RX7_Fanatic

okay here goes nothin...check out my profile to see everything done to my car, the car was tuned by XS-engineering (im asuming not a perfect tune but it ran hard strong and only little hicups on throttle let-up before)

the engine sputtering from taking my foot off the gas has gotten more violent. when at a stop the engine drops to like 500rpms and jumps to 1000, back down to 500, like its jumping, will do that until i tap the gas then it idles fine...this doesnt happen all the time however.
the thing that has me worried now, and i havent done anything modification wise to the car that might have set it off is...ill be driving..evne normal driving, and ill get into a gear and get on the gas and the engine sputters violently backfiring and shoots black smoke out the tail pipe. I took it to RRR and they thought it was the battery wire clamp that was loose, but that wasnt it. this doesnt happen often at all, but its a problem that is always waiting to happen, (probably once a day). i havent had time to take it in again to try to figure out what it was, but the fear of blowing my engine from fuel cutoff or something is scary...
If anyone could maybe throw out some diagnosis guesses that would be super helpful, maybe give me some ideas on where to start...

some things ive thought of are the fuel pump...maybe i need a new one although the walbro one i have isnt too old (10000 miles MAX), or i thought it could be an electrical problem so i was gonna pick up an APEX'i grounding system with voltage stabilization unit incorporated to try to even out the ignition signals, perhaps even upgrade the ignition system altogether.

If anyone has any feedback on my thoughts on the problem, the grounding system, or has some pointers about ignition on an FD leave a post...

thanks in advance for the support, and feel free to ask me for any aditional info you may need to figure this problem out

Junia

Have you checked for vacuum leaks? I know its a pain in the *** on a fd but its something you might wanna take a look at before you take it into a shop

RX7_Fanatic

will do, but its a XS engineering Single turbo, not many possibilities for vaccum leaks, but it could be

Mahjik

iTrader: (1)

I would look at getting a tune from someone else. People have had problems with XS in the past: https://www.rx7club.com/showthread.php?t=97836

RX7_Fanatic

thx mahjik, i took the car to the shop today and we concluded that the walbro fuel pump has gone bad. i invested in a skyline fuel pump and my shop (rotary reliability and racing) just got the PFC software to tune on the dyno so we are gonna put it up on the dyno when we get the pump and see if we can possibly smooth out some hard spots on the tune, however my whole car was tuned at XS, not just the computer...actually dyno'd 305 RWHP but i would agree with the general concensus that they do tune it towards the rich side.

thanks again.

RX7_Fanatic

any advice on that skyline fuel pump? does anyone else have one installed?

i was looking to upgrade the ignition at this time too, any suggestions on that would be great, was thinking about the XS engineering power pack II but i havent heard any feedback about it yet.

thx again guys,
Brian