Ferrari F355 - Revving high after new cats fitted

[Ian355]

Is there anyone out there who can give me some advice? I have a 1997 F355 Spider which had the cats removed before I bought it.

The car was extremely loud, so after almost going deaf and getting complaints from the neighbours, I bit the bullet and had new cats put on.

However, the car now frequently idles anywhere between 1500 and 2000 revs - very annoying - especially in traffic. The car has been checked out for air leaks and verified that all sensor plugs are connected correctly.

Any ideas/suggestions/experiences gratefully received.

[stevieturbo]

Was the battery disconnected during this ? perhaps it has lost its idle settings.

How much has it been driven since they were fitted ? Some ecu's can be oddballs when the battery has been cut for a long time. Some will sort themselves out over a short period of time....

[Ian355]

Thanks for the reply. The battery wasn't disconnected whilst the cats were being done.

I'd say it's done about 150 miles since the new cats have been on. It does behave itself sometimes, but not consistent in terms of whether engine warm or cold etc. Dipping clutch also makes it rev higher.

Cheers

[rev-erend]

Sounds like a problem with the idle air control .. I'm not a fezza expert but finding the idle control value and clamping the air pipe should make the revs drop and prove you have found the problem..

[stevieturbo]

I suspect the Ferarri has multiple throttles.....so not sure what sort of idle control it might have ?

[toohuge]

As suggested above, check (or have somebody check) the exhaust sensors, especially the air flow meters. It sounds like a straight forward sensor problem. It could just be coincidental that a sensor has gone/come dislodged or something as trivial as that.

Hope the problem gets sorted.

[spend]

Have you checked that there are no air leaks between the airbox to the throttles (my afms were connected to the airbox). Its easy to see if the throttles are closing smoothly by popping off the ducts at either side of the plenum (might just be a snag stopping the butterfly closing fully). Also check carefully the idle control (stepper motor) pipes and electrical connector - its near the front of the Y IIRC.

Sounds like they may have just not connected something back properly after dismantling to get access.

Dave

[Ian355]

Thanks for all the advice. Tried resetting the ECUs but the car idles pretty much the same,so now ordering some new 02 sensors, hopefully I should be able to fit them myself.

If that fails I will book it into ferrari for ECU reprogramming and take it from there

[stevieturbo]

I would suspect that any good competent garage that regularly does diagnostic work, might be able to look at it.
Although far too many people rely on simply plugging a scanner in, and hoping it tells them what is wrong, because they dont know how everything works.

O2 sensors are possible...and relatively cheap to swap.

http://www.lambdasensor.co.uk/main/mindex.htm

And here some brief info on testing. Basically when running, if closed loop and the sensors are working, you should see rapid changes around the stioch point.

http://www.lambdasensor.co.uk/main/mtesting.htm

But high revving would suggest extra air getting into the engine somehow. Whether by idle control, air leaks, sticking throttle etc etc.
That would account for a high idle...but not necessarily an erratic idle.

[skid-mark]

could be faulty temp sender on the coolant side and is telling the ecu to put more fuel in

[rev-erend]

skid-mark said:

could be faulty temp sender on the coolant side and is telling the ecu to put more fuel in

More fuel does not make it rev..

Extra air like a leak makes it rev..

Weird aint'it.

[AndrewW-G]

Have you checked Ferrari's built in idle increasing device ........the floor mats have a funny habbit of riding up onto the base of the throttle pedal

Failing that reset the ECU by either unplugging the battery or pluggin it into a diagnostic box......which will of course tell you if the lamba probes / exhaust ecus / maf etc are functioning correctly

[skid-mark]

rev-erend said:

skid-mark said:

could be faulty temp sender on the coolant side and is telling the ecu to put more fuel in

More fuel does not make it rev..

Extra air like a leak makes it rev..

Weird aint'it.

i know air leaks can cause a high idle and they are a pain to find but i'm sure that if you have a faulty temp sender it over fuels the engine this is picked up on the lamda, the lambda probes try to adjust the fueling with the ecu and throttle posistion by allowing more air in through the conrol valve hence eractic idle, cause it can't get the fueling right cause it's not getting the right signals from the sensors.
i'm not doubting any thing that has been said on here i'm just trying to give a different point of view of what could be wrong these are quite common for being faulty on many of the cars i've worked on in the past.
another thing is to check all the multi-plugs to the sensors and throttle housing are all pushed on firmly or don't have corroded terminals inside, plus any vacuum pipes even check the servo pipe for the brakes seen these things split in the past or the one way valve leak.