Still Hunting 900 to say 2000 revs

[del mar 2]

Any clever ideas as to why ?

No intake leaks
The Carbon cannister does make a click noise as the revs drop. - there are no new ones left, although McGrath could source one for £400...
They look oh so close to a Fiat Cinquecento one, but ours has three hoses and that one only has two.

The three hoses go to the petrol tank, intake manifold and the green sensor that plus into one of the coolant hoses.

The EVAP system seems fairly basic.
The Pump is still available and mines does seem to run.
A couple of vacuum hoses.

There is always a woosh of air when opening the petrol tank, and there is a small of fuel outside the car - i liked the manly smell !! These are Cannister related issues.

Noting that i changed all the sensors on the car last year and it is 25 years old is it worth swapping the pump and hoses ?

Could i just remove the cannister and block the vacuum hoses - not the fuel tank one?

thanks

 

[del mar 2]

Reading about Carbon Cannisters.

This is 25 year old technology so there is no Codes to read or even electrical signals from the ECU.

What they should do is;
When the engine is warmed up a signal goes to the purge valve that tells it to open and fumes from the tank are sent to the manifold to be burnt.
My car idles well until it is warmed up then it hunts.

After scanning Eurospares we don't seem to have a separate purge valve, i am assuming it is built into the cannister. Nor does the cannister have an electrical connection.

I think the following happens;
When the car warms ups, the Temp Vacuum Switch

Somehow sends a "signal" down the vacuum hose to the cannister/purge valve which tells it to open and release fumes down the other vacuum pipe to the manifold.

If this purge valve is stuck open then it is like large vacuum leak which is what i appear to have.

The Evac pump that appears to constantly run tests the system for leaks, they have a diaphragm that creates the seal which if damaged would also create a leak.

The cars also have a vacuum cylinder which is shown as part of the air con system and a check valve, god knows what they have to do with it but they are connected into the evap vacuum system.

If it only wasnt dark cold and raining i would go and have a play !!

 

[williamsmix]

What car is this, one of the bi-turbo models? If so, isn’t the throttle body something to consider(?)

 

[del mar 2]

its a Ghibli.

There are no air leaks from it so i was hoping not......

TPS sensor was replaced last year as was the Idle control valve.

 

[williamsmix]

Well, if you want to eliminate it by giving it a quick check pull off the two hoses, check the start routine and free movement of the butterfly …

 

[allandwf]

Does it have a fuel vapour return line? Mine had a pin hole leak in the 3200, made it stall .

 

[del mar 2]

The cannister is a Dayco B460 60511492.
The B460 are on lots of car but not a 60511492..... I might have found one in italy.

It does have a fuel return line - another thing to check.

I might get a chance to investigate further on friday otherwise it will be next week sometime.

 

[alpa]

I was too lazy to read everything but why do you connect an unstable idle to the canister ?
And there are no "signals" to the biturbo canister, it was a pure mecanical stuff.
Just block the air pick up that goes to the canister from the intake and you'll see if this improves the idle.
The tank is often incorrectly vented because of the anti-rollover valve in the trunk, a pure piece of ****. It's always either stuck or fully open. When it's stuck it prevent the canister from venting the tank.
If you modify the tank ventilation think of 3 things :
- fuel should not go out if the car is rolled over
- air must enter the tank while the fuel is consumed
- the tank should release an excessive pressure when it reaches a high temperature, like parked outside in summer
Well, almost none of remaining biturbo/ghibli have the three functions working today.

The green valve was quite common on ford and other cars of the same period.

 

[del mar 2]

A quick scan on line does list the symptoms of a failed Purge Valve as like a large intake manifold leak.
The Purge Valve is built into the cannister - i have found and ordered a new one they were also used on some Alfa 75's.

It may not be - but it is something i can easily eliminate for less than an hour's labour at a specialist.

I have the service manual and the entire evap system doesn't have too many parts to it, so when it stops raining and warms up slightly i will go through the evap hoses and connections.

Hoe does the green valve actually work ?

