Technical Rough running

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Technical Rough running

What year is your car Ad? are all the TPS units the same across the years? If so I should be able to measure mine on saturday so you can compare.
 
I called Fiat today and they said that the throttle position sensor is part of the throttle body and can only be purchased as a complete unit. Bearing in mind it is an exchange unit they want £331+vat! I think I'll spend some more time diagnosing.

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Forgot to mention, the car doesn't misfire when or hesitate when cold. Not sure if this will be any help though!

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LRB seems to have gone missing. Probably something to do with a combination of wife, hatchet, and unfinished hall :shrug:

Hey guy's, as Rich says I am working 200 miles away from home at the moment and am not getting much time to play - work, work, work! Cannot complain too much at the moment as there are lots of people who would give their right arm to be earning!

My initial thought is that you have a gummed up idle valve, when you checked it was the gasket intact? Mine had a similar issue, I cleaned the idle valve up and noticed that the gasket had torn, 1/2 a tube of instant gasket later and job done!

The other thing it sound like it condensation in one of the plug leads or water in one of the plug bores. Again this happened to me about this time last year when I was doing lots of short trips, I suffered from condensation under the plug cover - ran like a bag of bolts until I dried everything out.

Careful of looking too hard for a serious problem, the b's have a habit of presenting a serious issue that turns out to be a loose wire or water where it should not be!!
 
Ad, I spend my time thinking up wierd scenarios and seeing whatg comes out so here is what my imagination has come up with tonight!

So when the engine is cold, the ECU should richen the combustion mixture - dependant upon how hot the coolant is. It can only do this by increasing the duration the injectors are energised. As it warms up, this "choke" effect is reduced as the coolant warms up. If the engine is too lean it will misfire and be hesitant.

Now, imagine the injectors are blocked slightly.....when the injectors are firing for longer, more fuel goes through so the effect is not noticed but when the normal fueling occurs, the blockage is restricing the fuel delivery too much. Thus I would try injector cleaner for a few tanks and see what happens.

Well, its good theory anyway but may be complete crap!!!!
 
LRB seems to have gone missing. Probably something to do with a combination of wife, hatchet, and unfinished hall :shrug:

Actually, just thought of one of the other common causes of this. The temperature sender switch on the thermostat housing can cause this, I have heard of it a couple of times - the switch controls the fuel mixture, if the switch fails the car runs rich resulting in it missing at low revv's.

HTH
 
You guys are very helpful and I really appreciate it. Thank you, I will buy a multimeter and injector cleaner tomorrow and check the operation of the temp sender.

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If you are going shopping, the data I have shows 320 ohms at 80 deg for the coolant sensor, if my memory works, the plug is the female part of the connection so if you can buy one or a series of resistors at 320ohms and push it into the contacts, then let the car warm up, when it starts missfiring, pull the plug off and plug the resistors in, if the missfire stops, hey presto!!

But we seem to have forgotten that you said if you disconnected a different connector, all seemed to go away...............
 
.....and I thought LRB had one of the newer Barchettas so could explain exactly where the mass air sensor is situated! Tut, tut.

In terms of condensation: I found it got better when the engine warmed up, so it's probably not that.

The temperature sensor or injector ideas sound good though.
 
Just checked the injector and coil resistance starting from the cambelt;

1. Injector 17.1 ohms, Coil ~ 68 ohms
2. Injector 17.1 ohms, Coil ~ 68 ohms
3. Injector 16.9 ohms, Coil ~ 68 ohms
4. Injector 16.9 ohms, Coil ~ 68 ohms

Variator solenoid was ~16 ohms

Temperature sensor was a maximum of 320 ohms

I had just driven to and from Halfords to get the multimeter so the engine was hot.
 
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not sure about the coils, maybe the data I have is wrong??? Anyway, the injectors are higher than my data but that might just be because they were hot at the time of measuring. The water temop is smack on though so I would be pushing loads of injector cleaner through over the next few tanks!!
 
I have just filled up and put a bottle of Redex injector cleaner in the tank. It seems to misfire more frequently when idling now. Also I have noticed when accelerating lightly it misfires. I spoke to my friend who suggested the HT leads might be tracking.
 
Ok just pulled the plugs - I couldn't resist even though its late.

On inspection they seem as though they have normal wear, all except the third cylinder (bottom picture)
 

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