Having said THB set by factory so shouldn't be touched , I think this was what online was mentioned, as on some vehicles they could be reset after fitting different components on the THB. It was in reference to that resting point.
I think I have already read all the possible threads and forums online regarding to this
since I have the Cento at home...there is nothing left. I have already checked in MES and it doesn't have a resetting procedure... neither my 2011 Giulietta QV does which is drive by wire.
Just clutching at strawsI think I have already read all the possible threads and forums online regarding to this
The new throttle body I installed is from Magneti Marelli do has to be equivalent quality to OEM, even though it is made in China like most of the part nowadays. The BOSCH itself doesn't produce its parts here in Germany anymore because they can do this elsewhere for cheaper. That's why I changed the idle control valve of the new THB and I put one made in Germany but no change... So it has to be related with something else and not with the thb itself I guess
Cheers
Elvis
Just clutching at straws
:That engine should idle smoothly at 1000 RPM on a cold start and drop to a smooth 750-800 RPM when sufficiently warm. If it does your TSP is working correctly. The symptoms of a malfunctioning TPS are rough idle, slow or fast idle, stalling and hesitation."
"To adjust the TPS, you need to loosen the mounting screws and rotate the sensor slightly. You can use the DMM to monitor the voltage or ohms of the TPS while you adjust it. You need to align the sensor with the throttle valve position and match the desired voltage or ohms according to your vehicle's specifications."
This also on adjusting using a voltmeter?""
Maybe see if the voltage readings at those settings are the same as the video?
Back from a 550 km trip and nothing changed. The car ran like a dream in high ways and interurban streets but once you stay stationary it idles to low and it kind of misses and pops from the exhaust. Sometimes almost stalled and I could see the oil pressure light for half a second...then catching up and going on and on and on... If I disconnect the plug from the ICV it idles better but triggered the stepper motor error.
. This is the whole period after ECU reset (every time) until the car reaches the distance of 200-250 km when the ECU has settled.
Hi Mike,I don't use MES as when I went to purchase it was incompatible with one of my Fiats.
Given that the car runs so well at all other times, I think you are right to check throttle body area and comparisons with old one.
Also the instructions sent to it via ECU from temperature related sensors.
I have no data regarding that so probably beyond my skills.
Not wanting to be a "know it all", but in my initial post I mentioned.:-
Today for the first time since I owned it it stalled 3 times in traffic lights... it's getting worse and worse when engine gets really hot. I'll definitely try the hose trick but anyway I don't think even if there is a leak it would be so bad to locate it with a rubber hose just by listening, with all that noise in there. What should I be looking for ...a hiss or?Not wanting to be a "know it all", but in my initial post I mentioned.:-
"I know you have checked the two rubber hoses but an air leak can give those symptoms and sometimes you can locate them with a length of rubber hose held to your ear whilst checking around the engine with the other end of hose.
Another trick is to use brake cleaner spray around inlet area, if there is a leak the engine revs will pick up as it burns the brake cleaner. Obviously do in a safe manner.
I assume nothing like a brake servo vacuum leak?"
Recently I had a Fiat Doblo diesel that I spent ages trying to locate a fault, in the end I took it to an expensive diagnostic guy the motor trade uses and he found a small air leak at an EGR connection to the inlet manifold which solved the problem which considering I have been in the motortrade repairing vehicles since 1969 was slightly embarrassing, but no one knows everything. Mike
The hose trick does work for some air leaks, so worth a try. I have a mechanics "stethoscope" which goes in both ears like a doctors and you hold the pipe in areas you suspect. In the old days we used to balance twin carburetors using a piece of rubber tube to measure the induction hiss and then retighten the joining bar after setting them individually.Today for the first time since I owned it it stalled 3 times in traffic lights... it's getting worse and worse when engine gets really hot. I'll definitely try the hose trick but anyway I don't think even if there is a leak it would be so bad to locate it with a rubber hose just by listening, with all that noise in there. What should I be looking for ...a hiss or?
I personally don't think is broken a hose, more likely to be the intake manifold itself because there is only the two hoses there.
Regarding the brake booster...I think it's all good, I don't have a spongy pedal and if I keep my foot on the pedal it feels firm and doesn't drop.
I also measured the TPS with a multimeter and at fully closed it gave 0.5V and at fully open it gave 5V so more less acceptable values. The old one gave totally crazy values like 7.4V fully closed...or maybe my multimeter got somehow tricked out, because right after the new one was giving 4.5v at closed position too
Good morning MikeThe hose trick does work for some air leaks, so worth a try. I have a mechanics "stethoscope" which goes in both ears like a doctors and you hold the pipe in areas you suspect. In the old days we used to balance twin carburetors using a piece of rubber tube to measure the induction hiss and then retighten the joining bar after setting them individually.
However were you standing by when the garage tested with brake cleaner spray?
As, if you noticed the engine revs change when he did it and the general location then you may be able to start in that area.
Engine "easy start" spray may have the same testing effect, although try to just give a little spray in an exact area at a time as is quite volatile.
Sounds like the TPS was worth changing anyway.
If you can find a small air leak it could be the source of the bad idle/spluttering.
Re the vacuum servo usually it starts small and gets so bad that you would then find the hard brake pedal and poor stopping as Fiat servos are known for it.
It is always worth checking the vacuum piping side as rubber deteriorates, equally it can be a small gasket or split somewhere.
