On Friday night (4/22/05) I drove up to Erie, PA. Rained pretty heavily the entire time there and back. A round trip of about 160 miles.

I didn't notice anythink on the way up but coming back, when I tried to got WOT, when I got to 4000 RPM, the engine would "cough" and hesitate badly. It happened just about every time I tried it so I just kept it under 4K the rest of the way.

I noticed that when it did this, my A/F gauge dropped down to a rich 10 (the lowest the gauge goes). Up until the engine coughed it stayed pretty normal.

I get home and park the car hoping that it was just a glitch or due to the excessive water/humidity or something.

I take the car out again today since it was dry and went to see if it was still doing it. This time, when I go WOT, the car seemed to go into "limp mode". At least I think that is what is was since I couldn't go over 2500 RPMs without more coughing and hesitation.

Now, my CEL is ALWAYS on due to a bad heated O2 sensor. I can clear it with my Digitmoto OBD ll but it just comes back on when I start the car again. So the fact that my CEL is on, doesn't really tell me anything.

I pull over and open up the Digimoto and clear the CEL. Now I am out of limp mode and the car works perfectly normally! I can go WOT all the way to redline with no problems and the A/F gauge stays right at 11.5 as usual. The car pulls like crazy too!

I do need new plugs I think since I've had these for two years (since the Procharger went it). Also, after a spirited drive, I have ALWAYS smelled gasoline in my garage ever since I got the AAM fuel system installed. There has never been any visible leak of fuel onto the floor or anywhere I can see but this has been present for a year now.

My question is, can anyone explain what happened? Any theories?


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Hey Dr. B,
After the performance loss, did you pull the codes to see if there was more than just the O2 sensor code in the register? I'd bet that there is a second code in there that would give you some insight into what happened.

 

since I got the return fuel system . I to smell gas all the time in the garage . I cant find a leak .I would sure like to find out why and where the leak is . Dr Bonz...do you think the limp mode may have come from the bad o2 sensor ?

 

I don't know but the CEL has been on for nearly a year and I've never had a problem with it.

I didn't look up the codes unfortunately but I'm pretty sure it only showed one.

 

So does your OBD tool have the ability to display/read the codes? I've had to do the old "put the ECU in diag. mode and count the blinks". It's a pain, but it works. If there were no other codes, I'm at a loss. Sorry.

 

Maybe you pulled in some water into your S/C intake? Could have caused you a/f ratio to run rich.

Just a thought.

 

If it was unseasonably cold you might have been going into limp mode simply due to maxing out the MAF sensor below 4000 rpms (or whatever the threshhold is).

As for the gas smell, you might have a very small leak in the top of the gas pump (doesn't the AAM install require cutting a hole in the top??). You can use soap bubbles to see if you have any foaming. If it seems to be stronger right after you fill up the tank then that's an indicator of this problem.

--Steve

 

I can read the codes with the Digimoto but I didn't do it last night unfortunately. There was only one showing though.

Don't know about the AAM fuel install but if that were the case, I would think I would smell gas INSIDE the car since the pump is right behind the drivers seat. I have never smelled it inside the car. Only on the outside.

 

Don't know about the AAM fuel install but if that were the case, I would think I would smell gas INSIDE the car since the pump is right behind the drivers seat. I have never smelled it inside the car. Only on the outside.

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JUST ZAY-NO!

Same here....dont smell it inside...only outside the car

 

I have the fuel smell too on the AAM system and mine is not in the car either. My fuel pressure does not drop when I turn off the car at all, so a fuel leak seems unlikely. As far as the limp mode issue... not sure. Possibly condensation on the MAF freaking out the ecu.

 

Have you cleaned/re-oiled your air cleaner recently? Have you installed a new air cleaner recently?
One time I had installed a brand new filter(k&n)and the filter oiled my sensor up.I had to get electronic cleaner and clean the sensor & Z tube.After that, everything worked fine.

 

With the Procharger, I obviously don't have the stock air filter but I suppose the one I have now could have taken in some water with the long drive in the heavy rain.

Dave from AAM.

Can you please get an answer from Mike or any of the mechanics (HA! Mike and the Mechanics! ) at AAM concerning this heavy fuel smell that all of us with the AAM Spec fuel system seem to be experiencing?

 

Is the smell heavy or is it just an enclosed space? Raw liquid fuel has a stonger sweeter, more pungent smell. Small fume leaks tend to be much softer. Can you tell me if it is one of the two?

I'm not sure what the smell is caused by but the educated guess would be it has something to do witht he EVAP system since we converted the returnless system to a return system and we are not seeing any leaks. If you guys can give me some idea of the smell then it will help lead us in the right direction.

Ed...for the limp mode issue it could be any number of things....the general answer is that the car is gonna be more finiky due to the massive increase in power. My best guess is that the ECU freaked when the MAF saw boost+humidity+heat+high voltage+etc.+etc. Guessing at it again...the water in the air went through the charger, was compressed and slightly heated, this general moisture content freaked out the MAF, it hit a high circuit peak or maybe even shorted slightly, and the ecu assumed the MAF either was disconnected or malfunctioning. When this happens the "limp" mode map is enabled and the car runs pig rich, limits rpm, and retards ignition. That or some moisture found its way to the hot wire causing it to give a completely incorrect reading. Again these are all guesses. Did you have the chance to grab the codes.

 

The smell is as you discribed . Not a raw fuel . My shop said the same thing , that it may have to do with the EVAP system since we changed the system

 

I only smell it when the car is parked in my garage after I drive it but I STILL smell it the next day if the doors are closed. As I said, I have NEVER seen any fuel anywhere and I've really looked both with the engine running, when revving, and at idle, and when the ignition is off. As long as this is an expected benign complication (to use medical terms) of this system, then I'm OK with it.

Thanks for your help Dave.