LM7 Mustang Swap running too Lean
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Joined: Feb 2019
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LM7 Mustang Swap running too Lean I’m in the final stages of completing a LM7 swap into a 94 Mustang with a club at my college and we are running into an issue with the engine.
For some reason it’s running really really lean. Our wideband says it hovering in the low 20s for a/f ratio. It idles ok, but any throttle will cause it to surge and almost die.
Here’s what we know:
- Fuel pressure is a constant 58psi
- O2 sensors are plugged in and both new
- Tried 2 mafs and both seem to work
- Tested everywhere for vacuum leaks with ether, didn’t find any
- Engine is well grounded and voltage is good
- No codes when scanned or check engine light
The engine and computer are stock out of a 2000 silverado. The computer was flashed to run standalone but nothing on the fuel maps was changed.
We don’t know where to look next. Any ideas?
For some reason it’s running really really lean. Our wideband says it hovering in the low 20s for a/f ratio. It idles ok, but any throttle will cause it to surge and almost die.
Here’s what we know:
- Fuel pressure is a constant 58psi
- O2 sensors are plugged in and both new
- Tried 2 mafs and both seem to work
- Tested everywhere for vacuum leaks with ether, didn’t find any
- Engine is well grounded and voltage is good
- No codes when scanned or check engine light
The engine and computer are stock out of a 2000 silverado. The computer was flashed to run standalone but nothing on the fuel maps was changed.
We don’t know where to look next. Any ideas?
Last edited by Erik O; Feb 2, 2019 at 10:06 AM.
Teching In
Joined: Feb 2019
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Check injectors.. maybe one or multiple arent firing. Ether huh? super not safe.
also is it at operating temp when testing throttle input? O2 signals change i.e. open and closed loop for fuel tables dependent on engine temp. unplug the O2's and see if an engine code comes up.
also is it at operating temp when testing throttle input? O2 signals change i.e. open and closed loop for fuel tables dependent on engine temp. unplug the O2's and see if an engine code comes up.
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Thanks for the responses.
We have tried running it with the O2 sensors unplugged and that didn't change anything, but I didn't check whether or not that made it throw a code. It runs the same no matter whether warmed up or not.
The O2 and wideband sensors are near the end of the longtubes we are running open right now. We didn't think that was the issue, since we tried running with O2s unplugged and no change, but looks like we will mock up an exhaust this weekend and see if that changes anything.
I'm really leaning towards injectors after pondering this for a while. We did have an issue where the regulator was producing extremely high fuel pressure for a while, but that was fixed. Maybe this damaged the injectors or loosened some dirt to plug them? I'll have to grab some new ones to try out.
We have tried running it with the O2 sensors unplugged and that didn't change anything, but I didn't check whether or not that made it throw a code. It runs the same no matter whether warmed up or not.
The O2 and wideband sensors are near the end of the longtubes we are running open right now. We didn't think that was the issue, since we tried running with O2s unplugged and no change, but looks like we will mock up an exhaust this weekend and see if that changes anything.
I'm really leaning towards injectors after pondering this for a while. We did have an issue where the regulator was producing extremely high fuel pressure for a while, but that was fixed. Maybe this damaged the injectors or loosened some dirt to plug them? I'll have to grab some new ones to try out.
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Joined: Oct 2011
Posts: 408
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putt 18 inch extensions on your headers , or header mufflers , open headers sometimes effect af ratio , although usealy you run into a too rich issue , I agree with checking all injectors , they dont like sitting around , i have test an lq4 in the past that all 8 were bad
