Indio Monk

History of the car is that it has been sitting for a while. I am going to guess almost 2 years just from looking at the receipts for work done.
Work done.
The opti was supposedly changed a year ago, but I see that the opti vent hose is not hooked up. Plug wires look newer. I need to pull plugs to see how they look.
I was told gas was old. Fuel tank is almost empty.

Plan is to siphon out gas to inspect and pressure test fuel system at shrader valve.
Jack up car and inspect 02 sensor connections, and knock sensors.
Check ICM, do Optispark testing and hope for the best.

She idles a little rough and I need to fix these items to get inspected.

The other thing is I am going to rebuild the steering column since the tilt is broken and may be causing ignition switch to malfunction. Car sometimes has a hard time turning off when key is turned to off position. When I readjust tilt it works.

Washed car last night and can tell it going to need a clay job and good polish and wax!

Any tips/advice are greatly welcomed. I followed Chstitan42 s post on his 96 LT4 and I am hoping it is not the opti but hey you never know.


Current Fault Log
------------------
P0141: O2 Sensor Heater Circuit (Bank 1 Sensor 2)
P0161: O2 Sensor Heater Circuit (Bank 2 Sensor 2)
P0300: Random/Multiple Cylinder Misfire Detected

FASTAZU

Nice project. Sounds like you have a good plan, you may also want to check out the injectors.

antfarmer2

I would change all of the o2s and while under there pull the fuel filter and key it on till you empty the tank out the fuel line. Then a new filter and fuel then warm it up and do a oil change then drive it gently for a while. For the tilt there is a over sized bolt you can buy to fix this most of the time with just doing the left one. Looks like you're hooked on vettes.

lt4obsesses

Beautiful car my friend. Oh, how I miss my LT4.

Of course, I can't be positive in your case. But after you get the fuel cleaned out and refilled. Pressure test the fuel system. The first thing I might check is the Fuel pressure regulator, it's a quick and easy and cheap as well, but they are prone to failing.

Indio Monk

Thanks! I am going get a Loan a Fuel Pressure tester tomorrow at Autozone. I am also going to get the two downstream 02 sensors that are throwing codes. I looked at the downstream (after cat) today and they look like the originals!

lt4obsesses

I do know that my fuel pump went out slowly. Intermittently, I would get some hesitation. Then one day, it was running great, then just acted like it ran out of gas. Good news is that it is very easy and relatively inexpensive to replace.

Funny story about the 0300 code. I had put in a Hotcam a few years prior and would get the code from time to time. I thought, from research, that this was a normal side effect without a tune. The weird thing is, that when I replaced the dual mass flywheel with a 22 lb steel single mass, the code went away and never came back. The DMF was toast. ( I think the DMF being out of spec might have been triggering the knock sensor)

antfarmer2

I would change them all so they match. Do you change spark plugs a few at a time? Get a new fuel filter since your under there.

WVZR-1

OP - yours is an interesting project maybe. The post-cat codes are unusual I'd think and "both" maybe considered more unusual. I'd maybe check/inventory all related "to tune" components before just randomly going after a few.Your codes I believe are more directed towards the heater circuit.

Your under-hood snapshot in a previous post you had a pretty good image of the MAF and the connector. Tapped to that harness was a part# that looked like it referenced to mating harness that might have been used to adapt some very generic MAF to various applications.

This is the thread: https://www.corvetteforum.com/forums...cuum-hose.html

kg4fku pointed out the MAF wasn't original and I saw the tag and thought I'd try to verify maybe the validity of that. That number I interpreted as 19171545. Is that the number on the tag? I see that the ACD catalog mentions a MAF with adapter harness BUT is it the only choice or correct? I've no idea.You might visit a dealer in the area and see if there's maybe options for the MAF. The ACD MAF "kit" has 27 different applications for usage.

I believe that you verify all including the hanging vacuum dongle for efficient/correct routing before replacing anything. I'd start maybe at the MAF - is there any numbers on the MAF that might be used to ID it? O2 codes don't mean "replace" them -

Does the higher mileage justify replacement? That gets argued/debated from time to time. Your decision but I'd inventory every bit of the control devices first.

I'd do a complete read of the FSM for the codes and since you have BOTH I believe it might mention that the maybe more common issue is a "BLOWN" fuse.

Do you have the '96 FSM yet?

Indio Monk

WVZR-1, I have the 94 FSM 2 Red Books, I might need the FSM for the 96. I don't know if I need the electronic copy or just buy the red books for 96. I might just need to bite the bullet and get the FSM since there were many changes and also the LT4.

