Technical RPM drops under minimum

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Technical RPM drops under minimum

korithi

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Hi guys,
I have a fiat grande punto 1.4 8v year 2009 with gpl. When I press the clutch and whant to change gears rpm drops inder minimun and sometimes engine dies. This hapens on both gpl and gasoline.
Please help
Thank you!
 
Hi,
Thank you for your reply. Where is it located and what it does?
 
Do you sometimes have trouble selecting first or reverse gear without the gearbox "crunching"? My daughter's car suffered a failed cluch slave cylinder recently and the idle speed fluctuated wildly (sometimes stalling) when she went to engage first gear or reverse. In her case, it was because even with the clutch pedal pressed fully down, there was still some "clutch drag" (i.e. the engine was still trying to drive the car because the clutch had not fully disengaged). The fluctuating idle speed was the idle speed control valve trying to get the idle back up to where it was supposed to be - against the drag of the clutch.
 
Hi Avocet, the clutch seems ok to me, also idle speed. I only face this problem while changing gears the rpm drops quite fast and sometimes it drops under minimum causing engine to die.
 
Hi Avocet, the clutch seems ok to me, also idle speed. I only face this problem while changing gears the rpm drops quite fast and sometimes it drops under minimum causing engine to die.

Had the same problem with my gp.

I've tried to clean to throttle body, it got better but still. Then I removed MAP sensor, give it a clean with a spray (for MAF cleanning) and since then no problems.

Maybe try to clean both the throttle body and the sensor.

Sensor is on the intake.

Use the search function and you wll find a lot of similar threads.(y)
 
Hi,
I took it off and cleaned with the spray at the service but still the rpm goes under minimum sometimes. No problem with engine dying so far. The only error i used to get is p0172.
 
p0172 - system to rich.

1.check air filer and piping for something blocking the air flow.
2.use diagnostic software to check air quantity(or pressure) and the desired air quantity (pressure)
2.check fuel pressure
3. one injector might be stuck opened.

An other possible cause could be the LPG system not being setup right:
-gives to much or to little LPG at idle ...and the computer tries to compensate.
-when testing on petrol there is a opposite effect so the engine would still die.
 
Use only petrol for a while And see how it goes.

Don't just switch back to lpg. Drive many miles with petrol.
 
Hi,
I used it on petrol these days and situation is still the same. When i shwitch on air conditioner the situation gets better.
 
It's very hard to tell without a proper diagnose.

I believe the problem is the map sensor.

Since it's a converted lpg car it could be more like an intake leak somewhere (lpg map sensor line, injector hoses, lambda sensor etc)

If you can find an other map sensor (only original bosch part) just for a test...
 
When i took to mechanic for a diagnose there is no alarm at all. I have been using it all the time on gasoline.
 
Or maybe his valves are sticking/valve seats got corroded from the GPL.
 
Hi cmosfxx,
I have changed the map sensor yesterday. It is much better now but rarely the problem shows up.
 
Hello,

I have opened the engine and cleaned the valves, changed the flowmeter also. The problem still persists. I drops under minimum when I try to slow down the car and pres the clutch to change gears.

I have no idea what to do next. :(
 
I have opened the engine and cleaned the valves, changed the flowmeter also.
You did what? Show the pictures, how you "opened the engine". "Cleaning the valves" requires removing them from the engine head (and head must be separated from the block, so it's a "head gasket job"). I doubt you did this.
Plus, there is no "flowmeter" in this engine. You must do your homework ("mechanics" will use this against you, and rip you off - EDIT: like they already did, but car is still not fixed).

The problem still persists. I drops under minimum when I try to slow down the car and pres the clutch to change gears.

I have no idea what to do next. :(
0. Your car was neglected, abused. It needs a serious maintenance, servicing. Multiple things at once.

1. Intake vacuum leak. Many things, manifold itself, throttle, EVAP system solenoid valve, hoses, brake servo.

2. Idle air obstructed, blocked. PCV system - "breather hoses" (especially small one). Air filter dirty.

3. Sensors: MAP (it measures temperature too), coolant temperature, oxygen (lambdas), clutch switch (computer wants to know if clutch is depressed or not).

4. Timing belt and/or valve "lash", clearances. They must be adjusted (manually, with shims) very often on the LPG (it will eat the exhaust valves fast)! Every 20000-30000 km (almost no-one does that!). Same is true for sparkplugs (check the wear - colour, deposits and gap).

5. LPG set-up, adjustment. Check (professional LPG shop) the LPG fuel map (this should be done while driving, and ideally with extra probe/sensor in the exhaust). LPG injectors may be stuck or pressure regulator (reducer) misbehaving, "flooding" the engine.
If problem is still there, isolate the LPG system (use-up the fuel completely, close the valve near the tank), fix the car on gasoline/petrol first.

