Fuel Running lean but no o2 sensor codes?

Creomod

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Sep 14, 2018
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Ok Ive been having this issue for a while it started when Im assumming when I installed a set of gt 40 ported heads I also installed the afr gauge x series and thats when I notied spark plugs white afr in 20s.Cant figure It out.Going crazy I am getting code 85,67,11 no check engine light,A9L Good just had it redone,timming 14tdc,New pcv valve,bbk longtube headers tfs upper lower,New map sensor,I have new fuel pressure regulator new distrbutor.Changed some of the vaccum lines lines appear to be good not brittle(havent done smoke test yet).I installed a 190 walbro didnt change afr number.I DO HAVE A FUEL TANK LEAK AT THE GROUMET AT FILL TUBE,could this cause afr to be lean?Also where afr gauge bung was welded isnt perfectrly welded in you know what I mean.I also have the fuel tank vent line just hanging tucked in with fuel lines no charcol canister.I also have the egr connected not hooked up with the vaccum line,.The egr is capped off I just haver it connected so Ia dont get a code.I also checked the oxygen senor harness all wires seem to be good I just checked for contuntiy not voltage.The maf sensor I bought from someone on ebay so I havent checked it . The car ides good sounds good stays idel at 1k maybe slight surge.I also checked headers(bbk longtube) 3 or 4 were not tight meaning i had to turn them few times so just cuz I tighten them does that mean I could be leaking air there?I did the block months ago go if I didnt tighten intally when the glue was fresh will tighten them help make a differnce.They were hardly loose but THEY WERENT TIGHT SO MAYBE?I dont think it be the lower intake at the valley I used all thread rods to lower it into place.
So I guess here are my questions.

Can A (1) Clogged Fuel Injector cause my afr to be lean?
Can A not welded correctly afr sensor bung cause afr to be lean?Its not that bad but I see holes and just assume.
Can A leaky fuel tank groumet cause afr to be lean?Its niot pouring out but I know your supposed to have fuel at pressue.
Could It be the Header Gasket?Maybe installed backwords.Anyone know that symtom?I dont think I did that but ?
Could It be the fuel tank vent hose?I was running it this way with e7 heads with no issue.
Could WOT Relay cause this?Mine is full of dry dirt.I can hear it when I shake it around.

I dont have the purge canister solonid Connected?Just pugging it in w/o thw cansiter help remove the code?Any way to bipass the code85 purge canister?Will not connceting the canister to the purge solniod remove the code?Will removing the code change my afr or do I have run the line?Asking cuz I dint want to run smog stuff but could it be that I need to beacuse thats the only way to change the fuel stratgey?

What causes Car to run lean but no o2 sensor codes?New sensors.3 wire :(
 
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7991LXnSHO

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A clogged injector will show up on a cylinder balance test.

A poorly welded bung can throw off the sensor readings. So can leaking exhaust gaskets. Fix this then carefully go through the surging idle checklist. It is a checkup on the systems, even if it is idling ok.

The leaking fill tube grommet is a safety issue, but the pump does not work by pressurizing the tank. Fix it anyway.

The charcoal canister is your friend. Please reconsider hiding it in the fender and running the purge valve if you want it out of sight.

Why not run the smog stuff? Is it a track only car? The smog stuff shuts off at full throttle, and does not weigh that much. Not having it there on the street causes the computer to spit out codes and makes the exhaust smell.
 
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Creomod

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A clogged injector will show up on a cylinder balance test.

A poorly welded bung can throw off the sensor readings. So can leaking exhaust gaskets. Fix this then carefully go through the surging idle checklist. It is a checkup on the systems, even if it is idling ok.

The leaking fill tube grommet is a safety issue, but the pump does not work by pressurizing the tank. Fix it anyway.

The charcoal canister is your friend. Please reconsider hiding it in the fender and running the purge valve if you want it out of sight.

Why not run the smog stuff? Is it a track only car? The smog stuff shuts off at full throttle, and does not weigh that much. Not having it there on the street causes the computer to spit out codes and makes the exhaust smell.
Thanks for the reply brother,back to injector thing can 1 clogged cause a lean?So would adding back charol canister Fix the lean issue?Reason I aski s cuz I read that running it will richen fuel mixture and thats what I want but Is it the issueNot a track car just my daily.Dirty wot relay with dirt not problem possible cause?
 

7991LXnSHO

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I think the WOT relay is for the AC compressor, so if we are talking about the same part, no.
A clogged injector can cause a lean reading, but until your gauge is not getting external air for sure, the cylinder balance test is the best way to rule it out.
The canister will riches the mix dome, but will mostly safely vent the tank’s fumes and burn them instead of stinking up the garage.
So, get the exhaust leaks fixed first to see if it is really running lean and the wide band is reading right.
 
