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Old 3 Weeks Ago   #1
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Engine noise at high RPM and light load

I've got a rather annoying noise that sounds like the gates of hell are about to open.

It's the 899 engine in my Robin which has a pancake style air filter on it. At about 5k RPM it starts to make a mostly induction but also sounds mechanical kind of noise, almost a diesel knock. By 6k it sounds like Thor himself is trying to escape from the block. It also happens if I use light throttle at high RPM under low load, so at 30 MPH in 2nd.

I'm not too worried about it as under high load the engine is really quiet, no noise on the overrun either, but the times that it happens are where the ECU would be advancing the timing, which is slightly concerning.

I've got an ECU and lockset on the way so I should be able to swap that out when it arrives and rule out an ECU issue. The (frankly awesome) fella that gave me the engine and electricals said the ECU had been tempremantal in the past, and there was no sign of it having been open before when I read out the EEPROM to remove the immo so I think advanced timing from tuning isn't a cause either.

Alfo if anyone has an airbix and hose for sale I'm after one (if it will fit!).
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Old 3 Weeks Ago   #2
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Re: Engine noise at high RPM and light load

The description does suggest detonation.

I would be checking for vacuum leaks, are all the breathers from the engine piped up correctly?

An incorrect map reading can throw ignition advance off.

I'm not sure if your donor had a knock sensor, if it does that could be faulty
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Last edited by Prawny12009; 3 Weeks Ago at 16:35.
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Old 3 Weeks Ago   #3
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https://www.fiatforum.com/cinquecento-seicento-guides/146381-spi-throttle-body-where-pipes-go.html

1. Fuel return to tank
2. Fuel pressure regulator
3. Air Inlet Temperature (AIT) Sensor
4. Injector
5. Mating surface
6. Fuel intake for throttle body
7. Hot water feed (from coolant reservoir)
8. Feed from charcoal cannister (EVAP)(blue)
9. Breather take off (brown) from cam cover
10. Manifold Absolute Pressure (MAP) Sensor take off
11. Throttle body
12. Throttle Position Sensor (TPS)
13. Idle step motor (sometimes ICV or IAC)

On some cars the Feed from charcoal cannister (EVAP) and Breather take off from cam cover seem to have been marked blue and brown respectively, but this may not apply to all cars.
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Last edited by Prawny12009; 3 Weeks Ago at 16:43.
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Old 3 Weeks Ago   #4
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Re: Engine noise at high RPM and light load

From what I can tell 8+9 although located in a similar position they are not interchangable because one has a smaller hole than the other.
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Old 3 Weeks Ago   #5
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Re: Engine noise at high RPM and light load

Quote Originally Posted by Prawny12009 View Post
https://www.fiatforum.com/cinquecento-seicento-guides/146381-spi-throttle-body-where-pipes-go.html

1. Fuel return to tank
2. Fuel pressure regulator
3. Air Inlet Temperature (AIT) Sensor
4. Injector
5. Mating surface
6. Fuel intake for throttle body
7. Hot water feed (from coolant reservoir)
8. Feed from charcoal cannister (EVAP)(blue)
9. Breather take off (brown) from cam cover
10. Manifold Absolute Pressure (MAP) Sensor take off
11. Throttle body
12. Throttle Position Sensor (TPS)
13. Idle step motor (sometimes ICV or IAC)

On some cars the Feed from charcoal cannister (EVAP) and Breather take off from cam cover seem to have been marked blue and brown respectively, but this may not apply to all cars.
8 and 9 are linked together to effectively block them off as I have no EVAP canister and the breather goes straight to the air filter.

10 is a blank on mine as the MAP is connected to the inlet manifold.

Funnily enough today I did get a feeling that it was detonating from the pingy tingy noise it made every now and then.

No knock sensor on it, and it does have leaky stem seals so possible a really coked up head.
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Old 3 Weeks Ago   #6
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Re: Engine noise at high RPM and light load

Some of the breathers seem to go straight to the Airbox, some have a smaller pipe branching off to the throttle body.

the system may rely on that small bleed on the oil breather for idle control and at least some resistance from the airbox for a correct map reading.

There are systems available to live monitor even the earlier 3pin plug ECU's, you can then see what the advance is doing.

I think my launch has that adaptor but I will have to pick it up from the garage to check.

