Running Lean? New to me 1990 L98
05-20-2019, 12:26 AM
#1
Running Lean? New to me 1990 L98
Hi guys, I have a new to me 1990 C4 with an L98. A month ago I knew nothing about Corvettes at all, but when this one came up for sale it was too good to pass up.
Anyways I got it home and had it safetied. Needed tires and 3 wheel bearings. I had the shop do the work so I could get out and enjoy it sooner.
Fast forward to today, I'm installing my Hedman headers (68440), while doing this I found a few disturbing things. My biggest concern is the plugs are WHITE, it must be running lean, unless this is common on these cars. I am quite mechanical and relatively familiar with SBC motors, (although mostly marine carbeurated versions), and this is a toy for me so I would like to do all my own work going forward.
Any ideas what to look for? Where to start?
The second item is this thing leaks oil like a sieve. I was thinking of resealing the valve covers and intake as a start, although that might not do it. The oil filter is SOAKED with oil so it has to be in that area.
The car has about 260,000km, but has spent the majority of its last 6 years sitting.
I hope I'm not rambling, thanks for looking guys and gals!
Anyways I got it home and had it safetied. Needed tires and 3 wheel bearings. I had the shop do the work so I could get out and enjoy it sooner.
Fast forward to today, I'm installing my Hedman headers (68440), while doing this I found a few disturbing things. My biggest concern is the plugs are WHITE, it must be running lean, unless this is common on these cars. I am quite mechanical and relatively familiar with SBC motors, (although mostly marine carbeurated versions), and this is a toy for me so I would like to do all my own work going forward.
Any ideas what to look for? Where to start?
The second item is this thing leaks oil like a sieve. I was thinking of resealing the valve covers and intake as a start, although that might not do it. The oil filter is SOAKED with oil so it has to be in that area.
The car has about 260,000km, but has spent the majority of its last 6 years sitting.
I hope I'm not rambling, thanks for looking guys and gals!
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gman35 (09-28-2019)
05-20-2019, 05:19 AM
#2
Intermediate
The oil leak is probably one of the oil sensors on the back of the engine. There are two sensors there, connected to a manifold (pipe) that screws into the block. These are just left of the distributor, directly behind the plenum/manifold, looking from the back of the car to the front (that would be to the right if you're standing on the driver's side of the engine compartment, leaning in over the left front wheel). One sensor has a single pin, the other has three. To see if, or which one, is leaking, disconnect the wiring connector... a leaking sensor will be covered in oil to where the connector on the wire and on the sensor is coated with oil. These sensors often still work even though they're leaking, and this is a very common source for oil leaks.
Re what to look for, if you're going to work on your C4, get a service manual... invaluable. Are the plugs new? Did the shop clean them? Is the car lean after installing the headers (this would be expected). You may need to re-tune your C4... this is something that is beyond a reply. There are folks who can do this remotely, but it takes going back and forth, or you can buy the gear and do it yourself. Have you put a full can of Seafoam in the gas tank, and have you run a full tank through the engine? A car sitting for six years may need the injectors cleaned. How does it run otherwise?
I run all of my gas-powered vehicles using Seafoam in the tank. My new/old/new '91 was running a little bit rough after sitting for about 6 months... a can of Seafoam in the tank plus a fillup with ethanol-free 91 octane fuel made a huge difference. I will not run E10 in any of my older vehicles that don't get a lot of miles... it goes bad quickly and causes all sorts of problems. If you have an Android mobile phone, you can download the Pure Gas app to see where you can get this across the country. I'm surprised how much better my cars and motorcycles run on it, and I also get about 10% better mileage.
Re what to look for, if you're going to work on your C4, get a service manual... invaluable. Are the plugs new? Did the shop clean them? Is the car lean after installing the headers (this would be expected). You may need to re-tune your C4... this is something that is beyond a reply. There are folks who can do this remotely, but it takes going back and forth, or you can buy the gear and do it yourself. Have you put a full can of Seafoam in the gas tank, and have you run a full tank through the engine? A car sitting for six years may need the injectors cleaned. How does it run otherwise?
