Anyone here a C4 guy?

[Avatard]

I have some flaky shit going on with my '94 C4.

It's a later 94, and thus actually is one that has an ODBII connector (thank goodness), and it's coding "36 - ignition system problem loss of high res pulse signal"...which would suggest a bad opti...but the fucking thing is kinda acting stupid all around...like occasionally throwing other codes, lighting the ASR Service light, and even the fucking A/C went to the zoo for a bit, until the car was restarted.

It spits, sputters, and acts up...and then the "check engine" light comes on, and she runs fine :scratch:

I think it may be a bad wire, or connector, or maybe my ECM is hosed.

Anyone had any shit like this?

:bash:

[TommyHotWheel]

Run through the wiring harness and check all of the sensors. I seem to remember my uncle having the same sort of trouble and he had some wiring issues. Dont quote me, cuz I am not positive. I will see if I can get in touch with him tomorrow.

[Avatard]

Thanks, Tom.

[Particle Man]

I clicked on this thinking you wanted something blown up :lol:

[defector]

Faulty MAF? IIRC, that was a fairly common problem.

[Adeptus_Minor]

Tracy (GRex) could probably provide some insight as well.
Oh he of the cursed C4. :lol:

[Particle Man]

Tracy (GRex) could probably provide some insight as well.
Oh he of the cursed C4. :lol:

I was deliberately not going there :lol:

[goof2]

I don't know about the C4 specifically but in my experience when a lot of different things are going wrong like what you describe you may want to check your grounds. A faulty ground can cause all sorts of seemingly unrelated problems. Check them all and clean or replace where necessary before dumping a bunch of money in to the car.

[Avatard]

I clicked on this thinking you wanted something blown up :lol:

If I can't diagnose the fucking thing, that just may be an option...

:bash:

[Cutty72]

I clicked on this thinking you wanted something blown up :lol:

Me too. Though that could be the ultimate answer. :lol

[G-Rex]

Mine hasn't done anything wonky like that, but checking the grounds does have merit, as the body is fiberglass, the grounds are even more important.

Mine is a '94 as well, and I have the factory service manuals, all 2000 pages worth. If you want, I'll look through the troubleshooting section and see if I can find anything that will help! If so, I can easily scan and email you a PDF.

The '94 has 7 separate grounds as I recall.

Anyway, let me know. I'll look and see what I can come up with.

[Captain Morgan]

I definitely agree with checking the grounds, as that was always the first thing I was told to check if there were electrical issues on the vettes.

I'd also suggest going to the C4 section on to corvetteforum.com, if you haven't already done so.

[karl_1052]

Didn't the OptiSpark(sounds like something Optimus Prime is looking for) have to be repalced every time the gas tank is filled?

From: http://www.ls1lt1.com/forum/showthread.php?t=78
Who hasn't had problems with an optispark? LOL. THere's two parts to the opti. THere's an optical cam position sensor. This part is a Mistu build piece and is VERY accurate at reading cam position and delivering timing signals, but its very moisture sensitive.

The other half is the high voltage section where the rotor conducts the spark just like any other distributor. This half can also be affected by moisture and also over time the high voltage creates ozone inside the cap that corrodes the contacts.

They can be reliable if you keep them dry, which can be hard when its mounted on the front of the motor under the water pump. The upside is they are not hard to replace, a little messy with the w/p removal, and they are only about $200 a pop brand new from GM. If maintained properly you shouldn't have to replace it too often.

One mistake a lot of guys make is they add an MSD box onto the ignition. The multiple spark errodes the contacts inside the rotor very rapidly. MSDs have been responsible for lots of opti failures, particularly on boosted cars.

There are some nice options out there to eliminate the opti all together now, including just taking the high voltage side offline and continuing to use the cam sensor part. With the voltage removed from the opti the cam sensor section can live a very long life. Same basic sensor is used on lots of other vehicles out there minus the distributor half.

I would check for moisture first, then grounds, then change the optispark.

[Avatard]

Yeah, like I said in the first post, I'm really hoping it isn't the Opti...but the more I read, the more I fear it might be. It's just that the computer's been doing other flaky shit, and, well, it's topside...if that's what's wrong, my monkey ass don't need to get on the ground.

