Splutter/Misfire

[Salmon]

My puma (1.7) has just developed a bit of a splutter/misfire at low revs. Its only really noticable when you bog the car down in a low gear and then try to accelerate. Are there any likely culprits before I start replacing the usual plugs, leads etc?

Cheers!

 

[DOH]

First check the resistance of each spark plug lead with an ohm meter/ multimeter. they typically are about 5k ohms. Above 8 k ohms and the leads has got high resistance & needs replacing. next check plug gaps 1.3mm early coil pack with clips on plug leads to coil pack. 1mm later coil pack. check plugs are light brown biscuit colour & not oiled up, if so clean with carb cleaner. check connections on throttle position sensor and spray with wd40. There is no harm in also checking connector on MAF sensor also . Also put 125ml of Wynns or STP injector cleaner in the petrol tank, as your injectors may be gummed up, it's a good idea to add this every 20000 miles. but do this last after checking everything else.

 

[martinthrapston]

for the age of the car it would be worth checking the spark plug holes,usally oil may collect in 1/2 cylinder,either through topping up and spilling it,or the cam cover is leaking,if there is oil,it is best to change plugs,leads,maybe the coil pack,also DO NOT use injection cleaner,it can knacker up the nickisil linings,which will mean a new engine.
also maybe worth checking/cleaning the maf while you are at it and also do an ecu reset,thats disconnect battery for 30 mins and then reconnect,you can do this while checking plugs etc k:

 

[Salmon]

Cheers lads, not going to get a chance to check until later in the week - will let you know how I get on.

 

[DOH]

I also shared Martin's concerns regarding using injection cleaner.with Nickasil Linings because of BMW previously suffering Nickasil failures, when there was Sulphur in the petrol.As a result prior to using, I contacted both Wynns and STP to ask if their product was safe to use. They both said that the sulphur content was negligible and would be ok for occasional use .They were both of the view,that the product will be used up in a matter of miles. this is compared to BMW covering 40K with much higher levels of sulphur in the petrol and importantly in it all of the time.
Your other option is more costly /labour intensive. Which will require removing and cleaning the injectors off the car.
It would probably be best to carry out the other steps of action first and clean the injectors as the final thing , if the problem still exists. You could also reduce the dosage to 1/2 recommended on the bottle, to be on the safe side,
I have stated the resistance values of the ignition leads in an attempt to save you money purchasing them unnecessarily. (If you don't have a Digital multimeter, Toolstation sell them for £5.37 [http://www.toolstation.com/shop/Digital+Multi+Meter/p11867] .This would be a good investment as there are many items on the car that have known values of resitance and voltage which will be useful to know ,when fault finding). One example is testing the throttle position sensor with an ohm meter to establish if there is a dead spot, open circuit , in any of its travel. In case that is faulty. that could also cause the low speed jerking. so you could then rule that out. another use includes testing the resistance of ABS sensors, to determine which of the 4 is faulty.
Hope this helps

 

[crystalpuma]

I have this problem too. Have replaced the coil pack and that seemed to solve the problem at first but after about 75 miles the problem is coming back as worse as ever so will be checking some other things now too!

 

[evilrob]

Yep... can I join the rubbish low revs club too? Also replaced MAF, seemed good at first, problem come back. I'm thinking... lambdas next?

 

[DOH]

Before you buy any more expensive bits. Try the resistance test on the Throttle position sensor. if you initially get high resistance readings ,use some fine guide abrasive sand paper on the end of a flat blade screw driver to clean the contacts up & then spray with WD40.
If you get stuck, google "testing TPS using an ohmeter ". there's also footage on Youtube

 

[Salmon]

Bit of an update. Missus was driving the car and it dropped a cylinder completely combined with engine warning light. She called out RAC who said one of the plug leads had snapped completely. So bught a set of plugs and leads from halfords and went to replace. First problem is that the plugs are stuck solid, great! So thought I'd just try the new leads. First set of leads from halfords had one duff lead which didn't clip onto the plug properly so had to wait until today to get another set in stock. Just fitted those and car still misfiring. Cylinder seems to come and go so not off all the time, so going to have another go at plugs with a proper socket as mine is just a cheapy job and not the easiest to use..