'93 LT1 Starts and then dies when hot

[Vettebigguy]

Hi guys, I sure do hope someone can help me, I have a '93 LT1 with about 40,000 miles on it. Last month I was driving down the highway and all was fine , when suddenly the engine just quit ( at 60 MPH...that was fun ) I got it started again and she ran for a while, then quit again, like I was out of gas. Had a full tank or so , I managed to get it to my Buddy's place in Spokane Washington , and the problem just got worse. I had to have it towed to the Chevy Dealership. They put a 500 dollar fuel pump in it and she was fine for the first 5 blocks. Then it stared all over again. They have since changed the ECM ( 500 bucks ) tried a new BCM and still it will start get warm ( run about 1/2 hour ) and die. They are now at a loss as what to do next....do any of you guys have any idea of where we should look now? What about the ignition coil, he says he checked , but........???Any thoughts or ideas would be so greatly appreciated, they have had the car at the Chevy Store for over a month and we are no further ahead...any ideas....anyone?? Please....

 

[Hib Halverson]

Consult the factory service manual for all the locations but I'd check the condition and tightness of electrical grounds for the battery, charging system and the engine controls.

I believe the engine controls ground for an LT1 is the same as that of the L98...a big-assed bolt screwed into the block down near the oil filter. Look for a 19 or 21mm bolt with a lot of black wires connected to it. Remove the bolt, clean the connections and the block surface then replace the bolt and tighten the snot out of it.

 

[Vettebigguy]

Thanks Hib, I will suggest that...I hope it is as simple as that...I got a print out on what they have done...holy...nearly every thing except putting their finger in the exhaust pipe !

Seems as tho all the electrical readings are within the factory parameters...nad they don't show any codes on the DIC. Would the ground you mention work while cold and then quit? expansion?

 

[G Winter]

I recently replaced the clutch on my 90. The grounds were connected to a bolt in the drivers side of the bell housing with a stud and nut on it.

BTW. did they check the fuel pressure ? could be a bad new pump. Have they put a fuel pressure gauge on it to see what it does when it quits ?


Glenn

 

[Hib Halverson]

Does this problem always occur the same way, ie: you cold start, the car warms and, after about the same amount of time, then quits....or is the occurance not consistent?

 

[Vettebigguy]

Hi guys, they say they have good fuel pressure 40-45 lbs so I think that part is Ok. Nope it is relatively the same all the time, cold start runs till warm and then quits, I have a print out of what they did, quite a dissertation , but no mention of checking the ignition coil etc...seems as a code 41 did pop up, but according to what they did all shows normal...so I guess we could say it is consistent.....I really am beating my head here...

 

[Hib Halverson]

Can they tell you that the engine quits because it lack fuel or because it lacks spark?

When they said code 41 popped up but all shows normal, I'm a little confused. Does that mean the car set a 41 and they repaired accordingly, or do you mean they say DTC41, cleared codes and it has not returned?

I have to admit that DvI (diagnosis via Internet) may not work too well in this case. Nevertheless, my homework tonight will be to look up DTC41 for MY93.

 

[Vettebigguy]

Good morning all, here is what is written on the work report they sent me from the dealership, grab a coffee and read on..
40652 check no start. After engine runs for 20-30 minutes, it dies and will not restart, until it sits, for several minutes. Then will start and run for a few minutes and repeats the cycle. Check for spark, has spark. Check for fuel, pressure is at 40-45 pounds. Check for INJ pulse, there is no INJ pulse when engine will not start. Check codes, none stored in ECM, CCM,(BCM) has a history C0041 for no com with ECM stored. Cleared code to see if it would reset. It does reset when engine cranks and will not start. Test CCM for power inputs grounds all are OK. Voltage drop on B+ is about 200 mv, about 125 mv on B- side. Readings are the same when the engine runs. Intermittently CCM looses communication when eng won't start. Follow diag chart for C0041. Test comm circuits from CCM to ECM, all are okay, no shorts or opens. Tried a known good CCM engine still has same problem. Tested B= and B- to ECM all okay, similar to readings for CCM. Test all relays and loads on quad driver circuits to see if a component is shorting when hot, and shutting the ECM down.All readings are under the maximum allowed of 750 MA. Check signal for high and low RES crank sensors with a lab scope, both look okay when cranking and engine won't start. Captured data with tech2 and reviewed data. All readings appear to be within normal ranges. ;help
So that is the report directly from GM.....and that is the sum total of the info I have....does that help at all?? Thanks Hib...hope to hear more from you..cheers

