Technical Car Runs Rough With MAP Sensor On

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Technical Car Runs Rough With MAP Sensor On

Spark plugs will be black with the senor disconected as it can adjust the mixture correctly and will default to a safe rich mixture.


Let gets the obvious faults fixed first as they have a knock on affect.



By the way is the hole in the exhaust after the O2 sensor

Should I conduct the test with the MAP sensor on or off?
 
Which ever running best at the time. Normally there is a slight rise in the revs when you spray near the leak.

So I changed my strut today and did a vacuum leak search along with it. I used Start Spray and also a spray like WD-40. Neither of them gave any resaults in the rpm changing. With the map sensor attached there is a sudden rpm change every 10-15 seconds. This repeats continuously.

I even listened for vacuum holes with a hose and couldn't hear anything except for a little air on a hose next to the throttle body, but spraying gav no indication it was leaking.

Tested new and old sensor with backprobbing, no change in voltage when accelerating. But when I tested the map sensor by sucking on it it had a continuous change in the voltage. So atached to car gave no change in voltage, but unattached gave change.

What is there more to do? Seems like I've tried so much and no indication where it may be. However engine runs a little rich but steady without map sensor. So there's something wrong with it or something connected to it. If not the wires or vacuum leak, what more is there to test?
 
What brand of MAP sensor? I've got a brand new one in my "c**p" box which looks fine, reacts to air pressure changes, but makes any car it is installed on run like an asthmatic sloth. (I didn't buy it, it was fitted on the roadside by a breakdown mechanic on a friend's car).
Just re-read a post about crank sensors and it reminded me... any chance of trying a known good one from somewhere?
Other than that, my money is on a wiring problem if you're sure there are no induction leaks.

Have you hooked up an OBD reader and watched what sensor readings you are getting?

MultiECUScan is the best for working on a Panda, but even a simple app (like Torque), a phone and a cheap bluetooth OBD reader can help with this kind of problem as you can watch what changes in real time.
 
So I changed my strut today and did a vacuum leak search along with it. I used Start Spray and also a spray like WD-40. Neither of them gave any resaults in the rpm changing. With the map sensor attached there is a sudden rpm change every 10-15 seconds. This repeats continuously.

I even listened for vacuum holes with a hose and couldn't hear anything except for a little air on a hose next to the throttle body, but spraying gav no indication it was leaking.

Tested new and old sensor with backprobbing, no change in voltage when accelerating. But when I tested the map sensor by sucking on it it had a continuous change in the voltage. So atached to car gave no change in voltage, but unattached gave change.

What is there more to do? Seems like I've tried so much and no indication where it may be. However engine runs a little rich but steady without map sensor. So there's something wrong with it or something connected to it. If not the wires or vacuum leak, what more is there to test?

Strange working fine off but not on the car. Still sounds like a leak ?


I will have a listen to mine tomorrow. Can be bothered at the moment. Will have been awake for 48 hours soon.
 
Strange working fine off but not on the car. Still sounds like a leak ?

.

I think my junk one works fine, just the operating range is wrong. Might check it out just for interest - they are so simple to make it seems strange that someone goes to the effort of making them and then makes them so badly.

The 15 second cycle sounds vaguely familiar but can't quite place it at the moment.

I don't have the same excuse as koalar - I'm just getting old!
 
What brand of MAP sensor? I've got a brand new one in my "c**p" box which looks fine, reacts to air pressure changes, but makes any car it is installed on run like an asthmatic sloth. (I didn't buy it, it was fitted on the roadside by a breakdown mechanic on a friend's car).
Just re-read a post about crank sensors and it reminded me... any chance of trying a known good one from somewhere?
Other than that, my money is on a wiring problem if you're sure there are no induction leaks.

Have you hooked up an OBD reader and watched what sensor readings you are getting?

MultiECUScan is the best for working on a Panda, but even a simple app (like Torque), a phone and a cheap bluetooth OBD reader can help with this kind of problem as you can watch what changes in real time.

