Not To Stir THAT Pot Again, But....
03-20-2014, 02:26 PM
#1
Melting Slicks
Thread Starter
Not To Stir THAT Pot Again, But....
I have two issues: Hard to start, has a very rich mixture when it does. Once it's started and levels out a few seconds, it idles fine. The second issue is the dreaded hesitation.
So I did the appropriate research, and between that and my factory service manual have begun the elimination process. Here's what I've done so far:
Did jumper trick on OBD and only got C12 on module 1, and H83 on module 9. I didn't find any DTC 12 in the service manual (I'm sure it's in that massive manual somewhere though), but from what I can tell here on the web, a C12 says the system checks out OK. I know the H in H83 means "history", so I know it's just an old code that hasn't been reset yet. So to me, at this point, it looks like I'm getting no codes.
TPS checks out at .66 closed and 4.4 volts at WOT. OK.
MAP Sensor shows 4.97 volts at 0 in. Hg, and 3.5 volts at 10 in. Hg. OK.
Injectors all ohm at between 12.4 and 12.6 ohms. OK.
I'm going to go down the list of things to look for in the manual (fuel system and ignition checks), so fuel pressure is next. But what's stumping me is the rich start up. It takes like 5 to 10 seconds to start if I don't address the accelerator, but will start sooner if I feed it some throttle. Either way, once it starts, it runs rough for a few seconds, blows white smoke, and the smell of unburned fuel is very noticeable. The rich mixture seems to disappear once the engine has leveled out. And I can't help but wonder if the two problems, rough start and hesitation, are related.
I'll continue to run down the list, but if you've solved a similar problem in the past, I'd like to hear about what it took to solve it, so as to not necessarily have to reinvent the wheel.
Update #1: Assuming rented test gauge accuracy, fuel pressure checks out at 37 psi at idle, jumping to 46 upon quick application of throttle, and then drops down. Pressure stays at 37 if throttle is gradually applied. The service manual says pressure should be at least 41 to avoid lean conditions, and no more than 47 under any conditions. But because the engine smells rich upon start up, although the pressure is slightly low, I'm guessing fuel pressure isn't my problem. I'm at least temporarily ruling this out as the cause of my start up and hesitation problems.
Update #2: On my first fuel pressure check, I didn't pay attention to whether or not the rail held pressure once the system was shut off, so I redid the pressure test twice. Both times it leaked down to zero PSI within about 10 seconds or so. Will update once I figure out what's causing this.
Cheers!
Wendell
So I did the appropriate research, and between that and my factory service manual have begun the elimination process. Here's what I've done so far:
Did jumper trick on OBD and only got C12 on module 1, and H83 on module 9. I didn't find any DTC 12 in the service manual (I'm sure it's in that massive manual somewhere though), but from what I can tell here on the web, a C12 says the system checks out OK. I know the H in H83 means "history", so I know it's just an old code that hasn't been reset yet. So to me, at this point, it looks like I'm getting no codes.
TPS checks out at .66 closed and 4.4 volts at WOT. OK.
MAP Sensor shows 4.97 volts at 0 in. Hg, and 3.5 volts at 10 in. Hg. OK.
Injectors all ohm at between 12.4 and 12.6 ohms. OK.
I'm going to go down the list of things to look for in the manual (fuel system and ignition checks), so fuel pressure is next. But what's stumping me is the rich start up. It takes like 5 to 10 seconds to start if I don't address the accelerator, but will start sooner if I feed it some throttle. Either way, once it starts, it runs rough for a few seconds, blows white smoke, and the smell of unburned fuel is very noticeable. The rich mixture seems to disappear once the engine has leveled out. And I can't help but wonder if the two problems, rough start and hesitation, are related.
I'll continue to run down the list, but if you've solved a similar problem in the past, I'd like to hear about what it took to solve it, so as to not necessarily have to reinvent the wheel.
Update #1: Assuming rented test gauge accuracy, fuel pressure checks out at 37 psi at idle, jumping to 46 upon quick application of throttle, and then drops down. Pressure stays at 37 if throttle is gradually applied. The service manual says pressure should be at least 41 to avoid lean conditions, and no more than 47 under any conditions. But because the engine smells rich upon start up, although the pressure is slightly low, I'm guessing fuel pressure isn't my problem. I'm at least temporarily ruling this out as the cause of my start up and hesitation problems.
Update #2: On my first fuel pressure check, I didn't pay attention to whether or not the rail held pressure once the system was shut off, so I redid the pressure test twice. Both times it leaked down to zero PSI within about 10 seconds or so. Will update once I figure out what's causing this.
