So as you folks may have seen recently ive been chasing down a few issues with my 95 Z. As of right now, it has no drivetrain vibration anymore and the exhaust leak is slowly (but surely) getting fixed as i have time to address it. I have only one more problem, and ive decided that ill be selling the car whether i manage to solve this or not.

As it sits, the car runs fine. sometimes gives me trouble starting it but i always manage to get it turned over. However, somehow im having a misfire and the SES is not throwing any codes. Even after several engine cycles, long or short, the only code i saw with scan9495 was 18 for the fuel injector circuit, and the corresponding drivers side o2 lean reading. That was at the mechanics shop, and after we shut it off the codes have not come back up yet. The misfire is more prevalent at higher RPM and under load, obviously, and even makes the car buck a llittle bit while idling in gear at a red light. Ive done plugs and wires already, only about a month ago actually. MAF too. fuel pressure seems ok, im worried its the opti but its not throwing a code so im still optimistic that something simpler is the problem here. As far as new parts goes, im not willing to buy another opti. Not worth it if im going to sell. if i can get it running right ill be able to pull 2500 for it hopefully (asking 2800 initially) but if i cant solve this issue then it goes to the best cash offer i receive in the next few days.

I cant for the life of me figure this out. Mechanics have told me to start by checking the injector wiring (based on the ONE code it threw after my mechanic tried to set it off) but im just so tired. Dont get me wrong, if i can solve this with my own two hands ill be under the hood until its fixed, but i hardly even have any direction here. whats worse is i dont own my own lift or jack, i have to go to friends houses to work on anything. and i HATE being "that guy" you know? oh well, theyre used to it by now anyway But yeah, inspecting the injector wiring through the harness all the way back is just a task i dont have the energy to tackle unless im more than 50% sure thats my issue.

As far as possible causes, well i read that various gauge cluster connections and potential bad grounds can cause funny stuff.. lets just say generally the cause is a 1200 dollar parts and labor LT1 swap. Ive gone through vacuum lines and electrical connectors as i go along, but still some things i cannot solve:
-oil pressure gauge is through the roof. Connector is seated properly, and changing the actual sensor seems like it would be a pain in the ***.
-temp gauge isnt functional due to not even having a connector. If its wire is green, im pretty sure it got cut in the harness over by my ignition coil. If not, somebody please tell me what that wire might be for!!
-Braided grounding straps might not all be there, in fact i found one that used to be connected but fell out at some point. guess ill check to see if shoebox has a list of all chassis grounds.
-There is something hanging down near the starter and pass. o2 that looks like a sensor with a cut wire. its wrapped with the foil-ish tape and disappears into a shining threaded cylinder at the bottom of the block

There might be more small stuff, but if it doesnt potentially explain this misfire im experiencing then im not too concerned about it.

ANYBODY IN THE HOUSTON AREA:
I live in Katy, and the car is available for sale. interested parties from this forum take priority within 100 bucks. let me know if youre interested. 1500 as is, 2500-2800 if i can get it running well. Of course, if anybody wants to work with me ill provide the beer or whatever floats your boat. Im an audio/video professional as well, so if anybody needs that kind of skill set...

Guys, im ready not to worry about making it to work or back home anymore. Any and all advice is appreciated, hopefully together we can figure this thing out.

 

95 is OBD-1 and there is no misfire detection in OBD-1.

Opti only sets codes for problems with the optical cam position sensor. No codes for the high voltage section (cap/rotor) problems.

Did you investigate the DTC 18 code? Did it "fix" itself? At any point in doing testing did you disconnect an injector? That would set the code and it would remain stored.

What, EXACTLY is the fuel pressure at idle with and without the vacuum compensation line connected, and on the road with engine under heavy load - full throttle above 5,000 RPM?

 

well glad im at least not crazy about a miss throwing a code.. anyways, when DTC 18 showed it was after the mechanic had done a few random things to "feel it out" like giving it gas while applying brake to check the motor mounts, things like that. It disappeared and I havent seen it since, although i have checked the seating and position of each injector.

As far as the fuel pressure goes, i had to rent the kit from oreilly and do it in the parking lot. I dont even have my own floor jack (part of what makes my ordeal so frustrating.) Scan9495 doesnt read fuel pressure, right? Or else id just run a scan.. I really road because the tags are out (probably wont bother with them at all now since im selling, but even still why bother if its not running correctly, right?) As far as hitting 5000 rpm, ive always been pretty easy on the car, and especially while it hasnt been running correctly. I simply cant afford to cause myself more problems.

Im about to ask the neighbors if anybody has a fuel pressure tester, And i suppose i can tape to the windshield and give it a test while driving if you really want me to. Id prefer not to unless i absolutely have to though. As far as WOT goes, i wont put the pedal all the way down, ever. Not unless It was running perfectly. Ill still do the simulated test though, but i forget which vacuum line to play with. Is there anything else i could be doing to help diagnose this? Time is my issue here, and id hate to settle for less than 2500. But given how much extra gas im burning right now and everything else, im at the end of my rope.

