Faulty temperature sensor? Still doesn't explain no errors though...
Technical 1.6 engine won't rev
- Thread starter euge595
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Technical 1.6 engine won't rev
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this is a weird one.. could be a faulty lamda or possibly map/maf as these are large idle inputs once warmed up (extra fuel and more revs until op temp is reached) however, these will generate an error worthy of a MIL light. Re: mil - it wouldn't come on if the reading received from i.e. maf sensor is within parameters which is to say that there could be a strong resistance point throwing the reading off constantly (but not enough to flag a fault) all these wonderful theories are just that theories and i would not entertain them before cleaning the throttle valve properly.. also ensure that the vacuum lines from engine head to throttle are secured (and in place) as that would cause your issues (air coming in via these lines bypasses the sensors.. all the car reads is extra air from nowhere)..
seriously though what you describe is still, in my opinion, an issue with the throttle body.. and from what you described.. and given there are no errors.. there is no way you could have cleaned it properly.. open it completely (with your fingers) and give it and the surrounding walls a good clean with plenty of carb cleaner using a toothbrush.. especially at the fixture/pivot points and at the closed position contact points.. Simply opening it a bit and wiping carefully what you can reach with it partially opened would not clean it (and without the brush there is no way you can get to the pivot points.. i tried..).
To sum it up, if you wish to test the map/maf theory disconnect the sensors and start the car (after it is warm) this will throw up errors on the dash.. but if it stops stalling.. there’s your problem.. (i would also advise to clean the sensors and connections to throttle body and the sensors using a contact cleaner.. these are cheap btw.. so don’t be trying to constitute WD40 or vodka.. as that won’t work)
If you decide to properly clean the throttle valve.. go right ahead.. and then relearn.. since you’ve done throttle relearns while engine is cold (and it runs well while cold) i would advise you to repeat the procedure after the car stalls (after it is warm obviously) a few times.. each time ensure you remove the key for a min.. put it in and half turn to power everything on.. (do not start the car) keep everything powered up for a minute.. remove key for a minute and then start and try again.. It is feasible that the garage did register the ecu but did not perform a full re-train on engine dynamics (as this requires them to it there and rev every few minutes until the engine is fully warmed up etc. takes about 30 min) this could have, feasibly, caused your issues.. the above should rectify the problem.. All else failing and barring any further advice you may receive from more knowledgeable members on here, take it to another fiat authorised garage
Re: temp sensor - it will cause an odd lumpy idle but is inlikellly to cause the ar to cut out (as it won't be seriously overheating due to the mechanical based flow to radiator controll)
seriously though what you describe is still, in my opinion, an issue with the throttle body.. and from what you described.. and given there are no errors.. there is no way you could have cleaned it properly.. open it completely (with your fingers) and give it and the surrounding walls a good clean with plenty of carb cleaner using a toothbrush.. especially at the fixture/pivot points and at the closed position contact points.. Simply opening it a bit and wiping carefully what you can reach with it partially opened would not clean it (and without the brush there is no way you can get to the pivot points.. i tried..).
To sum it up, if you wish to test the map/maf theory disconnect the sensors and start the car (after it is warm) this will throw up errors on the dash.. but if it stops stalling.. there’s your problem.. (i would also advise to clean the sensors and connections to throttle body and the sensors using a contact cleaner.. these are cheap btw.. so don’t be trying to constitute WD40 or vodka.. as that won’t work)
If you decide to properly clean the throttle valve.. go right ahead.. and then relearn.. since you’ve done throttle relearns while engine is cold (and it runs well while cold) i would advise you to repeat the procedure after the car stalls (after it is warm obviously) a few times.. each time ensure you remove the key for a min.. put it in and half turn to power everything on.. (do not start the car) keep everything powered up for a minute.. remove key for a minute and then start and try again.. It is feasible that the garage did register the ecu but did not perform a full re-train on engine dynamics (as this requires them to it there and rev every few minutes until the engine is fully warmed up etc. takes about 30 min) this could have, feasibly, caused your issues.. the above should rectify the problem.. All else failing and barring any further advice you may receive from more knowledgeable members on here, take it to another fiat authorised garage
Re: temp sensor - it will cause an odd lumpy idle but is inlikellly to cause the ar to cut out (as it won't be seriously overheating due to the mechanical based flow to radiator controll)
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could also be timing related (see https://www.fiatforum.com/stilo/231331-revs-dropping.html) however, given that it is a fiat place (and as such would have all the required tools) it would not be likely
Have you checked the crank position sensor. Mine got knackered once, and it was a no-starter. It is the only time I've had to go to the garage in 4 years for an engine issue. I think if this is starting to jam up, it might be sensitive to heat due to expansion / loosing contact etc. Just a thought.
