Posted 28 August 2020 - 12:58 AM
Guys, had some time to work this over the last couple weeks. Here is an update. Sorry i didn't quite troubleshoot like suggested cause my fleet mechanic had some time to spare late one afternoon so i had him throw the new injectors on before i got to run the car with different plug gapping. Anyway, I found I was running NGK 7031 (BUR7EA-11) plugs gapped at 0.36 when the boost would not hold 12psi and before the new injectors. Found one plug was somehow gapped much lower at 0.29 for whatever reason. After reading some other posts about trying some different plug temperatures when tuning, I ran to the auto shop before they closed the first night to grab a different set of plugs to play with the plug temperature a bit and bought a set of 7133 (BPR6ES), which I think were a stock plug from the 1987 model year that run a little hotter than the NGK 7 series. I gapped the new 6ES plugs at 0.35 as a starting point. Rechecked the timing to confirm ~10btc (jumps around some). Checked TPS voltage and found it at 4.7. Checked CTS with meter and didn't get any readings that made sense (suspect my meter is dying) so i just unplugged it at engine startup and plugged it back in/out while idling and found the idle moved around between in/out so its providing some info to the ECU. Tested ignition and found cylinder #4 plug wire was intermintently shorting and then pulled it off and it came apart (new Magnacore wires can't believe it). So i replaced it temporarily with a cheap plug wire (had to buy the whole cheap set). After all this, took it out for a spin. Boost held at 12psi no problem and the car showed some wow factor. Throttle was crisp and when hitting boost, 5psi felt more like it was on 5psi boost than before. After driving it for a while maybe 15 minutes, i noticed quite a decrease in performance the hotter the engine got and after about 30 minutes it was difficult to even get back home. Based on the A/F gauge behavior and throwing O2 codes, brought it home to inspect starting with fuel pressure. My fuel pressure gauge was showing 39psi before i left home and 30psi when i got back. New Walbro pump was whining more upon return as well. Stopped for the week since i was POd at this point.
So, here is where i am as of today and after a week to cool off and tinker more. Reset the fuel pressure this time on a hot engine to 43.5psi, the recommended pressure from Trilogy, my injector manufacturer and other folks here on the boards. It seems to be holding at 43.5 even after 30 minutes of driving so i assume fuel pressure must need to be set on a hot engine, or i have an another problem to contend with. BTW, I notice fuel pressure drops by 10psi immediately after shutting the engine off and is back to 0psi after about 30 minutes from shut down. Besides this at the moment, my biggest problem is even with the new injectors and required higher (correct) fuel pressure, there is still a lean stumble between gear shifts particularly between 1st and 2nd gear and occasionally on light throttle. You can feel the stumble and see it on the A/F gauge, which i'm still using the narrow band for now but it confirms what you feel. Also, still at idle i'm showing lean when before the car sat it would always idle one bar rich like it was suppose to and smoother than it does now.
Other misc. info. I can hear the fuel pump humming along steady and when the 3 fans come on (i have them jumped), i can hear the pitch lower like it decreased its flow once the fans come on and then pickup pitch when they stop. You can follow this from the engine bay while watching the the fuel pressure gauge. From cold engine to hot engine, you can see each time the fans kick on, i will loose about 0.5psi of fuel pressure until it finally bottoms out at the 43.5psi i set it at on the hot engine. I have reworked 6 of the 11 grounds spelled out in the service manual to date and replaced all the upper fuseable links and cleaned the bottom set and all terminals.
Idle vacuum on my gauge is about 19"-20", so i think that's solid and doesn't indicate a vacuum leak. i did an AC, EGR and Secondary Air Filter delete years ago, but i didn't remove all the solenoid valves and little things, just plugged nipples that were open and plated the EGR base on the intake.
What should i try next? What problems are you all suspecting i still have? Sorry for the long re-post here but i wanted to give everyone as much detail as i could.
1989 TSI SHP - Upgrades: Marnal NJV Head, Ported/Polished/Gasket Matched, SS OS Valves, Schneider HD Springs, 14G TD05H, 1GMAS, Trilogy Injectors, Trilogy FPR, Custom Header by Chad, BS Removal, 2.5" TEP Downpipe/B-Pipe/HKS Exhaust (no cats oops)/4"Tip, *DM/101 Hardpipes, HKS Type BOV, Walbro 255 Fuel Pump, SS Fuel Lines, BOSCH Red Coil, S&M Strut Bar, Poly Bushings, Polk Audio/Sherwood AMP/w/8" Sub, and Polished SHP Rims. Working on Custom Interior, Brake Upgrades and Always on the Look for Hood Mods Including 83, Cowl, or Firebird Type.