Stuttering engine

[coolchris]

Hi,

When im travelling in my car when I get to around 75 ish the engine stutters anything less or above and it is fine.She idles ok and when driving all through the rev range and gears the car runs smooth.But this stuttering around 75 is puzzling me the engine bogs down and produces a deep base.
Anybody have any ideas what it could be and what I should be looking out for ?.Its a 2.5


Cheers

Chris

[joust]

First thing is check sparkplugs and gap them correctly. It can cause a multitude of issues it seems if they aren't right.

[Wooden Horse]

Could the gap on the plugs cause an issue with cold running?

[coolchris]

I will get the spark plugs checked if everything seems ok there what else should I be looking out for?

Cheers Chris

[RobP]

As Joust said first check plugs/gaps. Does the problem occur at all temps or only when the engine is hot? If it occurs only when the engine is hot it migh be cat/lambda sensor issue, or possibly a fuelling issue (low pressure fuel hose collapsing is quite a common one).

[joust]

What Rob said :-)

[Wooden Horse]

What should the gap be?

[R0162]

Depends on the plugs...the motorcraft original plugs are not really suitable for our cars but they were the best things available at the time.
There are a few much better plugs now available... NGK BR7EF...Bosch HR6DC are both tried an tested and the gap should be 0.030 in or 30thou.

I'm not sure its a plug problem, when you say it only happens at 75 are you talking about a speed or temp? oxygen sensors work at ranges i.e. there will be a certain range of compensation figures between 2000-3000rpm.
If you are saying it happens at 75mph with regards to speed, then surely this should be dependant on what gear you are in and then again relates to a range of rpm.
Lambda sensors go faulty quite often and mess with fuelling, but problems normally show up at low rpm, the problem can also change depending on engine temp, i.e. may stutter on cold or may tick over fine but starts to run lumpy at low rpm when warmed up.

If the problem si throttle related then i would look the fuel supply or throttle sensor...i.e. fine on half throttle but stutters if you put your foot down or for sensor it plays up at a certain throttle position in any gear...i would always approach situations like this by elimination, change plugs, change lambda sensors...see if its ok...give the e car a once over making sure nothing is visibly wrong with piping, vacuums or sensors not plugged in..

All this aside if not already done i would highly recommend anybody to modify/upgrade the fuel system, replace feed pipes to teflon coated...replace high pressure teflon coated pipes post pump, check fuel pressure, modify fuel tank and change outlet position, replace ARV, replace fuel filter and put some injector cleaner in the next tank full, and also replace the non return valve..oh and heat insulate as these cars suffer badly from fuel evaporation on hot days and heavy useage.. keeping fuel cool is very important and another reason to reduce those underhood temps.

So many people have suffered fuel starvation or fuelling problems on these cars..a faulty ARV on the fuel system almost killed my engine due to fuel starvation, the fuel tank is not baffled , the feed pipes are badly routed and can collapse and they deteriorate over time.

Find out what rpm is happens at rather than speed,i doubt it happens at 75mph in any gear, it could be an exhaust issue...are you sure it stuttering or does it "sound" like its stuttering at a certain rpm...a do you have stock exhaust? if so a broken exhaust bracket can allow a resonance at certain rpm which sound like the engine is struggling...

Edited by R0162 on Sunday 18th March 16:13

[Gadgeroonie]

check the map sensor is connected ok

[coolchris]

Thanks for the advice Chris,

It does it more when warmed up the engine def bogs down around the 75mph mark give or take a few mph either side of that speed but when you put foot down and press on the engine is fine and does not stutter.Gadge could you tell me where abouts this sensor is on my car that I need to check.

Thanks

Chris

[Gadgeroonie]

the map sensor is connected to some pipes on the intake manifold

what ecu does the car have ?

[R0162]

coolchris said:

Thanks for the advice Chris,

It does it more when warmed up the engine def bogs down around the 75mph mark give or take a few mph either side of that speed but when you put foot down and press on the engine is fine and does not stutter.Gadge could you tell me where abouts this sensor is on my car that I need to check.

Thanks

Chris

Hi,

i'm not sure why it would be speed related, i.e. 75mph in 4th is different to 75mph in 5th or 6th, because what we need to look at is the rpm at which is occurs..
It sounds like a minor issue, something not quite running right, it could be many things thats putting it out of whack a little, plugs, lambda, vacuum leak, exhaust, map sensor...
Unfortunately i do not think this is something that can be diagnosed online..i think you will need to take it for diagnostics.

[coolchris]

Hi Chris,

Yes I think you are right I will be getting it looked at in the next couple of weeks or so my car has the mbe ecu.Wrll let you know the diagnosis but like you say im hoping it is something straight forward and simple.

[Gadgeroonie]

where r you based - i could take a look

[daddysumo]

Hi Chris how are you ?

Do you have access to the Noble or Easimap software. If you do then just connect up
and make sure that you throttle potentiometer reads from 0 to 16 as you depress the throttle slowly. If it breaks down any where along the way ( or roughtly where the throttle is when you are cruising at 75) then that is the problem... maybe.

Worth a check if nothing else so far mentioned works.

[R0162]

[quote=R0162]

If the problem is throttle related then i would look the fuel supply or throttle sensor... for sensor it plays up at a certain throttle position in any gear...

[quote]

...just for the record Steve has taught me everything i know...i covered myself quite well with possible causes in the first post..how can you be wrong if you list every possible cause ...definately take it for a diagnostics and general health check Chris...

[coolchris]

Thanks for the kind offer Gadge in based about 10miles south of Guildford.I dont have the easimap software Steve so like Chris said im best getting her in for a diagnostic health check.Otherwise apart from this issue she drives fine.