I will PM you on the FSM I sent you an email maybe you did not get it.

Today was a 7am to 7pm day so ... no working on the vette. I have to agree with you though on doing more diagnostics than just the DTC codes. I really need to check the fuses etc. Last night I did look at the after cat 02's and they look to be original, but that does not mean they were the main problem. I really need to get to Autozone for that fuel pressure tool. I also just received my star sockets and pin removal tool for the steering column. I wonder if a pinched ignition wire might also be causing the P0300. I just want to rule that out by pulling that steering wheel off and column.
I did a visual inspection and the plug wires look newish. I want to pull the plugs to inspect but with time not being on my side I want to try and play it smart by doing the proper diagnostics and I think checking fuel pressure might be first and then going down the trouble shooting tree step by step.

I did try and clean that polishing splatter off the engine yesterday though. I'll post a pic.

Pics are after cat O2 sensors left and right, Engine bay cleaned up from splatter and funny ground wire that I do not know what is for.

Thanks!

Indio Monk

Yes looking at the wires this looks like it has been changed recently!

chstitans42

That ground wire might be for an alarm. Mine had something bubba like that but it was near the door jamb. Feel free to bring your car over to mine and compare engine bays.

Indio Monk

CHSTitan42 I would love to drive it over but When I purchased it I pulled the plates so it is sans plates!

To be legal per Texas Law since this has an out of state title "Cali" I have to get it inspected before the title can be transferred, and I have 30 days!

Wow! The pressure is on! And we are deep into AUDIT Season for our Education/School clients so I am working long days and weekends. That means less sleep and night time wrenching!

If you are ever near 121/Spring Creek (Toyota Headquarters) stop on by. My hood is 1 mile away!

Indio Monk

I need to jack this car up and inspect the Clutch. I have read some about the DMF and how they are discontinued. The journey will be interesting!

96GS#007

For clarity, that clearly is not the OEM MAF. In this pic of mine (which is OEM), you can see the dramatic visual difference...



I'd find a factory MAF. I can't ever recall seeing in person or hearing of an aftermarket MAF that actually benefitted the LT1/4 engines in the C4. Lots of claims.....no proof.

tlong

I have a '96 and had your codes. May I strongly suggest getting it on a Scantool to diagnose these problems. You can systematically check everything on that car quickly and have answers to DTCs. To get a clear OBDII SES light is the key to passing inspection, so why not let the machine tell you what's wrong?

The PO300 is enough to make you hate this engine because it's so general. Spark, gas, vacuum? Start guessing.

VikingTrad3r

i am drooling over these lt4 cars. i never knew how great the lt4 was. subbed.

Indio Monk

Had to work but made some time for the Vette. Rented Fuel Pressure gauge and checked with ignition on but car not started. Went to 41 psi then dropped to 29 psi in 24 minutes. I am thinking maybe Fuel Pump hopefully and not injectors. FPR seems fine.

The pics show 38 psi since it took me a while to get the pic and it dropped from 41 to 38psi. I read your post and yes this is going to be an adventure. Hopefully its just a fuel issue, Pump, Filter, Injectors etc.

96GS#007

If it's the filter, you'd see gas on the floor and smell the leak.

The fuel injector rail easily lifts away from the intake manifold...4 bolts. Lift the rail & injectors free of the intake, turn the key to "run" (do not crank the engine), and if the injectors are leaking you'll see gas drip from the offending injector.

Pull the vacuum line off the Fuel Pressure Regulator at the left rear of the fuel rail. If there is fuel in the line, the regulator is bad. If it's dry, the regulator is fine.

If all of the above check ok, then it may be the fuel pump. Frankly 41 to 29 psi in 24 minutes is not horrible. I've seen better, but that's still passable. Typically if they're bad, they'll bleed down to 0 psi in a matter of a minute or two, or even less than a minute. Another test is to tape the fuel pressure gauge to the windshield and make a few WOT runs as well as some low rpm/high load runs (ie 25 mph, 5th gear and accelerate). See if the fuel pressure keeps up or drops off.

A stutter on these cars is usually ignition. New plugs and wires are first. The opti is last.

VikingTrad3r

yeah that pressure loss has nothing to do with your issues.

Lazy Tom

What about the tires?
Have they flat spotted?
I bought a Jeep with 44s once that sat in the front yard for years.
Even though they were new they never rolled out.

Very nice car.