car problems. .

[turbotog]

ok.. ive been having problems with my twingo gt tce..
its a 57 reg with 65k.. I service myself and had the car since 29k little over 2 years ago..
anyway the problem is that its underpowered (from what it used to be) and the engine is sending a vibaration through the accelerator and there seems to be a low bassy note from the exhuast system.. although its hard to tell as the car is sporting a backbox..
so far i have had the car obd2 tested.. no faults and no stored faults..
replaced injectors as I have had a misfire on start up whilst driving up the road (fine on idle) but still hasnt fixed the vibrations..
I have checked spark plugs and they were new last service.
done a dry compression test. . all cylinders register appx 125psi each. .
I have also checked the cat converter (thought maybe it had collapsed)..
on cat removal I did find an oil leak from a oil feed pipe from the turbo into the block (on brass star banjo bolt on engine..
visual inspection doesnt show any leaks in the exhaust and all vacuum pipes are connected. .
would this be a possible coil pack or o2 sensor on its way out? im stumped and dont fancy taking it to the garage for them to replace god knows what for the problem not to be fixed..
any help would be great!

 

[Forza]

would this be a possible coil pack or o2 sensor on its way out?

Sounds like a problem I had twice. The first time it was the coilpack (well one of them) and the second time is was the o2 (lambda) sensor.

 

[oscar]

check the resistance of the the shortest HT lead to the longest, shortest should range at around 4-5,000 ohms and the longest should rate to around 15-17,000 ohms. give or take a thousand ohms is good.

check the fuel filter, is it blocked? pressure check the fuel rail with the vacuum pipe off, it should hold 45 psi or 3 bar this is good. then check with the vaccum pipe on at 0,5 bar vacuum - this should leave you with around 2,5 bar 37.5 psi ... this is good. this can show that the fuel pump isn't pumping enough fuel to maintain pressure ie humped, or that the fuel pressure regulator is not functioning correctly

have you tested for spark, and wether or not the spark is strong? remove the spark plug, with the spark plug in the HT lead ... get a pair of wooden insulated tongs and hold the ht lead / spark plug over the cylinder head with a mm or two clearance between the spark plug and cylinder head ; start the engine, is the spark good? repeat the same for all 4 cylinders. notice any colour variances in the colour of the sparks or is one cylinder sparking a tiny bit slower than the others? PLEASE NOTE that to perform this, you'll need an old spark plug to take the place of the old spark plug in the cylinder head otherwise fuel / air will leak out and cause an explosion in your face. you can also begin to use basic problem solving to figure the route cause of a weak spark. if you get weak spark on one cylinder it's either the spark plug - HT lead - coil pack, nothing else. you can switch spark plugs around to other cylinders to see if the same spark plug is weak on a different HT lead .... if it's weak still, but the spark plug that was previously in the HT lead was sparking strong then the spark plug is suspect and will need replacing.

check for leaks in the exhaust system, place your hand around pipe flange connections - do you feel any blowing? remove the upstream oxygen sensor and replace with a pressure guage and run the engine at say 2,000 rpm. do you get a reading of > 0.2 bar? this could indicate a partially blocked catalytic converter

generally with the coilpack, you'll notice a bogging down feeling when you plant your foot.

also check your ignition timing if you have an obd2 scanner with live data, this could be a big help. if the engine timings all over the place at various rpm's then it's your coil pack. if you reset fuel trims and they're all over the place after 5 minutes, it's going to be your pre-cat lambda sensor or possible fuel pump (check fuel delivery rates manually)

nobody could really answer your question as it could be a lot of things but i hope this helps you to track down the source of your problems

 

[turbotog]

ill check what I haven't from this list and see if it points to any problems!.I
I know no one will know exactly but youve given me a few other things to try out before giving up and taking it to the garage.
thanks for your help

 

[turbotog]

update on this problem..
ive done what checks I can with the tools I have available..
exhaust system definately has no leaks.. and pressure test on cat wouldnt even read a pressure so can assume theres no blockage there..
compression test on cylinders showed 125PSI on each cylinder, raising to 150psi on the wet test..
I have only a bluetooth obd11 connection which I use with torque.. its enough to check for codes and turns them off but I realise the live data obviously has a bit of lag..
here are some values anyway.. all values were taken at idle at 600-700rpm.
my fuel trim 1 varies between appx 9.4-26%.
fuel trim 2 says 100..
o2 sensor 1 voltage varies between 0.1-0.7
o2 sensor 2 voltage holds 0.4-0.5
and my timing advance jumps around between 1.5-8 degrees
would these results show a faulty pre cat o2 sensor?
any input would be appreciated anyway..

 

[turbotog]

for anyone interested, these problems have all been diagnosed!
o2 voltages are fine, I didnt realise, but the o2 sensor naturally goes up and down. so no problem there (goes from rich to lean)
my initial misfire was a blown coil pack (the bottom had cracked)
how ever, the vibrating, bassy sound turned out to be the gearbox mount..
the bolt has stripped from the mounnt (under the battery tray).. which has turned brittle from heating and cooling over the years.. and the gearbox is sat on the subframe.. obviously shaking the car!
hope this helps anyone..
if you hear a clunk on pulling off, and the car starts to shake and vibrate and sound bassy, its worth checking the gear box mount! heres a quick description on how to check yourself (takes 10min)
steps to check gearbox mount:
1. open bonnet(obviously)
2. pull off battery cover
3. remove positive and negative connections (10mm)
4. undo battery support (down the right hand side of battery) req a couple of extensions (16mm)
5. remove battery (use handle for ease)
6. undo 3 x 16mm bolts from under the battery
7. remove battery box (splits into 2 parts for ease of removal)
8. directly under the box will be the gear box mount, the bolt should NOT look like this:

 

[sullii94]

Hmm.. Had this go on mine a while ago aswell! I wondered what the f**k was happening when it went haha!

 

[oscar]

did it sound like a weird scraping noise when you accelerated at certain points in the rev range? almost like your intake on the turbo...at some point was rattling, then it would vannish lol?

 

[turbotog]

it wasnt exactly what I expected to have been the problem! didnt expect a mount on this little car to go and I drive it for mpg! lol
I didnt get any scraping noises.. the cabin, throttle pedal and steering wheel just started shaking more than it should... everyone I got to sit in it couldn't even tell - a few said it was just my backbox lol
I pretty much dismissed the clunk as I was on full steer in a carpark and my drivers side cv joint had started clicking..