[shifty babe]

i have a 1.7 puma engine and it seems to be overfuelling...when i leave my drive it stinks of fuel and its destroying cats so i need to get it fixed....is there any common problems with these engines that make them over fuel or is it just a case of checking all the sensors...i had it plugged into ids the other day and it came up with nothing so does anyone have any ides

[PG12]

have a similar problem with the frp - chewing up £500 cats every 2 years (doing 40K miles in that time)

suspect cats are being contaminated with fuel - however mpg is still good and there is no 'black soot' around the tailpipe

i've also been plugged into a ford diagnostic - found no fault except the cat last time

could be worn piston rings - not sure if this would show up on the diagnostic

had a new oem frp cat fitted last year - it's already hit co2 emissions limit after 20K miles in one year - just passed (ie limit 0.3 actual 0.3!!!)

This post has been edited by PG12: 06 March 2008 - 12:17 PM

[Sarah326]

If the engine is overfueling, surely that wouldn't be cause by piston rings being worn?! Thought that worn rings would show more with oil consumption than with fuel problems. Overfueling is related to the sensors and ignition failing. (e.g. fuel/air ratio not allowing fuel to be burnt efficiently, or misfire causing unburnt fuel to be dumped to waste)

Excess fuel or unburnt fuel going into the cat would be far more forgiving on the cat than burnt oil would be. A hot cat is fairly resistant to fuel deposits getting in as these burn off fairly easily..... Perhaps your Cat isn't heating up properly?.... exhaust temp low?...... (am not a mechanic!! so these are just educated ideas)

Any blue smoke out of the exhaust?

[mark_f1]

I thought all puma's overfuel when on over run in order to keep things cool. (This is why you get the popping and crackling, enhanced by a frp's exhaust system).

[shifty babe]

i dont think theres blue smoke but il have a check later tonight....i had the cat removed from the system yesterday to stop the cat from collapsing again but was warned this morning that if i leave the car overfuelling then it could harm the internals ....

im guessing the best place to start would be to check the exhaust fumes...should i do this with the engine hot or cold?

i really hope its not a case of sticking a £500 cat on as i do around 20k miles a year

[chrisd]

i dont think theres blue smoke but il have a check later tonight....i had the cat removed from the system yesterday to stop the cat from collapsing again but was warned this morning that if i leave the car overfuelling then it could harm the internals ....

im guessing the best place to start would be to check the exhaust fumes...should i do this with the engine hot or cold?

i really hope its not a case of sticking a £500 cat on as i do around 20k miles a year

if its over fueling it could be the air filter needs replacing and is blocked, check when it was last changed. or use it as an excuse to get a performance panel filter to let more air in.

[volcomstone411]

first place i would check is idle fueling. Go to mot centre and check that idle air fuel ratio is 14.7:1. They wont charge you much just to check that. If its at that idle then it should be fine. The fuel ratio leans of for demand so the higher up in the revs and load more fuel is used. If somethings up at idle then its more likely to be an air flow sensor, or icv causing an issue and disrupting the fuel.

The puma is mapped to be richer at starting due to the fact that:

1) at startup crank, the speed of crank means that the engine cant suck in sufficient amounts of air, so it makes up for it by adding a richer injector cycle (more fuel)

2)Ecu will be putting more fuel in to help allow the engine reach optimum operating temps, and to meet the demand of auxilary systems. This is known as a fast idle, which is why the car will rev higher when first started. All this means more fuel for the car.

The puma 1.7 ecu has no fueling after closed throttle, so the suggestion of wetwalling, or piston cooling above, is not due to this i would say. The engine determines this primarlily by the throttle position sensor....i suggest you check that this is working correctly. there is a way to do this, by taking it off and moving it manually. but this will just adjust the injection of fuel and not be letting added air into the engine which would make it momentarily very very lean.

If you are really concerned suggest going to a dyno, as they will be able to tell you if your fuel ratio and curve is good.

on the graph below you will be able to see the graph at the bottom, starts of on the scale on the left at 14.7:1 (stoichmeteric) and then leans off as the car is pulling. up the rev band. Its important to remember that the car under load, i.e. driving may fuel different to that of just revving it sat on your dirve.


