Westfield Miata forum

[tigbrother]

Hey guys

Here we go again.......

So after my last topic i now have the car running what seems to be all ok........ except for 11.5% co2 level

it should be under 3.5%, hydro carbon out put is perfectly normal.

the engine its self now runs beautifully, i do still still get a very small amount of black smoke on hard acceleration, but has a strong smell of unburnt fuel due to running very very rich.

now i have replaced/ tested most of the sensors (new MAF, New 02 sensor, water temp sensor running at 2.2k when cold, and 175 when hot)

the ECU is only throwing out a code 17 occasionally, which is 02 sensor value not changing, (due to detecting a rich mixture) even after fitting a new 02 sensor.

what are my other options to check?

Now reading on other forums the ECU can go into a 'limp mode' if one of the input sensors fails making it run very rich which is safer for the engine, but this should throw up an associated fault code, but i have nothing.

i have had all the plugs out , and they are not fouled with black soot, and they are all the same color which rules out a faulty injector?

i have all the air intake checked for vacuum leaks, all seals / gaskets have been replaced, including injector seals, and no sign of any problems there.

i suppose the next logical step would be to check fuel pressure, and possibly be looking at the throttle position sensor for any faults as well...

any idea on what other items to check or look for that i might have over looked,

Need to get this sorted for my IVA retest ASAP

[Big Cheese Dog]

Did you ever check the fuel pressure?

[tigbrother]

not yet big cheese, trying to get hold of some test kit this weekend,

[smokey mow]

[tigbrother]

Hi Mark

the take off for the brake servo has been bunged up and siliconed off so that shouldnt be an issue, as far as i can see every thing else is also sealed off now in terms of intake tubes etc,

It seems as if the engine is stuck in closed / open loop mode, and its running in a limp mode, where it enriches the mixture to get you home, (as apposed to leaning off which is dangerous)

[Big Cheese Dog]

Bet a fuel pressure gauge would cost less than the other guesses you've bought so far
It sounds like the 02 sensor is working ok in closed loop, but your mixture is so rich it's beyond the range of correction.
Is the vacuum hose hooked up to the FPR? Does it have vacuum?

[tigbrother]

fuel pressure test kit on its way this afternoon i hope, what pressure should i be looking for?

[tigbrother]

ok detailed instructions on how to test the system and pressures and a gauge in my possession, so ready for the big test tomorrow, i am actually hoping that its fuel pressure, but knowing my luck it wont be........

[Big Cheese Dog]

Make sure you Tee into the front/feed line, not the rear return from the fpr. Should be be maybe 36-40 with vac signal hose on and running, should jump 5-6 psi when you pull the vac hose off the fpr. Good luck!

[tigbrother]

well, have tested the fuel pressure and................. its running at 65psi

Houston - i think we have our problem, tracking down a new FPR now, possibly going for an adjustable one.

cheers for the advice Big Cheese Dog

[Big Cheese Dog]

I don't make this stuff up, you know