dirty idle control valve? or just throttle body in general?
Technical Stuttering loss of power on acceleration
- Thread starter DRSIK
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Technical Stuttering loss of power on acceleration
Does anyone know what was the culprit for this one ?
I have something that from the description sounds very similar.
in my case, the following parts were swapped just a year ago (when diagnosing a different issue, which turned to be a vacum leak)
MAP
lambda
TPS
plugs
coils
leads
fuel pump
vacum pipe from MAP to engine
Ive also checked the resistance across the CTS that is at the top of the thermostat, and it is changing as the coolant gets hotter, but i dont know if the readings are within spec (because i didnt know the temperature, neither the spec)
just to re-iterate, in my case.
when cold
car seems to be ok, both idle as well as revving the engine and theres power delivery.
when hot
idle is ok. but engine stalls if i open the throtle.
the strange thing about it is that just a couple of weeks ago. i drove it for a 40 mile return trip and it didnt miss a beat. admitedly it was mostly motorway driving, but the next time it started it barely made it out of the housing estate before it was turned around.
I have something that from the description sounds very similar.
in my case, the following parts were swapped just a year ago (when diagnosing a different issue, which turned to be a vacum leak)
MAP
lambda
TPS
plugs
coils
leads
fuel pump
vacum pipe from MAP to engine
Ive also checked the resistance across the CTS that is at the top of the thermostat, and it is changing as the coolant gets hotter, but i dont know if the readings are within spec (because i didnt know the temperature, neither the spec)
just to re-iterate, in my case.
when cold
car seems to be ok, both idle as well as revving the engine and theres power delivery.
when hot
idle is ok. but engine stalls if i open the throtle.
the strange thing about it is that just a couple of weeks ago. i drove it for a 40 mile return trip and it didnt miss a beat. admitedly it was mostly motorway driving, but the next time it started it barely made it out of the housing estate before it was turned around.
mine was also doing the same ,,changed all the usual bits,,,and found the car runs better after i took the TB off and properly cleaned it and had found that the pipe where the oil breather attached was clogged after rebuilding used new gasket paper with a fi e smear of rtv sealant and also fitted a proper ICV a good oem branded one not one of those cheap crap ebay chinese ones also fitted ngk plugs at the correct gap for the 1.1 sei 0.7mm and also fitted a new magnetti marrelli lambda sensor again dont buy cheapo ebay junk parts stick with oem these cars ive found dont get on with non oem also run the car on super unleaded preferably shell and also keep the oil changed regularly took me a long time to get mine sorted ....but id deffo 1st of all take the TB off anfd properly clean it if its an SPI the tb splits in two parts and make sure its cleaned inside and out through all the pipes etc and reassemble carefully and if using a sealant as a gasket go easy and only a thin smear ,issues can also happen if the tb is sucking in air due to gasket/seal leaks to quickly check is to spray some carb/brake cleaner or wd40 around the TB when the car is running and listen for any changes to the idle you can also spray around hoses to also check for leaks .....also check your spark plugs are clean and gapped properly and dont waste money on so called fancy plugs
ive cleanred the thrthle body and as a result all the hoses got new clamps (because the old ones were the crimp type that is not reusable.
also fitted new cranshfat sesnor and new coolant sesnor.
still bogs down when hot.
did the brake cleaner spray around the hoses near the TB and also no issues there.
i have no idea what to look at next. even compression test seems pointless since the car would be cold then i do that.
also fitted new cranshfat sesnor and new coolant sesnor.
still bogs down when hot.
did the brake cleaner spray around the hoses near the TB and also no issues there.
i have no idea what to look at next. even compression test seems pointless since the car would be cold then i do that.
i'd not be so sure on that tbh.. Do a cold test and then get it nice and hot, ideally the temp it starts being silly and then do another test, see if it changes. Things move around with heat cycles, it really could be early head gasket failure and if you keep going you'll get to doesnt work cold either.
