Technical 1.3Jtdm hesitation at 1400rpm
- Thread starter jaska121
- Start date
Currently reading:
Technical 1.3Jtdm hesitation at 1400rpm
Turbolag?
gr J
gr J
Airleak in your dieselsystem? Dieselfilter properly tightened?
gr J
gr J
I don't know if the 1.3 JTD has a lambda/oxygen sensor.. but if so, that's a possible cause.
The lambda sensor has a heater circuit to heat up the sensor at low rpm, when the volume of exhaust gas passing over it is insufficient to keep it at the operating temperature required for it to work correctly. Once the revs increase, the temperature of the exhaust gas keeps the lambo hot enough to operate normally, so the heater circuit is turned off.
The heater turns off around 1600-1800rpm although that probably varies for different engines. If your lambda is on the way out, then as the heater assistance is withdrawn, it can stop operating optimally, sends an incorrect signal to the ECU which would then trim the fuel based to what it thinks is happening and so you get the hesitation.
If you have a ECU scanner, you might see a lambda fault logged... although error codes only come up when the sensor is operating out of range, rather than just badly but still within range. If you get the shakes more when the engine is cold, and your fuel consumption has taken a -10% hit, then swapping the lambda is a good bet.
Ralf S.
The lambda sensor has a heater circuit to heat up the sensor at low rpm, when the volume of exhaust gas passing over it is insufficient to keep it at the operating temperature required for it to work correctly. Once the revs increase, the temperature of the exhaust gas keeps the lambo hot enough to operate normally, so the heater circuit is turned off.
The heater turns off around 1600-1800rpm although that probably varies for different engines. If your lambda is on the way out, then as the heater assistance is withdrawn, it can stop operating optimally, sends an incorrect signal to the ECU which would then trim the fuel based to what it thinks is happening and so you get the hesitation.
If you have a ECU scanner, you might see a lambda fault logged... although error codes only come up when the sensor is operating out of range, rather than just badly but still within range. If you get the shakes more when the engine is cold, and your fuel consumption has taken a -10% hit, then swapping the lambda is a good bet.
Ralf S.
Checked with multiecuscan and no faults were present. I haven’t noticed a real difference between hot and cold engine, I think it might work better when the engine is cold.
I do believe it has lambda.
I do believe it has lambda.
Bodga
New member
I too would replace the fuel filter first. Also check/replace the air filter.
I did have a similar problem on a Ford Focus years ago V reg, and it turned out to be the accelerator pedal, it’s a variable resistor on the focus. I’m guessing the Fiat is the same and it might have a dirty part of the resistor where the contacts run causing hesitation?
I did have a similar problem on a Ford Focus years ago V reg, and it turned out to be the accelerator pedal, it’s a variable resistor on the focus. I’m guessing the Fiat is the same and it might have a dirty part of the resistor where the contacts run causing hesitation?
- Joined
- May 10, 2010
- Messages
- 2,669
- Points
- 797
Stuttering on a steady cruise is often a sign the EGR valve is sticking or slow to close.
The valve allows exhaust gas to recirculate back into the engine when the running is lean as it lowers combustion and high combustion temps produce more nitrogen oxides.
When lean the engine is just pumping air and as we know, if you hold your finger over the end of a bike pump and pump, it gets very very hot.
Take the air away and replace with say exhaust gas and it's no where near as hot.
When you take your foot off the gas the valve will open, clog the throttle and it closes.
On a fairly low rpm cruise the valve tends to flutter open and closed as the engine is on or around the limit the valve closes and opens.
If the valve is slow to close or stuck open, when you reach the spot the valve should close, like accelerating slightly on an incline, the engine chokes on the exhaust gas so the engine stutters or hesitates and to over come it you have to clog the throttle more than is usually needed which now means your mpg starts to suffer.
You may or may not notice a bit more black smoke or soot from the exhaust when acclerating as well, this is because the fuel to air ratio is ruined.
The air has been replaced by exhaust gas effectively richening up the ratio.
I say may or may not as a DPF will try and trap the soot, which means it will start to regen more often until it starts to struggle coping.
You can usually replicate this time and again, low rpm cruise on the flat then squeeze the throttle slightly to increase speed and see if it judders or hesitates.
You'd think a fault with a EGR valve would flag up a DTC and an engine warning light and it might well do at sometime, but these types of faults usually need to occur a couple of times in the same drive cycle before the ECU will even start to think something isn't quite right. The ECU expects to see the valve open or closed at certian so it means the ECU needs to see it repeatedly open or closed at the wrong times.
If it's been happening for a while you might get a "pending" DTC with some decent diagnostic software.
EGRs tend to fail on all sorts of diesel models, the exhaust gas being recirculated it full of soot and the air entering the engine has a bit of oil and oil vapour in it from the crankcase breather system that's pumped into the intake.
Mix the two togther over thousands of miles and this horrid gunk gums up the valve until the spring/vacuum or motor driving the valve just can't over come the mess in there.
The valve allows exhaust gas to recirculate back into the engine when the running is lean as it lowers combustion and high combustion temps produce more nitrogen oxides.
When lean the engine is just pumping air and as we know, if you hold your finger over the end of a bike pump and pump, it gets very very hot.
Take the air away and replace with say exhaust gas and it's no where near as hot.
When you take your foot off the gas the valve will open, clog the throttle and it closes.
On a fairly low rpm cruise the valve tends to flutter open and closed as the engine is on or around the limit the valve closes and opens.
If the valve is slow to close or stuck open, when you reach the spot the valve should close, like accelerating slightly on an incline, the engine chokes on the exhaust gas so the engine stutters or hesitates and to over come it you have to clog the throttle more than is usually needed which now means your mpg starts to suffer.
You may or may not notice a bit more black smoke or soot from the exhaust when acclerating as well, this is because the fuel to air ratio is ruined.
The air has been replaced by exhaust gas effectively richening up the ratio.
I say may or may not as a DPF will try and trap the soot, which means it will start to regen more often until it starts to struggle coping.
You can usually replicate this time and again, low rpm cruise on the flat then squeeze the throttle slightly to increase speed and see if it judders or hesitates.
You'd think a fault with a EGR valve would flag up a DTC and an engine warning light and it might well do at sometime, but these types of faults usually need to occur a couple of times in the same drive cycle before the ECU will even start to think something isn't quite right. The ECU expects to see the valve open or closed at certian so it means the ECU needs to see it repeatedly open or closed at the wrong times.
If it's been happening for a while you might get a "pending" DTC with some decent diagnostic software.
EGRs tend to fail on all sorts of diesel models, the exhaust gas being recirculated it full of soot and the air entering the engine has a bit of oil and oil vapour in it from the crankcase breather system that's pumped into the intake.
Mix the two togther over thousands of miles and this horrid gunk gums up the valve until the spring/vacuum or motor driving the valve just can't over come the mess in there.
