OK, been on this forum for a while, but usually just to lurk and never in this section until I picked up a friend and fellow member's 88 F150 this past weekend. It is an 88 F150 4x4 with a C6, 3.55 gears, Long tubes, 3" single exhaust, MAF swap and elec fan. Heres the deal...

I was told the computer used in the swap came from a Fox Cobra. The meter that was on the truck went to a 4.6 Crown Vic and it ran like crap when you first fired it up cold and when you tried to idle for a while with the AC on. I dug thru my parts bins and found another meter layin around and threw it on there and she fires right up and runs like a champ. Only problem is, I looked up the part number and its to a non supercharged V6 t-bird Buddy of mine let me borrow a stock Fox MAF and an SN95housing with Fox sensor and the truck runs like crap with both. Switch back to the V6 meter and it runs nice. Ive read that the meters in the SN95 5.0/3.8 and Cobra mustangs were all the same and interchangable so if that also goes for the T-birds then that might make sense. Ive also read that the Cobra computers were programmed for 24lb injectors and im usin 19lbers. Can anyone help me verify whats actually up? She's gettin horrible gas mileage and Im tryin to sort this issue out so I can move on and get to work trackin down the little issues. Otherwise its an incredible truck and i couldnt ask for more! Ive never been so pleased with a vehicle, if I can get it to run right and get a little better MPG ide be in heaven!
Matt

 

What I have read agrees with what you have heard too, that the Fox Cobra used 24 lb/hr injectors, but the MAF meter used the same calibration as the Fox GT. I'm not sure if you can compensate for the smaller injectors by fooling the computer with a MAF tune or if you'll have to chip the computer to properly account for the smaller injector size.

 

you should be able to use a mirror to look at the sticker on the PCM to see what catch code it is. that will tell you what the PCM actually went to.. If the PCM is in the slot the correct direction then the sticker will be on the grey part of the PCM that the wiring connects to under the hood and should face the fender. you can use a mirror to look at it. Not too sure what the deal is with the MAF meter, but something must me mismatched for it to be doing that.

 

There were 19lb and 24lb "Cobra" motors and it sounds like you may have the 24lb version, if so the easy way to fix your issue would be to install 24lb injectors.. or just use the V6 meter is it's providing satisfactory results.

 

I swapped the 93 Cobra computer out for the A9L out of my 90 coupe and put in a 70mm MAF with the Fox sensor and she's alive and runnin better than ever!!! Ill put the cobra computer in the Fox and have it tuned for the 393 im building for it so all is well! Only ill side-effect so far is the check engine light came on after about 5 minutes of driving. If I shut the truck off itll stay off until another 5 minutes or so of driving lol. I pulled codes and got the normal EGR codes (smog crap removed) and code 41. The PO gave me a new O2 sensor so Im gonna try that as everything else seems to be in place. I put 60 miles on it last night and the gas gauge barely moved compared to before so Im hopin I got this mileage thing licked.
Matt

 

Back from the dead, still driving the truck and still tinkering along the way. STILL has the damned CEL comin on after about 10 minutes of driving. It seems to come on when I lift off the trottle entirely, if I run on the interstate, it could be an hour or two before I lift for traffic or to get off and get gas and itll pop up. Code 41 is the culprit. Heres what Ive done since the last post.

New copper plugs
New wires
Cap
Rotor
MSD coil
Timing has been set anywhere from 14* down to 9* and is currently at about 12 or so.
New fuel filter
New O2 sensor
Went thru a couple IACs and finally got one to idle consistently
New Longtubes that dont leak, O2 sensor located on collector
New 19lb injectors with the 4 hole pintles
Adj FPR, moving it up or down does nothin to change codes

Im averaging 13-14 mpg lately which appears to be about right but I wonder if I got rid of the danged CEL if I couldnt see 15. Im open to any other suggestions on where to look from here.
Matt

 

Cobra computers are not worth messing with unless you do some custom stuff with it. The A9L is the performance computer of choice. And you may already know this, but to clarify a SN95 is not a 95 mustang.

What is a code 41?

 

I got all that covered man, thanks. Cobra computer has been sold and and A9P is in its place as we speak. I have an A9L loaned to a buddy at the moment as well. You are correct about the SN95, but Im not entirely sure who you are talkin to. SN95 is the name for all 94-04 Mustangs...Im a mustang nut. Code 41 is a lean code. Ive done all I can to get the exhuast leak free but I swear I can still hear somethin when I accellerate under load. If I free rev the motor I can hear anything at all so Im not entirely sure whats going on. Im tired of it, she drives just fine with only a few small oddities but I hate seein the CEL every time I drive lol
Matt

 

Have you considered hooking it up to a wideband o2 and actually check your afr? If you are using a meter where the maf transfer function does not match the eec programming, that could definitely trip a lean code. Personally I would find a good reputable tuner to work with and get that afr checked...unless you are willing to learn the benefits of tuning and invest in the necessary equipment to so.

 

The MAF sensor itself is from my 90 Mustang 5.0, as is the A9L computer. There should be no issues between the two, nor with the A9P. I put the sensor in an SN95 housing which then bolted up to a 95 or so F150 I6 airbox. I run megasquirt in the 90 now and used an SCT chip before that so I know a bit about tuning, but Im learnin as I go. I could rob the LM1 off my 66, but the sensor is actin up again dangit. I ran my HCI 5.0 in my LX with no chip, stock 19lb injectors and a stock fuel pump with no issues so I dont think longtubes, a drop in K&N and an elec. fan should be too much for the same ECU...but Ive seen wierder things happen lol. Im gonna tie up all my grounds and see what happens, make sure nothin is frayed or not connected quite right.
Matt

 

I would still check afr's. Is it possible you have a bad injector or air leak down stream of the maf?

 

Been thru 3 sets of injectors, same issue every time, no changes to how it acts, drives or when the CEL shows up. The last set of injectors are new so Im hoping I ruled that outta the equation. Ive gone thru this sucker with a fine toothed comb, some thottle body cleaner and even a propane torch to try and find any vac leaks with NO results. I still have the SCT chip and could go get it dyno tuned...but if Im gonna spend any time and money on a dyno theres two more cars ahead of the truck that deserve the time more unfortunately. If I can ever get the danged LM1 to work I might check the afrs tho.
Matt

 

Checked all the grounds, even went as far as to run some redundant ground wires over near the ECU just to make sure they were gettin a good ground and the CEL is still around. Im hopin a buddy of mine has another sensor for the wideband then Ill check out whats goin on A/F wise.
Matt

 

Have you tried fatting it up a little, reducing the timing and increasing the fuel pressure. Pull the vacuum line off the FPR.

 

Increasing fp will only help in open loop....adaptives kick in during closed loop is adapting to the primary input from the o2.