Foxbody A/F issues...

89-LX

89-LX

Forum Member
I have a 93 Mustang with an 89 setup (all powertrain, electrical, etc) with the following work done:

  • 24# injctors with calibrated MAF
  • Trickflow street heat intake
  • Trickflow stage 1 cam
  • AFR165 heads
  • Shorty headers

At idle, it's running "burn your eyes out" lean, and the wideband confirms it by being pegged at 16.0. Cruising around town, I am getting anywhere between 14.5 and 15 AFR. At WOT, it's between 13.5 and 14. The car runs strong, and doesn't feel like it's missing at all to me. I believe the timing is set around 14*. When I ran the codes, I'm getting code 91. Now both o2 sensors are brand new, and I'll be honest, I haven't been able to check the wiring out yet. I was just wondering what to look for or where to go. The car is untuned, but I know someone with a blower, cam, heads, etc without a tune that's not running rich. I'll be able to get codes better tomorrow along with tracing some wires, but just looking for input on where to go.
 
Your either lucky or not one of my blower setups ran fine without a tune and another one didnt both builds were similar u should just have it tuned
 
90SuperchargedLx said:
Your either lucky or not one of my blower setups ran fine without a tune and another one didnt both builds were similar u should just have it tuned
Click to expand...

I'm just thinking these numbers and running dead lean should be fixed before tuning. I'm N/A btw.
 
you say burn your eyes out lean? you mean rich? 16.0 is very rich.

1.check your tps sensor voltage....maybe the computer is thinking your partially on the throttle so its turning the injectors up?

2. you may have a stuck open injector or two (happend to me before and had the same problem...3 were stuck open) if your bought used, this is a huge possibility.

3. your MAF isent calibrated or its broke..this could cause the air reading to be off and open your injectors more.
 
CTS might be bad or a damaged wire telling the computer it's running ice cold. Computer adds fuel. Check the CTS and it's wiring.
 
The higher the number, the leaner it's running. It's not a rich issue, it's lean. No smoke either.
 
The 16 at idle is to be expected. With any overlap in your cam you will get a false lean at idle as it is allowing unburnt oxygen through.

Have you cleared the KAMS? Unhook the battery for a while. If it was running rich, or the old o2's were reporting lean due to being lazy and not crossing the switch point enough then the adaptive would have been pulling fuel in an attempt to richen it up. The eec would still be trying to deliver fuel under the assumption that the adaptives table it is looking at was populated under current conditions.

So in short, pull the battery cable to reset the KAMS and give it another shot. It really should be richened up at WOT btw.
 
190 or 255 fuel pump, can't remember which one I put in when I threw the N2O on the engine a long time back.

I have the following codes:
KOEO:
31 - EGR Valve Position/Pressure Feedback EGR Circuit Below Minimum Voltage. 0.24 volts (O,CM,R)
81 - Secondary Air Diverter Circuit Failure (O)
82 - Secondary Air Bypass Circuit Failure (O)
84 - EGR Vacuum Regulator (EVR) Control Circuit Failure (O)

Go figure.....my EGR and smog is deleted.

KOER:
12 - RPM Not Within Self Test Lower Limit (R), DC Motor Did Not Move (O,CM,R), Idle Speed Control motor or Air Bypass not controlling idle properly -generally idle too low
31 - EGR Valve Position/Pressure Feedback EGR Circuit Below Minimum Voltage. 0.24 volts (O,CM,R)
91 - o2 Sensor Circuit Indicates Lean -driver side(R), No o2 Sensor Switching Detected. always lean -driver side(CM), Shift Solenoid 1 Circuit Failure (O)

Fuel pressure is set at 36 with vacuum on, 40 with vacuum disconnected.
Timing was set a little high at 16*, but I backed it down to 12*-14*.

A cylinder balance test gave me code 60, for cylinder 6 failing the test. I'm gonna let the engine cool down some and redo the CBT because my fan came on a few times while it was running and made the RPM's drop really quick for the initial draw.

I also changed the parameters for my gauge, and set the high point to read up to 20. At idle, it's still reading pegged at 20+, but it will bounce down to 18.5 really quick and then back up to 20+.



This is my cam specs BTW -
Duration @ .050" (degrees) - 221 intake/225 exhaust
Cam Lift (intake/exhaust) - .312"/.319"
Lift w/ 1.6 rocker (intake/exhaust) - .499"/.510"
Lobe seperation (degrees) - 112°


Just did another update with the balance test, code 90, so all pass.
 
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Another update. Ran a compression test on cylinders 5-6-7, and all 3 were at about 150-160 PSI with a cool engine. We were able to bring the AFR down, along with getting rid of code 91, drivers side lean, by upping the pressure at the regulator from 40 with the vacuum off up to 44-45. This brought the idle, cruising, and WOT AFR down.

I would also like to get some input on the spark plugs from cylinders 5-6-7-8. here is a few pics:



 
Look like plugs that came out of a lean engine.. Lean=Hot, cylinder #7's ground strap got hot as hell.. Check you fuel pressure gauge against a different one and make sure it's reading right.. Chased my tail for a bit with my old car because of a pressure gauge reading higher than what it was.. Keep in mind that the higher pressure could be masking another problem and will only work until the adaptive strategy starts correcting..
 
94 Drop said:
Look like plugs that came out of a lean engine.. Lean=Hot, cylinder #7's ground strap got hot as hell.. Check you fuel pressure gauge against a different one and make sure it's reading right.. Chased my tail for a bit with my old car because of a pressure gauge reading higher than what it was.. Keep in mind that the higher pressure could be masking another problem and will only work until the adaptive strategy starts correcting..
Click to expand...

What other problems do you think it could be that I could look into?

It's my understanding that with the setup before, if it was running lean, the system should have tried to richen it up, but it wasn't.
 
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Can you live time the o'2's? This will tell you a lot, if the O2 Voltage is sticking in the high range without the usually high low switching then there is something else going on and the processor is trying to real it back into to the set base values.. Once it goes in to closed loop the processor starts looking for base lambda for load vs. RPM with ECT and IAT dictating the table for target Lam.. If the conditions fall too far out of range then it will send it into a limp mode (processor knows something is wrong and gives up on trying to correct for it)
So long story short without being able to actually see what the processor sees than you just guessing.. Your fuel pressure increase wasn't a bunch so that's why I said check the gauge against another one, it really could be that simple.
 
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