, wet pistons, and the rough running I was more concerned with.

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Certainly there's some ideas to follow there I think. Closing up the manifold holes can't be a bad thing, and I wonder whether finding someone with the kit to do a leak down test would just satisfy the mind that the problem isn't ring or valve seat related... just so you can focus on the top end as the source of the oil problem. You could pop the injectors out and test them fairly easily with a syringe, a 12v battery and a measuring jug too :)... well, assuming they are standard Bosch type injectors.

 

Otherwise investigating the MEMS management is all I can think of, which you've already done. Obviously with a customiseable, wide-band equipped system you can see what's going on a bit more than a narrow band - but it's not entirely practical to suggest buying a wideband lambda just for the purposes of debugging what may or may not be a management issue. Worst case, later in the year you're welcome to borrow a wideband lambda setup I have that is non-permanent (I use it to just swap in to a car to check it every now and then)... just an innovate LC1 system. I'd say you could drop it in and check your fuelling accurately but I guess by removing the narrow-band you have, you'll put the fuelling all to cock anyway X-(. However it does have a configurable narrow-band simulated output so you might actually be OK - it can feed the MEMS with the necessary narrowband signal, and you can then monitor the wideband output (just with a multimeter) to get an accurate reading of the fueling.

 

Or you could just go to a garage with a gas analyser which, let's face it, is far quicker and simpler :D

 

But if you've checked the MEMS system and it all reports OK, then I'm not really sure where all the effort of the above would lead you.... :(

 

If oil is being burned through the system, I'd cure that first anyway. Burning 1.5 litres in 800 miles doesn't sound a good thing to me, irrespective of engine type, although I appreciate some engines burn oil more than others!

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Have you checked fuel pressure, quality reliable pressure regulator fitted and checked with reliable fuel pressure gauge? Is it set to the correct pressure? Not everything runs at 3bar!!

Not using a vacuum rising rate pressure adjuster on the gauge if it has one?

 

Otherwise it's down to sensors giving incorrect readings to fool the ECU, particularly under-reading CTS or over-reading MAF/MAP.

 

Nigel

Edited by Longboarder
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Thanks for the ideas Dan. I'm not sure I want to play around with wide band lambdas at this stage - the standard O2 and Rover MEMS should work reasonably well normally. I'm going to thoroughly check all gaskets and vacuum pipes for intake and exhaust leakage. Then need to find a garage with exhaust gas analyser to give me a proper diagnosis.

 

The Rover t16 engine doesn't normally burn any oil (maybe leaks it instead) so that's something that's developed since I did the head rebuild.

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Nigel, thanks for suggestions, but I don't have the tools to check fuel pressure, and no gauge so will have to give that a miss for now. The regulator on the fuel rail is the Rover original and I believe it's supposed to work at 3 bar but can't prove it is.

 

As I said, our analysis of the data in MEMS ECU shows that all sensors are giving what look like correct readings. CTS from ambient up to 100 deg C. No MAF on this engine. MAP shows 15 psi/100k pascal with engine off to about 4.5 psi/30k pascal at idle which seems to be in spec. All other sensors are giving correct looking values.

 

New plugs and air filter fitted so we're struggling to come with any other ideas for the poor fuel consumption. Have to see how it goes.

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