AFR too rich after injector swap?

945T w/ 16T @ 12.3psi. Not much of a problem here, I'm just curious if I can improve something.

I changed the injectors only because they were leaking and giving me starting problems. Stock were the 280-150-804 rated @ 32.07lbs, now I have the 280-155-766 rated @ 33.02lbs in there. I just had these around so they went in.

I'm getting 10.0 AFR dead on already at low boost up until WOT and it reads between 13.8 to 14.5 at cruise and idle.
Before it was around 11.0 at mid boost up to WOT and cruise & idle at 14.3 to 15.0 if I remember correctly.

I know these injectors flow a little bit more than the stock ones, but my question is does the AFR read too rich and can I improve something here? Reset the ECU?

Let LH 2.4 learn.

I've been driving 3 or 4 full tanks now.

In looking around the Internet those flow around 350cc/min and should be high impedance injectors. Did you bypass your resistor pack?

With such a minor Injector change in size LH should not care. Did you reset the ECU anyways when you swapped them so it can learn? For that small of a change you should not need to.

The largest issue I see is high impedance vs low imepdance Injectors.


There is a good chance you have other issues such as a major boost or vacuum leak.

thelostartof said:

In looking around the Internet those flow around 350cc/min and should be high impedance injectors. Did you bypass your resistor pack?

With such a minor Injector change in size LH should not care. Did you reset the ECU anyways when you swapped them so it can learn? For that small of a change you should not need to.

The largest issue I see is high impedance vs low imepdance Injectors.


There is a good chance you have other issues such as a major boost or vacuum leak.

Click to expand...

Yes, I made sure to bypass the resistors. I did not touch any boost or vacuum hoses when I swapped them, so I'm not sure this could be an issue since it was fine before.

I guess I'll just reset the ECU and let it learn again as a simple first try.

Many times problems happen at random. I had just fixed one issue on my wagon and the next day I had a bad rich spot under boost. Turned out my IAC hose had a tear in it.

I'm with Mike on this one. That very minor change in injector size won't be an issue for 2.4 to adapt to. You've got something else going on.

I would check grounds right off, since you had to remove them to pull the rail. If they aren't all back on, good, clean, that can cause some issues. Check that the FPR isn't leaking thru the vacuum port and that the fuel pressure is good.

Thanks guys, will inspect hoses, check and clean grounds at the rail and reset the ECU.
FPR is good, I switched it for a known good one some time ago while I was diagnosing my starting issues.
Unfortunately I don't have any equipment to measure fuel pressure, but wouldn't there be contrary issues than what I have if the pressure is not good?

Not necessarily. Low pressure could lead to poor atomization, increased DC, potential for lean misfires which would show on the WB as rich potentially.

Got it, thanks.

Did you bend your fuel rail during removal? If so, you might have a bad seal on the manifold side of the injectors