I just had my hi-flow cats switched (went from RT to Crawford) the other night. Car felt strong and I put it through 1-6th fairly WOT a couple of times before leaving installer to go home. On my way home I downshifted from 6th to 4th to pass someone and the car immediately bogged down and had no power whatsoever. I pulled over imediately. I found that I could rev to 2K RPM and it started bogging. There were no slip or CEL indicators (so I was not in "limp" mode). I was able to drive back to the installer (very slowly!) while I watched my wideband reading vary erratically from full lean to full rich.

With engine still running, we checked all vacuum lines and wiring and found no cause for bogging. We checked for error codes with OBDII and found nothing. Shut off the car for 2 minutes to check some of the lower vacuum lines & wiring. Then re-started. The problem went away! Finding no obvious causes, we hoped it was a fluke.

We think the issue was thatthe aux fuel pump was somehow "stuck" on and that's why it had been bogging.

So, I headed home with fingers crossed. I again pushed it through the gears hard a few times and it seemed fine. ABout 45 minutes later I happened to do the 6th to 4th shift again and IT HAPPENED AGAIN. I pulled over, shut car off for 30 sec, and restarted it and it was OK again. I was able to duplicate this 1 more time after trying about five 6th to 4th shifts.

Has anyone seen this before??? Once snow melts I will do some more troubleshooting. To confirm it is the aux pump, I will pull SS box fuse (which should shut off aux pump if it is indeed on) next time I get the car to start bogging to see if problem goes away.

 

Did you find out what the problem was ? I have a AT5 so I cant give you any insighht , but am interested to know if you found the problem .......Bill

 

Bill, No, I haven't had the car out yet. Snow is about gone here so I will probably take it out before the weekend to try to troubleshoot further. I will be sure to post results here.

~ Kevin

 

I still have not found the cause of this problem. I have only driven the car a handfull of times since problem started. I was not able to duplicate the problem until today in rush hour traffic. Down shifted from 6 to 5th, stepped on it, and engine went limp. Had to pull over and restart car.

Before I turned car off, I pulled fuse to the SS box (which I thought would turn off aux fuel pump) but the car still bogged over 2,000rpm.

if a cause is found I will let you know....

~ KZ

 

Sounds like a problem im having. Any updates on this?

 

No update yet. Car has been away all winter but I will be charging battery this weekend and start driving it in a week or two. I will update further then.

~ Kevin

 

I had the exact same thing happen to me last night driving from Ny to VA on 95. Downshifted to 4th from 6th and it booged down and i felt the most awful feeling in the world...seemed like repetitive jerks. Stopped at rest stop and turned car off. Restarted and all was fine except I could not build boost from then on. Serious problem or not? Need help. Could it be a MAF issue???

 

Did you try to rev match? does the aux fuel pump come on? Check the aux fuel pump fuse! Wouldn't think the MAF would suddenly go bad after down shifting..

 

Yeah I rev matched. Fuel pressure gauge shows pressure under boost up until about 4500 rpms or so then goes into limp mode where you cannot go above 2500 rpms. This sucks. I will go check the fuse now. The car idles horribly now and running extremely rich. Seems like it is dumping too much fuel. What type of cable connects to SS box to a laptop with a serial/usb port?

 

I think it might be a MAF thing or TPS thing combined w/ the Vortech fuel system. Here's my experience. My MAF connection came loose on the dyno last Nov. when I was getting tuned and went into limp mode. Then two weeks ago I put 440cc injectors on my AAM fuel system and forgot to plug in the TPS harness while it was idling.(that's OK 'cause I remembered the correct fax cover sheet! Little Office Space joke). Anywhooo... went into limp mode as well.
I really don't drive my car very hard in terms of down shifting and passing so I can't speak to the shifting thing causing the problem.
I do however know when I datalog a 2nd to 3rd gear upshift at WOT, the throttle closes and the A/F wants to go way lean 21:1 which is normal cause I'm dropping rpms and boost between upshifts. I'm thinking if you're down shifting from a partial throttle/vaccum situation, your already in a near stoich 14.7 fuel condition and then your rpms jump up possibly before you go to WOT. Maybe the ss box which is boost/rpm dependent can't compensate for that condition. My bet is an upgrade fuel system will cure the problem. But I'm not gonna try it on the way home from work to prove my point! Good luck fellas!

 

well fuse is not blown on the Aux pump. Going to check the MAF sensor. As long as I do not go into boost, I can go above 2500 rpms. As soon as I go WOT, it will kick into Limp mode. I really need to fix this guys. I know others have experienced this. How did you fix it???

 

bump

 

?

 

Dude I have the Same problem. My car is getting tunned next week so I hope to find out more!

 

The SS box has a vacuum line for manifold pressure. The manifold pressure and RPM establish a calibration value for the MAF input to the ECU.. Check to verify that vac connection is good.

 

Hmm I spliced in there for boost. Does anyone think a extra T close to the box could be the problem?

 

I was going to tell you what jpc said. The Vortech set up is very sensitive to vacuum problems. Check your vacuum lines and make sure one didn't come loose. Other than that, I have no suggestions. I've had no issues with power on downshifts with my kit

 

Are you saying that the splice is used to feed a boost gauge? If so you might want to find another source.

 

Yeah, and to think of it I didnt have the problem until then. Fark Im going to change it today and see what happens.