I went to get my car tuned a couple weeks ago, but every time It'd get to almost 5k rpm's it would lean out like crazy. It feels almost like hitting a rev limiter. After checking a few things, the tuner told me that he'd had an FD in there a few weeks ago that had the exact same symptoms and that it turned out to be the engine wiring harness was bad, and not opening the secondary injectors.

I haven't been able to check any continuities or anything yet, but I just wanted to ask if this seemed like a likely diagnosis. Any other things to check would also be greatly appreciated.

When this happens, fuel pressure is good. I had brand new spark plugs, changed at the shop, on the dyno.

Thanks for any help.

 

That could really make sense. Your secondaries come on at 4500. Definately worth checking out.

 

It would benefit you if you'd provide your full list of mods so we can provide more meaningful input.

 

mods are:

Stret port motor built by Pettit w/ 3mm seals
Power fc w/ datalogit
Greddy Type S boost controller
HKS dual intake
3" down pipe/ mid pipe/ RB cat back
BNR Stage 3, still sequential
Axiom solenoid kit
Supra fuel pump
850cc primary injectors
1300cc secondary injectors
Aeromotive A1000 fpr
Unorthodox underdrive pulleys for crank, alternator, power steering
Koyo radiator
Rotary Extreme 25 row dual oil cooler kit

That's all that I can think of right now. This happens pretty much right at 4800 rpm every time.

 

Are you sure you are running 850 primaries?
Is your map setup for 1300cc secondaries?
Did it ever run on the map loaded onto the PFC currently?
Who in Oregon is tuning it?
Do you have a datalogit that you can use to pull your map and show us screen prints of the map setup?

I'd lean more to an issue with the map not being setup for your mods.

 

Your fuel pressure might be dropping. Check wiring to the fuel pump etc. Ask your tuner/mechanic if he can hook up a temporary fuel pressure gauge. If its dropping its fuel pump, wiring, or regulator related.

thewird

 

gracer7: I've been running the base map that came on the pfc. I installed it at the same time as I rebuilt my motor, so up until now, I haven't gotten the rpm's up that high because I was still breaking it in. I will definitely keep in mind to check and make sure I have the right injectors in the right rails, but I do know that have 850's and 1300's. I could've mixed up which ones I put where, though. If I did mix them up, it still wouldn't feel like this, though, would it? It's pretty much like hitting a rev limiter at 4800 rpm. It goes up quick, has good primary boost, then pretty much stops at 4800.

I don't have the numbers on my computer, but I called rx7store, and he told me how to change the injector settings in Settings 5 and adjust it to compensate for the larger injectors. The tuner also played around with that, and the map to try and dial that out, but nothing worked.

I went to Forged Performance in Portland.

I'd been told on here that it was probably something with my map, which I told the tuner, but he tried adjusted the map a bunch before remembering about the previous customer. He said they replaced the entire fuel system, ignition system, and ecu before they tried replacing the wiring harness. Apparently it was broken inside the loom somewhere, with just a couple of the little wires still connected, so it still gave continuity.

thewird: I had the same thought when I hit it at first, so I checked to make sure the fpr was hooked up right and everything, and it is. I had fuel pump before my last engine blew, and I didn't touch it when I did the rebuild, so I think that's all good. The tuner did pull my fuel pressure gauge out and hook my fpr up to his computer which logged fuel pressure and afr's, and the fuel pressure was good. I forget exactly what it was, but it acted just like it should, and the leaning out wasn't a gradual thing, at 4700, everything was fine, then at 4800 my wideband is pegged at lean, I think it might even just go the the dashed lines, like when you just let off the gas.

Sorry for the long post, but I figure the more precisely I can answer questions, the better guesses you guys can make.

Oh, I also have a twin power

 

Could you post your map?

thewird

 

It's just the base map, so I don't really see how it could be that, but here's the Inj map. Under it, I put what is seen in Settings 5. Other than the Q Primary and Q Secondary, I'm guessing at the numbers, since I don't have them saved to my computer. I'll call rx7store tomorrow and get them again.