 

[Hib Halverson]

Well...I'm not much help tonight. Last night I misread posts in this thread and thought the code 41 you were talking about was an ECM code. But now, I see it's a CCM code.

 

[Vettebigguy]

Does this make a difference? I know they replaced the ECM, and tried a known good BCM...by the way they talk here a BCM and a CCM sounds like the same thing,?? do you think it might be an ignition module, going good till it gets hot and then breaks a contact. The car acts like it it out of fuel when she dies..also could it be a fuel pressure regulator? He says he has good fuel pressure, but that might just be at the pump/??? What kind of test should he be looking at AFTER she dies? Am I testing the old brain first thing in the morning? LOL:W

 

[G Winter]

Does this make a difference? I know they replaced the ECM, and tried a known good BCM...by the way they talk here a BCM and a CCM sounds like the same thing,?? do you think it might be an ignition module, going good till it gets hot and then breaks a contact. The car acts like it it out of fuel when she dies..also could it be a fuel pressure regulator? He says he has good fuel pressure, but that might just be at the pump/??? What kind of test should he be looking at AFTER she dies? Am I testing the old brain first thing in the morning? LOL:W

I know the ECM checks for either injector or ignition pulse or both and shuts off fuel pump in 2 seconds if not seen. This was in the 90 FSM . So you might be onto something with the ignition module . Electronics can be very sensitive to heat.
The thing that I see odd is the lose of communication with the CCM.

Glenn

 

[dogtag]

I have a 90 vette and you described the same exact problem I had last month.
I was driving on I5 in the heart of downtown Seattle and the damn thing just died at 60 mph.
I sat in the passing lane in my Glass car while others zoomed around me at 60.
Then I got it to start but it missed and rattled and smoked but I got it off to the side of the road.
Turns out it was a Temp sensor. It was telling the computer that the engine temp was below freezing.....LOL.
New sensor and everything works great. I've been told it's a common problem.

Good Luck,
DT

 

[Steve40th]

I would say the engine was washed, your Opti got wet, and yo need a new Opti. The 92-94 were not good, and with so little miles on your Vette, Iwould say the moisture finally got the best of the OPTI. You wont necessarily get codes with an Opti. The fuel pump is less than 150 bucks and takes about 20minutes to change, so the dealership wasnt very good.
Get the car home and change the Opti, put new wires while you are there. I am 95% positive this is your problem.
Been through 10-15 optis over the last 11 years with many LTx owners. Just my 2 cents.

 

[Vettebigguy]

You guys were right...I actually did manage to get her fixed....very painful, but it was absolutely the Opti-Spark distributor. ( If I could figure out how to post a picture, I'd show you ). In the end the Dealership could not fix it and had no clue.I ended up taking her to John's Automotive repair, just north of Spokane and he had it diagnosed and on the road in less than 24 hours !! Where the Chevy Dealership had her for almost 6 weeks and could not do it. It turned out to be the module inside the Opti-spark and as well the whole inside of the distributor was so rusty , i couldn't beleive she ran as long as she did. I really didn't notice much but over the past few years I was getting the occasional misfire with it, and I pout it down to maybe a little moisture in the fuel. Apparently not. It was an expensive adventure ..over a 1000 bucks to the dealership for virtually nothing ( altho Thanks to a good buddy of m ine I did get a few bucks back..only a few I might add) and then another 1500 to get her up and running. The Opti-spark from GM ( that is the only place thye could get one ) was over 700 bucks itself. I was going to try to get an MSD one , but it was on back order. So I have a brand spanking new ECM for the '93 LT1 that is not used and I would like to sell it to any one who can use one. They are on a huge back order too. If anyone knows of anybody, let me know...thanks for all your help and advice, I didn't realize how much good help and knowledge is out there. I just hope one day I can help someone. This is an awesome venue. I know I am hooked now. Thanks every one ...