I run all of my gas-powered vehicles using Seafoam in the tank. My new/old/new '91 was running a little bit rough after sitting for about 6 months... a can of Seafoam in the tank plus a fillup with ethanol-free 91 octane fuel made a huge difference. I will not run E10 in any of my older vehicles that don't get a lot of miles... it goes bad quickly and causes all sorts of problems. If you have an Android mobile phone, you can download the Pure Gas app to see where you can get this across the country. I'm surprised how much better my cars and motorcycles run on it, and I also get about 10% better mileage.
Last edited by obijohnkenobe; 05-20-2019 at 05:26 AM.
05-20-2019, 12:33 PM
#3
Replies in red below.
The oil leak is probably one of the oil sensors on the back of the engine. There are two sensors there, connected to a manifold (pipe) that screws into the block. These are just left of the distributor, directly behind the plenum/manifold, looking from the back of the car to the front (that would be to the right if you're standing on the driver's side of the engine compartment, leaning in over the left front wheel). One sensor has a single pin, the other has three. To see if, or which one, is leaking, disconnect the wiring connector... a leaking sensor will be covered in oil to where the connector on the wire and on the sensor is coated with oil. These sensors often still work even though they're leaking, and this is a very common source for oil leaks.
Thank you, I will check these areas as well.
Re what to look for, if you're going to work on your C4, get a service manual... invaluable. Are the plugs new? Did the shop clean them? Is the car lean after installing the headers (this would be expected). You may need to re-tune your C4... this is something that is beyond a reply. There are folks who can do this remotely, but it takes going back and forth, or you can buy the gear and do it yourself. Have you put a full can of Seafoam in the gas tank, and have you run a full tank through the engine? A car sitting for six years may need the injectors cleaned. How does it run otherwise?
I don't think I was clear enough here, the shop just did the safety, nothing else, they never had the plugs out. I discovered the plugs while doing the header job, so the car was stock with the exception of an exhaust system.
I do have a FSM (first thing I bought), and should probably spend more time hunting there.
Other than that the car runs not bad, after sitting a while it needs to crank for a few seconds to get going, and once it does it has a miss at idle until warm. If I have ran it earlier in the day it fires right up first crank. I'm thinking these injectors are leaking.
I run all of my gas-powered vehicles using Seafoam in the tank. My new/old/new '91 was running a little bit rough after sitting for about 6 months... a can of Seafoam in the tank plus a fillup with ethanol-free 91 octane fuel made a huge difference. I will not run E10 in any of my older vehicles that don't get a lot of miles... it goes bad quickly and causes all sorts of problems. If you have an Android mobile phone, you can download the Pure Gas app to see where you can get this across the country. I'm surprised how much better my cars and motorcycles run on it, and I also get about 10% better mileage.
The first thing I did was fill with good premium fuel. I forgot to buy a can of Seafoam though, although I usually do run this in my vehicles when having trouble as well.
Thank you, I will check these areas as well.
Re what to look for, if you're going to work on your C4, get a service manual... invaluable. Are the plugs new? Did the shop clean them? Is the car lean after installing the headers (this would be expected). You may need to re-tune your C4... this is something that is beyond a reply. There are folks who can do this remotely, but it takes going back and forth, or you can buy the gear and do it yourself. Have you put a full can of Seafoam in the gas tank, and have you run a full tank through the engine? A car sitting for six years may need the injectors cleaned. How does it run otherwise?
I don't think I was clear enough here, the shop just did the safety, nothing else, they never had the plugs out. I discovered the plugs while doing the header job, so the car was stock with the exception of an exhaust system.
I do have a FSM (first thing I bought), and should probably spend more time hunting there.
Other than that the car runs not bad, after sitting a while it needs to crank for a few seconds to get going, and once it does it has a miss at idle until warm. If I have ran it earlier in the day it fires right up first crank. I'm thinking these injectors are leaking.
I run all of my gas-powered vehicles using Seafoam in the tank. My new/old/new '91 was running a little bit rough after sitting for about 6 months... a can of Seafoam in the tank plus a fillup with ethanol-free 91 octane fuel made a huge difference. I will not run E10 in any of my older vehicles that don't get a lot of miles... it goes bad quickly and causes all sorts of problems. If you have an Android mobile phone, you can download the Pure Gas app to see where you can get this across the country. I'm surprised how much better my cars and motorcycles run on it, and I also get about 10% better mileage.
The first thing I did was fill with good premium fuel. I forgot to buy a can of Seafoam though, although I usually do run this in my vehicles when having trouble as well.
