Technical Uneven idle and blurrs when throttling

[Weebl]

Hi.
So I've had a long and annoying fight with my Fiat Punto 75 SX -97.

The last problem started out when I had the timing belt changed. I had an auto-mechanic that I know do the work and he was 100% certain that it was done correctly and he had no problems driving it back home to us. But the very next day my gf was driving the car to work and she noticed that it felt slow. When driving home from work it was running on three cylinders.

After a week or two of trying to figure out what was wrong I decided to have a workshop look at it. The immediatly said that the timing belt was positioned one cog wrong, so I told them to fix it.
After it was fixed it still ran on three cylinders...

Three weeks later, still no problems found, I had had it with them so I towed my car home. When I tried to fire it up I noticed that the battery was decharged. After recharging the battery with a battery-charger I fired up the engine and it ran on all four cylinders, weird.

BUT! now it had an uneven idle and it blurrs at first when I try to throttle and then revs up. Idle is moving around from 800-1100rpm and when I throttle from idle it goes down to 600rpm before increasing.
So I did a compression test (11bar, 11bar, 10.5bar, 10.5bar), had the sparkplugs changed, and tested the ignition system with a thingy I bought that has i light that flashes when you get a spark. This shows that all the cylinders have an equal spark.
I tried to measure the Ω on the ignition coils to see if they are ok without great success, I managed to measure the primary coil but I couldn't figure out how to measure the secondary coil. The primary was fine though.
I've changed the cable that goes from the ignition coil to the sparkplug (don't know the correct english term for theese being swedish).

One more interesting thing is that I have no warning lights on the dashboard come on when the engine is running. Not even when it was running on three cylinders.

My best guess at the moment is that one of the injectors fail to spray fine enough fuel mist so the drops in one cylinder doesn't get completly burned. But since there is a warning light for this on the dashboard that doesn't get turned on, I'm just not sure enough...
An injector costs the equivalent to £300 in Sweden, and thats to much for a guess.

So fellow fiat owners... Any ideas?

 

[thelad]

Is the exhaust smokeing?

 

[Weebl]

Is the exhaust smokeing?

No the exhausts looks just fine...

To confirm this I ran out to car just now and started it. It was a bit worse now had to give it a bit of throttle to get it to start and if I let go of the throttle the first 1-2 minutes it would die.

 

[Trist]

i had a problem with my old punto which involved me having to change my manifold as it had a crack in it, after i did the car was so much faster, and the blurring sound does sound like it could be a hole or crack in the exhaust maybe, although it wasnt obvious to me when i had it, no smoke coming from under the bonnet or anything

 

[Weebl]

i had a problem with my old punto which involved me having to change my manifold as it had a crack in it, after i did the car was so much faster, and the blurring sound does sound like it could be a hole or crack in the exhaust maybe, although it wasnt obvious to me when i had it, no smoke coming from under the bonnet or anything

But the blurring sound is because of that the rpm goes down. A crack in the exhaust shouldn't affect the rpm?

 

[Weebl]

Did some more testing... Tested alot of what is written in this thread: "mk1punto idle speed not rite..." (not allowed to link URL yet) some things made my car run really bad, some didn't change that much...

Also tested to unplug the cable between ignition coil and sparkplugs one at a time when running the engine, all of them made the engine sound the same kind of diffrent. I also tried unplugging the cable on the injectors, this made it sound worse than when unplugging a spark plug. But no difference in sounds between cylinders.

The engine clearly missfires, but it sounds like very random missfires...

Edit: Oh, and also. When the injectors were unplugged I still didn't get a warning lamp on the dashboard...

 

[Weebl]

I would say that there are none to very few misfires over 2000rpm, and misfire every other second at idle ~900rpm.

The spark plugs that are in now is called BRISK and has a 0,7mm spark gap, haynes say that Champion - RC9YCC is the recommended spark plug and it has a 0,9mm spark gap. Can this make a difference?

 

[Lozzy08]

Can you get hold of a MAP sensor? There cheap and easily available here, not sure about there. My old punto did similar to this, does the engine stick at 500 rpm when you put the accelerator all the way down to the floor? We suspected ECU on my old Punto as we changed literally EVERYTHING else, I.e sparks, leads, injector and throttle unit, cylinder head, crack sensor, map sensor, temp sensor, fuel filter and others stuff except the ecu, with no difference what so ever.