euge595
New member
Thank you for your very helpful replies, I haven't been able to fix it yet but at least I don't feel so impudent. Dr12 thank you for very detailed reply, I've got some time tomorrow so I'm going to have another go, in addition to the Carb cleaner, I've also got some electrical contact cleaner( Halfords ) would you suggest cleaning the maf/mas sensor and if so can you tell me where it is? Re the re-learn, the procedure I'm following is turn ignition on but don't start, leave for two minutes then turn off the ignition and remove the key, leave for two minutes, insert key and start the engine without using the throttle and allow to reach normal temp, although it cuts out before normal temp is reached. If this isn't the correct procedure perhaps someone will let me know. Dr12 your point about vacuum hoses is interesting, when I got my car back there were loads of clips missing from the hoses, I've replaced as many of them as I've found but tomorrow I'll have a more detailed look. Makes me wonder how competent the garage is.
Your relearn procedure is fine, but do repeat it after the car warms up and stalls (a few iterations of the stall-->retrain-->start might improve things). maf sensor would be on/in the throttle body (it’s a metal heat wire in the path of the air.. normally in a separate channel/tube near the throttle flap.. sorry am too tired to go and look it up for a 1.6 and, as i've a 1.8, it's different) map would be located somewhere in the air tubing (should be just after the filter.. look for a plug connecting to something on the air tube junction.. 1.8 doesn’t even have 1..) just spray the sensors (don't brush or touch.. although that treatment could be okish for the map mesh.. but it'll definitely kill your maf) erm.. the cleaning guide might mention where the sensors are (or just use search).. but neither sensors malfunctioning should cause your problems (and should flag up an error if something is this seriously wrong.. then again.. you are not losing anything by trying.. it might just tip the balance and make it more drivable)
As the car warms up.. is the idle normal? Same as it was before all this happened? Do you have any problems restarting the car after it stalls? Any interesting noises, e.g. metallic clicking, coming from the engine in tune with RPM? How’s your oil? Does it look nice and clean? Is there anything floating in the coolant tank (that does not look like coolant)? Overheating?
Ps: ensure you do not have a pool of contact cleaner around the maf as you start the car (heat wire + abundance of oxygen + near pure alcohol.. = boom... so.. blow it out using an air canister.. or some other imaginative means.. but be careful with the imaginative means.. in my experience it always goes for the eyes.. when you try to blow it out
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PPs: still think it most likely to be the throttle body (starts with no problems after it stalls?).. However, if the answer to all the questions is a ‘NO’ and cleaning does not help.. i can not advise anything further.. as it would be time to either start buying new parts.. or get a second opinion.. that being the case.. Morty dude is spot on! Once all the free options are exhausted - go for the crank sensor first! It’s the cheapest part and has a nasty habit of not logging a fault when starting to fail
PPPs: you’re not my student – no need to use the title
As the car warms up.. is the idle normal? Same as it was before all this happened? Do you have any problems restarting the car after it stalls? Any interesting noises, e.g. metallic clicking, coming from the engine in tune with RPM? How’s your oil? Does it look nice and clean? Is there anything floating in the coolant tank (that does not look like coolant)? Overheating?
Ps: ensure you do not have a pool of contact cleaner around the maf as you start the car (heat wire + abundance of oxygen + near pure alcohol.. = boom... so.. blow it out using an air canister.. or some other imaginative means.. but be careful with the imaginative means.. in my experience it always goes for the eyes.. when you try to blow it out
)PPs: still think it most likely to be the throttle body (starts with no problems after it stalls?).. However, if the answer to all the questions is a ‘NO’ and cleaning does not help.. i can not advise anything further.. as it would be time to either start buying new parts.. or get a second opinion.. that being the case.. Morty dude is spot on! Once all the free options are exhausted - go for the crank sensor first! It’s the cheapest part and has a nasty habit of not logging a fault when starting to fail
PPPs: you’re not my student – no need to use the title
euge595
New member
Today I though I was going to crack this problem, I removed the throttle body and gave it a good clean, loads of Carb cleaner, cotton cloth and tooth brush, checked all the fixings on the hoses, disconnected the battery for an hour before initiating the re-learn procedure and still no joy. At first I thought it had worked because when the engine was cold it was ticking over OK, but as soon as the temp approached normal, it cut out. took it for a run but every time I slowed to a junction it just stalled, started OK again and as long as I didn't slow down it was fine but as soon as I'd take my foot of the accelerator at low speed the engine died. I'd like to thank you all for taking the time to reply to this epic, I think now it's going to be a trip to my Fiat Dealer.. One other thing that naffs me off is the only reason I took my car to this Garage "Fiat Specialist" and not my local Fiat dealer was because the RAC recommended them, I've duly complained to the RAC and have basically been told tuff! They didn't say they'd take it up with the garage, They didn't offer any help just got very defensive, a thoroughly bad show. I've always been a big fan of the RAC, been with them for year, but I've sorry to say their customer service department sucks!
