Jinx099

I have an '86 GXL that is stock except for a streetport, turbo injectors, SAFC, removed rats nest, and "stuck open" aux ports, all done by the previous owner. The problem is that when driving at WOT, the car runs a bit rough over 6000 RPMs. Right now I have the SAFC set to +50% (the highest it will go) for high-throttle for 5k-8k rpms, and this has helped the problem. If I lower the setting for that range, it will do the exact same thing, but at a lower rpm, around 4000 rpms, but it will run fine below 4k rpms at -20% on the SAFC. When I rev it in the driveway, it will rev freely up to and over 7k rpms, and usually backfires a little bit.

Questions:

1) Could it be secondaries not kicking in? Could I test this by just unplugging the secondaries and seeing if it runs differently?
2) Could it be low fuel pressure? I have a sorta broken fuel pressure gauge I could throw in there (all the fluid leaked out of the gauge).
3) Could it be clogged cats? I have a RB header ready to be installed, would that be worthwhile diagnostically to install it? Theres an exhaust leak at the manifold right now too.
4) Should I look into the aux ports? I have no idea how to tell if they are open or closed, and I'm not sure I trust the PO.
5) Could it be timing? I set the timing a while ago, not sure if its perfectly set.
6) Are there other things I should look closely at? Spark? AFM? Vac leaks?

Thanks in advance!

SpeedOfLife

iTrader: (16)

yes.

Jinx099

Could you please elaborate?

Jinx099

I've finally had some time to work on this car. I unplugged the secondaries, and it did not run well at 3800 rpms, so those appear to be functioning fine. I adjusted the TPS, and it seems to have helped a little, still not running perfectly above 6k rpms.

I noticed on my SAFC that the throttle position, at WOT, dips down below 100% occasionally. I also noticed that I'm getting an o2 sensor error code now. I'm planning on putting the header with a new o2 sensor soon, so hopefully that will solve that problem. Could either of those issues cause the 6k rpm issue though?

RotaryRocket88

iTrader: (7)

It's common to see WOT TPS value under 100% on an Rtek, so I don't think I'd worry about it.

The ECU won't go into closed loop over about 3500 RPM. The 02 sensor is only used for cruising.

I'd test fuel pressure to be sure it's around 36 - 40 psi with the FPR line disconnected (atmospheric pressure). A problem with one secondary injector could also be the issue. I've read a thread about a similar problem that ended up being a problem with just one injector wire. You can test continuity between injector clips and the ECU.

Jinx099

I tried to test my fuel pressure with my sketchy inline fuel pressure gauge. It leaked, so I didn't want to have it running any more. It was reading around 30-35 PSI, with the FPR under normal vacuum. With the FPR at atmosheric pressure, would you expect the pressure reading to be higher or lower? Would this be indicating a weak fuel pump?

RotaryRocket88

iTrader: (7)

Under engine vacuum, ~30 psi is normal. There are specs for this in the FSM.

MadScience_7

Is the +50% on the SAFC richer or leaner? If you added TII injectors and the SAFC is dumping even more fuel it's going to be rich as all hell and will probably stumble up top. Do you have a wideband by chance? Mine stumbles up top at about 10:1 AFR.

Jinx099

Yeah, +50% is richer (50% richer than stock). That's why I think something might be wrong with the fuel system. If I try to lean it out, the problem seems to get worse.

Jinx099

I just wanted to update this and say that I've solved the problem. I believe the problem was the vac line going to the pressure sensor. I replaced it with a new line, but didn't realize there is a restrictor pill in it. I put the stock line with the pill back in it, and it runs smooth up top now. After that, I was able to lean out the fuel mixture with the SAFC to about what I expected it should be set to with the TII injectors.

Is there a certain size of pill that should be used in that line? I'd like to get a new one to use with my new vac line for it.