94' lt1 trouble codes
02-21-2015, 04:16 PM
#1
Melting Slicks
Thread Starter
94' lt1 trouble codes
Hi all, recently replaced my opti due to a Code 16 back in December, and car has been fine ever since. I also just installed an LTCC coil per cylinder conversion, all went well, and drives very well.
Weird thing happened today, went out for a 2 hour or so long drive with no issues. Stopped and got some lunch in Dunedin, went back out and started up fine and drove up alternate 19 to Tarpon Springs and then headed back towards my place in Palm Harbor. Pulled into the drive, shut her down, and did a few things in the garage. Came back out to start her up and pull the car in the garage and it started and just died. My first thought was opti (AGAIN!) or LTCC problem. 2nd try fired up no problem at all and pulled in garage and then shut her down again. Immediately turned the key and started with a real rough idle and then died. I hook up the Fuel Pressure Gauge and the car starts fine. With the FPR still hooked up to vacuum it shows around 36 PSI. Kill the engine and the pressure climbs to 42 where it stays indefinitely. Then, I try to crank it again, and the fuel pressure is hovering around 10-20 PSI, drops to 5 and engine stumbles and quits...
I figure good, atleast I am getting somewhere, maybe my 130k mile fuel pump is finally starting to take a dump. Then I see the SES light on. I pull codes:
h62- Engine Oil Temperature Sensor Circuit (Signal Voltage Low, High Temperature Indicated)
h64-Bank 2 (Right Front) Heated Oxygen Sensor (HO2S) #1 Circuit (Lean Exhaust Indicated)
h65-Bank 2 (Right Front) Heated Oxygen Sensor (HO2S) #t Circuit (Rich Exhaust Indicated)
The last two codes don't really make sense to me as I don't see how you can have a lean and rich condition at the same time. Can a bad fuel pump cause these codes? Not really sure where to go. Trying to diagnose the best I can.
My spark appears to be good. HELP!
Weird thing happened today, went out for a 2 hour or so long drive with no issues. Stopped and got some lunch in Dunedin, went back out and started up fine and drove up alternate 19 to Tarpon Springs and then headed back towards my place in Palm Harbor. Pulled into the drive, shut her down, and did a few things in the garage. Came back out to start her up and pull the car in the garage and it started and just died. My first thought was opti (AGAIN!) or LTCC problem. 2nd try fired up no problem at all and pulled in garage and then shut her down again. Immediately turned the key and started with a real rough idle and then died. I hook up the Fuel Pressure Gauge and the car starts fine. With the FPR still hooked up to vacuum it shows around 36 PSI. Kill the engine and the pressure climbs to 42 where it stays indefinitely. Then, I try to crank it again, and the fuel pressure is hovering around 10-20 PSI, drops to 5 and engine stumbles and quits...
I figure good, atleast I am getting somewhere, maybe my 130k mile fuel pump is finally starting to take a dump. Then I see the SES light on. I pull codes:
h62- Engine Oil Temperature Sensor Circuit (Signal Voltage Low, High Temperature Indicated)
h64-Bank 2 (Right Front) Heated Oxygen Sensor (HO2S) #1 Circuit (Lean Exhaust Indicated)
h65-Bank 2 (Right Front) Heated Oxygen Sensor (HO2S) #t Circuit (Rich Exhaust Indicated)
The last two codes don't really make sense to me as I don't see how you can have a lean and rich condition at the same time. Can a bad fuel pump cause these codes? Not really sure where to go. Trying to diagnose the best I can.
My spark appears to be good. HELP!
02-22-2015, 01:06 PM
#2
Le Mans Master
Member Since: Oct 2002
Location: Las Vegas - Just stop perpetuating myths please.
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With only 10-20psi fuel press U have a bad fuel pump or at least a clogged fuel filter. Dont worry 'bout the fuel trims until u get the fuel press corrected.
As far fuel trims alot of owners dont realize the O2 sensors are a normal wear item. Keith McCord writes to replace them every time u replace the brakes/tires. Could be u did some engine work that contaminated them recently but only u would know this. Correct this later once u get the press back - if the problem even remains.
The oil temp dont make sense either but again fix the fuel press first then attack the others - if they still remain. Good luck and hope this helps. Oh unless u have big hp needs then stay with a stockish level fuel pump. The hi-flow pumps like walbro need a little modification to install and seem to wear out faster do to higher motor heat, a low stock flow and intermittent lower voltages.
Hope this helps.
As far fuel trims alot of owners dont realize the O2 sensors are a normal wear item. Keith McCord writes to replace them every time u replace the brakes/tires. Could be u did some engine work that contaminated them recently but only u would know this. Correct this later once u get the press back - if the problem even remains.
The oil temp dont make sense either but again fix the fuel press first then attack the others - if they still remain. Good luck and hope this helps. Oh unless u have big hp needs then stay with a stockish level fuel pump. The hi-flow pumps like walbro need a little modification to install and seem to wear out faster do to higher motor heat, a low stock flow and intermittent lower voltages.
Hope this helps.