 

[Weebl]

Can you get hold of a MAP sensor? There cheap and easily available here, not sure about there. My old punto did similar to this, does the engine stick at 500 rpm when you put the accelerator all the way down to the floor? We suspected ECU on my old Punto as we changed literally EVERYTHING else, I.e sparks, leads, injector and throttle unit, cylinder head, crack sensor, map sensor, temp sensor, fuel filter and others stuff except the ecu, with no difference what so ever.

I haven't tried to put the pedal to the metal, will do that tomorrow.
If I knew what a MAP sensor was I would atleast look at it... now I will look for what a MAP sensor is first

Big thanks for the tips though! It feels like the more I read the more confused I get... I'm in desperate need for good pointers.

 

[Lozzy08]

The MAP sensor is inside the red circle


It is attached with one 10mm nut, and has a connection with a red clip yo have to slide out to remove.

 

[Weebl]

Big thanks! A new one is £60 here... I might do some import from the UK, it seems that everything is alot cheaper there.

 

[Trist]

yeah you're right there, £300 for a fuel injector is silly money

 

[Lozzy08]

You pay the postage and I'll mail you a working one I have spare for free

However try and find one you could borrow before that, to rule it out as a incorrect cause.

 

[Weebl]

You pay the postage and I'll mail you a working one I have spare for free

However try and find one you could borrow before that, to rule it out as a incorrect cause.

Wow that is very kind of you! Borrowing one could be hard, because of that punto is fairly rare in Sweden due to Fiat's bad reputation. I don't know anyone with a punto...

 

[Weebl]

Now this car is really giving me a headache...

I read in another thread about cleaning the butterfly valve, apparently it helped alot of people. So I just did this. Didn't think it was that dirty but I got a little dirt out...
Also cleaned the sensor by the crankshaft pulley for the generator. Fired up the engine and I had to give it gas constantly so it wouldn't die, then it tried some quick throttles and it reacted a lot quicker and didn't blurr.

BUT!... after I let go of the gaspedal the rpm went down to about 500rpm and fought for a couple of seconds not to stall, then it went up to maybe 800rpm, and you know what?

It is now running on three cylinders again.

I did the test from the ECU/Coil test guide and when I disconnected one of the coils I had a nice smooth-running 2 cylinder fiat. When I disconnected the other coil it wouldn't really start, just firing on one cylinder was not enough to pull the engine around.

This should mean that the coils and ECU are ok, right? Since it is just one cylinder that is troubleing me.

The weird thing is that from the beginning I didn't need to give throttle for it to start and I ran fairly stable on idle but with misfires, the big problem then was the slow reaction on the gaspedal and the blurr. Now it barely runs on idle, it's idling between 500-1200rpm, not hunting but slowly changeing rpm, and stalls easely. And now it runs on three cylinders...

Just need to test which one out of cyl 2 and 3 that is giving me trouble and then I will move around coils, HT leads, plugs and injectors and see if that makes a difference.

Any other thoughts and ideas?


Edit: Ran out to the car and started it up again... it ran on four cylinders... But I did like last time revving it up to 2000rpm just to let go of the pedal and let the rpm sink to 500rpm and almost stalling the engine. This again caused it to start running on three cylinders and I now know that it is cyl no. 2 that is giving me the trouble.

 

[Weebl]

So which one is the MAP sensor?

 

[Weebl]

Does anyone know where I could buy an injector in UK and ship to Sweden?

 

[MADJIB]

have yo checked that the vacum hoses are connected, in good nick and free from obstructions, kinks etc, this can cause rough running also worth checking the plug leads again, check in the dark make sure leads are not arcing to earth

 

[Lozzy08]

The map sensor is that white box in the middle of your picture. To be honest reading what else has happened I'm not sure the MAP sensor would be the problem. Have you done a compression test at all?

 

[Weebl]

The map sensor is that white box in the middle of your picture. To be honest reading what else has happened I'm not sure the MAP sensor would be the problem. Have you done a compression test at all?

Yes I have. Got 11bar, 11bar, 10.5bar, 10.5bar.


Edit:

I have taken down the fuelrail now and just did some measuring on the injectors. 14,6Ω, 14,6Ω, 14,7Ω, 14,7Ω. According to haynes a pre-1998 model should have 16,2Ω. My simple multimeters lowest scale for resistance is 2000 so I would consider this within a decent range, and the fact that they are all pretty much the same does point to that they are ok.

What do you all say?


Edit 2:

Visually all of the injectors look good. I have switched places between cyl 1 and 2 now. So if the problem remains in cyl 2 it's not the injector and if it moves to cyl 1 it's definatly the injector since the cyl 1/4 coil worked perfectly yesterday.