Technical GT Lumpy idle

[Eklipze3k]

Hello all, I've recently acquired Molly from the venerable blu73 and am after some advice.

Firstly, before I picked her up on Saturday she'd been sat for 1yr+ unused so I was under no illusions that she'd be perfect and ready to be a daily driver.
I did, however, have to get her home from York to Huddersfield and driving seemed to be the easiest way. She fired into life without any complaints, and ran faultlessly (as far as I could tell) for the first 35-40 miles of the journey. Then, suddenly, she started misfiring. Occasionally at first but as I got nearer to home it got worse and worse, to the point where I was basically crawling along in 5th gear at tickover limping her home.

I stopped a few times thinking perhaps she was overheating or something, and one time when I stopped (literally about 2 miles from home) I went to restart her to be met with the unmistakeable greetings of a flat battery.

Having now managed to drag her back to the house, and recharged the battery, she still runs lumpy but the battery is not charging at all (confirmed with a multimeter reading of 12.8v with engine off, and 11.4v with engine on across battery terminals). This leads me to believe that the alternator is either goosed, or the belt is too loose, the lack of voltage causing a weak spark.

Would that hold water with other people's experience/opinions? Is there anything else I should be looking at?

Cheers

 

[Liquid Knight]

Sounds like a duff battery or alternator and your coil packs aren't receiving enough charge to work properly.

If you have a spare battery kicking about swap that first and see if it makes a difference but I'd say especially after being laid up for a year the alternator bushes may be diff.

Squirt some WD40 into the back of the alternator to see if this helps clean any crap in there. If the symptoms persist you'll probably need to replace it.

While you're at it replace the belts at the same time as they don't like being laid up either.

 

[Eklipze3k]

AFAIK the belts were replaced not too long ago during her sabbatical, so should be (are) still good. I couldn't get my hand in there but my OH poked what I think is the alt belt and said it did feel a bit loose. Saturday is set aside for getting Molly up some ramps though so the more things I have to look at the better, so I'm not running in and out of the house all day asking questions

 

[flisko]

ill take it off your hands for 12 squid, on the other hand it could be faulty lambda sensor

 

[oldhammer]

Take alt belt off,
and spin the pulley on alternator, if feels rough or stiff to turn,
bin it and buy another one,

ifind these alternators go fubar if on a un-used car thats been sat awhile,

might be ok,but id check...ive seen afew lock up,

 

[blu73]

ah Saturday will go down in history as one of the most momentously rubbish days ever!!

The very last thing i had done to Molly was water pump so belts have been off yes, but on the GT the belt for the alternator does the water pump as well so if it was the belt it would have overheated and blown up way before battery ran out.

see eper:
http://eper.fiatforum.com/eper/navi...3&WINDOW_ID=1&SGRP_COD=15&SGS_COD=2&DRW_NUM=3

So i think best thing to do first is jack it up (did you take your trolley jack back with you??). Drivers wheel and arch off jut for better view etc. Check wires to it are on properly, take them off and clean up contacts and try again. If that don't work then yeah drop belt off and see how free it is - it defo spun ok when i did the waterpump but like already said, its been a while.

So sorry she didn't make it home!!!

 

[Eklipze3k]

ill take it off your hands for 12 squid

No

on the other hand it could be faulty lambda sensor

Not likely, pretty sure that's only in circuit when the car is up to temp and it does it from cold idle.

Will try and belt off and spin, but will try just tightening it up first. No, I left the trolley jack there. Lucy's through on Thurs though, I could ask her to pick it up?

 

[blu73]

will try remember to get it back to mine then, off down there tomorrow (after a skip has been delivered and filled)

 

[Razman]

Sounds like it gradually got worse as the battery discharged.

Try another fully charged battery, test starting with it and get a voltage reading. At least if it stops misfiring you know that it is because of the alternator/battery. If it starts well, let it run for a while and if the alternator is dodgy, it'll quickly turn sour. Check belt tightness (mine came loose once before, with similar results). The battery might not be holding any charge, but then, if it's only getting 11 odd volts, the battery might be fine.

 

[Liquid Knight]

Old school alternator test. Start the car and take the earth battery terminal off. If the engine cuts out your alternator is knackered. If she still runs normally; your battery is knackered. If she splutters, coughs and farts; your alternator is on its way out.

I'm not sure if it will kill your ecu (there's most probably some kind of circuit protection in place) so I wouldn't bother but that's how we used to do it.

 

[flisko]

Old school alternator test. Start the car and take the earth battery terminal off. If the engine cuts out your alternator is knackered. If she still runs normally; your battery is knackered. If she splutters, coughs and farts; your alternator is on its way out.

I'm not sure if it will kill your ecu (there's most probably some kind of circuit protection in place) so I wouldn't bother but that's how we used to do it.

what

 

[Liquid Knight]

what

As I said with pre-ECU cars doing this was never a problem.

 

[Eklipze3k]

Well then, don't suggest someone do it on a car that has an ECU if there's a chance it'll kill it

 

[flisko]

Well then, don't suggest someone do it on a car that has an ECU if there's a chance it'll kill it

i think he is jealous on that gt and tried to secretly destroy it

 

[Liquid Knight]

I'm not sure if it will kill your ecu (there's most probably some kind of circuit protection in place) so I wouldn't bother but that's how we used to do it.

 

[Liquid Knight]

Just
in
case
you're
due
an eye
test.​

 

[Eklipze3k]

We also used to think the Earth was flat ... don't give out-dated advise. Simples.

 

[J.R Racing]

Did you get a host of warning lights on the dash before you came to a stop? That used to be the main sign when my alternator was failing. Then within a mile the car ground to a halt.

Used to get airbag light, then ABS and a host of others in quick succession then the slow and painful closing down of the entire car!

Do check the belt tension anyway on the Alt belt, sounds like the voltage regulator in the alternator has gone bad.

If it is a general misfire, I'd check the obvious things first i.e. all ignition components, fuel pressure (change the fuel filter if Chris hasn't done it) and all the boost pipes then see where you are at.

If after checking all this all seems ok, then it sounds like you have a bad MAF, they all go bad sooner or later. If you do need to replace it always buy a genuine Bosch, even if 2nd hand. The aftermarket cheap ebay MAFs are a nightmare on this engine.

 

[Eklipze3k]

So I had a bit of a play yesterday, though where the car was most of the time was spent just getting it up on axle stands! Anyway, with the drivers side wheel off I was able to better check belt tension and it was absolutely fine, the belt itself still in very good condition. Ran her just as she was and the lumpiness was still there, EML and airbag light on dash but no others. Connected jump leads to my GF's car and with her providing some extra juice Molly ran perfectly, so it's definitely a voltage issue. With her car connected the voltage across the battery terminals was around 14.3v, as soon as it was disconnected this dropped down to around 9v, and fell rapidly until the battery just couldn't spark anymore and the engine died.

The alternator itself appeared to be spinning freely, wasn't making any unusual noises. At this point it was getting kind of late but obviously the next thing I'm going to check is that all of the electrical connections to the alt are attached and correct, if so then I guess it probably going to be time for a replacement alternator ....

J.R Racing the MAF wouldn't stop the battery charging though, surely?

 

[J.R Racing]

No of course not, I was just giving more options if it wasn't the alternator.

But sounds like classic alternator faliure. Normally happends when the car has been laid up unused for sometime.

Had to replace on mine after the original went bad. Similarly my car had been laid up for along period before hand. That said they are not the most reliable on the GT and expect to replace anyway once they get past ten years old.