Alfa Romeo Forum banner
61 - 80 of 109 Posts

·
Banned
Joined
·
642 Posts
Fuel pump inspected today. It is in mint condition and therefore not the cause of the issue. No leaks, no cracks. Output is within the expected parameters.
Picked up my GTV runners yesterday- really pleased.

However found a new scenic route to Thetford and a different one coming back. Been here 41 years and we keep finding new roads and boy are they scenic. Parts of Thetford Forest are really beautiful this time of year.

So we did about 100 mile round trip. That gave me a real opportunity to test the engine since fitting the new NTC Sensor.

Fantastic! It has been a long time coming but “Silken”. “Hole - free performance”. Super smooth. Gutsy at low revs but much more civilised. Wound her up on the slip road joining the A14 to 5000 - seamlessly piling on the revs, not a hint of hesitation anywhere. This must have been what Alfa thought they were going to give us!

I am still in disbelief of the way that sensor has changed things. I am in awe! Before I changed it, the statement the car made was brash with more than a hint of boy racer about it - it is quick; under-geared is the enduring impression.

Now? Very, very Sophisticated. Better than any Beemer or Merc by miles. An absolute delight. Throttle response is out of this world for such a heavy car and cruise control has the engine firmly under control with no noticeable “Pumping” as it cuts in and out - smooth as silk.

Hope there is nothing more to burst my balloon!
956503
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #62 ·
I just had a call from the indie and it is confirmed that there is no issue with neither the fuel pump in the back, nor the HP pump...which is rather pleasing, since the cost of a new pump is rather high. The most probable cause of the issue is bad fuel, since in his words the cold start today was from half a turn and I refueled yesterday just before leaving the car with him. This is a common issue here in Bulgaria, but might not be the case in other countries. Will keep you guys posted.
 

·
Registered
Joined
·
174 Posts
Fixed! 2 cold starts and running perfectly. It was the temp sensor. Initially replaced it with the cheapest one I could find think it was £6. Having removed the connector and it running fine bought the original Bosch Sensor 0280130122. And is now perfect. Was only £14 from Ebay. Would suggest everyone does the same when experiencing hesitancy from cold. It would seem that a failed reading on this sensor appears to be significant in fuelling from cold. Started this morning temp 15 degrees and ran perfectly and again at about 5pm temp was about 22 degrees. Both times perfect. It regardless of temp engine seems to needs increased fuel when water temp is ambient.
 

·
Banned
Joined
·
642 Posts
Fixed! 2 cold starts and running perfectly. It was the temp sensor. Initially replaced it with the cheapest one I could find think it was £6. Having removed the connector and it running fine bought the original Bosch Sensor 0280130122. And is now perfect. Was only £14 from Ebay. Would suggest everyone does the same when experiencing hesitancy from cold. It would seem that a failed reading on this sensor appears to be significant in fuelling from cold. Started this morning temp 15 degrees and ran perfectly and again at about 5pm temp was about 22 degrees. Both times perfect. It regardless of temp engine seems to needs increased fuel when water temp is ambient.
Glad you got a new sensor at such a good price. However, we mustn‘t let ambiguity of its function pass into JTS Folklore! Dealerships and Independents love that!

The ECU is not artificial intelligence, it only does what it is told to, by the preconditions it has been programmed to respond to.

This Engine - 3.2 JTS - is ”Lean Burn up to 1500 RPM”. There are no exceptions to this wrt the warm up phase!

The NTC Sensor in the cylinder head water jacket, close to number two cylinder exhaust port responds very quickly to temperature fluctuations at this point, which is very close to the Manifold Catalytic converter.

It’s fast changing temperature is seen by the ecu as an indication of how “Hot” the Cat is. If it is below a figure which light-off occurs, the ecu advances the exhaust camshaft, opening the exhaust valve early at a time when there is still considerable pressure in the cylinder, gas temperature is still higher than normal and unburnt fuel is sufficient to catalyse in the cat canister and produce further heat to reach and maintain light-off.

“However, no extra fuel has been injected”.

There are two ways to enrich a mixture.:-

1.) One can maintain the quantity of air and increase the fuel injected.

2.) One can maintain the quantity of fuel and decrease the amount of air.

The 3.2 JTS does the latter of the Two.

So, whilst the ecu is acting upon the exhaust camshaft, on the basis of the NTC Sensor Value, it is also acting upon the inlet camshaft - retarding it so it opens the inlet valve late in the induction stroke. This greatly reduces the amount of air in the cylinder, but because the fuel injected has not changed, the net result is an over-rich mixture.