I'm NOT looking forward to doing that fucking Opti...looks like a HUGE pain in the dick. You have to take 400 fucking plastic pieces off the front of the fucking engine bay, take out the rad, pull the waterpump, extract the harmonic balancer...

AARGGGHHH!

If I do it myself, it can be done for under $200...if I take it somewhere, it's like $1500+

Really hoping it's something stupid.

[G-Rex]

Yeah, like I said in the first post, I'm really hoping it isn't the Opti...but the more I read, the more I fear it might be. It's just that the computer's been doing other flaky shit, and, well, it's topside...if that's what's wrong, my monkey ass don't need to get on the ground.

I'm NOT looking forward to doing that fucking Opti...looks like a HUGE pain in the dick. You have to take 400 fucking plastic pieces off the front of the fucking engine bay, take out the rad, pull the waterpump, extract the harmonic balancer...

AARGGGHHH!

If I do it myself, it can be done for under $200...if I take it somewhere, it's like $1500+

Really hoping it's something stupid.

I replaced my Optispark with an MSD vented unit a couple of years ago when I had a leaky waterpump. My original Optispark was fine, and I still have it. I just replaced it as preventative maintenance. I'm not sure if my old one would help much with your troubleshooting, but if you think it will, we can talk.

Also, if you do decide to do the Optispark yourself, it's not "that" bad a job. I have some tips and pointers I can give you that will make the job infinitely easier.

[Avatard]

Thanks, man...I just may hit you up for some of those pointers, if it looks like I have to dive into that Opti.

Right now, I have my kid's car to contend with first, and some FWD wheel bearings I need to do (joy). She managed to wreck the fucking 'Stang I got her, and now I have to coax a little '91 Celica convertible into shape as a driver, so she can get to work.

[Adeptus_Minor]

Right now, I have my kid's car to contend with first, and some FWD wheel bearings I need to do (joy). She managed to wreck the fucking 'Stang I got her, and now I have to coax a little '91 Celica convertible into shape as a driver, so she can get to work.

Don't you love how her car becomes your job? :lol:
My team leader at work has similar issues with one of his sons.

[TommyHotWheel]

Is the 'stang totalled? My Uncle is in Alaska, but my Aunt said she remembers the harness being replaced. When he gets to a signal she will ask.

[Avatard]

Is the 'stang totalled?

Yeah man, I'm afraid so. '87 5.0 GT. It needed paint, but it was all there One or two tiny rust spots on the hatch. Coulda been a classic in another model year. I think I'm more heartbroken than she was.

T-boned, at the left front fender, and the door. The A pillar took a good whack (good enough to crack the windshield), and the hit took out the upper ball joint, so it came home on wrecker. I had just gotten done dumping a shitload of new parts in it too; brakes, water pump, tires, it even had Flowmasters on it. Nice little Fox Body. Sniff.

I've been looking for maybe another shell to drop everything into...breaks my fucking heart, although I myself am responsible for sending my share of classics to the boneyard (but who knew back then?). If I knew some of those rusty old shitbuckets would be worth all that today, I'd have held on to them. Now you can buy replacement panels for fucking everything, and those old shitbuckets are worth more than I paid for my first house.

Who knew?

:shrug:

My Uncle is in Alaska, but my Aunt said she remembers the harness being replaced. When he gets to a signal she will ask.

Thanks, bro. Like I said, I have a minute. I'm gonna take my time. I'm in no hurry to tear into that plastic POS.

What I really wanna do is trade it for a 68-72. Something with ZERO computers in it. Motor, trans, rear, seats, and a wheel. A real car.

I miss that shit. Fucking cars today, you open the hood, you can't even see the fucking motor.

Alright, enough...I sound like the get outta my yard guy...

[Avatard]

Don't you love how her car becomes your job? :lol:
My team leader at work has similar issues with one of his sons.

Well, this one's #3. She wrecks this, I'm getting her a bicycle.

