Members Dustin M. Posted March 20, 2014 Members Share Posted March 20, 2014 First off, some background: prior to me purchasing the car, it ate an opti on the guy I bought it from. He only ran like 2 or 3 races before I bought it, he bought it to get it to this region. On my initial shakedown, the car developed a misfire that worsened throughout the day. Upon inspection at home, the water pump was leaking (pretty sure it actually started in the garage, it never left a puddle prior) and the opti was soaked in oil. Pretty cut and dry, so I installed the spare opti, new seal, new water pump, and proceeded to comp school. The car was flawless until the last run of the weekend, which was 40 minutes worth of an enduro (first 40 minutes were free!). Near the end, I axle hopped and the car started misfiring. When I got home, I found the opti was soaked in oil again, so I figured new opti again. Fast forward to this year, I want no bullshit so I ordered a new Delphi opti from Amazon, Jegs plug wires as they were previously on the car and seemed to work, and AC Delco 41-629 copper spark plugs. These plugs are OE for the TPI L98 and cross referenced to a POS Autolite spark plug that was listed as compatible for my car. Plugs were gapped to .035" per the recommendations I found for that plug. Car idles perfect, it's snappy, so I warmed it up on the dyno, floored it, and it IMMEDIATELY started misfiring all the way from 2,000 RM to redline. It still put down 244whp. I swapped a coil/ICM on the dyno and nothing changed, so I unstrapped it and went home livid at all the money I'd blown to have the car still be fucked up. Today I received a new opti jumper harness from Casper's Electronics, installed that, and no change. With the car off the dyno, it's really difficult to perceive the miss because it's not nearly as pronounced without that load. I just ran out and grabbed some NGK G Power single platinum plugs to throw in. I'd wanted copper, but they only had 1 of the TR55. So I'm going to throw these in and see if anything changes, probably not but knowing they're single plats gives me peace of mind as that's what the car came from the factory with anyway. Factory gap was .050" per the FSM (with single plats), so I wonder if the narrow gap on the AC Delco copper plugs was causing issues? I've got another opti on the way too and if that's not it I'm COMPLETELY out of ideas. Anyone? Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 20, 2014 Share Posted March 20, 2014 Change the water temp sender in the water pump. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 20, 2014 Author Members Share Posted March 20, 2014 Motor's piss warm and I got 1230 ohms. This is a good reading, right? Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 20, 2014 Share Posted March 20, 2014 If you havent changed it, change it. It is a cheap sensor. I spent well over $800 in parts and waisted a few weekends of racing on what sounds like your issue. The part is $10 or so. Make sure you have heat sink compound under the ICM. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 20, 2014 Author Members Share Posted March 20, 2014 It's interesting you bring this up, because I've been wondering if it isn't just pig rich and overwhelming a healthy ignition system. I'll grab one for the hell of it, it could rear its head down the road if it's not it now. I think I'll weld a bung in the exhaust this weekend and get the wideband installed too. How do you guys validate the repairs made to your car? With the giant yellow numbers on the side, lack of headlights, and everything else that screams race car I've got to think it's just a matter of time before I'm explaining my actions to an officer of the law. Quote Link to comment Share on other sites More sharing options...
cozog1548534733 Posted March 21, 2014 Share Posted March 21, 2014 Maybe I missed it, but did you fix the oil leak? the opti is super sensitive to moisture of any kind. Is the check valve in the vacuum line to the opti? Have you changed opti pig tail that plugs into engine harness? Cheap thing to check. What about fuel? How old are the injectors? Are you able to get any codes from obd? that would be the most helpful to diagnose. FYI, when you change the opti, disassemble it and red loctite the screw inside. They love to come loose, even on brand new optis. Quote Link to comment Share on other sites More sharing options...