02-23-2015, 11:36 AM
#3
Melting Slicks
Thread Starter
Excellent advice thank you very much! Do you recommend any specific brand of fuel pump? All the local auto parts stores carry an Airtex and Carquest brand. A search shows a lot of people unhappy with the reliability of the Airtex units. AC/Delco a safe bet?
02-23-2015, 08:58 PM
#4
Le Mans Master
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Go with AC delco unless u need one really fast u can price shop on the internet. Dont know bout corvettes but for my camaro u can order just the AC delco pump w/o the sending unit. Many copy cat pumps need their brand sending unit also.
Good luck.
Good luck.
02-24-2015, 09:49 AM
#5
Melting Slicks
Thread Starter
Trying to get in touch with Jon @ Fuel Injector Connection, I hear his Bosch III injectors change the way the car feels entirely.
02-24-2015, 06:37 PM
#6
Le Mans Master
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Thats what they want u to believe. Fix your fuel press problem first. Injectors get cleaned and cal'd/flow matched at top flow. But more likely none will flow match for the entire operating range. Now u want to change injectors? U will have to retune with all the new injector characteristics.
Once u fix the fuel press u need to pull the PCM fuse (or briefly disconnect the batt - and i like to step on the brake for 10 sec also) to clear the DTC's and get the PCM to relearn your driving. If u still have problems after like 40 engine starts and stops then troubleshoot/look at the injectors.
Injectors are expensive, save your $$$.
Once u fix the fuel press u need to pull the PCM fuse (or briefly disconnect the batt - and i like to step on the brake for 10 sec also) to clear the DTC's and get the PCM to relearn your driving. If u still have problems after like 40 engine starts and stops then troubleshoot/look at the injectors.
Injectors are expensive, save your $$$.
02-25-2015, 07:01 AM
#7
Melting Slicks
Thread Starter
Thats what they want u to believe. Fix your fuel press problem first. Injectors get cleaned and cal'd/flow matched at top flow. But more likely none will flow match for the entire operating range. Now u want to change injectors? U will have to retune with all the new injector characteristics.
Once u fix the fuel press u need to pull the PCM fuse (or briefly disconnect the batt - and i like to step on the brake for 10 sec also) to clear the DTC's and get the PCM to relearn your driving. If u still have problems after like 40 engine starts and stops then troubleshoot/look at the injectors.
Injectors are expensive, save your $$$.
Once u fix the fuel press u need to pull the PCM fuse (or briefly disconnect the batt - and i like to step on the brake for 10 sec also) to clear the DTC's and get the PCM to relearn your driving. If u still have problems after like 40 engine starts and stops then troubleshoot/look at the injectors.
Injectors are expensive, save your $$$.
New pump and sock should be in by the weekend. I appreicate the help so far!
Patrick
03-03-2015, 09:58 PM
#8
Race Director
Patrick I have Bosch III's on my 93 LT1. I spoke with him on the phone and he assured me no tune is needed. What did I notice with them installed? Smoother idle. Good luck on the fix
03-04-2015, 07:26 AM
#9
Melting Slicks
Thread Starter
03-04-2015, 07:29 AM
#10
Melting Slicks
Thread Starter
The Fuel Pump swap seems to have fixed my issue. No more hard starts when warm. Car fires right back up everytime even after a 2 hour long drive. Put about 150 miles on it this past weekend. Seems to be good 
03-06-2015, 01:23 AM
#11
Le Mans Master
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Are u going scan it again for those other issues?
If u want to clear your DTC history u can pull the PCM fuse(s) or disconnect the batt for 10 sec. But this will also put the PCM back into learn mode so it will take like 40 starts and stops to adjust to your driving. Then a new scan will tell u if any of those other issues remain.
congrats on repairing it yourself and saving a truck load of $$$$.
If u want to clear your DTC history u can pull the PCM fuse(s) or disconnect the batt for 10 sec. But this will also put the PCM back into learn mode so it will take like 40 starts and stops to adjust to your driving. Then a new scan will tell u if any of those other issues remain.
congrats on repairing it yourself and saving a truck load of $$$$.
03-06-2015, 05:59 AM
#12
Melting Slicks
Thread Starter
Are u going scan it again for those other issues?
If u want to clear your DTC history u can pull the PCM fuse(s) or disconnect the batt for 10 sec. But this will also put the PCM back into learn mode so it will take like 40 starts and stops to adjust to your driving. Then a new scan will tell u if any of those other issues remain.
congrats on repairing it yourself and saving a truck load of $$$$.
If u want to clear your DTC history u can pull the PCM fuse(s) or disconnect the batt for 10 sec. But this will also put the PCM back into learn mode so it will take like 40 starts and stops to adjust to your driving. Then a new scan will tell u if any of those other issues remain.
congrats on repairing it yourself and saving a truck load of $$$$.
Yes sir I did clear the DTC history. I had the battery unhooked the entire time I changed the fuel pump. The codes are no longer there and even after driving 150+ miles last weekend it never tripped a check engine light and just to be safe I checked to see if there were any codes when I got home via the paper clip method. All seems well so far! The new pump is certainly more quiet.
Wish me luck on my drive over to Daytona this weekend. Anything else other than the normal fluid/tire pressure checks I should give attention to before I head out?
Last edited by TorchTarga94; 03-06-2015 at 06:02 AM.