It would be virtually impossible, and certainly beyond the ability of this ecu, to compute both VVT angles and AFR figures, when one depends upon the other, and vice versa, simultaneously!

This however, is no consolation to me, other than to highlight a further issue with my modified engine.

Replacing my NTC Sensor has greatly improved performance but it is still not what I believe it should be. The sensor is chosen because of the “known characteristics of the manifold cats. They both trap and generate heat which assists the way the JTS reduces emissions, albeit the engine runs extremely hot as a consequence.

But my engine no longer has manifold cats, therefore it runs a lot cooler and as a consequence the ecu is acting upon a NTC Sensor value which suggests the Cats are still below light-off. Thus, the exhaust camshaft angle is “x” degrees too far advanced, and the inlet camshaft is “y” degrees too far retarded.

Although my engine is performing well, the consequence of this is a lower power output than should be expected. Just how much lower - I won’t know until further testing are carried out.


PS. Because of the position of the NTC sensor, it is advisable to ensure coolant levels are never allowed to drop below minimum. The position it occupies in the water jacket virtually ensures it could easily be damaged if it is not always immersed in coolant!
 

·
Registered
Joined
·
108 Posts
Glad you got a new sensor at such a good price. However, we mustn‘t let ambiguity of its function pass into JTS Folklore! Dealerships and Independents love that!

The ECU is not artificial intelligence, it only does what it is told to, by the preconditions it has been programmed to respond to.

This Engine - 3.2 JTS - is ”Lean Burn up to 1500 RPM”. There are no exceptions to this wrt the warm up phase!

The NTC Sensor in the cylinder head water jacket, close to number two cylinder exhaust port responds very quickly to temperature fluctuations at this point, which is very close to the Manifold Catalytic converter.

It’s fast changing temperature is seen by the ecu as an indication of how “Hot” the Cat is. If it is below a figure which light-off occurs, the ecu advances the exhaust camshaft, opening the exhaust valve early at a time when there is still considerable pressure in the cylinder, gas temperature is still higher than normal and unburnt fuel is sufficient to catalyse in the cat canister and produce further heat to reach and maintain light-off.

“However, no extra fuel has been injected”.

There are two ways to enrich a mixture.:-

1.) One can maintain the quantity of air and increase the fuel injected.

2.) One can maintain the quantity of fuel and decrease the amount of air.

The 3.2 JTS does the latter of the Two.

So, whilst the ecu is acting upon the exhaust camshaft, on the basis of the NTC Sensor Value, it is also acting upon the inlet camshaft - retarding it so it opens the inlet valve late in the induction stroke. This greatly reduces the amount of air in the cylinder, but because the fuel injected has not changed, the net result is an over-rich mixture.


It would be virtually impossible, and certainly beyond the ability of this ecu, to compute both VVT angles and AFR figures, when one depends upon the other, and vice versa, simultaneously!

This however, is no consolation to me, other than to highlight a further issue with my modified engine.

Replacing my NTC Sensor has greatly improved performance but it is still not what I believe it should be. The sensor is chosen because of the “known characteristics of the manifold cats. They both trap and generate heat which assists the way the JTS reduces emissions, albeit the engine runs extremely hot as a consequence.

But my engine no longer has manifold cats, therefore it runs a lot cooler and as a consequence the ecu is acting upon a NTC Sensor value which suggests the Cats are still below light-off. Thus, the exhaust camshaft angle is “x” degrees too far advanced, and the inlet camshaft is “y” degrees too far retarded.

Although my engine is performing well, the consequence of this is a lower power output than should be expected. Just how much lower - I won’t know until further testing are carried out.


PS. Because of the position of the NTC sensor, it is advisable to ensure coolant levels are never allowed to drop below minimum. The position it occupies in the water jacket virtually ensures it could easily be damaged if it is not always immersed in coolant!
As suggested elsewhere, grab yourself diagnostic software for a qualified dissertation. For instance @ idle or revving the engine while the vehicle is stationary the inlet VVT's remain parked. Rear Bank VVT is timed differently to front bank VVT on both the exhaust and inlet camshafts.
 

·
Registered
Joined
·
174 Posts
The contributors in this thread are far more knowledgable than I am. I do have the ability to measure values but had the temp sensor not resolved itself I would have come back to the forum for guidance on the readings.