Den341548534727 Posted March 21, 2014 Share Posted March 21, 2014 Is it throwing any codes? DTC 16 or 36? Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 21, 2014 Author Members Share Posted March 21, 2014 Maybe I missed it, but did you fix the oil leak? the opti is super sensitive to moisture of any kind.Is the check valve in the vacuum line to the opti? Have you changed opti pig tail that plugs into engine harness? Cheap thing to check. What about fuel? How old are the injectors? Are you able to get any codes from obd? that would be the most helpful to diagnose. FYI, when you change the opti, disassemble it and red loctite the screw inside. They love to come loose, even on brand new optis. I believe I've fixed the oil leak, the motor's still dry but it's barely been run. The water pump drive seal was flipped outward, I managed to install it properly without the tool and without a lot of force, but only time will tell if I've won that battle. Check valve is present, the flow limiter is in the trash as it plugged last year before installing the first spare opti. Installed a new jumper harness from Casper's Electronics, seems like nothing changed. Fuel is a combination of whatever was leftover last year plus 3 fresh gallons. I can't seem to positively identify the injectors. They're clean looking, but I can't seem to see a part number anywhere. I did do the red loctite on the rotor screws and even laid a thin bead of silicone down where the rubber seals mate up. Is it throwing any codes? DTC 16 or 36? Only codes for missing VSS and something else that didn't matter, no driveability codes. It's a 93, so it's a pretty dumb ECU. I've got the wideband installed, so I'll report back what I find there. I'm supposed to do a test and tune tomorrow, but there's snow and rain in the forecast and I don't think the track is as gung ho about open track days as NASA is about racing in crap weather. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 22, 2014 Author Members Share Posted March 22, 2014 In addition to the wideband, I added a 2nd bonding strap from the block to the chassis. The first looked like ass and was the only one. The car rolled over noticeably quicker when it started, then proceeded to run at 17-18:1 until around 125* when the thing flicked right over to ~14.9 and stayed there. With the 160 stat, I was only able to get it up to 165 putting around the neighborhood. I snuck out on the street for a quick trip through 2nd gear, I went from 2,000 to redline and the AFRs started around 13.0:1 and ended at 11.4:1, about what I thought I'd see. That's not rich enough for a misfire (especially with copper plugs gapped at .035") and although I was only in 2nd gear, the car didn't seem to hiccup. It's so subtle when it does in in the lower gears though it can be difficult to discern. I'm really leaning toward taking it to the track tomorrow rain or shine to get it hot, beat on it, and run it side by side with Brad's car. If it is indeed good to go now, my only theory is shitty grounding. Quote Link to comment Share on other sites More sharing options...
cozog1548534733 Posted March 22, 2014 Share Posted March 22, 2014 In addition to the wideband, I added a 2nd bonding strap from the block to the chassis. The first looked like ass and was the only one. The car rolled over noticeably quicker when it started, then proceeded to run at 17-18:1 until around 125* when the thing flicked right over to ~14.9 and stayed there. With the 160 stat, I was only able to get it up to 165 putting around the neighborhood. I snuck out on the street for a quick trip through 2nd gear, I went from 2,000 to redline and the AFRs started around 13.0:1 and ended at 11.4:1, about what I thought I'd see. That's not rich enough for a misfire (especially with copper plugs gapped at .035") and although I was only in 2nd gear, the car didn't seem to hiccup. It's so subtle when it does in in the lower gears though it can be difficult to discern. I'm really leaning toward taking it to the track tomorrow rain or shine to get it hot, beat on it, and run it side by side with Brad's car. If it is indeed good to go now, my only theory is shitty grounding. So it sounds like you've got good fuel (based on AFRs) and air, the only thing left is spark. New plugs, wires, opti, coil, pigtail to harness... not much else to replace. Have you traced each wire in the wire harness to check for a possible exposed wire? What about the connections at the PCM? Any corrosion between wire harness and PCM? By all means, put it on the track. I wouldn't lose a race weekend over this issue. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 22, 2014 Author Members Share Posted March 22, 2014 I've got no qualms tracking it down 10whp, my biggest concern is a clean dyno pull here. If it is still misfiring I could just pull the plate and be damn close to my 259whp target, but then if it cleans up I'm a cheating rookie bastard. As I look out the window now, it's 21* and threatening to snow. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 23, 2014 Author Members Share Posted March 23, 2014 I tore into the car today to rewire the alternator, starter signal wire, temp gauge, and rerouted a power wire that was routed retardedly (basically fed the whole car). That and a junction block under the hood, the fucking car looks like it was wired between track sessions and forgotten about. Holy fucking shit! I've seen better stereo wiring from an 18 year old. Anyway, when I removed what was the only ground between the motor and car (prior to me adding the 2nd one the other day), I found it wasn't that tight, the connection was dirty, and the terminal was a wee bit corroded. This sort of goes with me thinking the car pulled cleaner with that 2nd ground added. How viable does that sound now? I mean I probably could have taken 2 minutes of my life before the dyno to clean and retighten that single ground terminal if that's all it was. Shame on me for not checking my shit sooner. Quote Link to comment Share on other sites More sharing options...
Pranav Posted March 23, 2014 Share Posted March 23, 2014 Check valve is present, the flow limiter is in the trash as it plugged last year before installing the first spare opti. ? Careful on this, you will pull enough vacuum to cause the opti cap to bend inwards and case the rotor to scrape on it. Trust me I've done it. They talk about it at the 10:00 mark: Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 24, 2014 Author Members Share Posted March 24, 2014 LOL, what a blast from the past! Very informative though, luckily under race conditions (i.e. WOT) very little vacuum is present on the opti. He did mention that, if one were to hook a vacuum gauge to the air filter vacuum line, that one would see close to intake manifold vacuum readings. Either way, a new opti vacuum harness is (and has been) on the list of things to buy so I can say with confidence (some day) that this is not the cause of my probem. Quote Link to comment Share on other sites More sharing options...
