Recently on a long drive my AFR at idle got richer and richer. Now car idles at 13 but sometimes at 12. It doesnt fluctuate once idling but if I switch the engine off and turn it on again a few minutes later the AFR would be at a slightly different level of richness but quite constant at that level.

When I accelerate slowly the AFR rises slightly and then richens again. WOT AFR is fine and not affected.

Have checked vacuum tubes and no leaks.

Anyone can suggest what I should do next? I dont think I should retune as I think the problem is mechanical. Is it possible that dirt or oil or wtare has entered the vacuum tube leading to the MAP sensor thus causing wrong readings?

I'm using Autronics SMC. THanks for any views and suggestions

 

I'd plug the laptop in and ensure the sensors are reading correctly. Then I'd look to see how much fuel the compensations are adding or subtracting (AT, ET, MAP, etc.)

 

is the car idling at the same rpm? if you had a vacuum leak it would lean out and the idle would rise from the unmetered air entering into the system ..

 

As usual, thanks Geoffrey for jumping in so quickly to help.

Sounds like something for the pros as I wouldn't know what readings would be out of place. As my tuner is like a thousand miles away, I will capture a few screen shots and post it here and see if you can see a problem.

On the drive, my buddies also mentioned that my exhaust is flaming more often than before and they smell unburnt petrol. It flames when I brake hard from high speed and downshift for a corner. Flame is blue in center and orange at the edges and lasts for 5 seconds (one of them mentioned 15 seconds but I think it was an exageration). Things were fine the last time I drove the car a couple of weeks ago. On the drive it was raining cats & dogs and the spray my car kicked up covered the whole of the back of my car in a layer of mud

Targa, car's idle rpm is as before at aroudn 900rpm. I think if there was a vacuum leak in the tube leading to the MAP sensor it would read a lower vacuum and think the car was accelerating, but I dont know if that logic is sound. I thought it might have been a faulty O2 sensor but reading is OK for lean AFR when I do trailing throttle.

BTW my MAP sensor tube is connected to the intake manifold post throttle butterfly

 

you may be right on that about the MAP sensor , i have no expierence with MAP sensor setups so i can't help you with that ...

but if you have no air leaks and the O2 sensors are good , i would say maybe the cylinder head temp sensor but that would show on AFR. maybe a rise on base fuel pressure?

good luck!

 

Make sure that the line to the ECU which has the MAP sensor in it has not become disconnected. This will make the car run really bad. Also check the fuel pressure. Make sure the regulator has not gone nuts.

 

I don't think that it is a MAP sensor issue because the car generally will not run with a failed MAP sensor, and it certainly will have less fuel than it needs at the higher RPMs. This is assuming of course that the engine load is determined by manifold pressure, not something like Throttle position.

 

Sorry I did not mean to imply that the MAP was bad. What I meant was to check the line as a whole. The only reason I suggest this is because I had a customer with a similar situation and it ended up being that he had moved something in an area where the line passed to the ECU and pinched the hose. Caused all sorts of issues with the MAP reading incorrect.

 

Which is why you need to plug the laptop into the ECU and see if everything is reading properly.

 

Thanks guys. I'll be going to the garage where my car is and check out the things you mentioned.
BTW my setup is using MAP for sure but I think I also have TPS but dont know if that's been used at all in the tuning setup. Hope its just issue with tube leading to MAP sensor

Also I understand many tuned cars flame but usually it's orange in color. What does a blue flame indicate? could it be retarded ignition such that exhaust valve is opening while fuel charge is still combusting in the chamber?

If I didn't have an AFR meter I would not think that there was anything wrong with the car other than the smell of petrol in the exhaust as it still runs pretty well.....except the one time when idling AFR was 12 and engine was lumpy at idle. doesn't seem to have affected acceleration by the seat of the pants and AFR at WOT is spot on

 

The TPS is used to provide accelaration enrichment, so the acutal position is not necessarily important, but rather the rate of change of throttle position is what keys the acceleration enrichment. You don't want to let the engine idle rich too long as it will dilute your oil and that is never a good thing.

 

Cleaned out tube leading to MAP sensor and MAP sensor and AFR was only slightly better at 13.5-13.8.

On the way home ran low on gas and filled up with e10 gasohol, drove around a bit and it returned to normal (for the moment) at 14.5-14.7

Car was tuned for e10 but for long trip only regular non-gasohol benzene was available....but if fuel was the issue then it theoretically only be 5% richer with AFR at say 14 but it was doing 12-13 during the trip.

Anyway here are some screen shots from autronic. Please let me know if you see anything amiss (AFR on screen is not correct as I have no O2 sensor connected to autronic)

 

On my Link system, if I showed the high intake temp you show (56C), I would have about 10% less fuel based in intake temp correction table. My car is tuned for 20C and no correction.

 

My car was tuned at about 33C ambient temp and intake temp was around mid50s during tuning.
What's your usual difference between ambient and intake temp?

 

Gremlins are back. Was OK for awhile and now idles at 13.5 AFR. Engine also suddenly died while driving slow but crank the key and it started with no problem. Did all the checks above and running the correct fuel....so what's next?