What I have not said, apologies, is for my situation thank you to everyone who posted. My nearest specialist is far from me and I would have needed to take time off to try and resolve all for what turned out to be a cheap sensor!

The car now has had valve cleaning, injector cleaning and refurbish, new plugs and still hasn't reached 20K miles.

Again thank you everyone.

Nick
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #68 · (Edited)
Returned from shopping - always a joy, particularly when there are zillions of mums and dads picking up the kids from school and coaches parked up everywhere to ferry the remainder back to the villages.

Grabbed a ratchet, extension and socket, and fitted the new NTC sensor - only took 3 - 4 minutes. I really didn’t know what to expect, other than perhaps engine running a bit quieter on start - up. I lost about a pint of Paraflu in the process, but the old one came out a treat. Mind you, so it should given the engine is a brand new rebuild.

Start - up ever so quiet - comparatively speaking - much more subdued. Engine quickly warmed and water droplets from the tail pipes, masking the heavy soot.

So has this NTC sensor always been faulty and has it been making life even more difficult to get the engine to perform better? The sensor came from the original 159 engine - I asked the garage to move all the sensors across to the new engine when it was being installed.

Not really knowing too much of the original engines history, other than having had its chains and tensioners done, it seems as if it was faulty. The front bank cat showed evidence of overheating as it had a large area of scorched metal on the front face. Could this have also caused the NTC sensor to fail?

It may well have done as on testing it intermittently showed a short circuit, an open circuit and occasionally a value which did not change with temperature.

Running conditions have changed and a few test miles should give some indication as to whether this is the last, or just one of a few remaining niggles. Bottom end torque is brilliant and she piles on the revs very quickly. But the racket it produced under hard acceleration just seemed a little too loud and I have long recognised it was due to over-richness at tick-over/low revs - Valve timing having changed dramatically.

From what I have read, the sensor temperature determines when the exhaust camshaft starts to retard, ie, when the port temperature is high enough to maintain ” Light-off” in the Man Cats.

If; as this one has, it fails, the camshafts won’t assume the correct angle, but how much error this creates over the full rpm range is unknown. As it invariable happens under acceleration, this must be at a time when the camshafts ought to be adjusting to new angles. So did any errors result in prolonged early exhaust valve opening, generating excess noise in the exhaust system? And noise levels only dropping as they approached the correct angles at cruising speed? The engine is very quiet and resonance-free at cruising speeds.

The sensor came from Auto doc - Berlin and I was starting to believe it would never arrive, what with all this EU/Brit tariff nonsense. However, it’s a Delphi Sensor - I fitted a set of Delphi coil packs recently - and they were recently bought by Borg-Warner. By the time postage and vat was added it was about 20 quid delivered - 7 quid for the sensor. The six coil packs cost ~ 180 quid, so I‘m pleased with the price.
How do I unplug this sensor? Is it the one right next to the dipstick? It is wrapped around with something like heat insulation tube...I am not able to unplug it. The plastic is brittle and I think I managed to break off small bits of the corrector, so I was afraid not to inflict more damage...
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #69 ·
The issue described by the OP sounds like a problem with the in-tank fuel pump (not the high pressure one on the engine). The only way to test it is to tap into the fuel line and attach a gauge.
this test was performed and no issues were found...
 

·
Registered
Joined
·
174 Posts
The connector came off easily for me. It is the same pinch connector on the MAF but with only 2 pins so smaller. You pull the heat shroud up as far as it will go, pinch and remove. The sensor, if the car is completely cold then you'll most likely get no water coming out. If there's any pressure in the system you'll get about 100ml.

I would suggest you replace with exactly the same sensor, make and part number.

Good luck

Nick
 

·
Banned
Joined
·
642 Posts
As suggested elsewhere, grab yourself diagnostic software for a qualified dissertation. For instance @ idle or revving the engine while the vehicle is stationary the inlet VVT's remain parked. Rear Bank VVT is timed differently to front bank VVT on both the exhaust and inlet camshafts.
Eventually I shall grab myself some diagnostic software, but for the moment I shall persevere with my experiments - after all this is as much about getting to a point where there will be recognisable benefits to be had from remapping, as it is in screwing as much extra performance from the engine, without software changes.

Since the NTC sensor was changed, the ECU, has been re-adjusting to the new static conditions. Initially there was quite violent popping and farting of unburnt fuel in the exhaust manifolds/sports-cat area. This occurs when first starting the car after being parked overnight.