The only other thing that was changed was the PIM scale and offset in Settings 3. I got a GM 3 Bar map sensor (yet another thing I forgot to mention), so I set the scale to 43000, and the offset to 0. I ran into this fuel problem before I changed map sensors, and changing sensors and settings for it didn't affect the problem at all.

 

I'd like to see the entire tune pulled from your computer if you could provide it?

thewird

 

ok, how do I do that? If you have the FC-edit software, you can just open it, without loading any maps, and what it shows is what I have, with the Settings 3 and Settings 5 changes tha I've posted.

 

Connect your laptop to the car. Connect the USB between laptop and datalogit. Run the Datalogit software. Do Read ALL. Do File > Save As and save it to a new file so you don't overwrite anything.

It could be wiring but for it to go full lean and fall on its face the way you described would seem as if neither of the secondary injectors are even wired. How many miles on your harness?

It could be a fuel delivery issue. Might want to search on posts about other problems with fuel injectors or fuel delivery.

It could be a problem with the map. Unless I see the .dat file pulled from the ECU as I described above, I'm not sure exactly how you have it setup. The Power FC section has a lot of good info on this kind of stuff including the PFC manual. You can also get support from the moderator there and buy his tuning notes which is a worthwhile expense and cheap.

 

I can't get to my car right now, but the map is the base map, with the modifications I've listed.

My wiring harness is the original, so it's from '93 and has about 95k miles. I'll look around for other fuel delivery related threads, and post something up in the Powerfc section.

 

You said the tuner played with settings 5. he could have done anything. and those settings can have a huge effect on the way the car drives. It sound like he may not know all the quirks of the PFC.

Post the whole map. I'm thinking you need to change your injector transition and overlap setting first in addition to checking fuel pump wiring.

 

It was doing this before I took it to him too. It's been doing it ever since I finished with the rebuild. He changed some things to try and fix the problem, but it didn't change anything. I don't have the car with me, right now so I can't pull the map off of it, but I posted the map that it had before going to get it tuned, and it was doing the exact same thing, at the exact same rpm level, then too. In the .doc file I attached I typed out the only changes made in Settings 5.

Those changes and changing the PIM scale to 43000 and offset to 0 for my 3bar map sensor, are the ONLY changes that were made to the base map, or any of the settings, that came already on it out of the box. I'm not really sure how I can be any more clear on this, those are the only changes, there is nothing else.

I'm sorry if I'm sounding like a jackass, it just doesn't seem like I'm being understood on this point.

 

ok, I just got the settings 5 numbers again from rx7store, but it saved it as a .dat file, and I can't attach a .dat file to my posts. How do I get it so I can attach it?

I know, I'm a retard with computers.

 

Zip ir or rename it to .jpg instead of .dat . I suspect this is related "changing the PIM scale to 43000 and offset to 0 for my 3bar map sensor" but I'd like to see the whole thing.

thewird

 

Check also page 5 of the settings page.

What is your Pri/Sec Transition (%)?? Pri/Sec Transition (%) is the duty cycle point at which the secondary injectors are suppose to come on line

And also

What is your Sec Transition (ms)?? Sec Transition (ms) which affects the starting pulse width of the secondary's and should be changed when secondary size is changed.

- side note this info is taken from chucks notes. Buy his notes if you plan on doing anymore messing around with the datalogit.

 

thewird: Ok, i couldn't get it to work as a .jpg file, so I zipped it. Hopefully it works. I was told to change the PIM scale and offset to those numbers by rx7.com, when I got the sensor.

RotaryBuddha: My Pri/Sec transition (%) is 40.0 and my Sec transition (ms) is 1.500

 

Everything seems fine as far as I can tell. The fuel curves are a little wacky but shouldn't be the difference your talking about.

thewird

 

ok, thanks. I guess I'll start tearing into the harness, then. I'm gonna check the connectors at the injectors, first, to see if they're broken there, but I think it might be something farther in, because it seems like neither secondary injector is firing at all.

 

Do you have a wideband or a EGT? Then you could see a lean spike when your secondaries are supposed to come on, and then you would know if you had a problem with them.

 

How else would he know he was going lean without a wideband lolool.

thewird

 

A higher than normal EGT would be considered lean. And of course it depends on where the sensor is located.

 

Or rich, or too retarded timing.

thewird