Well I gave up..I checked everything I could check, to find a intermittant problem, and finally turned my '89 over to my mechanic. He's had the car for a week now (Grrrr the weather is getting nice for a top down ride) and yesterday told me that he's 100% sure its a bad ground some where causing me the grief. He said he was waiting for a fax with the ECM ground locations so he could clean them up. Well he never go the fax, and my vette is sitting in his garage. Question: Can anyone tell me where these grounds (for the ECM) are located?

 

...some of the grounds, ECM and anything else in the engine bay, all wind up at the bell housing bolts at the top on either side of the motor. Each of the four ECM plugs has ground wires in those individual harnesses(sp?) they should be bundled and go over to the left top bolts on the bell housing. On the right side bell housing top bolts there might be another bundle of ground wires, on my 90 there are. The fuel pump relays are under my ECM and they ground to those bell housing bolts.

There are a few ground wires that attach to the frame rails (motor cradle/K-assembly) up by the radiator on both the right & left sides. On the left side the frame carries my fan relay(2) grounds. I think the head lights are grounded to the frame on both sides up front.

That's all I can think of off the top o the head. Do you have the helm wiring diagram from the FSM set? I'm sure that there other ground points on the frame else where on the car. What's happening with the electrical system that is making you chase the wiring down? Man you have my empathy! What a PIA!


Tom

 

I appreciate it. I don't have the Helms FSM...but you know what.... I'm gonna buy every book I can find now. I trust my mechanic, but I know he will not put the same time and effort into it as I will. I bought a special ALDL/ USB cable just to hook in to my laptop. I'm gonna get an inverter so I can run the laptop 24/7 without worring about the laptop battery quiting. Hopefully the diagnostic software will give me all the information I will ever need to keep my sweet ride runing purrrrfectly.
(I can't wait to tell my mechanic the ground locations...Thanks again)

 

I cleaned up a ground by the o2 a while back that was pretty bad. It gets a lot of dirt and water in that location. Might be worth a look. What is the cars problem?

 

All my ECM grounds go to G104.
http://members.shaw.ca/agent86/Ground%20104.pdf

 

You don't need to buy every book, just the HELMS FSM, its the only one you'll need...

 

For all the help! Here's the "saga"
The car runs great...most of the time...then without warning it'll be like someone pulling the plug out. Example: I was about to "test" the acceleration on a nice straight road in my area, it got up to about 4000 - 5000 RPM (a guess?) and it just died! It would crank, but wouldn't start. I had it towed home, and after checking spark (good) fuel pressure (good) and getting more and more annoyed, I put it in the garage on slow trickle charge. About 6 weeks later on a warm sunny day,I decided to try to start it up. I put the key in, and it started imediatly with about 1/2 a revolution from the start motor, and was running great! I took it around the block...stopped to visit a friend...started it again, (ran great) and drove it home. Then I decided to drive it over to the gas station to fill it up. I started it up and it was still running/sounding great. I pulled out of my driveway, got about 100 yards down the road, and again it was like someone pulled the plug out ! I was able to get it started this time, and got about a 1/2 mile towards the gas station but it started to run so rough I had to pull over. I waited and tried to start it several times...each time it would start, but was impossible to drive because it was running so rough. Well like I said in my first post...I gave up on it, and took it to my mechanic. He called me this past Saturday...he's convinced its a bad ground. I'll let you know if the problem has been solved after I get it back, and can drive it for a few days without a problem.

 

I got a call from my mechanic last night. He's giving up on it. He suggested a auto electrics specialist in the area. He told me he was sure he'd find the problem. My mechanic checked and (I would hope) cleaned all the grounds I asked him if it could possibly be the O2 sensor. He said it could be, but added that replacing it would be like shootin' in the dark. Well I'm gonna take the car home and take a shot, (not too sure how expensive an O2 sensor is) and install a new one. I Hope I can make it home with it, but it usually ruins good until it warms up. I'm gonna keep posting with updates, but if ANYONE can give me a "heads up" I will forever be grateful

 

I would check for spark immediately after it dies. Don't wait for things to cool down.
Good luck.

 

with the spark idea.

Actually I would suggest that if you are sure that this symptom only happens after the motor gets to "closed loop" operation put a scanner on it and start it up and let it go to normal operating temp and see what the scanner tells ya.

You would need to have a Helm FSM though. In the Helm book for your yr there will be a page in the "Drivability and Emissions" section that will have a complete scan tool data display snap shot of a normal L98 in closed loop operation. I'm a noob so that page is my best friend for drivability issue trouble shooting.

All that stuff left aside to me there is an issue in the ignition or starter circuit or both. No codes for most of that stuff I think. My LT5 is just different enough that I can't be of much help....but if the coil overheats in the electronic ing system the motor could stop from lack of coil output and it may not re-start until it cools enough to not short out. The original GM HEI systems back in the mid 70's had those teething troubles...the coils & modules over heated on the early systems & drove ya nuts.


Tom

Forgot this Q. Does your yr L98 have fusable links in the ignition circuit? If so I would check those out also. Also if when your car quits & you check fuel pump pressure is it okay?...fuel pump relays?