 

If you're firm on selling it you would just be wasting your time. No - nothing on the car measures the fuel pressure. There is no fuel pressure sensor, so no way for the PCM to know the pressure. The pressure is controlled by a self-actuating regulator. If the regulator fails you will only know by measuring the pressure, or seeing fuel running out of the vacuum line, or body.

 

I never thought id disagree with you fred, but in my opinion as long as im not spending money and purely investing my time and effort into something to improve it, thats worth it. Im willing to go the extra mile all day if the situation calls for it. I will do everything i can in the engine bay as far as labor goes, but the cutoff in my mind is when i start to spend money. not gaskets or anything small like that, maybe even a fuel injector, but if the opti is my problem then ill probably rethink everything. As long as the monetary investment matches or is less than my projected return, its justified in my mind. If i was ABSOLUTELY SURE changing the opti would solve all my problems then id do it in a heartbeat. It would mean all the difference in selling it, adding at least 500 bucks to what id ask for it the way it sits now.

Anyway, on back to the issue at hand here, im hoping that this ground strap will be my problem. The timing ive had discovering the braid compared to the misfire seems consistent. It appears to me that it used to be connected to the block and run to a stud on the firewall. I cant be sure though, as ive never seen an LT1 out of the bay and laid eyes on the back side. Sheltered, i know. i mean ive done my own plugs and stock manifold gaskets so im not uncomfortable pulling a superman over the intake and hugging the block to get back there. Still trying to find a fuel pressure tester.. i dont really have time to go rent one if i have to keep it longer than my visit to the store (lets hear it for those parking lot jobs). Im worried its gonna be my opti in the end, but there are SOOOO MANY posts about how people got new optis to chase this problem and either got bad ones out of the box or it didnt end up fixing things. I cant go spending 250-350 bucks with the shotgun approach. I mean ill do it with gaskets and stuff like that, but even the shops are telling me they dont want to try and diagnose it.

So now im sitting next to my most knowledgeable mechanic buddy and were looking over things trying to make sure its not the opti. well see what happens when i put this braided ground strap back on. anybody know the stock mount location? Im an electronics engineer and i know electricity flow like the back of my hand, so before you say it yes, im aware ground is ground (in MOST applications, sometimes distance ratios need to be considered) but ive always tried to go for stock when it comes to maintenance. Easier for future reference that way in case i forget some stuff.

 

1. Do what Fred suggested and measure the fuel pressure while the misfire is happening. Report back here with the results.

2. Investigate the injector code 18, which is an electrical failure, not a performance failure: With the engine idling, try wiggling the connector on each injector. See if that sets the 18 code again. If it does, reset and do it again, this time while checking the scan for code 18 after each injector "wiggle".
Or..., the next time you see code 18, don't reset it. Unplug each connector briefly with the engine idling. Each one should have a negative effect on the idle except the one that is faulty. It will have been disabled by the PCM after it sets code 18.

 

I think I'm just discouraged by the fact you plan to sell it, because of the problems. I put some time into trying to help, but it didn't go anywhere. The data log showed it was running extremely rich.

By starting a new thread, you've lost all continuity with the previous discussions.

 

I felt the previous discussions were resolved, as this seemed like a different issue. Apologies for that, but new developments might shed some light on the situation. I went to replace one of the exhaust manifold bolts (drivers side, second from the firewall) that i noticed was missing when i changed the gaskets last week. Guess what... Yeah, it wasnt missing. 5 minutes turned into all day as i battled with the y-pipe flange so i could remove the manifold, only to confirm what i hoped wasnt true. But i knew better. Its definitely still stuck in the block.

So now here i am, new manifold and flange gaskets in hand. Also picked up a screw extractor (never done anything like this) and new plugs because i cracked one and #7 looked like it was arcing. Hopefully that was causing my misfire, but ill have to wait for confirmation. Im stuck right now because I cant seem to find a way to drill into this bolt to use the extractor. If only i could affix it to my air ratchet all would be well. Im at a loss for ideas now, and id really like to fix this while the manifold is out. It definitely took alot of effort, especially considering ive never done anything like this on my own. I ran a scan on my way to the auto parts store but it seems useless to post it now. ill run another one after this gets resolved. Who knows i might keep it but im just so frustrated with it right now. Help me figure out how to extract this bolt and ill stick with her for awhile. Perhaps she deserves another chance, and after all im becoming pretty familiar with this motor. Your efforts are never wasted Fred!

 

He man don't give up on her they are jus like our chicks they give us hell, bitch moan n complain but at the end of the day they will give you so much pleasure, and she's always, outside waiting for ya. Lol keep up head up and keep at her and you'll get her.

Sent from my SGH-T989 using Tapatalk