Rover V8 14CUX hot idle problems

[MikBoje]

Unfortunately I don't own a a TVR - but this forum seems to be the place where a lot of knowledge is held regarding the Rover V8/14CUX ECU, so I hope it's ok I'm asking for help anyway, as I'm getting pretty desperat.

I have a RRC with a brand new Turner Engineering 3.9 V8 long block just fitted - and I'm a lot of problems with hot idle. Startup and cold idle is fine, as well as normal driving - but when hot, idle gradually gets worse and worse and the lambda figures are not that far off it seems to me, but when iddling hot, the lamda figures raises to 18-22 (where the lamdba gets out of range), and the engine nearly stalls.

It has gasflowed performance heads, a H180 Sports torque camshaft, and stainless steel headers and 3" exchaust system - all brand new. It's a non-cat 1990, so in order to see whats happening I've put on an Innovate LC1 wideband lamba connected to a Innovate MTX-L gauge.

I'm not big mechanic myself, but have read a lot on the subject - all of the testing and fitting has been done by proff. mechanis, but specific 14CUX experts appears to be non-existant here in Denmark

While trying to take some of the old parts out the equation, the following has been exchanged for new parts, testing it at along when fitting it:

The AFM, fuelpressure regulator, stepper motor, fuelt temp, water temp, and injectors are all new. Crank-case breather has been checked and all components of the PCV system has been changed too.

Brake Cleaner/Diesel starthas been sprayed directly onto the various joints around the plenum - with no change in rpm - so no clue of false air as far as we can detect.

The throttle heater pad is not removed. The T-piece of the PCV system has still got the small restrictor in place.

The Ignition system is a programable 123Iginition electronic unit, running a very modest ignition curve. This was fitted with brand new Magnecor HT leads and an genuine Land Rover coil.

AFM is set to 1.3V, TPS is set to 0.35V, Fuel pressure is set to 40 psi.

Would it help increasing fueling on hot idle via a Mark Adams chip or a Megasquirt ? - or would that just cause more problems ?

I'm running out of ideas

Please advice
Thank you
Michael

[MikBoje]

I've monitored the temps and stepper motor with Rovergauge and everything seem to be behaving correctly. Temp sensor show Ohm readings corresponding to the manual as well. Base idle has been set according to the manual as well.

Its running the correct resistor for a non-cat car, so you're right it won't be able to do any adjustments.

No errors are showing in the ECU, according to Rovergauge.

[MikBoje]

Hi SHPub

Thank you for your comments. I don't think the ignition is misfiring - the 123Ignition has a pretty good reputation, and the timing at idle is spot-on when checked with a timing gun.

The AFM is set to 1.3V on Red/Black and Blue/Red when ignition is on, but engine not started - shouldn't that be correct ? I've read somwhere that Ohm measured between "the two outside pins should read 300 Ohms" - mine does only measure 120 - would that be an indication of something ?

[MikBoje]

Two different mechanics have checked for air-leaks using Brake Cleaner/Diesel start, which has been sprayed liberally around the plenum area - with no no luck in detacting any airlieaks.

Lambda is showing:
Cold idle approx 12.5 - 13.5
Cruising at 50 mph approx 14-15
Kickdown at 50 mpx approx 11.5 to 12.5
Warm idle starting around 16, and gradually rising to 22 if left idling, at which point it can barely keep itself alive.

I know that the cold fueling will be compensating a bit, but wouldn't an air leak also be more apparent when cold ?

The last mechanic who checked for an airleak commented that the vacuum was too low - but I don't know if that can be related?

Cold and stable idle: 0,41 bar
Warm idle starting to get rough: 0,38 bar

Edited by MikBoje on Friday 14th September 06:03

[MikBoje]

Hi Ron,

Well in the end after spending a lot of money and hours on checking out different error sources, it turned out that the bloody &/%&/(% mechanic that put in the new Turner engine had put a copper washer on the stepper motor - thereby not enabling it to close properly and sucking in false air...

Suddenly I had a lot of spare time because the thing was now running fine with the 14CUX - so I decided to MegaSquirt the beast - haven't looked back since

Cheers
Michael

[MikBoje]

It's an MS2 Extra.

I went through 5 (!) stepper motors - each acting differently from the other. Try and see if you have any gasket/spacers on them.

I also found a cheap spare 14CUX on Fleabay that I tested with - may be worth a shot in your situation

Cheers
Michael