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McFly2

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Ok Ive been having this issue for a while it started when Im assumming when I installed a set of gt 40 ported heads I also installed the afr gauge x series and thats when I notied spark plugs white afr in 20s.Cant figure It out.Going crazy I am getting code 85,67,11 no check engine light,A9L Good just had it redone,timming 14tdc,New pcv valve,bbk longtube headers tfs upper lower,New map sensor,I have new fuel pressure regulator new distrbutor.Changed some of the vaccum lines lines appear to be good not brittle(havent done smoke test yet).I installed a 190 walbro didnt change afr number.I DO HAVE A FUEL TANK LEAK AT THE GROUMET AT FILL TUBE,could this cause afr to be lean?Also where afr gauge bung was welded isnt perfectrly welded in you know what I mean.I also have the fuel tank vent line just hanging tucked in with fuel lines no charcol canister.I also have the egr connected not hooked up with the vaccum line,.The egr is capped off I just haver it connected so Ia dont get a code.I also checked the oxygen senor harness all wires seem to be good I just checked for contuntiy not voltage.The maf sensor I bought from someone on ebay so I havent checked it . The car ides good sounds good stays idel at 1k maybe slight surge.I also checked headers(bbk longtube) 3 or 4 were not tight meaning i had to turn them few times so just cuz I tighten them does that mean I could be leaking air there?I did the block months ago go if I didnt tighten intally when the glue was fresh will tighten them help make a differnce.They were hardly loose but THEY WERENT TIGHT SO MAYBE?I dont think it be the lower intake at the valley I used all thread rods to lower it into place.
So I guess here are my questions.

Can A (1) Clogged Fuel Injector cause my afr to be lean?
Can A not welded correctly afr sensor bung cause afr to be lean?Its not that bad but I see holes and just assume.
Can A leaky fuel tank groumet cause afr to be lean?Its niot pouring out but I know your supposed to have fuel at pressue.
Could It be the Header Gasket?Maybe installed backwords.Anyone know that symtom?I dont think I did that but ?
Could It be the fuel tank vent hose?I was running it this way with e7 heads with no issue.
Could WOT Relay cause this?Mine is full of dry dirt.I can hear it when I shake it around.

I dont have the purge canister solonid Connected?Just pugging it in w/o thw cansiter help remove the code?Any way to bipass the code85 purge canister?Will not connceting the canister to the purge solniod remove the code?Will removing the code change my afr or do I have run the line?Asking cuz I dint want to run smog stuff but could it be that I need to beacuse thats the only way to change the fuel stratgey?

What causes Car to run lean but no o2 sensor codes?New sensors.3 wire :(
o2 sensors detect air/fuel/ratios; so I'm thinking that o2 will detect lean condition and not send bad o2 sensor codes because the o2 sensors are working. I understand OBD2 systems- not the pre OBD2 system so take that into consideration.
It seems that if you have a clogged or defective injector; you would be getting a misfire (and running with less power). Not written in stone. Just another clue to consider.
Like 7991LXnSHO implied' any air leaks at long tubes connections will cause lean condition (because that would change the air/fuel ratio.) That AFR change will be detected at o2 sensors.
The effect would be the same as vacuum leak (lean condition for all cylinders on that bank.)
Smoke test to completely eliminate that possibility (vacuum leak).
Then tighten long tube bolts more if possible.
You might be able to take temperature reading with hand held infrared temp gauge to help detect exhaust leak at engine to long tube connection.

Amazon productView: https://www.amazon.com/Thermometer-Temperature-58-716%C2%B0F-Backlight-ANNMETER/dp/B08B85T21Q/ref=asc_df_B08B85T21Q/?tag=hyprod-20&linkCode=df0&hvadid=476087217314&hvpos=&hvnetw=g&hvrand=2045791292172295205&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1023818&hvtargid=pla-1216542749244&psc=1


Header gasket sides are the same. You can call tech support for mustangs parts support from where you bought gaskets to make sure.
The basic idea I'm conveying is: vacuum leaks, and exhaust leaks will cause lean condition.

 
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McFly2

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Hey brother man, I do realize you know way more about this subject (modified engine) then I.
When I re read your post "I noticed spark plugs white, afr in 20s." I'm wondering; are plugs running lean on bank 1 and 2? That would be a noteworthy clue.
2. AFR in 20s. Is that at idle and at 2500rpm? 20% af ratio at idle might be normal for your engine as it is for 2001 Bullitt (because of larger air intake) or ported heads on GT.
Either way 2500 rpm AFR data - might be a more decisive troubleshooting reading. If afr does not drop (from 20% down to less then 10%) at higher rpm you have a greater probability of vac or exhaust leak.

Header bolts are going to expand and shrink no matter what. They might loosen; unless you got the bolt lock type retainers.
 
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7991LXnSHO

wanna catch the space herp
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Hey brother man, I do realize you know way more about this subject (modified engine) then I.
When I re read your post "I noticed spark plugs white, afr in 20s." I'm wondering; are plugs running lean on bank 1 and 2? That would be a noteworthy clue.
2. AFR in 20s. Is that at idle and at 2500rpm? 20% af ratio at idle might be normal for your engine as it is for 2001 Bullitt (because of larger air intake) or ported heads on GT.
Either way 2500 rpm AFR data - might be a more decisive troubleshooting reading. If afr drops (from 20%) at higher rpm you have a greater probability of vac or exhaust leak.