 

A bad o2 is not going to kill your car. It could be a couple of things like, fuel pump, spark module, loose wire connections, etc. Are there any codes? If you decide to trouble shoot this yourself, a service manual would help and start a new topic over in tech.

 

So here's the latest....My mechanic gave up, and so did I. I don't have a Helms FSM (yet) but my mechanic told me about a auto electric guy up in Mahopac NY and said he's the best. I drove the car up to him yesterday. Its about a 15 minute drive. The car reached operating temp, and (typical when I take it to a mechanic!) was running as good as it ever has. I'm gonna look for a Helms in the mean time, (although my "financial advisor" is giving me a lot of flack about spending $, I figure if push comes to shove I can always sleep in the car for a few days). LOL I am going to copy and paste all the great suggestions I have from this forum, so when I get the car back (and its running the way its supposed to run) I can varify the proper operation of all the relavent systems with my new Helms FSM. I'll update as soon as I get my car back..Thanks to everyone

 

The last time it happened and I had the car at home, I did check the spark, and the fuel pressure while the car was warm. Both were good...
My mechanic said the rough running condition was related to the injectors not opening enough. This apparently only happens when the engine warms up...Why its happening is the million dollar question
Thanks again

 

Yes the injectors. On the early multi-tech (GM/OEM) injectors, say before 92 or 93 there was no ethanol in our gas. Then after 92 or 93 they took out something and substituted ethanol to do something....anyway the early injectors will eventually have shorts in the coils (part of the injector that fires it) and that causes a lean condition.

Do an ohm test on the fuel injector coils, ya should see above or arround 15 ohms for each when they are cold and when they are hot. I'm fairly sure about that ohm #. If you get #'s all over the map or all are low when tested cold or hot then that could very well be your problem. One way to test the injectors is use a scan tool and look at the "Integrator #'s" and the "Block Learn #'s". In the FSM in the driveability and emissions section there is a snap shot of a normal motor's scan data. You just compare your data to the data in the FSM. If the injectors are really bad the scan tool will show a lean condition. If enough of the injectors are shorting you will even smell the lean condition at the tail pipes or you can pull the plugs and you will find that they have almost no evidence of fuel being feed to that cylinder...the plugs will look sooo clean that you swear the motor never was run on them.


Tom

 

Hey Jim I feel like a dunce! If I would have realized that you were near me I would have put a scan on your vette!

I'm in Mt. Vernon!

 

Yepper...we're neighbors....I think you may be on to something about the injectors....I'm gonna call the "Wire Shop" with this information so he can check injector resistance cold, and hot. It may very well be you've hit the nail on the head!
Thanks

 

He told me the injectors are causing the problem> (now I'm wondering about the qualifications of my regular mechanic you would think after having the car for a week that would be one of the things he checked)
Anyways the garu said 3 injectors are bad...(if only 3 are bad, would it cause to car to run so bad I can't even "limp" it 1/2 mile home?)
Frankly I find it hard to believe that he's solved the problem. and thats because it came on so suddenly...It's not like the car ran a little bit bad, and then got progressively worse. (again it only happens when the car warms up, and (the baffeling part) not all the time
Ok so I take his solution, and replace all injectors...Does anyone have any expierience with rebuilt injectors? Money is a factor here. What kind should I tell him to install?
Can I rebuild the injectors myself??

 

Ok so I got a hint to check Ebay for injectors...(the prices are great!)
I find 22.5# injectors there, but (correct me if I'n wrong) specs for my 5.7 Y series 89 "Vette" call for 22# injectors. Will I have any problems installing 22.5# injectors? If so what can I expect?

 

Ok so I got a hint to check Ebay for injectors...(the prices are great!)
I find 22.5# injectors there, but (correct me if I'n wrong) specs for my 5.7 Y series 89 "Vette" call for 22# injectors. Will I have any problems installing 22.5# injectors? If so what can I expect?

 

Jim,

The answer to most of your Q's are yes. Without warning due to the electrical nature of the source of the malfunction. On an L98 motor it is easier to do an ohm test on the injectors because you can get to the electrical harness and put the VOMeter on each injector....LT5's the injectors are under the Intake manifold. The reason car runs sooo badly soooo quickly is again related to the coils being shorted. The shorts are due to the fact that when the early style injectors were designed ethanol was not in the gas...the epoxy coating(an insulator) that is used in the windings in the coils is disolved eventually by the ethanol and that's when the short happens...also once shorted the hotter the injector gets(more use=more currant flow) the more dramatic the shorting becomes. A shorting injector creates a lean fuel condition so the car misses alot and can shut down due to lack of fuel. That shows up if you scan the motor in closed loop, O2 sensors and the block learn and the integrator #'s give the bad injectors away.....or you can look at the plugs & see which cylinder isn't getting fuel.

No you can't rebuild them and I would advise to do a search in the "Tech & Performance section on what brand to buy, Accell seems to be favored by many L98/LT1/4 owners. Oh please do yourself a favor and buy 8 new injectors because the good ones will fail eventually from the ethanol. Sorry but the only cure is new injectors...but you will not have this happen again if you DO NOT buy GM/ACDelco/Delphi...use aftermarket.


Tom