 

[alpa]

The green valve is a temperature controlled valve: it's a T connection with the foot connected to either of two other connections. The flip temp is at about 75C.
On your car only one of branches is connected, the one that opens above 75C. So when the engine is hot and intake has vacuum it sucks through the canister to purge it. A check valve prevents the intake from pushing air inside the canister.

Don't remember how the rest is connected. There must be a way to expel vapors from the tank to the atmosphere through the canister.

 

[general_piffle]

Let us know how you get on!

 

[del mar 2]

I had a play this weekend

Cannister removed.
You can feel one of the hoses pulling a vacuum so that is a good connection to the intake manifold.
Blocked up the two vacuum hoses and left the tank breather open

Didn't make any difference.

Further observations;
Once warmed up if you unplug the Idle control valve the car stalls immediately. You are supposed to do this in order to set the idle screw, if it stalls you cant set the idle correctly. It was replaced last year, so unlikely that it is at fault ???

The Fuel pump has always been a but noisy perhaps it has now seen better days ?
It has hard to start, once running is you press the accelerator it pops and bangs a lot, until it has warmed up.
Idle is poor.

Replacements aren't atrocious.

Will check Fuel pressure next.

McGraths are booking from mid Jan.......

 

[alpa]

Further observations;
Once warmed up if you unplug the Idle control valve the car stalls immediately. You are supposed to do this in order to set the idle screw, if it stalls you cant set the idle correctly.

Read carefully the instructions and try to understand their reasons. They say to adjust the screw. Means there are positions where the adjustment could be wrong.
Unscrew multiple turns so that the engine does not stall. Then follow instructions.

 

[del mar 2]

that is a fair point.

will try at various positions

 

[F456M]

You must make sure the cable to the accellerator / throttle pedal has some slack in it. And adjust the throttle body butterfly "idle/stop screw" enough out so the TPI (Throttle Position Sensor) is at zero. Only then can the electronic idle air control valve function properly. If you go down a downhill and step off the throttle completely, and above 1500 rpm., the engine shall run totally without any fuel and any rumble in the exhaust. If the TPI is not completely in zero position, your engine will sound a bit like a carburettor Birurbo and burble from the exhaust in downhills above 1500 rpm. If so, the TPI is not correctly adjusted. It has its own two screws to adjust it. But it usually don't come out of its correct position unless its internals are worn. I had this fluctuating idle on a 1994 2,8 Spyder and just adjusted the stop screw out enough for the throttle to shut properly and get the TPi to zero. Then the idle control valve started to operate properly and the idle was smooth and compensated for load (if you put the car in Drive or start to release the clutch etc). It is the ECU that controls the idle rpms, not the opening of the throttle body. In addition, there is a bypass air screw which (I believe) is to "soften" the transition from idle closed and open. Post your progress and results.

Erik
Oslo

 

[alpa]

Idle rpm is controlled by the injection ecu but the ecu wants the bypass to be open enough but not too much. It's a stupid system and the controller is quite unstable, that's why the adjustment is so important. With any normal ecu you would not even have any bypass and nothing to adjust.
In idle position the TPS should deliver at max 0.3 volts on 2.8 and 0.2v on 2.0 24v (will usually be less).

 

[del mar 2]

Morning,

Something to think about here - thank you.

I did purchase a new TPS last year and set it with the engine off to read 163 mv, which is in line with the manual.
It did appear to start hunting after that. The manual states turn the ignition to on but doesn't say start the car.

The idle screw is wound right in, so my next check will be to wind it out start the car and then disconnect the ICV and see what happens.
Perhaps i will try to re measure the voltage on the TPS.

The porsche has returned from the body shop so that will sneak to the front of the queue for the moment.


Thanks

 

[F456M]

Morning,

Something to think about here - thank you.

I did purchase a new TPS last year and set it with the engine off to read 163 mv, which is in line with the manual.
It did appear to start hunting after that. The manual states turn the ignition to on but doesn't say start the car.

The idle screw is wound right in, so my next check will be to wind it out start the car and then disconnect the ICV and see what happens.
Perhaps i will try to re measure the voltage on the TPS.

The porsche has returned from the body shop so that will sneak to the front of the queue for the moment.


Thanks

Report back when you have updates.