christy Posted April 16, 2010 Report Share Posted April 16, 2010 Can someone help me please. Mrs has 98 Fiesta. Runs great apart from when you hit 4500 revs then a flat spot appears. It will pass through slowly and clears around 5000rpm. This happens in every gear! Had it serviced, asked them they don't know. Fitted new fuel filter last week-no change. This problem has been around for 6 months. Never bothered to much just thought about it. Now mrs has learnt to use the motorway and it is a problem when overtaking. I have asked three different mechanics, non have any idea what is causing this. I thought diaphram in the carb perhaps??? It is a 1250 Zetec s engine with 100,000 miles on the clock. The car is reliable in every way-never let us down in 7 yrs. Any ideas would be greatly appreciated. Thanks. Quote Link to comment Share on other sites More sharing options...
12borejimbo Posted April 16, 2010 Report Share Posted April 16, 2010 head gasket, my mates MG TF had the same thing, turns out he blew the gasket but it didnt show in the oil, or your spark plugs need changing! Quote Link to comment Share on other sites More sharing options...
Pushkin Posted April 16, 2010 Report Share Posted April 16, 2010 I think you would be better getting someone to check your carburettor for you first. Flat spots are often caused by the spindle in the carb wearing or the jets needing replaced. You might even be able to pick up a second hand one fairly cheap to try it out. Pushkin Quote Link to comment Share on other sites More sharing options...
christy Posted April 16, 2010 Author Report Share Posted April 16, 2010 I think you would be better getting someone to check your carburettor for you first. Flat spots are often caused by the spindle in the carb wearing or the jets needing replaced. You might even be able to pick up a second hand one fairly cheap to try it out. Pushkin Thanks. Interesting idea. I'll follow it up. Quote Link to comment Share on other sites More sharing options...
Paul223 Posted April 17, 2010 Report Share Posted April 17, 2010 It won't have a carb as such, the part that looks like a carb houses the throttle body and a single point injection system. Check for air leaking into the inlet manifold, have a good look at the various vacuum pipes and the engine breather make sure non have rubbed through or split. Quote Link to comment Share on other sites More sharing options...
garyb Posted April 17, 2010 Report Share Posted April 17, 2010 Compression test it. Like the other poster - I've seen similar symptoms from Head Gasket Failure before. Does the coolant bottle smell of exhaust? Quote Link to comment Share on other sites More sharing options...
The Clay Rascal Posted April 17, 2010 Report Share Posted April 17, 2010 Can someone help me please. Mrs has 98 Fiesta. Runs great apart from when you hit 4500 revs then a flat spot appears. It will pass through slowly and clears around 5000rpm. This happens in every gear! Had it serviced, asked them they don't know. Fitted new fuel filter last week-no change. This problem has been around for 6 months. Never bothered to much just thought about it. Now mrs has learnt to use the motorway and it is a problem when overtaking. I have asked three different mechanics, non have any idea what is causing this. I thought diaphram in the carb perhaps??? It is a 1250 Zetec s engine with 100,000 miles on the clock. The car is reliable in every way-never let us down in 7 yrs. Any ideas would be greatly appreciated. Thanks. I had similar prob with escort, zetec, took it to a garage put it on the computer was air flow meter, Quote Link to comment Share on other sites More sharing options...
christy Posted April 17, 2010 Author Report Share Posted April 17, 2010 Thanks to all. Looks like I need a garage with a computer. Hope someone apart from main dealer has one. Are they common Quote Link to comment Share on other sites More sharing options...
Paul223 Posted April 17, 2010 Report Share Posted April 17, 2010 Yes very common, my guess is they'll pull a fault code saying low voltage on oxygen sensor, if so don't change the oxygen sensor, check for air ingress as above first To rule out head gasket ask them to do a 'block test', this is a device which holds coloured liquid and fits on top of the expansion bottle, the liquid will change colour if there is combustion gas present Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.