Pranav Posted March 24, 2014 Share Posted March 24, 2014 (edited) Yeah, on second thought I think maybe the restrictor missing may not be an issue; in my case I think the issue was my own "fuel filter" i had on the vent (supply) hose in combination with no restrictor. I never knew I had an issue with a bent cap until I swapped motors and opened up the opti to see why it was making scraping noises when I spun it by hand; found the rotor had carved up the inside of the cap. Ended up swapping the cap as a precaution with another MSD cap I found on craigslist, which may have started a new issue: -Had some High RPM miss issues during last race of the year with new motor + new MSD cap, never pinned down cause before blowing clutch -Ran car on dyno week prior to Race #1 of this year, started high RPM miss on 3rd pull, had to let car cool off to make 3rd pull. A/F ratio was fine, running rich when it starts to miss. -High RPM miss continued after fiddling around prior to Friday practice, tried swapping coil/ICM -Friday night I find suction hose was unhooked. Looks like I accidentally unhooked vent hose on dyno before 1st pull (plate swap), sucked in crap into opti, reconnected it and hoped for the best -Sat morning car falls over and dies during practice -Swap in a borrowed acdelco opti, car ran strong with no misses all weekend; noticeably smoother and less poppy/rich idle) -After Race #1 I replace borrowed opti with a new delphi opti, ditch cap/rotor and REUSE my MSD cap/rotor. Idle becomes rich/poppy again. Test drives around neighborhood lead me to believe all is OK. -Race #2 with the new opti and reused cap/rotor: high RPM miss returns, not as bad as previous event, but similar to last race of the year. Videos from behind me show intermittent puffs of black smoke, definitely loosing spark randomly. -No trouble codes in OBDII Since everything else (coil, icm, plug wires, plugs) has been swapped/checked and ruled out, with the only factor that invokes a high RPM miss is changing optis (borrowed unit was solid with no misses and smooth idle, new opti with old MSD cap/rotor brings behavior back), I'm going to swap my cap/rotor for a new one and see if the idle improves. Just hope I haven't screwed up the new opti... No codes through all of this, oddly enough. Edited March 25, 2014 by Guest Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 24, 2014 Author Members Share Posted March 24, 2014 Can you slowly suck/blow through your flow limiter? I can't which is what's led me to believe it's plugged. That and the harness had fallen off among other things I assume is what contributed to the demise of opti #1. Quote Link to comment Share on other sites More sharing options...
Pranav Posted March 25, 2014 Share Posted March 25, 2014 I rarely admit to sucking/blowing on a public forum, but yes I can. An unhooked opti harness is definitely what killed off my last opti. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 25, 2014 Author Members Share Posted March 25, 2014 That's sig material right there. I can't suck/blow mine, so that just confirms that it's plugged. How long did you run with a sucked in cap for? Quote Link to comment Share on other sites More sharing options...
Pranav Posted March 25, 2014 Share Posted March 25, 2014 Probably 2-3 events. It ran fine that way with no misses, even with a blown #1 piston ring and other issues with the motor. Didn't start having problems until I swapped the cap, then finished it off with leaving the hose off. Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 26, 2014 Author Members Share Posted March 26, 2014 New vacuum harness gets here tomorrow, dyno on Saturday, sure hope it all goes well this time! I think it will, but then again I thought the same thing the last time. . . Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 30, 2014 Author Members Share Posted March 30, 2014 Well it wasn't the ground, I guess I'll throw in ANOTHER set of new plugs and see if that fixes it. Followed by ANOTHER new opti. FML. Quote Link to comment Share on other sites More sharing options...
Pranav Posted March 30, 2014 Share Posted March 30, 2014 Did you take care of the coolant sensor? So you've got new plugs, wires, opti, did you try swapping the coil/icm? Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 30, 2014 Author Members Share Posted March 30, 2014 Swapped the coil/ICM last time to no avail. Put a wideband in the car, AFRs were what GM typically commands in PE mode. Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 30, 2014 Share Posted March 30, 2014 Did you take care of the coolant sensor? So you've got new plugs, wires, opti, did you try swapping the coil/icm? This???? Quote Link to comment Share on other sites More sharing options...
Members Dustin M. Posted March 30, 2014 Author Members Share Posted March 30, 2014 Didn't change the ECT, still have one. AFRs were good and it ohmed good so I didn't see a need to change. Glenn did your bad ECT ohm out good? Did the car start good in the cold with the bad sensor? Mine fires instantly when cold. Quote Link to comment Share on other sites More sharing options...
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