Having trouble passing Emissions New O2 sensor. changed MAP scan tool reads proper temp 190 and above

A feeling that maybe 1 of the injectors were bad .. So I tested the spray pattern with an (adjustable) timing light .. One injector sprayed nice ( injector A) they other (injector B) I could not find the spray pattern... So I changed injectors( both A& B ) still the same issue no spray pattern on one injector (b).. I thought maybe i would switch the injector feed leads. Guess what the injector that I could not see the pattern on ( B) Now has a pattern. But injector (a) cannot find pattern .. Is the injector driver in the ecm going bad.

Or is this typical can someone verify for me on a running vehicle

Thanks Scott

 

Try timing light on #6 cylinder. I believe the injectors fire 180 degrees apart. I doubt the timing light has that much adjustability to it.

 

just in case, try PaulD's suggestion first.


but when i did that with my timing light, i saw both..

before i call the ECM dead, id check the wires to be sure they didnt melt/rub/break somewhere.

 

I will check #6 to see if they fire 180^ apart . Thanks for your input I will also check the wiring.


Thanks Guys

 

They do fire asynchronously (180 degrees apart) under most conditions. There's adjustments for it in the chip.

 

Yup 1 injector fires off cylinder one and the other spray pattern can be found off cylinder #4 Thanks GUYS for your help. the spray patterns look good.

 

Hmmm... I always thought that they are fired both simultaniously twice per revolution (in syncronous fueling) to keep the tbi/manifold supplied with gas. Async I think they fire together as well but in fixed intervals, like 80 Hz or something, out of sync with the engine revolution. I dont recall them being fired 180 degrees out of phase. From the schematics it looks like there is only one output that drives the injector driver circuitry but Im not an ecm expert so I could be wrong.

 

Ok, got off my *** and found it. Each injector alternates firings and in async they fire together at 80 Hz. The injector firings in sync are controlled by the dist. reference pulses so theyre not necesarily coupled to a specific cyl or cyls.

 

could someone put That in "Stupid terms"

 

The asyncronous, or not in syncrony with the engine, is when the pulse widths, which is the time the injector is supposed to be open, gets too short. This can happen with injectors that are too large for an engine. The injectors basically can only spray out so little fuel before they dont open anymore. The ecm goes into async so it can get, or try to get, the gasoline to air ratios to what theyre supposed to be so the engine doesnt run rich. The ecm basically switches in and out of these modes as needed. Like, when the pulse widths get too short, the ecm will go into async and come back to sync. when the pulse widths get long enough. There are some threads that discuss the fueling strategy of the tbi computers. Its been awhile since ive seen them (does it show? ) but the threads describe it quite nicely. Do some searches and they should turn up.

 

simple terms would be:

you have a super soaker squirt gun.

when you're at high RPM you can tap the trigger and give the right size squirt.

but when the RPM is low, you only need a little fuel. if you tried to pull the trigger that fast to get only a tiny bit, nothing would come out.

so you wait until it needs more fuel, then you pull the trigger for a lil longer to make up for the wait.





get it?