All my tests conducted with the standard JTS MAF element indicated the volts/airflow Transfer Characteristic is too acute at low rpm. This I believe is due to the MAF having lost 11.5deg. beyond TDC, of air flowing through it, wrt Alfa’s Standard valve timing. However, the C.B. cams open at 0.5deg. btdc, which results in much higher MAF output voltage at low revs, resulting in an over-rich AFR. This I believe was the cause of the popping and farting when the NTC was changed.

So, I reverted to the Porsche 911T 055 element. Drive tests again indicate the 055 element appears better suited to the engines new operating conditions. And the car is noticeably quicker as the 055 element goes up to 1200 kg./hr air flow.

Now, in the morning, on start-up, although there is no popping and farting, the volume is pronounced and bassy at 1250/1300 rpm. At ~ 90 seconds after starting the engine, the revs wind back to 750 rpm and the volume drops dramatically. It is during this period I believe, the NTC sensor is warming up and the ECU is re-adjusting the exhaust camshaft. The tailpipes go through a Smokey/water-vapour phase, then that clears on entering a phase when water droplets appear, eventually settling down at 750 rpm with pretty much very little by way of fumes.

Whilst parked, there is no load on the engine and I presume the ECU maintains the inlet camshaft timing at fully retarded, so the compressive load on the engine is at its lowest level and the ECU is acting upon the NTC’s changing value to progressively retard the exhaust camshaft to an angle to its optimum position - for this phase of operation. Consequently, the reduction in volume of noise from the exhaust and the revs of the engine is occurring as increasingly the unburnt fuel in the manifold/sport-cat diminishes as the exhaust valves progressively open later.

I have long believed the difference in the timing between the front and rear bank VVT’s was a man factor in the delay of this engines development. I remain of the opinion that it is due to the differing oil flow inertia between the two banks which is quite substantial given the number of restrictions that exist beyond the point where the front bank VVT feeds are taken off the main gallery.
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #72 ·
update. The BTC sensor is not the cause. I unplugged it,but starting struggle remains. It sure did bring all the Christmas lights on,but I cleared the error code and away they went. My indie says that after checking everything, the only remaining option is spark plugs...What do you think?
 

·
Registered
Joined
·
174 Posts
There are far more knowledgeable members than me but I would suggest you inspect the plugs on the front bank first, easy access to assess the condition. Also be cautious you have the right plugs. There are some manufacturers that list a plug variants for the car which do fit but the centre isn't long enough so they do not sit far enough into the cylinder.
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #74 ·
I have hr7mpp302x bosch installed 2 years ago. Done not more than 20 000km on them.
 

·
Registered
Joined
·
174 Posts
The condition of the plugs would give you some idea. All of my attempts were very much analogue like seeking the smell of fuel on cold start from the exhaust. You could inspect the plugs for condition, check the battery, static, cranking and charging, vacuum leaks on the inlet. If none of those I guess the next step would be injector cleaning.
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #76 ·
battery is brand new, no vacuum leaks, alternator is charging, fuel and HP pumps are in spec, no misfires..jyst ran a can of bardahl injector cleaner. No change whatsoever...
 

·
Registered
Joined
·
174 Posts
I would suggest you still have the injectors cleaned. Mine had covered 19K miles and were heavily gummed up. Or I would guess you could compression test the cylinders but either way if it runs fine once started I would be more sceptical about these suggestions. Have you checked the condition of the MAF?

Nick
 

·
Registered
Joined
·
210 Posts
Discussion Starter · #78 ·
I would suggest you still have the injectors cleaned. Mine had covered 19K miles and were heavily gummed up. Or I would guess you could compression test the cylinders but either way if it runs fine once started I would be more sceptical about these suggestions. Have you checked the condition of the MAF?

Nick
MAF tested and is OK. Low compression is highly unlikely, since idle is fine and car runs well. Besides, if low compression was present, wouldn't it struggle to start every single time?
 

·
Registered
Joined
·
174 Posts
This is where I run out of ideas. I have, probably most like you, read everything I could on this. The temp sensor was suggested and the issue. My problem was slightly different in that it started every time first time but ran roughly for 30 seconds. From reading everything you have said to me points to the injectors being fouled. By deduction, and excluding some of the other sensors that would seem to point to the problem.

Mine cost £90 to have all cleaned new filter and washers. The company is based on the UK but I am guessing you have ones closers to you.
 
61 - 80 of 109 Posts
Top