I do have a obd scanner, gives me P0110 and P0105 like I mentioned earlier. It's for the MAP sensor and the IAT sensor. But new sensor wasn't able to remove fault code, it just reappears. And I don't know where the IAT sensor is located.

I was spraying everywhere air could get out, even with and without MAP sensor, didn't hear any difference in rpm change other than the 10-15s sudden quick rise in rpm.

The map sensor is a original Bosch 0 261 230 030. The new one is an aftermarket one from Ebay, has same idle voltage as old one. However what makes me really wonder is why the voltage doesn't change when my car is accelerating, it's like there's no vacuum at all. Not even a 0.1V change when fully accelerating.

If you want I could take pictures of the car if it's necessary. Something is really fishy with the car and I am feeling confident that the old owner did something temporary to hide the faults. Then they all appeared one week after I bought it. He changed O2 sensors and one that sits on top of the engine. Maybe he gave up on looking for the fault? Or it's a major one and he sold it without conscious?

Don't know what to do other than seek a mechanic to be honest. It has been running rich for a while now and gas bills are stacking up. I don't want the engine to get damaged as well.

EDIT: No activity on map sensor when connected to OBD which confirms why I don't see a change in voltage when accelerating? But then why would it work when sucking on it and have a normal idle voltage? I suspect as well that there's a wiring issue. I used a multi tool and they all seemed to work fine though, maybe something fishy with the wires connected the ECU? Sadly enough I don't have the tools or knowledge to test these. Or where these things are on my car, it's so hard to find any information on a Fiat.
 
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Are the breather and vacuum hosts connected correctly to the inlet manifold? If it's sucking in air from the unmetered side, this could cause it too. Perhaps remove the airbox and run the engine, just to make sure it begins to stall when you cover the throttle body with a cloth or similar.

You still need to try a known good MAP sensor, or to buy a new one and see what makes I think.
 
Are the breather and vacuum hosts connected correctly to the inlet manifold? If it's sucking in air from the unmetered side, this could cause it too. Perhaps remove the airbox and run the engine, just to make sure it begins to stall when you cover the throttle body with a cloth or similar.

You still need to try a known good MAP sensor, or to buy a new one and see what makes I think.

Follow this advice.

If it doesn't stall, you still have a vacuum leak (which backs up the theory as to why your MAP sensor doesn't change reading while on the car). At which point you should be able to hear where the leak is.

For reference, the IAT sensor is part of the MAP sensor. It's the little yellow bit in the MAP sensor ;)
 
You mean completely cover the throttle body? Covering it with my hand turns it off comletely, haven't tried with a cloth. I still have to find a MAP sensor to try on, I checked the local scrapyard and they didn't have anything. The throttle body hisses a lot if I remove the air box and it's kinda annoying to listen to and work on it at the same time. I don't know if that's normal, but the hissing is kinda loud.
 
You mean completely cover the throttle body? Covering it with my hand turns it off comletely, haven't tried with a cloth. I still have to find a MAP sensor to try on, I checked the local scrapyard and they didn't have anything. The throttle body hisses a lot if I remove the air box and it's kinda annoying to listen to and work on it at the same time. I don't know if that's normal, but the hissing is kinda loud.

That hissing is normal with the airbox removed. It is just air flowing past the throttle plate at idle.
 
Just a thought.
Clear the codes.
Warm up the car with a good run to normal operating temp.
Turn off the engine and restart.

Does it still hunt around at idle?

It was a good few years ago with our old 1.1 Active, but it started to run rough, use lots of fuel and hunt around at idle.

I chased vacuum leaks and throttle body ghosts for a while with no luck.
I might even have had related codes, which was why I was routing around there.

It turned out the upstream O2 heater element was knackered, though it coughed up no related codes.

It was tripping into a fuel system fault soon after a cold start and run rough due to that. I could hear the safe running mode switching the fueling back and forth. The idle change up and down was very rhythmical.

Once the sensor had been warmed up naturally be the hot exhaust gasses and the engine restarted, it ran ok until it cooled off.

As the up and down stream sensors are the same, I confirmed the issue by swapping them over. Unlike the up stream sensor, the down stream doesn't influence the fueling, it just monitors the cat's performance.