Using super unleaded on your next fill up might help if it is detonation.
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Last edited by Prawny12009; 3 Weeks Ago at 23:52.
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Old 3 Weeks Ago   #7
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Re: Engine noise at high RPM and light load

Quote Originally Posted by Prawny12009 View Post
Some of the breathers seem to go straight to the Airbox, some have a smaller pipe branching off to the throttle body.

the system may rely on that small bleed on the oil breather for idle control and at least some resistance from the airbox for a correct map reading.

There are systems available to live monitor even the earlier 3pin plug ECU's, you can then see what the advance is doing.

I think my launch has that adaptor but I will have to pick it up from the garage to check.

Using super unleaded on your next fill up might help if it is detonation.
Was definately timing related, jammed another ECU in and it was fine (apart from the over fuelling issue). I may try clearing the microcontroller EEPROM to see if that sorts it, bad adaptation parameter maybe. Got 2 new units on the way though so hopefully I can get something working properly tomorrow.
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Old 3 Weeks Ago   #8
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Re: Engine noise at high RPM and light load

Try lowering the fuel pressure at the throttle body, there is an adjuster screw on them from what I have read.

Perhaps some one has turned it up too high in the past.
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Old 3 Weeks Ago   #9
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Re: Engine noise at high RPM and light load

It was overfuelling due to being for a bigger engine and having been chipped.

I got 2 more 899 ECUs to try, both are exactly the same as the original. I'm thinking there's some other fault somewhere, I'll have to go out with a passenger keeping an eye on the ignition advance, rpm and manifold pressure.
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Old 3 Weeks Ago   #10
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Re: Engine noise at high RPM and light load

Were you running an 1108 ECU to begin with then?

Edit, just realised you meant you are over fueling with the ECU you've just fitted to test.
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Last edited by Prawny12009; 3 Weeks Ago at 22:18.
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Old 2 Weeks Ago   #11
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Re: Engine noise at high RPM and light load

Where have you got the lambda?

What temp sensor are you using?

D
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Last edited by rallycinq; 2 Weeks Ago at 10:23.
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Old 2 Weeks Ago   #12
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Quote Originally Posted by rallycinq View Post
Where have you got the lambda?

What temp sensor are you using?

D
Standard temp sensor and lambda is in the usual place below manifold.
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Re: Engine noise at high RPM and light load

The lambda should stop it overfuelling or be throwing the fault light.

have you checked the temp sensor against the nominals?

D
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Old 2 Weeks Ago   #14
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Quote Originally Posted by rallycinq View Post
The lambda should stop it overfuelling or be throwing the fault light.

have you checked the temp sensor against the nominals?

D
It doesn't have a fault light fitted yet, that's a job for this weekend.

Not checked sensor as it's a bugger to access, from what I can tell it's reading the correct values. Reads ambient when cold and stays at around 86 when driving around.
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Old 2 Weeks Ago   #15
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Re: Engine noise at high RPM and light load

I've just looked at the EOBD menu on my launch (x431 pros mini), it says it supports the following as OBD2/eobd

Without hooking it up I don't know if just selecting the fiat specific menu would auto select the correct protocol or whether I would have to use the EOBD generic menu.

Sae j1850 vpw
Sae j1850 pwm
Iso 9241-2
Iso 14230-4 kwp fast
Iso 14230-4 kwp address
Iso 15765
Iso 15765-4 canbus
Iso 9141-2 iso address

The are several model specific adapters and a female serial to OBD 16 pin female socket labelled as "obd1 adapter" included with this model of launch the adaptor also has a 12v barrel connector at the 16 pin end.

Toyota-17 ta-17
Toyota-22 ta-22
Chrysler-6 cr-6
Honda-3 ha-3
GM vaz-12 g/v-12
Bmw-20 b-20
Benz-38 bz-38

Then there are a few dual piggyback cable's they have a male obd 16 pin on one end, the other has both a male serial and a model specific multipin plug.

Nn-14+16 (Google says this is nissan)
M/h-12+16 (Google says this is mitsubishi/Hyundai)

And finally the one that looks like fiat 3 pin which is labelled ft-3

The manual doesn't say much about the above connectors other than describing them all as "non 16 pin" obd1 adapters.


I can only assume that if they have supplied a fiat adapter then one of the above protocols should be compatible with the early fiat diagnostic functions.
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Last edited by Prawny12009; 2 Weeks Ago at 02:03.
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