(T) Mystery Flatspot

Hi Guys and Gals,

Just the other day my Cinq has started some really bad hesitation problems and feels like it's not revving cleanly.

I searched the forums and have narrowed it down to the following order

1. Most likely Lambda Sensor

2. Possible Map Sensor

3. Maybe fuel filter

My main question is will a Diagnostic show up faults without any warning lights being seen on the dash?

Any help or advice appreciated.

Cheers

Liam

Hi,
Check for signs of head gasket leaking if there's no warning lights on, water in the oil, oil in the water etc......

Thanks
Paul T

Sometimes yes but most times no. As the computer is a lot slower than the ecu anyway so you only see 1/20th of what is happening anyway. As long as the plugs are good and leads are good and you have a good spark from the coils then it will more than likley to be a slow lambda sensor. no responding quick enough when throttle is required. Lamdba sensor only work at light throttle or when cruising. They do not work at full throttle or when deaccelerating, at this point the lambda goes to open loop allowing the full fuel mixture to be entered into the engine, a slow lambda does not go open loop as quick thus trying to keep the correct fuel air ratio of 14.7 /1 and that then gives the hesitation.

Decided to start with the cheapest items to eliminate the possibles, these are plugs and leads.

I'll get some decent insulated pliers and see if I can get a good spark from each one then I'll move onto the bigger stuff.

Does anyone know how to test coils with a multimeter?

Thanks

Liam

Update, check plugs and leads, seemed fine, erm coolant and oil seem fine too, I'm puzzled.

Liam

Liam
Sounds like a problem that i`ve been dicussing with a guy on here called tom,he tried everything even replaced the lambda with a new one,still had the hesitation so he took it to fiat for a diagnostic check and it turned out to be the lambda,(the new one he had fitted was faulty too)
Car now runs fine
Cheers
Adrian

God Adrian, I was following that thread and I do hope it's the Lambda or MAP or indeed something other than the head gasket!

Oil is fine looking, plugs are fine as are lead but on start up it's more sluggish than usual, sounds lumpy or rough on idle and has numerous flatspots through the rev range in any gear though with time will still do 110 with coaxing!

I wonder?

Liam

Liam didnt it stall the other day or summat for ages then started bak up!

Perhaps whatever is causing these problems also caused that!

Sneaky bas*ard told me it wasn't excepting the key and refused to start with the code light on! Cheeky c*nt!

Got it going like 5 mins later and it's never done it again.

Liam

I searched the forums and have narrowed it down to the following order

1. Most likely Lambda Sensor

2. Possible Map Sensor - fitted one today and it seemed a bit better but will find out for definate tomorrow on cold start up.

3. Maybe fuel filter

Would a Lambda from a MPI 1.1 work?

Liam

MPI's have 2 lambdas, so may confuse things if they're slightly different etc not 100% sure though

It could be head gasket, but not between a cylinder and a water way, between two cylinders. At low gas speeds there is no compression because it is leaking into the other cylinder. At higher engine speeds the engine will appear to run normally.

Cheers chum

D

I have been thinking this D, do you think it will show up on a simple DIY compression test? My mate has one from his K-series days.

Liam

Update: Tried the car today with the new MAP sensor and it wasn't any better, well maybe it was but I felt it still isn't revving cleanly through the gears.

Will get a hold of the compression tester and hope for the best.

I've ruled out Lambda since th ewarnign light hasn't come on after nearly two weeks of strange running.

Liam

Hi Liam
I wouldn`t rule out lambda i don`t think Toms warning light came on and he had 2 different faulty lambdas.
His diagnostics check only cost him £30 at his local fiat dealership,could have gone on forever changing bits but would never have sussed the brand new lambda was faulty!!!!
Cheers
Adrian