05-23-2019, 12:15 PM
#4
Well now I have more problems, I finished my header install, with the AIR pump and EGR delete, and now I have the Service Engine Soon light illuminated. The car was running much better than it had yesterday, I added a can of SeaFoam to the gas yesterday as well. Now the car runs like crap and has the SES light on. I have yet to get the codes off, I was going to use the paper clip trick for now, but I would like to get a better scan tool for future use. I have a whole lot of OBD II tools, but I don't have any OBD I right now. Maybe someone has a suggestion on a relatively cheap tool for OBD I?
05-23-2019, 12:48 PM
#5
Melting Slicks
Well now I have more problems, I finished my header install, with the AIR pump and EGR delete, and now I have the Service Engine Soon light illuminated. The car was running much better than it had yesterday, I added a can of SeaFoam to the gas yesterday as well. Now the car runs like crap and has the SES light on. I have yet to get the codes off, I was going to use the paper clip trick for now, but I would like to get a better scan tool for future use. I have a whole lot of OBD II tools, but I don't have any OBD I right now. Maybe someone has a suggestion on a relatively cheap tool for OBD I?
05-23-2019, 12:52 PM
#6
Team Owner
Member Since: Sep 2001
Location: Athens AL
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Well now I have more problems, I finished my header install, with the AIR pump and EGR delete, and now I have the Service Engine Soon light illuminated. The car was running much better than it had yesterday, I added a can of SeaFoam to the gas yesterday as well. Now the car runs like crap and has the SES light on. I have yet to get the codes off, I was going to use the paper clip trick for now, but I would like to get a better scan tool for future use. I have a whole lot of OBD II tools, but I don't have any OBD I right now. Maybe someone has a suggestion on a relatively cheap tool for OBD I?
I use an Actron scanner with an OBD1 adapter from Autozone. You can also order the correct OBD1 cable and use DataMaster to log data and read it on the screen in real time.
You can get an indication of the fuel injector leak by hooking up a fuel pressure gauge at the rail, noting the pressure (should be about 42psi) and then cutting it off. If it holds steady, they're good. If the pressure drops immediately, theres likely an injector leaking all that gas into the engine.
Last edited by vader86; 05-23-2019 at 12:55 PM.
05-23-2019, 01:09 PM
#7
05-23-2019, 01:10 PM
#8
Gotta pull the code, probably something with the O2 sensor, but hard to say. EGR wouldnt run at idle so that wouldnt set an immediate code 32.
I use an Actron scanner with an OBD1 adapter from Autozone. You can also order the correct OBD1 cable and use DataMaster to log data and read it on the screen in real time.
You can get an indication of the fuel injector leak by hooking up a fuel pressure gauge at the rail, noting the pressure (should be about 42psi) and then cutting it off. If it holds steady, they're good. If the pressure drops immediately, theres likely an injector leaking all that gas into the engine.
I use an Actron scanner with an OBD1 adapter from Autozone. You can also order the correct OBD1 cable and use DataMaster to log data and read it on the screen in real time.
You can get an indication of the fuel injector leak by hooking up a fuel pressure gauge at the rail, noting the pressure (should be about 42psi) and then cutting it off. If it holds steady, they're good. If the pressure drops immediately, theres likely an injector leaking all that gas into the engine.
05-23-2019, 01:24 PM
#9
OK so only 1 code comes up, and it is a "Code 32", from what Vader86 is saying, it sounds like an EGR problem. I'm not sure what I did wrong but there must be something. I removed the EGR tube going under the throttle body, and unplugged the little vacuum box (2 pin connector) that is right behind the thermostat housing, under the intake. I thought this was all that was needed, but I guess not?
05-23-2019, 01:47 PM
#10
Team Owner
Member Since: Sep 2001
Location: Athens AL
Posts: 59,654
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EGR tube from the rear of the base intake manifold to the header and the green wire to the solenoid? What did you do with that?
EGR should also not function at idle. Its only at part-throttle cruise when the engine has reached temps over 170F. When is the SES light flipping on?
EGR should also not function at idle. Its only at part-throttle cruise when the engine has reached temps over 170F. When is the SES light flipping on?
09-24-2019, 05:53 PM
#11
Sorry for the long delay in replying, I really haven't had any time to mess with this car at all, or even drive it for that matter. Anyways now I do.
So here is where I'm at right now:
-I have a fuel pressure issue, I loose pressure within about 2 seconds after it building up.
