Hi Guys,
Firstly can I say great forum
, it’s already been super helpful. Hoping for some help to sort the problem. My car's a totally bog standard 1992 Saff 4x4 (yep I know not many left in standard form) It’s the N5C Catalyst engine, with the green cam cover, and at this moment I wish it wasn't. It's a one owner car before me, covered 130K miles, but has a full and virtually unbroken mainly Ford service history. Most of the miles are motorway miles and a recent compression test shows virtually no engine wear, so assuming all's well mechanically anyway.
I took the car for it’s MOT Test last week and the tester insisted being registered in September 1992, the car had to have the more stringent Cat test, on which it failed on CO emmissions. As the IACV (Idle valve) had been playing up, we tried the test again with the valve disconnected, and it passed the fast running test, but then failed the idle test.
Have sinced replaced the idle valve, fitted a new TPS (throttle position sensor, and set it to 0.20v at idle, set base idle to 900rpm, replaced both ACT and ECT sensors and cleaned out the throttle body. Took it back for retest yesterday and it was no better, although it seems to be idling slightly better, failed the fast running test, I think the figure was 1.45 when it should have been around 0.30. (If it fails this test the computer won't let the idle test be performed)
I’ve also noticed that there’s a slight misfire at idle, which fades out at around 1500 rpm, which is obviously not helping the case, and when I removed the ACT sensor it was wet and reaked of petrol. I've also tried adjusting the idle mixture screw on the ECU and it's not making enough difference.
When I got the car home yesterday evening I removed the throttle body, and I’m going to set the TPS to nearer 0v at idle, as I’ve read this is the correct setting for the 4x4. I’ve also removed and cleaned the injectors, inspected the phase sensor, dist cap etc and all looks well there.
After having trawled loads of threads on here I'm now thinking either MAP or Lambda sensor is/are the culprits. However I'm leaning towards a dodgy MAP as I've read Lamda isn't active at idle (correct me if I'm wrong!) Despite all the above, the car runs absolutely fine and boosts as is should.
Finally just one final thing, and not related, when I replaced the ECT (Coolant sensor) I broke the temperature sensor for the gauge (what a b*****d place to get to!), so have replaced that too, however since fitting the new one the temperature gauge reads higher, but there's no marked changes to the behaviour of the enine (fans cuts in as they should, no boiling, no over pressuring, heater works as it did etc, etc) The sender I fitted was listed in the Intermotor catalogue as being suitable for the Cossie, as well as quite a few other Sierras etc but I'm not 100% convinced as I would have thought a Turbo'd engine would runs hotter than a normally aspirated engine????
Any help/suggestions would be greatly appreciated!
Mark.