I would say as well just because parts were changed within a year don't assume they still work, even more so depending on what stuff was used to replace them. Remember even if you use genuine parts at this point most of them will have been sat on a shelf in god knows what storage conditions for who knows how many years. It might be a new sensor, it might be a 15 year old sensor that spent 10 years in a damp unconditioned storage unit - you just don't know. So really if its been working fine for i assume about a year you need to start diagnosing from the start to eliminate things. Which i hope without reading this whole thread back should give you some stuff to try. So start with the easy/free things to check - compression, timing etc
Hi Tuga. As Blu says, the heat can make head gasket leak, missfires etc. Also check vacuum line to brake servo is in good condition.
Only other thing i'd add to the list above is that cheap coil packs are faulty from the start and can be intermittent. Buy branded coil packs only. I've learnt this from experience. The coil packs can also be affected by water, after the wet winter we've had this could be a potential cause of failure.
Compression testers are not expensive and useful to have.
compression results
1 - 150
2 - 150
3 - 150
4 - 150
hot
1 - 125
2 - 125
3 - 140
4 - 140
figures are rounded as my gauge is not very accurate
the 125 results when hot a little bit low by comparison, but is this enough to explain why the engine bogs down completely when i open the throtle ?
a head gasket change on this engine doesnt appear to be too much of a hassle, but i have no intention of going to that effort without good reason.
i have a lot of parts from last year that i know were good when they came out, but making the assumption that parts with less than 300 miles are already gone, seems unlikely.
i have a follow up question.
theres a sensor near spark plug 1 at the top of the engine, it has a single wire connecting which is green with a white tracer. what is this sensor ?
1 - 150
2 - 150
3 - 150
4 - 150
hot
1 - 125
2 - 125
3 - 140
4 - 140
figures are rounded as my gauge is not very accurate
the 125 results when hot a little bit low by comparison, but is this enough to explain why the engine bogs down completely when i open the throtle ?
a head gasket change on this engine doesnt appear to be too much of a hassle, but i have no intention of going to that effort without good reason.
i have a lot of parts from last year that i know were good when they came out, but making the assumption that parts with less than 300 miles are already gone, seems unlikely.
i have a follow up question.
theres a sensor near spark plug 1 at the top of the engine, it has a single wire connecting which is green with a white tracer. what is this sensor ?
is there a guide to check the timing somehwer ? i thought the car having a timing chain, that would be something that cannot be adjusted ?
The sensor on top of the cam cover is the knock sensor which protects against pre detonation I believe.
Timing would only be off if someone had adjusted or fitted a new timing belt incorectly. Or if the belt had jumped for some reason but fairly unlikely.
Check for leaks/cracks in the exhaust manifold or exhaust pipe before the lamda sensor. If oxygen is getting in then it can make the ecu deliver too much fuel. Faulty (pre cat) lambda sensor can also cause this symptom. Full throttle might make it go away for a minute but then it might stutter again when you are maitaining steady speed. I've had a Fiat with cracked exhaust manifold which became undrivable when hot due to cracked manifold - due to previous owner mistreatment... completely flooded itself.
Check for leaks in vacuum line to brake servo.
Compression test doesnt seem too bad, but how hot was the engine? Presume underside of oil cap is clean?
Have you tried swapping coil packs?
When it misbehaves, does it idle properly or not? If it does not, you can try unplugging each cylinder and see if it makes any difference to diagnose coil packs.
Timing would only be off if someone had adjusted or fitted a new timing belt incorectly. Or if the belt had jumped for some reason but fairly unlikely.
Check for leaks/cracks in the exhaust manifold or exhaust pipe before the lamda sensor. If oxygen is getting in then it can make the ecu deliver too much fuel. Faulty (pre cat) lambda sensor can also cause this symptom. Full throttle might make it go away for a minute but then it might stutter again when you are maitaining steady speed. I've had a Fiat with cracked exhaust manifold which became undrivable when hot due to cracked manifold - due to previous owner mistreatment... completely flooded itself.
Check for leaks in vacuum line to brake servo.
Compression test doesnt seem too bad, but how hot was the engine? Presume underside of oil cap is clean?
Have you tried swapping coil packs?