IM pretty sure that the cats failing is abnormal. Ive had my puma for quite a while, and even decat and substatially modded i can still get through mot emissions test. So i suspect that there is probably one fo the following failing:

1) Primarily maf (as the ecu, when these fails uses a set of preprogrammed failsafe lookup tables, which at a glance look like leaning towards the rich side, probably for safety)

2) Throttle position sensor

3) ICV, or certainly its air supply through throttle body

4) Inlet Air Temp sensor

5) Abnormally high fuel pressure...a poorly setup power boost valve could be causing this

I would check these first. Failing that it could be a lambda sensor but...im sure that most pumas have 2 of them, so i woulda thaught the likely hood of two failing would be unlikely.

If it were me, i would goto a dyno with the ability to do a diagnostic too. This way you can find out exactly what is wrong, and probably gain a bit of drivability and maybe power from a properly runing motor.

Hope my wittering helps

This post has been edited by volcomstone411: 06 March 2008 - 09:53 PM

[PG12]

if its over fueling it could be the air filter needs replacing and is blocked, check when it was last changed. or use it as an excuse to get a performance panel filter to let more air in.

hmm, interesting - had a piper panel air filter fitted a couple of years ago - cleaned/oiled every 20k miles

i've had 2 £500 cats fitted since - perhaps too much dirt retention oil sprayed on the filter? - wouldn't any issues with air intake have been detected during the ford diagnostic i had?

had a look at the exhaust - the tailpipe bar is coated in black 'soot' - might go back to the oem filter - see what happens

This post has been edited by PG12: 06 March 2008 - 11:52 PM

[shifty babe]

thanks for that volcomstone...i have a mot bay at work so il see if they can check the air fuel ratio, if not then il just get it on a dyno...might as well do the job properly seeing as iv already spet enough putting it in lol...would it still be safe to run the car hard even when i know its overfuelling as i am hoping to take it up the 1/4 mile at santa pod on sunday? obv if its going to damage it then its not worth it lol

[PG12]

interesting pdf document explaining possible reasons for catalytic failure...

http://www.fpuk.co.uk/pdfs/catalytic%20con...cal%20guide.pdf

Emission related.
(i) Failure of an emission control device (lambda sensor).
(ii) Failure of an engine management system component (ECU, Injectors, EMS
sensor etc).
(iii) Basic maintenance (plugs, filters leads) requiring attention.
(iv) Any engine that is operating “out of tune” can potentially damage a catalytic
converter.

going to replace my piper panel filter with an oem

Engine wear
An engine that is operating inefficiently due to general wear (low compressions, burning
oil etc) will result in converter failure.

This post has been edited by PG12: 07 March 2008 - 12:17 PM

[shifty babe]

thanks for that im going to read it during my mechanical manitenence lesson...should make it a bit more interesting...

[clairestracey]

is this just a problem thats restircted to the 1.7s then the cats failing or does it affect the 1.4 aswell

[volcomstone411]

overfueling can cause damage over time. If you could restrict your use of it. But if it is overfueling, then high revving it isnt such a bad idea as it leans off a bit then.

Need to speak to a mechanic on this but main damage would be to piston rings, lambda 02 sensor and cat.

It could also contribute to pinking as if its injection spraypattern is somehow too long then it would inject after exhaust valves closed and it would wet wall, where the cylinder and valves get a lining of hot fuel. this would mean that the car under pressure and heat could accidently ignite, or prematurely ignit causing pinking (knocking), and its a loud audible sound like a tin can being hit on the side by a spanner. If the car doesn do this at any point i would stop driving it, as the reverberation through the conrods and pistons could cause terminal damage.

I also found out if you car isnt getting a good spark then fuel may remain unignited. Loss of performance would be the best sign. Check plugs are clean and if you can get a new coilpack and leads i would. Also take coilpack off and make sure there is good contact on the contact plate underneath.