:bash:

[Inferno]

I had a '94 Firebird Formula that I pulled and rebuilt the engine. It could be either the Opti, MAF, IAC or the O2 sensors on the headers/manifolds. Maybe the computer, but I have not heard of the computer going it on them.
The LT1 is a tried and true iron block SBC that has been around for decades and is one of the best engines ever built IMO. It is one of the sensors, can be a pain in the ass to find the prob, but should be an easy fix.
Re-Reading your post, check the O2 sensors, sounds like your problem. The other things like A/C...no idea lol

[TommyHotWheel]

[QUOTE=Avatard;399837]Yeah man, I'm afraid so. '87 5.0 GT. It needed paint, but it was all there One or two tiny rust spots on the hatch. Coulda been a classic in another model year. I think I'm more heartbroken than she was.

T-boned, at the left front fender, and the door. The A pillar took a good whack (good enough to crack the windshield), and the hit took out the upper ball joint, so it came home on wrecker. I had just gotten done dumping a shitload of new parts in it too; brakes, water pump, tires, it even had Flowmasters on it. Nice little Fox Body. Sniff.

I've been looking for maybe another shell to drop everything into...breaks my fucking heart, although I myself am responsible for sending my share of classics to the boneyard (but who knew back then?). If I knew some of those rusty old shitbuckets would be worth all that today, I'd have held on to them. Now you can buy replacement panels for fucking everything, and those old shitbuckets are worth more than I paid for my first house.[QUOTE=Avatard;399837]


Find a four cylinder and swap that stuff over! Or if you wanna make some money and are not in a hurry, part that Mustang out on Corral forum and get some of that back.


Here are a few in Jersey...
http://newjersey.craigslist.org/cto/1889637170.html

http://newjersey.craigslist.org/cto/1887533336.html

http://newjersey.craigslist.org/cto/1885024282.html

[Avatard]

OK, so I decided to take the C4 out this evening. I had started it up, and for whatever reason, the intermittent clusterfuck issue was on hiatus. Or so I thought.

I go a few miles out to the Hess station, and fill 'er up with some fresh premium.

Should have never switched it off.

When it restarted, it was misfire city. I made it away from the pumps, and pulled over by the dumpster to fuck with it/wait for it to blow over/consider my next move.

My GF drives right past me, in her car. Didn't even see me, even though her headlights had to shine directly on my car, and she passed within 3.5 feet of me. I swear, this woman is sharp as a bowling ball (when I got home later I asked her if she heard a whistling sound in her head when the wind blew; fuck my life).

Mind you, as luck would have it, I left the house with no cell phone...so of course I was kinda screwed. I waited about 20 minutes, and it restarted running at least well enough to drive it (although it sounded like the Beverly Hillbillies truck), and limped home sputtering all the way.

The car gods are out to get me.

I need a new car, and a new GF...

[Avatard]

Re-Reading your post, check the O2 sensors, sounds like your problem. The other things like A/C...no idea lol

Why would the code scanner not pick that up?

BTW, it seems to get worse when it gets hot. I let it cool a bit, and it restarts feeling much better.

It misfires so fucking bad that the cats start to smoke.

[Gas Man]

I'm so sorry man... I'm over here laughing my ass off right now. I'm truely sorry...

[Particle Man]

Why would the code scanner not pick that up?

BTW, it seems to get worse when it gets hot. I let it cool a bit, and it restarts feeling much better.

It misfires so fucking bad that the cats start to smoke.

Something electrical is swelling with the heat and then contracting when it's cold. If it were older I'd swear it was the distributer cap (had a similar issue with an older car some years back). Check the electrics to feeding the spark plugs...

[101lifts2]

Why would the code scanner not pick that up?

BTW, it seems to get worse when it gets hot. I let it cool a bit, and it restarts feeling much better.

It misfires so fucking bad that the cats start to smoke.

I would run the engine with the MAF sensor unplugged (has to be unplugged when ignition is OFF). Let the computer run off of speed density instead of air mass. If the misfire is never apparent, then replace the MAF sensor (they are notorously junk). If it still misfires, then look into the optical spark system, though they usually only fail if they get wet. My 93 Firebird with a 5.7 used to act up (misfire) on occasion come to find out it was the opti spark getting wet.