euge595
New member
One thing I meant to ask in my earlier reply, when I took the throttle body off, at the resting closed position the flap wasn't completely closed, holding it up to the light I could see a gap at the top and bottom of the flap so instead of the flap being dead flush it was sitting at a slight angle, is this how it's suppose to be?
yes mine is the same.. it goes into fully closed position when retraining though.. also (am sure you have done.. but just in case.. have you tried to retrain the throttle with the engine warmed up? i.e. right after it stalls?) The fact that you’ve no problems restarting after the engine is stalled tells me that the crank sensor is most likely working as it should be.. so.. you might need a new throttle body.. that’s a VERY expensive part thus take it to your usual place for a second opinion
best of luck
best of luck
Should you be 100% sure that you need another throttlebody, shoot me a PM. I have a spare one.
Although they usually are fine and the problem lies elsewhere (the reason why I have a spare one)
gr J
Although they usually are fine and the problem lies elsewhere (the reason why I have a spare one)
gr J
euge595
New member
Yesterday I managed to borrow a Throttle Body From the garage that repaired my Head Gasket. Thoroughly cleaned it before fitting, disconnected the Battery for an hour (I understand this cancels the previous Throttle Body configuration) seems a bit unlikely to me, you'd have to relearn the T/B every time you disconnected the Battery. But I'm working on the basis that it can't hurt. Re-connected the Battery and initiated the relearn process, started the Engine and at first though I'd cracked it, even took it for a short run. However as soon as the temp reached normal the Throttle started hunting and then stalled. As usual started ok after stalling, which meant I was able to get it home. I then went through the re-learn process continuously for about an hour, finally I gave up, I thinking I can probably discount the Throttle Body as the source of the problem. On the up side at least I can give the Throttle Body back.
Yes. I couldn't return my TB.....
Tempsensor Ok?
gr J
Tempsensor Ok?
gr J
As you've had a head gasket repaired then that means the garage has needed to reset the cambelt crank to valve timing. If that hasn't been done correctly (and the pages here are full of 1.6 owners who trusted their garage to do it correctly and ended in tears) then a decent tickover will never be possible. Fiat garages also get it wrong on occasions, they shouldn't but they do. Car coming back with hose clips missing is the first clue that things are not as they should be
Next thing I'd check out is the lambda sensor, you might expect it to kick out a fault code but it will only do so if the values are outside limits. Lambda sensor is essential for a steady low speed tickover. When you first start up the tickover is set high but then it gradually reduces to as low as it can get using lambda feedback
But my first check would be on the valve timing as it sounds like you're getting nowhere near a tickover
Next thing I'd check out is the lambda sensor, you might expect it to kick out a fault code but it will only do so if the values are outside limits. Lambda sensor is essential for a steady low speed tickover. When you first start up the tickover is set high but then it gradually reduces to as low as it can get using lambda feedback
But my first check would be on the valve timing as it sounds like you're getting nowhere near a tickover
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if timing is this far out.. then his (or her?) tick over while cold would not be normal either (and he did say that the car feels like it did before.. until it warms up that is); temp sensor can certainly cause a bad tick over but i am yet to see one that stalls the engine (and the gauge on the dash would do interesting things); would have to go with lambda on this one; what you will need to do is get an obd2 interface and take a live reading of the lambda sensors.. temp sensor is very cheap.. thus it is easier to just change it! So.. get started..
if it were me i’d go for OBD readings (hoping to detect what the problem is) then start doing the following (this is in order of price): swap the temp sensor --> crank sensor --> check timing
(your issue may well be caused by a combination of faults.. i.e. either one on their own may not be enough to stall the engine but the collective effect..)