Header bolts are going to expand and shrink no matter what. They might loosen; unless you got the bolt lock type retainers.
Some good thoughts, but I’m not sure you have the right 5.0 in mind. I figure since it is under Fox 5.0 tech, and the bad welding mention for the wide band, that it is a 302/5.0 88-93, (or 87 up with a MAF conversion), the wide band is add on, and the A9L means a stock or chipped stock computer and a manual transmission.
@Creomod how close is your car to the one I am picturing? (Hatch or coupe and color are just wild guesses.)
 

Creomod

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Sep 14, 2018
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Hey brother man, I do realize you know way more about this subject (modified engine) then I.
When I re read your post "I noticed spark plugs white, afr in 20s." I'm wondering; are plugs running lean on bank 1 and 2? That would be a noteworthy clue.
2. AFR in 20s. Is that at idle and at 2500rpm? 20% af ratio at idle might be normal for your engine as it is for 2001 Bullitt (because of larger air intake) or ported heads on GT.
Either way 2500 rpm AFR data - might be a more decisive troubleshooting reading. If afr drops (from 20%) at higher rpm you have a greater probability of vac or exhaust leak.

Header bolts are going to expand and shrink no matter what. They might loosen; unless you got the bolt lock type retainers.
Hey brother man, I do realize you know way more about this subject (modified engine) then I.
When I re read your post "I noticed spark plugs white, afr in 20s." I'm wondering; are plugs running lean on bank 1 and 2? That would be a noteworthy clue.
2. AFR in 20s. Is that at idle and at 2500rpm? 20% af ratio at idle might be normal for your engine as it is for 2001 Bullitt (because of larger air intake) or ported heads on GT.
Either way 2500 rpm AFR data - might be a more decisive troubleshooting reading. If afr drops (from 20%) at higher rpm you have a greater probability of vac or exhaust leak.

Header bolts are going to expand and shrink no matter what. They might loosen; unless you got the bolt lock type retainers.
Sorry late response Bought Another 5.0 a gt.But as for the 20s afr thats at idel just parked.As for the bolts I I tighten the hell out of them.It started when I installed these heads gt40 3 bar.As for when Im driving I just notice afr all over the place from 14s to 20s
 

McFly2

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Nov 21, 2020
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I edited my previous post; but edit just confused matter. I will try to clarify the confusion on my part; you can double check me on other blogs concerning fuel trims.
If afr does not drop (from 20% down to less then a steady 10%) at higher rpms you probably have a vac or exhaust leak. That is my previous experience when I had the same (afr) issue. Smoke test eliminated vacuum leaks. I ended up having an exhaust leak (at manifold exhaust) at x-pipe connection. Shoulder bolts would not allow fully tightend connection on bank 2. I could feel the air leaking by putting my hand up to manifold / x-pipe connection. What a relief it was to solve the lean problem. Replaced those bolts with threaded type to bolt head and magic happened. I hope Im not adding insult to the craziness. Sounds like you got a lot going on.
 
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Creomod

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I edited my previous post; but edit just confused matter. I will try to clarify the confusion on my part; you can double check me on other blogs concerning fuel trims.
If afr does not drop (from 20% down to less then a steady 10%) at higher rpms you probably have a vac or exhaust leak. That is my previous experience when I had the same (afr) issue. Smoke test eliminated vacuum leaks. I ended up having an exhaust leak (at manifold exhaust) at x-pipe connection. Shoulder bolts would not allow fully tightend connection on bank 2. I could feel the air leaking by putting my hand up to manifold / x-pipe connection. What a relief it was to solve the lean problem. Replaced those bolts with threaded type to bolt head and magic happened. I hope Im not adding insult to the craziness. Sounds like you got a lot going on.
Thats crazy,Yea Its something weird.I will check on that I apprecite the response.
 

Bree

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Besides, a cloged injector would only burn the plug that corasponds to the clogged injector. I wonder if you got an intake leak someplace letting to much air in. I'd take a can of starting fluid/eather and sqirt it around the top end. If the RPM's pick up you found your leak.
 
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manicmechanic007

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WOT relay shuts off the compressor at wide open throttle. All the above posts are mostly correct. Any unmetered air the processor sees results in a richer mixture. Do Brees test. Also do a fuel volume test. No spec unless you go back to 85 ranger with 2.3 has an additional in line filter between the FG800 and the rail. Spec was approx 16 ounce pop bottle full of fuel in about 8 seconds. When I worked at the dealer the lean issues that we saw that never set codes were fuel pump failure one way valve etc related. Not gaskets injectors processor drivers ignition modules or any other electronics. Up the fuel pressure a bit by pulling the vacuum line off from the regulator. Run it with a fuel injector cleaner apparatus at say 50 lbs and retest