-I also have a bad oil leak coming form the back of the intake.
Everything is dissasembled now, so I am going to clean the injectors, new o-rings, new fuel pressure regulator diaphragm, reseal intake and paint the runners and intake, new valve cover gaskets, new thermostat, new cap, rotor, coil, plugs, wires. I want to do a full tune up, along with diagnose the fuel issue completeley.
Is there anything else I should be doing while I have the intake and valve covers off?
So here is where I'm at right now:
-I have a fuel pressure issue, I loose pressure within about 2 seconds after it building up.
-I also have a bad oil leak coming form the back of the intake.
Everything is dissasembled now, so I am going to clean the injectors, new o-rings, new fuel pressure regulator diaphragm, reseal intake and paint the runners and intake, new valve cover gaskets, new thermostat, new cap, rotor, coil, plugs, wires. I want to do a full tune up, along with diagnose the fuel issue completeley.
Is there anything else I should be doing while I have the intake and valve covers off?
09-24-2019, 05:56 PM
#12
EGR tube from the rear of the base intake manifold to the header and the green wire to the solenoid? What did you do with that?
EGR should also not function at idle. Its only at part-throttle cruise when the engine has reached temps over 170F. When is the SES light flipping on?
EGR should also not function at idle. Its only at part-throttle cruise when the engine has reached temps over 170F. When is the SES light flipping on?
The SEL only come on while cursing on the highway after being warmed up, goes away each startup.
09-25-2019, 01:25 PM
#13
Safety Car
Has anyone burned a new Prom for your Corvette since you removed the EGR?
This is from: How to Understand, Service and Modify Corvette Fuel Injection & Electronic Engine management Author: Charles D. Probst Publisher: Bentley Publishers Pages: 205-206
"The Engine control already shuts off EGR under high-performance conditions, at idle and at cold operation.
The rate of fuel injection and the spark advance are calculated for EGR under part-throttle conditions. If you block off the EGR you stand a good chance of experiencing knock and wasting fuel. You might even lose power output and you are dirtying the air!"
So your fuel injection program needs to take into account that you have removed and disabled the EGR system on your engine. There are people here on the Forum who can point you in the right direction to somebody who has a chip with this done already.
For the best possible performance this modification will complete what you started by removing the EGR. Once you do this it would be interesting in any power gains. Good luck with your Corvette!
Chris
This is from: How to Understand, Service and Modify Corvette Fuel Injection & Electronic Engine management Author: Charles D. Probst Publisher: Bentley Publishers Pages: 205-206
"The Engine control already shuts off EGR under high-performance conditions, at idle and at cold operation.
The rate of fuel injection and the spark advance are calculated for EGR under part-throttle conditions. If you block off the EGR you stand a good chance of experiencing knock and wasting fuel. You might even lose power output and you are dirtying the air!"
So your fuel injection program needs to take into account that you have removed and disabled the EGR system on your engine. There are people here on the Forum who can point you in the right direction to somebody who has a chip with this done already.
For the best possible performance this modification will complete what you started by removing the EGR. Once you do this it would be interesting in any power gains. Good luck with your Corvette!
Chris
09-25-2019, 01:38 PM
#15
Has anyone burned a new Prom for your Corvette since you removed the EGR?
This is from: How to Understand, Service and Modify Corvette Fuel Injection & Electronic Engine management Author: Charles D. Probst Publisher: Bentley Publishers Pages: 205-206
"The Engine control already shuts off EGR under high-performance conditions, at idle and at cold operation.
The rate of fuel injection and the spark advance are calculated for EGR under part-throttle conditions. If you block off the EGR you stand a good chance of experiencing knock and wasting fuel. You might even lose power output and you are dirtying the air!"
So your fuel injection program needs to take into account that you have removed and disabled the EGR system on your engine. There are people here on the Forum who can point you in the right direction to somebody who has a chip with this done already.
For the best possible performance this modification will complete what you started by removing the EGR. Once you do this it would be interesting in any power gains. Good luck with your Corvette!
Chris
This is from: How to Understand, Service and Modify Corvette Fuel Injection & Electronic Engine management Author: Charles D. Probst Publisher: Bentley Publishers Pages: 205-206
"The Engine control already shuts off EGR under high-performance conditions, at idle and at cold operation.
