Engine 93 Cobra, Dreaded 94/44, Terrible Fuel economy, Runs great! (FIXED)

[someone82]

Update, new solinoids in, no change. Still 94/44 code

 

[General karthief]

Did you reset the computer?

 

[someone82]

Did you reset the computer?

I thought soft codes produced during koer werent stored in memory? I have no hard codes. Passes koeo

 

[someone82]

Reset the computer for s and giggles and I have no change, still getting the same code (94/44) during koer and fuel economy sucks (11-13 mpg, and driving it like a grandma) any other idea where to look?

 

[General karthief]

Did you verify the pump is pumping air?
curious, what is your timing set at?

 

[someone82]

Did you verify the pump is pumping air?
curious, what is your timing set at?

Pump is new and pumps air. Timing is at 12*, fuel pressure is at 39 psi.

 

[Talon Tranter]

Short story, been restoring my father's 93 Cobra, top end, front end, exhaust all freshened up. It's running great and feels better then when it left the showroom floor but my fuel economy sucks (11 mpg). She is basically stock on the motor besides an adjustable fuel pressure regulator (set at 39), 165 pump, and a pro-m maf (factory bit the bullet).

So I am getting 94/44 KOER test (passes key off test), air pump is new, solenoids check out OK (ground out OK and operate), wiring is correct, vacuum lines are correct, diverter is new (old one collapsed), check valve ok, cross over pipe is clear, and are the heads.

When engine is cold air is diverted to the heads, once some temp is built air is diverted to the cats. Now here is the problem, when the engine is revved and comes down on decel, air is diverted to the heads, not bypassed as stated in Jrichker's posts. I am stumped the bypass is responsive to vacuum, and what I'm stating sounds like the solenoids are reversed, but they are not as the diverter is acting properly when cold and warm at idle.

Any advise before I bite the bullet and take it to the stealership?

Thanks, Matt

I mean, it is the Cobra, and they aren't really known for their fuel economy, but no mustang should be that bad . You may be using poor quality fuel. Try draining the tank and putting some high quality go juice in there. it should at least help. if that doesnt do anything, try a fuel additive, they are pretty inexpensive,and work great from what i hear.

 

[Mustang5L5]

Two suggestions..unfortunately not easy to do. But I would verify that upon cold startup you have air at the tube to the heads, and that it switches to the tube going to the cats once warmed up.

Remove the hose going to the tube to the back of the heads. The silver thing mounted on the tube is a check valve, so you shouldn't need to cap the hard line. Start the engine cold and see if air is coming from the tube. When the car warms up, it should stop as it's diverted to the h-pipe then.

If you do have air coming out, I would check to see if the check valve is not plugged. Without removing the tube, you could fasten a tube to the end and gently blow compressed air through. Only worry about doing this on the car is risk of blowing crap into the engine. However, taking it off is a PITA but would eliminate that risk

 

[StratTone]

I've never tried to actually repair anything in the air diverter set up but what 5L5 says makes sense to me. If everything is clear and the solenoids are switching correctly and the pump is working then maybe the check valve is bad.

 

[jrichker]

I've never tried to actually repair anything in the air diverter set up but what 5L5 says makes sense to me. If everything is clear and the solenoids are switching correctly and the pump is working then maybe the check valve is bad.

The primary purpose of the check valve is to prevent backfiring in the exhaust from damaging the control valves and the smog pump.

 

[someone82]

Check valves are A OK. The problem is the bypass valve (only for a split second according to a vacuum gauge is opening long enough during decal as stated in one of my earlier posts and air flow is being diverted to the head. Something is not right! I am going to run a test and have the diverted disconnected so Air is only diverted to the cats. I'm going to see how this affects fuel economy.

 

[someone82]

Update! After purchasing a breakout box and chasing a few bad grounds I was still getting code 44. I decided on a whim to replace my already "brand new" smog pump back with my old noisy oem pump. Codes went away! The replacement pump was not producing enough air flow to satisfy the o2 sensors. Got another pump on it now and all is better, driveablitly and fuel economy.