Cheers!
Wendell
Last edited by Wendell Allen; 03-20-2014 at 04:46 PM. Reason: Updated
03-20-2014, 03:45 PM
#3
Melting Slicks
Thread Starter
Not to doubt you, but two things come to mind. First, what are the chances of all 8 injectors going bad at one time? Secondly, I have a 1992 vert, and the injectors on that car are even less, at 12.1 to 12.3 volts, and it runs just fine.
03-20-2014, 04:15 PM
#4
Le Mans Master
A couple of things to look at if you haven't already.
First, of course, there's plugs, wires, and coil wire. A weak spark at start up can cause just such an issue, been there done that.
Take a look at your MAF sensor, clean it up if needed.
Second, is the Fuel pressure regulator. Check it for gas. I've had one that didn't appear shot until I pulled the vacuum off while it was running, and whala, out came the fuel. I was having the same symptoms you described. The new FPR fixed it.
Check your opti harness, specifially the connector at the opti under the coil. That's a pretty rough environment there, and it's amazing what can find it's way down there after some time.
On your fuel pressure, if you still have the gauge, check and see how quickly it is pressuing up when you turn the key on, engine off. Then turn the key off and see how long it is holding pressure. You could have a leaky injector, or your fuel pump could be getting ready for retirement.
Lastly, and certainly hopefully not. When you say a puff of white smoke, do you mean grey?
Because if it's white, that's water, as in coolant. There is a chance that a head gasket could be letting coolant in a cylinder after shut down, while the system is still pressurized. This can happen if the leak is just small enough that heat from combustion essencially seals the hole running, but as the engine cools, it opens up, and a little bit of coolant is seeping into a cylinder. This restricts the spark on start up briefly, and once it lights, it burns the coolant up. You should easily be able to figure this out by pulling the plugs after cooldown. Coolant will be present on at least one. Again, hopefully this is not the issue.
First, of course, there's plugs, wires, and coil wire. A weak spark at start up can cause just such an issue, been there done that.
Take a look at your MAF sensor, clean it up if needed.
Second, is the Fuel pressure regulator. Check it for gas. I've had one that didn't appear shot until I pulled the vacuum off while it was running, and whala, out came the fuel. I was having the same symptoms you described. The new FPR fixed it.
Check your opti harness, specifially the connector at the opti under the coil. That's a pretty rough environment there, and it's amazing what can find it's way down there after some time.
On your fuel pressure, if you still have the gauge, check and see how quickly it is pressuing up when you turn the key on, engine off. Then turn the key off and see how long it is holding pressure. You could have a leaky injector, or your fuel pump could be getting ready for retirement.
Lastly, and certainly hopefully not. When you say a puff of white smoke, do you mean grey?
Because if it's white, that's water, as in coolant. There is a chance that a head gasket could be letting coolant in a cylinder after shut down, while the system is still pressurized. This can happen if the leak is just small enough that heat from combustion essencially seals the hole running, but as the engine cools, it opens up, and a little bit of coolant is seeping into a cylinder. This restricts the spark on start up briefly, and once it lights, it burns the coolant up. You should easily be able to figure this out by pulling the plugs after cooldown. Coolant will be present on at least one. Again, hopefully this is not the issue.
03-20-2014, 04:50 PM
#5
Melting Slicks
Thread Starter
A couple of things to look at if you haven't already.
First, of course, there's plugs, wires, and coil wire. A weak spark at start up can cause just such an issue, been there done that.
Take a look at your MAF sensor, clean it up if needed.
Second, is the Fuel pressure regulator. Check it for gas. I've had one that didn't appear shot until I pulled the vacuum off while it was running, and whala, out came the fuel. I was having the same symptoms you described. The new FPR fixed it.
Check your opti harness, specifially the connector at the opti under the coil. That's a pretty rough environment there, and it's amazing what can find it's way down there after some time.
On your fuel pressure, if you still have the gauge, check and see how quickly it is pressuing up when you turn the key on, engine off. Then turn the key off and see how long it is holding pressure. You could have a leaky injector, or your fuel pump could be getting ready for retirement.
Lastly, and certainly hopefully not. When you say a puff of white smoke, do you mean grey?
Because if it's white, that's water, as in coolant. There is a chance that a head gasket could be letting coolant in a cylinder after shut down, while the system is still pressurized. This can happen if the leak is just small enough that heat from combustion essencially seals the hole running, but as the engine cools, it opens up, and a little bit of coolant is seeping into a cylinder. This restricts the spark on start up briefly, and once it lights, it burns the coolant up. You should easily be able to figure this out by pulling the plugs after cooldown. Coolant will be present on at least one. Again, hopefully this is not the issue.
