1988 Vette, wont stay running when cold. Once it warms up and gets into closed loop it runs OK.
New Injectors, Cap, rotor, plugs, plug wires, fuel filter, fuel pump, PCV valve:banghead: :banghead: :banghead:

1988 Vette, wont stay running when cold. Once it warms up and gets into closed loop it runs OK.
New Injectors, Cap, rotor, plugs, plug wires, fuel filter, fuel pump, PCV valve:banghead: :banghead: :banghead:Interesting, are you keeping your vette in a garage or out in the elements?

Interesting, are you keeping your vette in a garage or out in the elements?



It stays inside right now, what are you thinking?? Some of those parts are just maintenance items. Not troubleshooting parts.

Eagle

will it stay running if you lightly apply pressure on the throttle? Idle air control motor's can go bad on these!
There are many reasons though, it's difficult diagnosis over the web.

will it stay running if you lightly apply pressure on the throttle? Idle air control motor's can go bad on these!
There are many reasons though, it's difficult diagnosis over the web.


Nope, it slowly dies off, if you blip the throttle it will pick up and backfire some times, then contionue and die or pickup and start all over again.:banghead:

Eagle

I have seen the exact same symptoms when a pulse arrester started going bad. Real funny thing is that when the temps got above 65 or so it would run fairly well with only some hesitation.
Good luck.

I have seen the exact same symptoms when a pulse arrester started going bad. Real funny thing is that when the temps got above 65 or so it would run fairly well with only some hesitation.
Good luck.

what's a pulse arrester? I have the same symptoms and thought it could be the CTS causing the engine to run to rich and causing hesitation and back firing when cold.

Its in the tank, it is a rubber vibration damper in the fuel line,they will split, and you fuel pressure will be low and very inconsiderate to you, causing surging etc.
I have seen this alot, but you need to run a fuel pressure test on the line. Pressure should hold for 30 minutes without dropping back, key on engine off to pressure the rail, then key off.
Do not replace any parts, get accurate diagnosis on this vehicle from a pro if it's over your head, the tools are not cheap!!
Make sure your technician warrantee's his diagnosis, and allows you to be involved.
All advice given over the web, is a shot in the dark, it's strictly advice, not hard diagnostics.

1988 Vette, wont stay running when cold. Once it warms up and gets into closed loop it runs OK.
New Injectors, Cap, rotor, plugs, plug wires, fuel filter, fuel pump, PCV valve:banghead: :banghead: :banghead:
Hello
Replace the Coolant Temp Sensor and it should run fine.
David Steele

Hello
Replace the Coolant Temp Sensor and it should run fine.
David Steele

Does the CTS throw any codes if its bad?

Hello
Replace the Coolant Temp Sensor and it should run fine.
David Steele:thumbsup3: :iagree: CTS

:thumbsup3: :iagree: CTS



OK, I will repalce the coolant sensor, now explain why the CTS is the problem. I understand that the ECM needs that signal when its warm, but I thoight that in open loop the ecm would use a predetermined settings???:1zhelp:

OK, I will repalce the coolant sensor, now explain why the CTS is the problem. I understand that the ECM needs that signal when its warm, but I thoight that in open loop the ecm would use a predetermined settings???:1zhelp:

ecm uses the CTS input to richen mixture at cold start, sorta like an olden day carb choke...you can check the CTS prior to changeout using a DVOM, check ohms both cold and warmed up and compare with Service Manual

ecm uses the CTS input to richen mixture at cold start, sorta like an olden day carb choke...you can check the CTS prior to changeout using a DVOM, check ohms both cold and warmed up and compare with Service Manual




I just looked up the price for a CTS...only 14.95 from Ecklers, I will just replace it. Dont have a Manual for the Vette yet....can you tell me what the cold reading should be? Just for curiosity sake.:DeadHorse:

Does the CTS throw any codes if its bad?
Hello Burt
No, Not all the time, It will depend on how far out of specs the CTS is.
A CTS is just a Thermistor, The ECM sends a 5 volt signal to the CTS and a Variable Voltage Signal is returned depending on the temp of the coolant, The ECM then reads this voltage signal, Low volts when cold and up to 5 volts hot.
The Computer Chip in your ECM has a Voltage Map stored in it. For example: 2.5 volts=40 degree coolant temp or 3.4 volts=54 degree coolant temp and so on( i just made these numbers up for an example) The ECM takes this volt reading along with the volts out of the MAF,IAT,TPS (they all start with 5 volts from the ECM) To set the air/fuel mixture using fuel mapping from the CHIP, Mostly depending on air and coolant temp for cold start.
My point being if the CTS is off by say 9 degrees in temp it mite not be enough to set a code but more then enough to make a cold start very hard.
David Steele

Hello Burt
No, Not all the time, It will depend on how far out of specs the CTS is.
A CTS is just a Thermistor, The ECM sends a 5 volt signal to the CTS and a Variable Voltage Signal is returned depending on the temp of the coolant, The ECM then reads this voltage signal, Low volts when cold and up to 5 volts hot.
The Computer Chip in your ECM has a Voltage Map stored in it. For example: 2.5 volts=40 degree coolant temp or 3.4 volts=54 degree coolant temp and so on( i just made these numbers up for an example) The ECM takes this volt reading along with the volts out of the MAF,IAT,TPS (they all start with 5 volts from the ECM) To set the air/fuel mixture using fuel mapping from the CHIP, Mostly depending on air and coolant temp for cold start.
My point being if the CTS is off by say 9 degrees in temp it mite not be enough to set a code but more then enough to make a cold start very hard.
David SteeleVery interesting! good info David, thanks!:thumbsup3:

Hello Burt
No, Not all the time, It will depend on how far out of specs the CTS is.
A CTS is just a Thermistor, The ECM sends a 5 volt signal to the CTS and a Variable Voltage Signal is returned depending on the temp of the coolant, The ECM then reads this voltage signal, Low volts when cold and up to 5 volts hot.
The Computer Chip in your ECM has a Voltage Map stored in it. For example: 2.5 volts=40 degree coolant temp or 3.4 volts=54 degree coolant temp and so on( i just made these numbers up for an example) The ECM takes this volt reading along with the volts out of the MAF,IAT,TPS (they all start with 5 volts from the ECM) To set the air/fuel mixture using fuel mapping from the CHIP, Mostly depending on air and coolant temp for cold start.
My point being if the CTS is off by say 9 degrees in temp it mite not be enough to set a code but more then enough to make a cold start very hard.
David Steele

Thanks David,

Great info as always!! :thumbsup3:

Umm kinda a dumb Q but where is the CTS located? Is it hard to get to? Like underneath the distributor? I think thats the oil pressure switch. It cant be the one next to the numberr 1 plug. That would be too easy haha. Im having the same cold start issues although my cold start is a bit stumbling not stalling. Thanks in advance:D

Hello Burt
No, Not all the time, It will depend on how far out of specs the CTS is.
A CTS is just a Thermistor, The ECM sends a 5 volt signal to the CTS and a Variable Voltage Signal is returned depending on the temp of the coolant, The ECM then reads this voltage signal, Low volts when cold and up to 5 volts hot.
The Computer Chip in your ECM has a Voltage Map stored in it. For example: 2.5 volts=40 degree coolant temp or 3.4 volts=54 degree coolant temp and so on( i just made these numbers up for an example) The ECM takes this volt reading along with the volts out of the MAF,IAT,TPS (they all start with 5 volts from the ECM) To set the air/fuel mixture using fuel mapping from the CHIP, Mostly depending on air and coolant temp for cold start.
My point being if the CTS is off by say 9 degrees in temp it mite not be enough to set a code but more then enough to make a cold start very hard.
David Steele



Thanks David, very good run down!!:worship:
I replaced the cts and it was no help. I then unplugged the MAF sensor and it statred and ran fine. I will replace the MAF relays today aand see if that helps, if not I will be in the market for another MAF sensor(unless you have other advice)
Thanks,
Lloyd:cheers:

Thanks David, very good run down!!:worship:
I replaced the cts and it was no help. I then unplugged the MAF sensor and it statred and ran fine. I will replace the MAF relays today aand see if that helps, if not I will be in the market for another MAF sensor(unless you have other advice)
Thanks,
Lloyd:cheers:
Hello Lloyd
Try the MAF burn off relay first. It sends a small voltages to the heated wire in the MAF meter to burn off anything that mite be contaminating the wire before start up. If its not working it should set a code as should the MAF meter. Have you pulled the codes from the ECM? Don't start buying parts, This is a very simple system just need all the information you have, Like ECM codes.
David Steele

:cheers: Hello Lloyd
Try the MAF burn off relay first. It sends a small voltages to the heated wire in the MAF meter to burn off anything that mite be contaminating the wire before start up. If its not working it should set a code as should the MAF meter. Have you pulled the codes from the ECM? Don't start buying parts, This is a very simple system just need all the information you have, Like ECM codes.
David Steele



HI David,
I replaced the relays first, no good. Then installed a REMANed MAF, set a code 33 as soon as it started. Took it back and bought a new one from Auto ZOne for $180.00. Started and ran great.....until it hit closed loop and imediatley set a code 44. Troubleshot the lean o2 sensor and found it hanging by the wire. Well tomorow I will throw down for a ne o2 sensor and take it out and put some miles on it. The poor car has been sitting in someones garge/barn for a while, it will take time to get all the gremilins worked out. To this point I havent put anything on it it didnt need(except the CTS). I am takling the seat covers now....Oh My Lord!!! Some knucklehead started and couldnt/didnt finish.


Thanks for all the help,
Lloyd:yay: :burnout: :burnout:

:cheers:



HI David,
I replaced the relays first, no good. Then installed a REMANed MAF, set a code 33 as soon as it started. Took it back and bought a new one from Auto ZOne for $180.00. Started and ran great.....until it hit closed loop and imediatley set a code 44. Troubleshot the lean o2 sensor and found it hanging by the wire. Well tomorow I will throw down for a ne o2 sensor and take it out and put some miles on it. The poor car has been sitting in someones garge/barn for a while, it will take time to get all the gremilins worked out. To this point I havent put anything on it it didnt need(except the CTS). I am takling the seat covers now....Oh My Lord!!! Some knucklehead started and couldnt/didnt finish.


Thanks for all the help,
Lloyd:yay: :burnout: :burnout:
Hello Lloyd
It your replacing the seat covers make sure you have some extra foam padding to fill in the low spots or you will never get them to look right, That is if your not installing new foam. Good luck, its not a fun thing to do!
David Steele

Hello Lloyd
It your replacing the seat covers make sure you have some extra foam padding to fill in the low spots or you will never get them to look right, That is if your not installing new foam. Good luck, its not a fun thing to do!
David Steele


Thanks David. I am going to buy a pneumatic nail gun and put those seat covers on right, by golly.:rofl: :rofl:

Lloyd