| As I've mentioned in a previous post (was locked due to tt.net going down) I am having issues with running lean, primarily when cruising around. My fuel pressure seemed to drop off at idle from before driving and after driving (~35 psi to ~31psi). I figured this meant dropping fuel pressure was the source of my lean condition when driving around and the consensus between me and two other members was that I had a rusty fuel tank as the car had sat for some time. Well, fast forward and I thoroughly cleaned the gas tank (there was plenty of sediment build-up) and changed the fuel filter, which was also filthy. I was confident the problem was fixed. After driving the car I learned nothing was fixed in regards to the a/f ratio (cruises ~16). The next step I have taken is I purchased a fuel pressure gauge for inside the car so I could see more than just my idle pressure. I just now took a 15 mile drive to see how the a/f and pressure acted. I had expectations that the fuel would drop off when I drove around but the pressure actually reacted perfectly to the boost pressure. Uggh! It may idle 2psi lower from cold idle and hot idle but this shouldn't make much if any of a difference. I think it can probably be attributed to temperature differences, the bay gets toasty. This is slightly less of a drop-off so sediment may have caused some issues after all. So on that note, now I am thinking I can safely rule out the pump, fpr, and fpc. Please correct me if I am wrong. Now I am wondering what the next step should be. There are only a few possibilities I can think of and they are essentially shots in the dark. Here they are: -Clogged injectors which flow enough at idle but not enough at load. The car is ~15.5a/f at light cruise and ~12a/f at WOT with boost controller off. Idle is 14, which is on purpose. These readings are with o2's disconnected, connecting them doesn't fix the issue. The Z should be much richer than this based on the k-value I have supplied to attempt to overcome this. This seems like the most likely culprit, I used to have proper a/f's with a 211 k-value and now I am currently running 230, it should be really rich! Who would you recommend I send the injectors to for ultrasonic cleaning? I would love to switch from my DW to Nismo injectors but that is simply not in the budget. -Un-calibrated wideband sensor (lc-1). This seems unlikely as the car has driven maybe 500 miles since the sensor was installed and besides that just idled a lot. The car sat for a year but I don't think that would cause this to read so erratically. It was calibrated before installation and worked fine so I assume it is not the problem. -Bad MAF? This seems feasible but also unlikely, someone let me know. -Valve or compression issues? This is a long-shot...and seems unlikely. Bottom end has ~3k miles and heads were left untouched. Compression (last tested 1k miles ago) was about 155 +/- 5 psi on all cylinders with the differences attributed to the heads probably needing some love as well. I would like to get this solved so I can drive the car again and enjoy it instead of worrying about every little thing. I enjoyed my automatic n/a a hell of a lot more than this and I had it for far less time. I am thinking the injectors are likely to be my next step but I really can't afford to keep guessing. I'd like to solve this issue, lock in a safe tune via Nistune, and finally go to Z nationals with my Z now that I just missed Zcon. Then I can mod for fun instead of to chase problems and eventually have Ash, Harry, or Greg tune it. As it stands it is un-tunable so I can't do any of that as they would be trying to fix this as well! Thank you for any help. I really am at my wits end, nothing has gone smoothly with this car. Everything that could stop working or cause a problem has. Most everything has less than 3k miles at this point so it should run like a top. The brief times when I had it running smoothly (still had an issue when cold but smoothly besides that) it was great and that is just about all that is keeping me going at this point.
'91 TT |
