Ok,

so my car is back to running rich and stalling again on cold only.
once car is warm it idles and runs well.
not running rich at all when warm
So it is definitely changing between hot and cold mode.
really not sure what it could be.
the idle speed is ok when cold.
it is blowing black smoke and smells really rich.
and will stall on acceleration at times.

can’t think what this could be that only causes issues when cold.

 

You have gone through the thermostat and you probably have a way to tell coolant true temp and separately by an independent device ( ELM - 327 ? ) if it is in closed loop and if the device says closed loop ?

 

Bluetooth elm indicates coolant temp is warming up.

have not checked resistance of temp sensor however given the fact that the car idles slightly lower and it runs well once warm i assume it is changing running mode.

 

Are we talking about issue below or above 88 C closed loop ?

 

below.
once car is warmed up, runs beautiful.

When cold terrible.
black smoke, stalling.

before was always issue cus thermostat was broken and car was not warming up.
fixed that tho

 

I have swapped mafs between my 2 cars and no noticeable difference.
i hear new ones are nla.
any part substitute?

how about fuel injectors? Maybe them?

i dunno as like i said it runs well when warm so i am at a loss

 

The MAF as a Lucas AM 20 ( or something like that ) was used on the Land Rover model P38 ( ? )

at the proper idle speed you should see on yours 1.2 volts DC on the middle wire ( Green / Pink ) at the connector ( pin stab method ), this would prove the MAF is alive

The MAF is powered as B + voltage and has a splice and same large ECU controlled relay # right 5

Warm at the idle speed and faulting would not be related to injectors unless they warm up also ( ? )

Power " sitting " on the injectors check and how , current limited ? , there is a large ECU controlled relay # right 5 as the source and some splices

In reality the mega splice can not fit so is broke down into 3 or 4 splices to fit loom space

Print is more clear with a double click

 

To check maf do whilst connected? And ground out multimeter anywhere?

 

A good read of the attached info on the fuel injection/maf may be worthwhile.
I presume you have checked/replaced the coolant temperature sensor that goes to the EMS, not the actual temp. gauge sensor.

John Herbert
1996 XJR

 

To read the MAF with hand meter it has to stay connected as a return to ECU signal , it needs to be powered by one of the other wires the 3rd being a car frame ground

The engine valve cover is not a good ground , it is electrically isolated by plastic shouldered bushings

Probably the best one is the small ground terminal on the rear engine firewall

Someone used the large B + on the firewall by mistake ( easy ) and flashed his meter

 

i replaced that temp sensor a little while ago.
back at the beginning of 22.
it does appear to read accurately based on what my torque app shows.
it appears it operates fine as car is good once warmed

 

So we are looking at open loop mode

Question is how is that regulated ( O2 sensors are not used for fuel trim )

Question as the throttle butterfly is at the idle stop ( minus throttle butterfly stop screw inside the TB ) My X300 did not seem to have one when I took mine apart

So when the ECU sees the TPS voltage value as a trigger to command certain things to " fixed " values , injector pulse width , IAC valve to arrive at the on paper idle speed

or the ECU changes things to arrive at the paper idle speed , obviously not

In the back ground you have vacuum leaks , Evap system fails including Rochester valve back by the tank , smog pump that has 2 check valves

The smog pump will run for 60 ( ? ) seconds only triggered by ?

injector cleaner ? EGR valve clean ?

The EGR has a position sensor to read position error as target 0 % PID = EGR_Error with ELM - 327 device , there is a common meter value on X wire per wiring guide values sheet on the page before the actual wiring picture / schematic

Someone " recovered " their idle with a EGR cleaning and another with Rochester valve replacement ( watch proper Rochester tubing positions as that was found )

One EVAP system tube was totally missing on mine , from under the intake manifold fitting

And one last mystery item seldom talked about is the brake booster and that wierd fitting at the intake manifold , this leak should be overcome in effect by the engine suppling more vacuum on throttle up

My Mom says I have to go to bed , dialysis in the morning

 

There is a couple of correction done above

 

No egr here.

could be air leaks.
i have no way to test.
need a smoke machine.

idle speed is good so i don’t think it is iacv.

o2 sensors only used once warm is good to know.
can rule those out. I replaced them not long ago so assumed it is not them

 

Running rich would be a clue of a vac leak and not exhaust manifold leak into biasing the O2 sensors ( not being used ) to run rich fuel trims

Short term fuel trim #s until it shifts

I'm not clicking at this time the relationship between vac leak and running rich

Again as you throttle up the vac supply amount overcomes a leak so would see a change in stumble ( ? )

 

Will see if i can look to fix on the weekend.
will see if driving it with MAF unplugged for the next day and a bit makes a difference

 

Unplugging the MAF will run in a less then optimum engine regulation using a different set of maps minus the MAF and making assumptions and not having timing advance under load that it can't determine minus the MAF to TPS expected correlation ( spread ) as a load determination

 

Ok so won’t start with maf unplugged. And idles badly if unplugged when car running

 

Also checked the MAF voltage just now. Was at 1.4v just after starting the car. And then as idle stabilised is was sitting at 1.25v

mayb it reads differently when car is cold? But that makes 0 sense

 

Check also the Air Temperature sensor as this will have an influence on fueling in open loop.