Technical Seicento dies when hot

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Technical Seicento dies when hot

TugaChan

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Hello! just made an account to post this 😅

I have a 1999 Seicento and it's been sat in the front yard for ages not moving, we recently reconnected the battery to see if it still works, and replaced the oil and antifreeze. after taking it around for a spin in the neighborhood we realised it was often just dying anytime we put the accelerator down. it brakes fine, it starts first time, it idles fine, but if you try and go forward or speed up it has even odds of just dying. we found this gets worse the longer the car is running, meaning it'd die more and more often to the point it was completely stop start.
after a bit of research we decided to replace the air filter and the crank position sensor, but after those were fitted the problems are still persisting. we can't use our OBD2 tool as it's with a friend atm so it's a complete mystery trying to diagnose this.
anything we look up just points to the crank position sensor, but we know it's not that. any suggestions? feel free to ask things, I'm not a car person so I don't know what information is pertinent 😅
 

purf

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Perhaps the fuel injector is stuck? Is it earlier single point injection?
 

vexorg

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ECU engine temp sensor? if it thinks the engine is cold when it's really hot, then it'll over fuel and run really bad
 

purf

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ECU engine temp sensor? if it thinks the engine is cold when it's really hot, then it'll over fuel and run really bad
Would the lamda sensor not try to correct the mixture though and at least stop it from stalling? Lambda or exhaust manifold leak could also be the problem however and cause overfuel too...?
 

vexorg

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Usually the ecu wont use the lambda if cold (cant speak for fiat), but runs open loop until the engine is hotter.
 
Joined
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Hello! just made an account to post this 😅

I have a 1999 Seicento and it's been sat in the front yard for ages not moving, we recently reconnected the battery to see if it still works, and replaced the oil and antifreeze. after taking it around for a spin in the neighborhood we realised it was often just dying anytime we put the accelerator down. it brakes fine, it starts first time, it idles fine, but if you try and go forward or speed up it has even odds of just dying. we found this gets worse the longer the car is running, meaning it'd die more and more often to the point it was completely stop start.
after a bit of research we decided to replace the air filter and the crank position sensor, but after those were fitted the problems are still persisting. we can't use our OBD2 tool as it's with a friend atm so it's a complete mystery trying to diagnose this.
anything we look up just points to the crank position sensor, but we know it's not that. any suggestions? feel free to ask things, I'm not a car person so I don't know what information is pertinent 😅
I have had this with mine.
Started fine, although a bit lumpy. drove fine but cut out when hot and died when coming onto roundabouts unless brought to high revs.
Did what all the others suggested. OBD showed correct temperature so not that.
BTW, Temp "sensor" beside the cam belt is a switch - learned that tonight.
Had done a full service with T-belt, so not plugs or such.

I changed the Lambda with a spare and it improved briefly, then changed out the second spare and that improved much more.
It's still a little juddery when accelerating low down in the range but much improved.
I think it was running really rich, that looks improved.

Am waiting on a new Lambda which I hope will solve the last bit of acceleration reluctance and slightly rough idling.
Other than that, I'm out of ideas.

Dave
 

purf

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Yes my cinq had the same problem, lambda sensor goes bad and tells ecu there is still unburnt oxygen or lean fuel/air mixture so it puts more fuel in and floods it.

Full throttle allows the ecu to ignore the labda sensor for overtaking I guess which is why it can keep running.

Later MPI cars have two labda sensors which i think helps avoid this problem unless perhaps they both fail?

I had a petrol multipla with a cracked exhaust manifold which had similar symptoms with two lambda sensors and full throttle didnt help!
 
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So, the new Lambda sensor came. Put it on and no difference. Traced the wires back to the ECU and measured the 1.0V at the ECU. Completely lost. Got MES connected again to OBD and went for a drive with the most obvious parameters being monitored. Strange that the manifold pressure didn't change! It had done, to some extent, previously. Got home checked the hose from the manifold to the sensor and found a big split at the sensor. New pipe and the car is like new. It would want to be, it only has 12k miles on the clock. FFS! I can't believe months of messing about with plugs, coils and Lambdas was only due to a leaky pipe.
 

purf

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So, the new Lambda sensor came. Put it on and no difference. Traced the wires back to the ECU and measured the 1.0V at the ECU. Completely lost. Got MES connected again to OBD and went for a drive with the most obvious parameters being monitored. Strange that the manifold pressure didn't change! It had done, to some extent, previously. Got home checked the hose from the manifold to the sensor and found a big split at the sensor. New pipe and the car is like new. It would want to be, it only has 12k miles on the clock. FFS! I can't believe months of messing about with plugs, coils and Lambdas was only due to a leaky pipe.
Well done for persevering with it!
 
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