 

[Steve40th]

Vettebigguy, You defintiely learned allot. Stealerships, i mean dealerships arent always the best place for your vehicle, especially after warranty.
ANother thing, Optis dont cost 700 dollars, that is list price. Chris May at superior chevrolet can get it for you, for less than 300 bucks.
Superior Chevrolet, 1.800.728.8267, ask for Chris May
93 Opti 10457702
GM LIST: $701.11
OUR PRICE: $364.57
http://www.gmpartsdirect.com
Also, get the part number that you need and go to www.gmpartsdirect.com
their prices are cheap too, and they are a dealership, Flow Chevrolet in NC.
If Flow or Chris dont have it, get the part number and email this company, vintage parts inc, http://www.vpartsinc.com
They have NOS they bought. ANd they deliever to anywhere in the lower 48 states.

 

[Vettebigguy]

Stealerships !!! I love that one, can I use it? Yeah, well of cousre they are going to throw it to me, the car was stuck in the beautiful USA and I live in Canada...can you spell ' sucker' ? I wish I had that info when I was looking, oh well live and learn I guess. Thanks for the detialed info. I am going to take the Superior Chevrolet info and keep it and give it to our Club, for others to have and use. Thanks for the Vintage parts one too. The Dealership told my Pal, when he was helping me negotiate a refund, that they get at least one car per week they can't fix !! That is out rageous, and even more so they admit it!! What kind of after sales service is that?? The thing that got me was I was at a GM Dealership, not a Nissan dealership !!!

 

[Steve40th]

Spread the information with your club. It sickens me when people get ripped off. I had a friend here in Hawaii get ripped 2000 dollars for opti replacement, and they didnt even do the water pump at the same time, which is HIGHLY recommended on an LT1.

 

[Vettebigguy]

I must admit, I do feel I did get diddled a bit . I was trying to give them every opportunity to fix the car, and I thought as it was a Chev and I was at a Chev dealership things should fit together rather well. Silly me. I know , to the dealerships they are ' just another car', but to me , it is huge, my first Corvette, my baby etc, etc...the stress leve was insurmountable. Technically it was in another country, I don't see any difference between us, but the guys att he U.S./Canadian border sure do. I was really fretting over that. They can be very difficult sometimes , but in the end I did stress for nothing and it all worked out for the best....but still.....

 

[John Robinson]

Something to share

Sorry to hear about your stealership problem thought you might like to share this information with your club

http://www.corvetteactioncenter.com/forums/showthread.php?t=108907

I am chasing a problem right now with my 93 it starts and runs great until the engine gets to 190F and then it backfires and misses. If I put it in second gear and get up to 3000 RPM it will run without the miss. I have new plugs and wires an am working on the EGR right now trying to avoid removing the water pump to get to optihnoes

http://www.corvetteactioncenter.com/forums/showthread.php?t=108907

 

[Vettebigguy]

Hey, John, that sounds exactly what happened to me. After a whole bunch of miss diagnosis, it turned out to be the opti-spark . many guys told me that and it was true. There is a module inside the opitspark that fails. If if was like mine and origonal, there is no way to change the module without changing the whole distributor. ( you can change some of them with the aftermarket distributors ) If you can email me direct I will show you the pictures of the inside of my opti-spark, it was rusted so bad it is hard to believe the car ran at all. IF by chance it isn't the Opti-spark I do have abrand new ECM for the '93 LT1 I want to sell. Thney thought it was the ECM , so i bought one , only to find it wasn't. So I have ane ECM that is really of no need to me.
I would see if someone has a good Sun Scope and see if it is the Opti-spark,. The guy that diagnosed mine , showed me a print out of it whejn cold and running fine, and then when she got hot and then died. It is eaxctly like a heart monitor, and shows the heart beat and then , it is like the car is having a heart attack, the Opti-saprk can't figure out which cylinder to fire...email me.. Jeff