. Double carburettor is a nightmare to balance right, it reminds me my old Alfa Romeo 33 VL with double Webber carburettors wich were never balanced wright . In fact a mechanic stethoscope would be a good idea to have in the garage though..Twin SUs were common on many semi sporting or big engine cars as an apprentice , particularly BMC/Austin/MG etc. My 1971 Alfa Romeo GTV I think was on twin Dellortos carbs.Good morning Mike
Even though I'm over 40 and I have already lived in the carburetors era, I have heard of it before but never seen someone doing...I guess is more less the same principle like the screwdriver trick
No we were in open area when he did the brake cleaner trick, I repeated than the test later inside my garage but the results where closed to 0 because the amount I sprayed was a lot less (just had a little quantity left)
In which are was the engine sensitive I cannot really tell because he used quite a large amount of brake cleaner and sprayed all over the place.
The TPS and throttle body was definitely a good idea to change. The new one is a bit on the higher side of voltage but still ok I think. In the video you sent it says it should be around 0.45v at idle and 4.5v at open throttle...mine is 0.5v and 5v (not that bad I guess) and with engine of I can hear also the stepper motor activating when you release the throttle, so I guess all is working as it should.
Regarding the brake servo, I really don't have much experience as I never had one failing. The problem is that with such a light weight car you don't notice if the car it's taking longer to brake, I drove also without my abs when the sensor broke and it would still brake the same
How can I disconnect the plastic pipe from the servo so I can blank it and see if anything changes with the idle.
My bet would be a gasket somewhere in the intake manifold
. I can still hear this kind of cough/missing but it's like 80% less now but at least the engine is not hunting anymore like it was doing before. Good if that is the answer, I always assumed that throttle butterfly would be open a fraction at idle in most cases unless there is an air bleed system similar to some carburetors in the old days where they had a mixture screw as normal , but also a larger screw known as a volume screw which controlled idle speed , but unlike a conventional throttle stop screw, the more you screwed it out the faster the engine revs would increase as it bled more air through.Hi Mike, a little update here...
I don't know how I couldn't see it wright but the measurements in Volt that I have done with the THB are wrong. I have been measuring from the wrong wire (the supply wire and not the signal wire), so the reading were 4.6v (the 5v wire). I found then the signal wire and the measurements are as following
@ closed throttle 0.66v
@full open throttle 4.6v
Then I measured the old throttle body which was previously upset through that little screw. It wasn't way off and I set it at the same values as the new THB.
Now even though they are set at the same V values there is clearly a difference between the two. In the new THB the butterfly in the rest position remains a few ° open, because it lets some light go through. Instead the old THB at the same V setup is totally closed and not letting any light passing through
(the new throttle body at idle is not totally closed/the old one is totally closed at the same 0.66 V setting)
So I thought the new Chinese THB might be multiplying the problem and upsetting the engine letting some extra air through the butterfly at idle and therefore the ECU doesn't know how to control wright the stepper motor.
I then decided to install the old THB after setting it at 0.65V at idle (it doesn't get less than 0.65 because the throttle valve will stick/scratch on the body). To my surprise after a few turn on/off and a couple of hundred km of drive the car sounds a lot more stable at idle
One question here please, should the throttle be slightly open at idle or the butterfly should stay completely closed? I know this engine uses the stepper motor to idle so logically it doesn't need to have the butterfly open for it to idle, right? I didn't reset the ECU this time so it may take a while until it learns the new values and it might settle further down.
The only fear I have is if at idle it will pass the pollution values at the MOT.
Regards
Elvis
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which I was not expecting to see. This seems to be to much of a difference, but looking with the camera inside as I said the piston and cylinder walls look good.Sounds like a good check over.Hi, next week I'll leave the car to some garage in hoping they will find any clues on what is happening to my Seicento!
Today I had the chance to meet with a friend of mine who has his own hobby garage with a lot of tools and all this good stuff
We took the car there and thought to try do a couple of tests to check at least the basics:
Took the new spark plugs out and inspected them. They look a bit to whitish (a bit lean in my opinion). They were all almost the same colour.
Then we entered inside the cylinders with an endoscopic camera. There are some carbon deposits but this is normal. The cylinder walls are still perfect and I didn't notice any scars.
Than we decided to use the smoke test machine and test the intake side of the engine. Fitted the smoke pipe there were the brake servo pipe connects to it, blocked the throttle body with one hand and pressurised the system. We could see some smoke coming out from the oil cap (normal) and some smoke coming out from the butterfly axe were the mechanism and the accelerator wire meet together (don't know if this is normal, but I don't think so), but the rest looks ok and lo leaks. Also a brakes servo leakage coul be excluded because the car idles the same if I blank the inlet were the brakes servo pipe enters the inlet manifold.
In the end we did a compression test and the results were not what I was hoping to see. Cylinders 1, 2 and 3 starting from timing belt side gave a compression of +/-12 bar, but cylinder 4 measured only 8 bar
Could this tell a possible problem with the valves/cam lobe/valve seal on that cylinder which may also explain the terrible idle speed? Could it be a valve clearance problem and valves needs registering. The engine has started to shut itself off when idling at operating temperature (when it gets to warm).
I think it's time to open the rocker cover and inspect the camshaft and valve clearance
I also noticed under load I can hear some kind of rotation/resonating noise at certain rpm under load which I cannot pinpoint which side of the engine it's coming from.
But anyway I think I can exclude a possible head gasket problem I think. For the rest I can't do much but just taking it at the garage and have it checked properly by the professional.
