I keep getting this code when I start my vette. What do I most likely need to fix to make this go away?

 

code 15 on 85 is coolant sensor signal signal voltage high. needs further checking. may be sensor.

 

http://members.shaw.ca/corvette86/Code%2015.pdf

 

Thats a lot of info to digest. I adjusted my valves and then tried to start it up and thats when I got Code 14 and 15. After replacing the connector I only have code 15 now. So its either a bad sensor or a bad ECM if i'm reading that correctly. The engine runs like crap right now, my dad thinks its out of time, but my Hayne's manual says not to adjust timing if there are codes. I've heard that running like crap can be a symptom for a bad ECM.

It will only stay running if I give it gas for a little while, when its warmed up I dont have to give it gas, but it idles at 400 rpms. I'd like to hear what you guys think.

 

If the sensor is toast, it will make you car run like crap. The flow charts will help you determine if it is the wiring, sensor or ECM.
http://members.shaw.ca/corvette86/Code%2014.pdf
http://members.shaw.ca/corvette86/Code%2015.pdf

 

Following the flow charts, I get a code 15 on startup and the check engine light stays on until I turn the car off. Clear the codes and the same thing happens again. Jumping the two terminals yields the same result so I move on to step 3 on your flow chart. Either way you go it says possible ECM failure. The sensor should work because it still tells me the temp on the dash.

So what i'm trying to ask is if I get a code 15 repeatedly, could this be a sign of a bad ECM?

 

Yes Jeremy it COULD be a bad ECM but probably isn't. As Central Coaster pointed out in your girlfriends other thread the dash gauge takes it's reading from an entirely different sensor in the left cylinder head.
In the flow chart Agent 86 was kind enough to provide the coolant sensor readings mentioned are taken with a scan tool from the EFI coolant sensor (the one you have replaced the connector on). I believe you still have a bad connection there causing your code 15. If the connection is good I would at least try a replacement sensor before replacing the ECM since it is far less money.
As far as the root cause of your running problem I think you need to go back to where you started removing your rocker arms, cylinders 2, 4 & 6. I would first check the compression on those cylinders and compare the reading to one on the opposite bank.
I don't think it is a coincidence the problems started after the valve adjustment and expect there is something damaged in the valve train as a result. Either a bent valve, bent pushrod, collapsed lifter, perforated rocker or worn cam lobe. If the compression on all three cylinders is within 20% of a cylinder on the opposite bank I would again remove the valve cover and inspect the valve movement on cylinders 2, 4 & 6 . Compare with cylinder #8, watch for anything that is different then find out why with a careful visual inspection.
If you haven't moved your distributor I think a timing problem is unlikely, but nutz4C4 does raise a good point about a jumped timing chain especially since that is something else that could have been caused by binding in the valve train on an older car.
Usually if the car starts running bad immediately after maintenance or repairs those repairs are the most likely cause. It happens to everyone regardless of experience, but don't let this snowball by guessing at a cause and buying unneccesary parts.
Everyone here on the forum is pulling for you and wants to help, feel free to PM for further assistance, best of luck.

 

Did you follow the flow chart all the way to the bottom ?? You checked voltage in wires??, checked for open circuits ??

 

I didnt disconnect the EST wire when rotating the engine (thanks stupid Haynes manual) and its never ran right since. Thats why I think its the computer. Never had a problem with the coolant sensor before either and the stupid thing wasnt even connected!

I dont know how to test the voltage to the computer. I dont have anyone to help me out with electronics and stuff. To me time is more important than money and replacing the coolant sensor would take about 3-4 hours, while the computer only takes about 15 min.

 

I did this when I last had the valve covers off. I also made sure that they were all tightened down around the same distance on the studs. I know some have different lengths or how much load they take so I also took that into account. I visually inspected the pushrods, nothing bent whatsoever there. It sounds fine when I give it gas, just idles horribly at a very low rpm. Everyone who has heard it, says its the timing, but they dont know that much about TPI engines.

