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Discussion Starter · #1 ·
Hey all, in need of help with my project that i will list now. The car is a 85 sb coupe that i purchased as a complete roller, by complete it came with a 94-95 5.0 and T5. This 85 was a v6/4cly car, the engine harness is from an 86 5.0 along with the o2 harness and a A9P. I have changed it over to maf and used houseofdulas video and did exactly as him. The car left me stranded with what seem to be a bad PIP/ TFI so i purchased a replacement distributor and a TFI relocation kit, along with a BAR sensor to fix code 21. After putting all new parts in i decided to check fuel pressure which i found set at 50 no vacc i dropped it to 40 and set timing, now the car gave me a koer 41,91 code and feels like it has a rev limiter at around 2k rpm that never goes above or past 4k but it idles perfectly fine. I feel like it's one thing after another, not sure where to look since all information i've found on these codes relates to 87-93 o2 sensors. Engine has aluminum heads, tfs1 cam, LT, edelbrock 5.0 intake stock maf and tube most sensors are new including the o2s, where do i begun my trouble shooting?
 

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41 & 91 indicate always lean, no o2 switching. what sensor did you replace for the 21 code? isn't 21 ECT out of range?

so it idles fine, but runs rough under load. have you checked for vacuum leaks?


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The code says its running lean. My bet is it has a chip with a tune for 50psi as the base fuel pressure, by changing the pressure its now running lean. Check if you have a chip on the J3 port in the ecu. If you do, set the fuel back to 50 psi.
 

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Discussion Starter · #4 ·
41 & 91 indicate always lean, no o2 switching. what sensor did you replace for the 21 code? isn't 21 ECT out of range?

so it idles fine, but runs rough under load. have you checked for vacuum leaks?


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Replaced the BAR/MAP sensor for code 21, which is now gone. Have yet to smoke test for leaks.
 

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Discussion Starter · #5 ·
The code says its running lean. My bet is it has a chip with a tune for 50psi as the base fuel pressure, by changing the pressure its now running lean. Check if you have a chip on the J3 port in the ecu. If you do, set the fuel back to 50 psi.
No chip I purchased and installed the a9p.
 

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Here is a possibility. If the long term fuel trims were say -25% to combat extra pressure and then you changed pressure, its possible they are keeping it so lean the oxygen sensors cant switch. It takes a while for the trims to move. Try resetting the computer by unplugging the battery negative for 15 minutes. You can also hold the brake pedal after disconnecting the battery for 1 minute to clear all the caps instead of waiting 15 minutes
 

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I had a bad miss/limiter like issue on my 86 at 3000 RPM. Unfortunately, I'd used low impedance injectors thinking they were high impedance. The A9P needs high impedance injectors.
 

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Discussion Starter · #10 ·
I had a bad miss/limiter like issue on my 86 at 3000 RPM. Unfortunately, I'd used low impedance injectors thinking they were high impedance. The A9P needs high impedance injectors.
I’m running the explorer #19 stock injectors. If it was an injector issue it would have a miss at all times would it not?
 

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Wonder what sensor he changed then?
That's a good question. OP, can you post a picture or provide a link to the sensor you replaced?
 

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Indy? Where are you Indy? ;)
 

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Discussion Starter · #15 ·
One thing I’m thinking could be the cause of my issues is the throttle body gasket I’m using an explorer gasket on a 70mm throttle body because I didn’t want to wait on shipping.. any thoughts?
 

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Did you reset the computer? And yes, a vacuum leak can cause it to run lean. You really need to reset the computer.
 

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Discussion Starter · #17 ·
Did you reset the computer? And yes, a vacuum leak can cause it to run lean. You really need to reset the computer.
It’s now reset waiting for it to get up to temp and see if it changed also plugged the tank vent hose back to the canister since it melted on the first drive and was left open unplugged
 

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Discussion Starter · #18 ·
Ok so it sounds like it’s backfiring through the intake tube unplugged the iac and it’s working properly unplugged the maf and the issues went away. Plugged the maf back in and the rev limiter symptoms came back... So is this a maf issue or a sure vacuum leak?
 

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Discussion Starter · #19 ·
The maf I bought used i pulled it out and it was really dirty gave the maf and housing a cleaning and it seems the lower stumble is gone. I drive it around the block and at 3/4 it’s still cutting out so I’ll drive it some more and pull codes see what I get... But this might be fixed!
 
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