In earlier years (pre OBD2) the oxygen sensors had a large amount of authority in which would actually make the engine misfire. After OBD2, the calibrations were such that at the 21% +/- fuel correction would set the code, but not cause the engine to miss. You can also unplug the O2 sensors and see if it still misfires.

[Avatard]

Mine has the ODB2 connector, even though it's a '94 (it must be a late '94, as I think it come online mid-year)

[101lifts2]

Mine has the ODB2 connector, even though it's a '94 (it must be a late '94, as I think it come online mid-year)

How many pins is it?

[Avatard]

Geez, I dunno...the standard D-shaped connector. Same one on my '99 Expedition...the standard ODB2

I was kinda shocked, and expecting to find the older connector, so it was a relief. I was smart enough to get the to-of-the-line Actron scanner with the complete kit, and ALL the cables, though, because I tend to be a magnet for older cars...

I haven't had the heart to drive it since...in fact, I don't think I'll take it out without someone riding alongside as "backup". When I do, though, I'll unplug the MAF as you suggested, and try it.

[101lifts2]

Geez, I dunno...the standard D-shaped connector. Same one on my '99 Expedition...the standard ODB2....

1984-1993 Corvettes used the OBD1 12-pin D shaped connector. 1994 and 1995 used the OBD1 system as well, but was equipped with the OBD2 16 pin connector. These cars are still OBD1, not OBD2. I doubt if the Actron scanner will work on your car as I think the controller uses UART communication, not J1850 Class 2.

The 1999 Expedition is OBD2.

[Avatard]

The scanner works, it talks to the animal, it uses the regular ODB2 connector...

Now, I do have the top of the line Actron (http://www.amazon.com/Actron-CP9190-AutoScanner-Diagnostic-Scanner/dp/B000KGCUMA/ref=sr_1_3?s=automotive&ie=UTF8&qid=1282516704&sr=1-3), which, like I said, even has ODB1 cables and other early proprietary cables in the kit as well, it may fall back to whatever communication standard is required...but it does recognize it by name, and retrieve codes...

[101lifts2]

Unless the codes are designated as PXXXX, it is not OBD2. And I think if all you needed was to flash codes you could have done that through the IP cluster. IIRC.

[Avatard]

Took it out again today. It's nice and warm, and dry, so the likelihood of moisture in the Optispark would be nil.

It ran OK at first, and started running increasingly like shit as it got hotter.

I removed the MAF connector, and restarted. Same shit...only, of course, now it threw a code for the MAF.

I reset the codes.

Did some reading on a Vette forum while the POS cooled.

According to what I read, it could be the ECM, the ICM, the Optispark, the MAF, the O2 sensor, or aliens from space...or a chafed harness, or bad connection.

I pulled every fucking connector I could find, inspected, and sprayed every contact with Deoxit D5 (best contact cleaner on the planet). It seemed to improve a bit, but is still throwing codes:

http://poopnugget.com/files/vettecode1.jpg
http://poopnugget.com/files/vettecode2.jpg
http://poopnugget.com/files/vettecodes.jpg

I'm at wit's end with this piece of crap. To read the Vette forum is to have nothing but pity for LT1 owners. GM owes a lot of people an apology.

This thing is pure fucking crap. I want a 68-72 with no fucking computer.

Anyone wanna trade?

[Dave]

Convert to carbs, fuck it

[Avatard]

Update:

Went out and restarted it. ASR indicator on dash went out, engine still runs rough.

Check engine light is out, but it still throws code 36 (WTF?).

Let's here it for GM's random fucking computer bullshit!

Yay!

[101lifts2]

You have a DTC 36...so get a service manual and start diagnosing it.

Man do I have to tell you everyting?

[Avatard]

It comes and goes...that's the weird thing.

It seems to throw codes (and light the ASR service light) rather fucking randomly.

I'm still not entirely convinced it isn't something else. On the vette forum I was reading, other people with this (and other) codes were reporting it being any number of five or six possible things...ECM, ICM, Opti, etc.

The error messages seem to be about as relevant as MS error msgs.

Did Microsoft write GM's code, by any chance?

This is pure shit.