The rate of fuel injection and the spark advance are calculated for EGR under part-throttle conditions. If you block off the EGR you stand a good chance of experiencing knock and wasting fuel. You might even lose power output and you are dirtying the air!"
So your fuel injection program needs to take into account that you have removed and disabled the EGR system on your engine. There are people here on the Forum who can point you in the right direction to somebody who has a chip with this done already.
For the best possible performance this modification will complete what you started by removing the EGR. Once you do this it would be interesting in any power gains. Good luck with your Corvette!
Chris
09-27-2019, 04:58 PM
#17
Safety Car
Hello again bpan,
You can not disable the EGR by simply unplugging it. That EGR waits until the car is fully warmed up but the EGR operates completely unknown to the driver of the Car. It operates regularly when cruising or driving around doing errands without anybody knowing it is turning on and off hundreds of times.
If you removed the vacuum or even the solenoid itself it won't stop the damage from happening to your engine.
I can tell you what will happen "In my Mind" is that your engine will start to develop all kinds of issues unless you remove the EGR completely and block it off. THEN purchase and install a new PROM for your Corvette that disables the EGR functions and compensates for it not being there to help. Your mileage will go down and performance will be lackluster and the engine will start to knock, detonate or whatever you want to call it. The engine will run hotter without the EGR and I doubt simply changing the thermostat will fix anything. You will have to start using 93 octane just to be able to drive the Corvette.
By unplugging the EGR passageways start to fill with carbon and eventually plug up inside the intake manifold. My EGR went bad and it cost me a bunch to fix it properly fix it afterwards. I fixed mine because the car runs better with the EGR then it does without one. My whole EGR system failed due to the EGR Vacuum Solenoid failing. In Virginia I have to have an operating emissions system to use the cars on the road regularly. They have been cracking down on antique plates being driven during the week around here.
I am not trying to be a PIA but I am really trying to help you understand why you shouldn't play with things we don't understand. The EGR valves have been around now sine the 1970's and they really are part of the whole emissions system and unless disabled properly the engine will suffer.
I have them on all my cars except my 1968 C3 427 and that only has a PCV valve for it's emissions equipment. My C4 has a High Flow catalytic converter with chambered cat-back system and sounds really nice and gets 30 mpg.
Good luck and don't "avoid this issue", You started the job now you need to either finish it completely or repair it to work properly. A thermostat will not solve the problems here I am afraid, it might help a bit but not enough.
Check out the link sent to you by the earlier poster.
Best regards,
Chris
You can not disable the EGR by simply unplugging it. That EGR waits until the car is fully warmed up but the EGR operates completely unknown to the driver of the Car. It operates regularly when cruising or driving around doing errands without anybody knowing it is turning on and off hundreds of times.
If you removed the vacuum or even the solenoid itself it won't stop the damage from happening to your engine.
I can tell you what will happen "In my Mind" is that your engine will start to develop all kinds of issues unless you remove the EGR completely and block it off. THEN purchase and install a new PROM for your Corvette that disables the EGR functions and compensates for it not being there to help. Your mileage will go down and performance will be lackluster and the engine will start to knock, detonate or whatever you want to call it. The engine will run hotter without the EGR and I doubt simply changing the thermostat will fix anything. You will have to start using 93 octane just to be able to drive the Corvette.
By unplugging the EGR passageways start to fill with carbon and eventually plug up inside the intake manifold. My EGR went bad and it cost me a bunch to fix it properly fix it afterwards. I fixed mine because the car runs better with the EGR then it does without one. My whole EGR system failed due to the EGR Vacuum Solenoid failing. In Virginia I have to have an operating emissions system to use the cars on the road regularly. They have been cracking down on antique plates being driven during the week around here.
I am not trying to be a PIA but I am really trying to help you understand why you shouldn't play with things we don't understand. The EGR valves have been around now sine the 1970's and they really are part of the whole emissions system and unless disabled properly the engine will suffer.
I have them on all my cars except my 1968 C3 427 and that only has a PCV valve for it's emissions equipment. My C4 has a High Flow catalytic converter with chambered cat-back system and sounds really nice and gets 30 mpg.
Good luck and don't "avoid this issue", You started the job now you need to either finish it completely or repair it to work properly. A thermostat will not solve the problems here I am afraid, it might help a bit but not enough.
Check out the link sent to you by the earlier poster.
Best regards,
Chris