Hey guys,

I'm currently finishing up a big overhaul/engine replacement and have run into an issue I can't get my head around and was wondering if anyone else has run into this issue. Take note that all of these issues have taken effect while I've been running the stock ECU on an engine with these mods:
-Judge Ito "Aggressive Street Port"
-Racing Beat Dual-Tip Catback Exhaust
-Upgraded Downpipe
-Upgraded to 850cc injectors in secondary rail (so 850's all around now)

I have also installed a Supra TT pump and performed the common fuel pump rewire suggested all over the forum.

After getting a few other issues sorted out I got the car running only to find out it has a really rough and surging idle that will eventually culminate in it dying after starting to warm up. I thought it might be grounds and did a comprehensive cleaning of all the grounds as well as adding a few grounding wires suggested in the "Hyper Grounding System" that can be found on the forums. This did not fix the problem.

One time i accidentally started the car without the fuel pump fuse in and the idle was extremely smooth until the car ran out of fuel. I have since found that the issue is extreme enough I can start the car with the fuse out and upon inserting it the car will die almost immediately. The change was sudden enough to think that the problem is with the electrical powering circuit and not related to the amount of fuel/pressure in the rail supplied by the pump. From here I measured the amperage to the pump thinking it could be drawing a huge amount of power and adding a lot of resistance to the alternator but found it was only drawing a measly 143 mA. I'm thinking that I either installed the pump incorrectly or minorly messed up the rewire, but does anyone have any idea where to start looking?

I can upload videos of it idling both with and without the fuel pump fuse in if need be.

Thanks for any help,
Ryan

 

If you are running 850's on both the primary and secondary rails, and a stock ECU, then it seems like you will be way too rich at idle and low speeds since the ECU is assuming that the primary's are 550cc...

 

I know it will be running rich and both my wideband and all the white smoke is telling me so but what has me confused is that with the fuse to the fuel pump removed the car runs smoother than I've ever heard it. I'm led to believe the fuel pump is causing a huge draw on the alternator which is bogging the motor down. I know it won't be ideal on the stock ECU but I want to get it running as best as I can before running on my New PFC so I'm not adding any more variables to an already very complicated setup I'm trying to work the kinks out of.

 

I tested today with my PFC that was set up for all my mods and still had the same issue. The whole car was shuddering at idle and when I gave it throttle the PFC was detecting a little bit of knock so I immediately got off the throttle and let it idle roughly for a bit. When I pulled the fuel pump fuse it ran incredibly smoothly for about 3 seconds before dying.

 

It should be obvious that running too rich is the cause of your rough idle.

The reason it runs better with the fuel pump disabled is that without the pump running to maintain pressure and volume, it leans out until it dies.

To confirm this condition, induce a vacuum leak at idle to see if it smooths out. A small leak would be good, because a large one will affect the map sensor enough to try to richen the mixture.

With the power fc, you can adjust the idle fuel mixture without affecting the rest of your map as far as I know.

The real solution though is a real tune. You have changed enough parameters that an off the shelf tune probably is not the best or safest option.

Vince

 

Thanks for the help Vince. I'll try a few things including inducing a vacuum leak when I get home.

My current hypothesis is that for some reason the pressure regulator isn't working and the pressure in the rails is too high. Do you think that could cause these issues? It would certainly lead to the car running too rich.

 

So when I got the PFC I got it from Rx7.com and gave them a list of mods including the upgraded injectors so they could put at least a functional base map on according to those mods. I had planned on taking it to get a real tune on a dyno shortly after finishing the rest of the mods, but I had hoped it would at least be drive able with the base tune.

So I went and tested and the fuel pump is getting 12.45 V and current on the order of milliamperes. I tested the fuel pressure regulator with an external vacuum and it seemed to be performing properly. The vacuum leak didn't seem to help much though it was a very small leak I made.

My current guess is that the map wasn't set up properly for the larger primary injectors and will simply need a retune to get running properly. I installed PCEdit to take a look at what's going on with the map but I'm a little over my head with it. Any other ideas what t might be?

 

I wish I could help you with that part, but I don't have any experience with anything beyond the basic adjustments in the commander menu.

If you visit the Power FC subforum, you can find more help there. Lots of good info there.

Good luck!

Vince