 

Well at least adjusting the timing won't cost you anything more now that you bought a timing light, try it if you are convinced it may help.
I don't recall you posting any compression figures so if you are saying you did the test I'd love to know the results. Visual inspection is less accurate for identifing a problem like this unless the engine is disassembled. You indicated you don't know how to do the voltage and electronic checks, unfortunately a diagnostic chart is virtually worthless if you skip steps or even do them out of sequence.
I recall you saying you are a student and thought that money WAS an issue, that is why I hate to see you waste it on an ECM if it isn't needed. If I got that part wrong then I guess you can throw parts at the problem, An ECM like most electrical parts will not be returnable unless you know someone at the store who will bend the rules. If you do have funds available in all honesty at this point I think taking it to someone would be more cost effective, just my opinion.
My son in law used to work at a GM dealer near Dayton which I think is reasonably close? He has moved but may still know someone who could look at your car, let me know if you are interested in that option and I can give him a call, again good luck.

 

I debated long and hard, went back and read my Haynes manual several times because you guys seem convinced that it wasnt the ECM. I bought a new coolant sensor and connector at NAPA instead of the ECM to give it a try. Sure enough I just took the old sensor out, the end (black part) fell right off like it was dry rotted. It looks soooo old on the other end too. I'm taking a break right now, but after I get the new sensor in i'll let you guys know whats going on.

No I did not do a compression test, dont have a gauge for that yet. Looks like i'll have to get one if the timing and sensor arent a fix.

 

Use that ECM money you saved for a compression gauge! All kidding aside, glad to hear you made some progress today. I'd also be delighted if your compression check is good, if you did ding a valve it is a real tough lesson to learn about adjusting Vette rockers, my sincere wish that it turns out to be something easier and less expensive.
I'm impressed by your perseverance, keep hanging in there and you will get it yet.

 

Alright new coolant sensor is installed, new wiring (broke the other new one). Started it up with same results, rpms around 400. It did seem to run a little better though. Good news is that the Code 15 is gone

Looks like its down to timing or compression. I'm kinda scared to check the compression. I really dont want to tear into the engine. I did read somewhere that when the coolant sensor (I think it was this sensor) goes bad, it reads as -40* and retards the timing 20*. Could be mistaken on that, but since i was messing with the rocker arms, gonna do the compression test.... soon as I find one of those gauges.

 

Good job, you got past the codes without buying an ECM! It willl do no harm to check your ignition timing now since you have the timing light but doubt it wll be the answer, I hope I'm wrong and it gets you back to normal. Again good luck.

 

I cant get the timing light to work, grrr. So I did the dummy thing and lined up the damper at 6* BTDC and rotated the distributor about 15* to line it up with #1 spark plug. Obviously this didnt work, car wont even start now. I did go to the store yesterday, they didnt have any compression gauges. So until I get my hands on one, i'm gonna keep playing with the timing and the light, hopefully get it working. I really dont want to tear into the engine in the middle of summer, i'm dying right now as it is not being able to drive it.

 

Use and ohm meter on the CTS. Look at what Agent86 posted and see what the engine temp is and what ohms the sensor reads. Your answer should be in the pdf. A bad CTS, wiring, or connection will give all sorts of drivability problems. Once that is fixed then set the base timing and go from there.

 

I've already fixed the sensor and the wiring, its the timing i'm having trouble with. I couldnt get the car to stay running long enough to actually use the timing light. It stalls out. While the engine is not running it only only be adjusted in large increments like 25* or something like that.

 

Sorry, didn't read all the way through. You can have someone crank on the engine while you turn the distrubitor until it will run on it's on. Then get the timing light connected and working and look for the timing mark. Make sure the EST wire is disconnected and set at 6* BTDC. If that doesn't work there is a problem elsewhere.

 

Yeah but thats something still unclear to me. How do I turn the distributor while cranking the engine or while its running? The rotor seems to be the only part that can make any adjustments and I dont want to touch it while the engine is running. I might get fried. I'm not really sure how much I would need to adjust it, could be a whole lot and so I figured moving the whole distributor would throw things out of whack in terms of lining up with the wires.

Yes I finally figured out how to use the timing light though. I know its been a whole mess. I'm supposed to be going on vacation all next week (I had this planned long before my cars died) and I really want to get at least one of them running, preferably the vette. My buick is having some kind of EGR issue, will start and run but stalls out and runs crappy. I've used and abused that poor car, but has always been reliable. I kinda wish I hadnt gave my '77 C10 to my gf, damn thing runs perfect and has a ton of miles on it.

I just wanted to thank you guys for helping out and giving me advice (not to mention saving me money!). Like I said going on vacation so you wont hear from me for about a week.