First, of course, there's plugs, wires, and coil wire. A weak spark at start up can cause just such an issue, been there done that.
Take a look at your MAF sensor, clean it up if needed.
Second, is the Fuel pressure regulator. Check it for gas. I've had one that didn't appear shot until I pulled the vacuum off while it was running, and whala, out came the fuel. I was having the same symptoms you described. The new FPR fixed it.
Check your opti harness, specifially the connector at the opti under the coil. That's a pretty rough environment there, and it's amazing what can find it's way down there after some time.
On your fuel pressure, if you still have the gauge, check and see how quickly it is pressuing up when you turn the key on, engine off. Then turn the key off and see how long it is holding pressure. You could have a leaky injector, or your fuel pump could be getting ready for retirement.
Lastly, and certainly hopefully not. When you say a puff of white smoke, do you mean grey?
Because if it's white, that's water, as in coolant. There is a chance that a head gasket could be letting coolant in a cylinder after shut down, while the system is still pressurized. This can happen if the leak is just small enough that heat from combustion essencially seals the hole running, but as the engine cools, it opens up, and a little bit of coolant is seeping into a cylinder. This restricts the spark on start up briefly, and once it lights, it burns the coolant up. You should easily be able to figure this out by pulling the plugs after cooldown. Coolant will be present on at least one. Again, hopefully this is not the issue.
Last edited by Wendell Allen; 03-20-2014 at 04:59 PM. Reason: Addition info.
03-20-2014, 06:29 PM
#7
Melting Slicks
Thread Starter
Many thanks to lt4obsesses! Such an easy fix too. I pulled the vacuum line off the pressure regulator and nothing happened...at first. But after a 15 seconds or so, fuel started to bubble out so I replaced it and the problem has been solved. Once again, CF rocks!
Fixing cars really isn't so bad. Trouble shooting on the other hand, is a dog sometimes. I've spent literally hours trouble shooting this when the problem was just a 15 minute fix. I spent more time going to the auto parts store to get the darned thing than I did replacing. Go figure....
03-21-2014, 12:35 AM
#8
Le Mans Master
Yeah, cars can be like women sometimes. Act all funny, huffy and puffy, ask then what's wrong, and they say "nothing". So you take her out to dinner, buy flowers, candy, the works. Later you find out she was mad because you left the seat up three days ago. Go figure...
Glad it was the simple thing. I have a fairly new coil and ICM because my damn FPR shot craps.
Glad it was the simple thing. I have a fairly new coil and ICM because my damn FPR shot craps.
03-21-2014, 12:52 AM
#9
Team Owner
Member Since: Sep 2003
Location: Freedom is never more than one generation away from extinction.
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St. Jude '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-‘19-'20-'21-'22-'23-'24
Ya know Wendel, its nice that you have some patience and capacity to troubleshoot.
So many here have no clue, and want someone to tell them from a cryptic description of the problem.
People like you are what makes guys like LT4* appreciate their time and effort to help.
So many here have no clue, and want someone to tell them from a cryptic description of the problem.
People like you are what makes guys like LT4* appreciate their time and effort to help.
03-21-2014, 09:49 AM
#10
Drifting
Member Since: Feb 2005
Location: St. Petersburg, Fla.
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Ya know Wendel, its nice that you have some patience and capacity to troubleshoot.
So many here have no clue, and want someone to tell them from a cryptic description of the problem.
People like you are what makes guys like LT4* appreciate their time and effort to help.
So many here have no clue, and want someone to tell them from a cryptic description of the problem.
People like you are what makes guys like LT4* appreciate their time and effort to help.
I love the threads like "HELP! I have a Corvette and it won't start." And when you ask for more more info they get upset.
03-21-2014, 11:12 AM
#11
Le Mans Master
Member Since: Oct 2004
Location: South-central Missouri
Posts: 6,314
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Ya know Wendel, its nice that you have some patience and capacity to troubleshoot.
So many here have no clue, and want someone to tell them from a cryptic description of the problem.
People like you are what makes guys like LT4* appreciate their time and effort to help.
So many here have no clue, and want someone to tell them from a cryptic description of the problem.
People like you are what makes guys like LT4* appreciate their time and effort to help.
03-21-2014, 01:08 PM
#12
Le Mans Master
What I really appreciate here is that he told us what it turned out to be and what fixed it. It really helps to make the 'search' function more useful. How many threads do you see where there is a symptom, many suggestions, and no end result is known? Especially when it is something like this where it could one or more of several different things causing it.