6. Clutch, mechanical/hydraulic issue. Slave cylinder leak (check under the rubber boot, must be dry), air-lock, old brake fluid, bearing or fork wear.

7. Catalytic converter inefficient. Or lambdas. Or (petrol) injector(s).

8. Maybe something is stalling the engine mechanically, like A/C compressor or alternator (yes, possible).

PS
For "breather hoses" and "valve clearance adjustment", go to Guides section (page 1 & 2). Plus, search for other threads (scroll down this page, there is "Similar Threads" bar).
 
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Hello,

I appreciate your quick reply.
I am not mechanic and I have not done it myself of course. :)
I may not know all the names of car parts.
The idea is that I have taken the car to many services and nobody fixed my issue.
I have changed many things and payed a lot of money. That is why I am asking for help in here.

I have also search the forum for any similar issues and I have found this.

https://www.fiatforum.com/stilo/304586-stalling-when-clutch-revs-drop.html

I will try to do that maybe it is the same issue with my car.

Thanks
You did what? Show the pictures, how you "opened the engine". "Cleaning the valves" requires removing them from the engine head (and head must be separated from the block, so it's a "head gasket job"). I doubt you did this.
Plus, there is no "flowmeter" in this engine. You must do your homework.


Car was neglected. It needs a serious maintenance, servicing. Multiple things.

1. Intake vacuum leak. Many things, manifold itself, throttle, EVAP system solenoid valve, hoses, brake servo.

2. Idle air obstructed, blocked. Breather hoses (especially small one). Air filter.

3. Sensors: MAP (it measures temperature too), coolant temperature, oxygen (lambdas), clutch switch (computer wants to know if clutch is depressed or not).

4. Timing belt and/or valve "lash", clearances. They must be adjusted (manually, with shims) very often on the LPG (it will eat the exhaust valves fast)! Every 20000-30000 km (almost no-one does that!). Same is true for sparkplugs.

5. LPG set-up, adjustment. Check (professional LPG shop) the LPG fuel map (this should be done while driving, and ideally with extra probe/sensor in the exhaust). LPG injectors may be stuck or pressure regulator (reducer) misbehaving.
If problem is still there, isolate the LPG system (use-up the fuel completely, close the valve near the tank), fix the car on gasoline/petrol first.

6. Clutch, mechanical/hydraulic issue. Slave cylinder leak (check under the rubber boot, must be dry), air-lock, old brake fluid, bearing or fork wear.

7. Catalytic converter inefficient.

PS
For "breather hoses" and "valve clearance adjustment", go to Guides section (page 1 & 2). Plus, search for other threads (scroll down this page, there is "Similar Threads" bar).
 
Hello guys,

I took thw car to mechanic and checked the real values of clutch pedal switch. They do not change when the clutch pedal is pressed. It always stay closed status. Is this the default behaveior feom ECU or it should change the status?
The mechanic checked the wiring from pedal to ECU and they are ok. The switch was measured by ohm meter and shows circuit changes from 0 to infinit of ohm.
Might it be problem of ECU ar smth else?

Thanks,
 
Why two topics/threads?
https://www.fiatforum.com/grande-punto/453872-clutch-pedal-sensor.html
We can see you. One is enough. Wait for reply.

So...you are "solving" the problem...for 4 years (2016-2020) now!?
That means you don't really care about your car. It is abused, neglected. Wait another year or 2...

Unfortunately, yes, ECU might be "shot" (maybe that one input only). But double, triple check the clutch sensor (limit switch) and wiring, plugs ("backprobe" it at the ECU). And use Fiat specific diagnostic software (FES, MES, Examiner) to view the parameters live.

BTW, Grande has inferior software (other models with the same engines but different ECUs, won't behave like that): it is normal to swing the RPMs a bit when you operate brakes and/or clutch (engine should not die - but it is more pronounced on LPG fuel, because it adds a time lag to the fuel/ignition control). Other causes (mentioned earlier) are still valid tho', they add, stack-up, overlap.
 
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Hello,

I do care about my car.
All these time I have changed a lot of mechanics to solve my problem. Spent a lot of money for that but no one solve it until now. That is why I thought to ask for ideas in here. I am no mechanic but I try to find a solution for my problem. Just replace parts and see no changes. Even the engine is opened because they suspected due to lack of power from it. The clutch pedal switch is new. The software the last mechanic checked is fiat software. The problem occurs even when using with gasoline.
Anyway, if you have any idea about this issue, please let me know.
Thanks and regards.
 
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