Might be worth a shot.
 
The first time I changed the MAP sensor I took it for a long drive, about 90kms to my parents house. After 3/4 of the way the car was at its best performance. After I arrived and turned it on the next morning, it starting behaving the same way. So I was suspecting that something that was calculating temperature had to be wrong. Well it turns out that the MAP sensor does the temperature calculating on my car.
 
In case anyone stumbles on this problem in the future, the faulty was an O2/Lambda sensor. The upper one since the Panda has two of them, on the catalytic converter and one closer to the engine. The one closer to the engine was the faulty one. I changed the Throttle body, MAP sensor, Air filter, Spark plugs + Wires and the engine oil and muffler without having the issue go away.

What I did to test the O2 sensor was to get a OBDII tester from ebay, costs like 6$? Plug it in, download or buy an the app for it. I use Torque which works fine. Then find a diagram for the O2 voltage check. Drive the car until it gets really hot, I had to drive it at least 30 min I think. Then read the voltage on the bank 1 sensor and bank 2. If they both work fine you can see on the diagram that the voltage is somewhere between 0.1-0.9. If it doesn't move above 0.1 and the line is constantly flat, there is an issue with the O2 sensor. Usually the bank 2 sensor turns on a lot later than the bank 1 sensor. Or you could test it via a multimeter, but that didn't work for me, my values were very different than those on Youtube, which I found very strange.

Symptoms of the bad O2 sensor were high gas usage, almost 300% more, black smoke from exhaust, smell of gas, black spark splugs, very bad idle and constanly at 1200rpm until warm. The car suttered during acceleration, had almost no power but was fine on higher gears. Undriveable at lower gears, especially on gear one where it would almost suffocate. It still has misfires but has decreased to an acceptable amount.

Hope this helps.
 
Wow this was a long time ago.

Did you fix the hole in the exhaust. I have just fixed the girlfriends car. Only just passed the emissions. But failed on exhaust leak. After fitting the new exhaust the smell of petrol on idle at startup has gone and it idled smoother.
 
There weren't any holes in the exhaust. The mechanic told me my muffler was bad so I changed it, still sounds bad to me. His excuse was that it was engine misfire causing the sound. Pretty bad excuse to me and the fact that he didn't look for a misfire before telling me to switch the muffler.

There was air leaking between the clamps at the catalytic converter and on the muffler. Used some paste to fix this, don't know if it made any difference.

Even though I changed so many sensors to new ones, the emission reached it's max limit. So I was lucky I guess?

The only faulty now is that the servo is giving up I think, maybe a bad sensor, I don't know. I don't trust any mechanics around here, the official ones are expensive as hell and my knowledge is so limit.
 
There weren't any holes in the exhaust. The mechanic told me my muffler was bad so I changed it, still sounds bad to me. His excuse was that it was engine misfire causing the sound. Pretty bad excuse to me and the fact that he didn't look for a misfire before telling me to switch the muffler.

There was air leaking between the clamps at the catalytic converter and on the muffler. Used some paste to fix this, don't know if it made any difference.

Even though I changed so many sensors to new ones, the emission reached it's max limit. So I was lucky I guess?

The only faulty now is that the servo is giving up I think, maybe a bad sensor, I don't know. I don't trust any mechanics around here, the official ones are expensive as hell and my knowledge is so limit.


Yes it makes a difference.


The original owner had welded a new replacement flexible joint on mine. But only welded around the bottom half so it was leaking like a sieve next to the CAT. It was enough to confuse the sensors and give petrol smell on warm up.
 
Maybe that's why my car isn't smelling gas anymore. But why is my muffler making a loud sound before it's warm? Could be it be a misfire? I remember having a faulty code on cylinder 4 saying it was misfiring, however that code never came back and the muffler still sounds a lot. I changed the sparks and wires, can't bother changing the coil as well.
 
Put your hand over the tailpipe. Can you feel the pressure build or is it escaping somewhere.



Maybe a YouTube of the sound might help to diagnose. Sounds are hard to describe.
 
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