Ps you would do better listening to Deck’s advice on this
if it were me i’d go for OBD readings (hoping to detect what the problem is) then start doing the following (this is in order of price): swap the temp sensor --> crank sensor --> check timing
(your issue may well be caused by a combination of faults.. i.e. either one on their own may not be enough to stall the engine but the collective effect..)
Ps you would do better listening to Deck’s advice on this
On first start the tickover is so high, around 1000 rpm that it's difficult to tell if valve timing is off. The car just pumps in whatever it needs to sustain that rpm. It's only when it warms up after a few minutes that the tickover starts to decrease and it goes into closed loop, using the lambda sensor and others and it will try to get down to 700rpm
Best bet would be to use Fiatecuscan or similar and then you can check engine temp and lambda readouts without needing to replace anything but for valve timing, unless it's a long way out where you might get fault code of a "timing error" then that needs a physical check
You don't say why it needed a head gasket. A water leak or a compression problem? I wonder if it's been done properly
Best bet would be to use Fiatecuscan or similar and then you can check engine temp and lambda readouts without needing to replace anything but for valve timing, unless it's a long way out where you might get fault code of a "timing error" then that needs a physical check
You don't say why it needed a head gasket. A water leak or a compression problem? I wonder if it's been done properly
I cant help thinking that this might be related to the head gasket change and incorrect timing but just to throw another suggestion into the pot ..there is a spring in the T/B and this can snap which in turn cause idle problems ..see this thread for a pic of it..wouldnt take much effort to check it out..
https://www.fiatforum.com/stilo/221354-my-stilo-block-ice-engine-turns-over-but-will-not-start.html
https://www.fiatforum.com/stilo/221354-my-stilo-block-ice-engine-turns-over-but-will-not-start.html
euge595
New member
Hi All, Sorry for not getting back earlier, I've been working away and a big thank you for all your replies they've been really useful . Since my last tread, I've invested in a vagcom 409.1 cable and I've downloaded the software from fiatecuscan (brilliant) . I also purchased a Lambda Sensor, Crank Sensor and Temp Sensor and sensor removal tool (22m). Connected the vagcom and got the following reading P0135-02 sensor (6). I'm not sure whether this is referring to the pre-cat or post-cat sensor but as I've bought the pre-cat I decided to change it. Easier said than done, on first inspection, things aren't looking good, it's obvious that there have been attempts to remove it previously, there are plier crimp marks on the copper body, and the hex nut is a bit rounded. Now to cut a long story short I've tried everything to remove the Lambda Sensor, I've run the engine so it hot, I've used all sorts of release sprays including one that freezes it to -40c without success, I've also cut away most of the body of the Lambda Sensor so that I could get better purchase on the nut, unfortunately all this effort has rounded the hex nut even more so I'm in the doo-doo good and proper. Tomorrow I'm going to try heating the area around the sensor with a blowtorch, any comments, tips suggestion, advise would be greatly appreciated, seriously It's the support from this forum that is keeping my spirits up, I think without it I've have just chopped it in for scrap!
P0135 is the precat lambda and shows heater performance poor so it's probably had its day
Really the lambda sensor tool is for installing a new one, you can use anything you like to get the old one out. Maybe chop off the wires and get a long ring spanner on it or if you have access then get a pipe wrench or a set of large footprints locked on there
Really the lambda sensor tool is for installing a new one, you can use anything you like to get the old one out. Maybe chop off the wires and get a long ring spanner on it or if you have access then get a pipe wrench or a set of large footprints locked on there
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euge595
New member
Oooh I'm so pleased it's the pre-cat, I would have been really naffed off it it was the post-cat after spending two days trying to get the pre-cat out, thanks for that DC.
euge595
New member
Hi, over the last few days I've been trying to change the pre-cat lam, it seemed to be welded fast, I tried everything, -40c spray, blow torch, the lot finally I had to drill it out. however having replaced it, the error code has cleared but the problem hasn't gone, it's improved a little but the throttle still hunts once the engine is warm and although if I just leave the throttle it will continue running with a slight amount of hunting as soon as I try to drive it , it stalls if I take my foot of the throttle. I've also changed the temp sensor and I'm going to change the crank sensor but I don't know where it is can anyone let me know please.
I don't know if it's significant but when connected to the obd the reading showed the the Pre-cat was fluctuating between rich and lean but the post cat was showing rich.
I don't know if it's significant but when connected to the obd the reading showed the the Pre-cat was fluctuating between rich and lean but the post cat was showing rich.