When it misbehaves, does it idle properly or not? If it does not, you can try unplugging each cylinder and see if it makes any difference to diagnose coil packs.
there is some smoke coming from the back of the engine when hot. i am not sure if its a exaust leak, or just the oil burning (i dropped a fair bit in that area when topping up
the lambda sensor is "new" (again, less than 300 miles use)
When i did the compression test. the engine was hot enough to bog down when i open the throthle, in fact, i did it just after "killing" the engine with the open throtle test.
again, coil packs are 1 year old, with less than 300 miles. I can swap them back wit the old ones. tomorow after work i guess.
your cracked manifold mention seems rather intereting to investigate. as i have been assuming the smoke to be related to oil but if its what you suggest its worth a go
Potentially also bad gasket seal on the exhaust manifold could cause similar issue?
i was thinking from what you said that is possible. and a gasket only costs 7-10 quid. so theres one on the way here already.
the issue with the manifold is that you cant use soapy water to find a leak because it boils when hot. i have plenty of gumgum paste. i could in theory jsut smear a bunch in the area to help diagnose
You might be able to hear or feel the exhaust leaking at the gasket if it's bad enough. If it's cracked them the crack might open up when it's hot.
I'd expect a crack would be caused by lack of exhaust mounts or support.
In my cars case It was a 16v Multipla and the manicat mount hadn't been re-fitted...
If you disconnect the lambda sensor does it make any difference? Is this an spi or mpi car?
I'd expect a crack would be caused by lack of exhaust mounts or support.
In my cars case It was a 16v Multipla and the manicat mount hadn't been re-fitted...
If you disconnect the lambda sensor does it make any difference? Is this an spi or mpi car?
It's a 0.9 spi car.
I can disconnect the lambda easily, what kind of effect are you expecting from doing that?
intake leaks just go around with some carb cleaner while its running and spray it around joints, pipes etc. not too liberally obviously lol. You'll find any leaks pretty quickly.
compression test is kind of borderline.. I'm not saying just accept it now and take the head off, its hard to argue with that cold result! But it might still be the answer. To get a lower numbers hot is a very bad sign if we are honest, thats not the right way haha. Its not the only thing that holds compression though, you mentioned some smoke, perhaps valve seals?? Puff of smoke on startup? or if you coast downhill for a while, they can pull oil in past the valve seals under the prolonged vacuum coasting.
compression test is kind of borderline.. I'm not saying just accept it now and take the head off, its hard to argue with that cold result! But it might still be the answer. To get a lower numbers hot is a very bad sign if we are honest, thats not the right way haha. Its not the only thing that holds compression though, you mentioned some smoke, perhaps valve seals?? Puff of smoke on startup? or if you coast downhill for a while, they can pull oil in past the valve seals under the prolonged vacuum coasting.
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i have checked for intake leaks using carb cleaner and there was no signs of leaks.
as far as the smoke, it only appears when the engine is hot.. i mean up to temperature hot. and its a very thin smoke coming from the exaust manifold area, in the begining it was more noticeable than now, but there is still some smoke coming from that area.
i will be trying a little bit of oil on the cilinders when cold to see if theres a difference in the readings later on
as far as the smoke, it only appears when the engine is hot.. i mean up to temperature hot. and its a very thin smoke coming from the exaust manifold area, in the begining it was more noticeable than now, but there is still some smoke coming from that area.
i will be trying a little bit of oil on the cilinders when cold to see if theres a difference in the readings later on
If you disconnect the lambda then it would run a 'baseline' fuel map which should eliminate any false readings from the lambda sensor. As far as I understand...
You will/should get a dash warning light but it should clear once its connected again for a few miles. Or leave battery disconnected for ecu reset.
Pretty consistent really. It's cold I guess?
The slightly different pressures are due to slight differences in tolerance and wear between the cylinders. With oil added it helps seal the small gaps around the rings a little. Like a wet suction cup sticks better than a dry one.
The faster the engine turns over the higher the pressure will be. I turned one slowly over with a battery drill and it indicated 25psi on 3 cylinders and zero on one!
When the engine is hot the metal expands and opens up new gaps. Potentially between the head and the block. Also the head and exhaust manifold.
The slightly different pressures are due to slight differences in tolerance and wear between the cylinders. With oil added it helps seal the small gaps around the rings a little. Like a wet suction cup sticks better than a dry one.
The faster the engine turns over the higher the pressure will be. I turned one slowly over with a battery drill and it indicated 25psi on 3 cylinders and zero on one!
When the engine is hot the metal expands and opens up new gaps. Potentially between the head and the block. Also the head and exhaust manifold.
