hesitates
Thread Starter
Heel & Toe
Joined: Oct 2017
Posts: 19
Likes: 2
hesitates
I have a 1994 with 72000 miles on it. I don't know much history of the car. The car always starts right up first time. If it hasn't been driven for a couple of days It hesitates
For a minute or two when taking off. IT idles just fine just has that minute or two of sputtering under load.
There is nothing popping up no codes no nothing. After this it runs fine for hours. When I received the car the gas tank was almost bone dry... Nice guy huh. Not sure if this has anything to do with it. I always use 93 octane and have tried fuel injector cleaner with no results. Any help would be appreciated
For a minute or two when taking off. IT idles just fine just has that minute or two of sputtering under load.
There is nothing popping up no codes no nothing. After this it runs fine for hours. When I received the car the gas tank was almost bone dry... Nice guy huh. Not sure if this has anything to do with it. I always use 93 octane and have tried fuel injector cleaner with no results. Any help would be appreciated
Racer
Joined: Feb 2017
Posts: 388
Likes: 54
From: Sparta New Jersey
I'm dealing with a driveability issue with my 1993 LT1 - 6 spd. that I got earlier this summer (110K miles). I have a thread going about it documenting what I've done. I'm not one of the big dogs on the forum, technically speaking, but I'll step out on a limb and suggest that, unless you decide you want to lay out the $$$$ to have a 'professional' work on it, you'll need to start learning. You need to get the GM shop manual and start reading. I hope you're lucky and discover it's something very simple. As an example, I discovered the vent for the passenger side rocker cover was off. Putting it on helped my issue but didn't solve it. I also discovered the PO had installed new plugs but never gapped them, they should have been 50 thousandths and instead they were 65 thousandths. My expectation is I could spend months looking for my issue but I'm in this as a hobby and I'm in it for the long haul. Hang in there.
Safety Car
Joined: May 2001
Posts: 4,720
Likes: 1,625
From: Fairfax Virginia
I would try a can of B&G 44K Fuel Injection system cleaner. If it is a minor dirty injector or something that will help. I use it when my idle starts to get a bit rougher than usual and it does the trick most of the time. Check your fuel filter also.
How old is the oxygen sensor in your Corvette? The older oxygen sensors get slower in their response time and their signal weakens until they finally just fail. If your O2 is older than a couple years or has some miles on it you might consider replacing the O2. The performance of an O2 deteriorates and so does the car's performance and mileage. An older O2 is not able to handle high speeds and fast changes as well.
The sputtering under load has me curious, how do you mean sputtering, Bucking, missing, surging? MAP sensors measure the volume of air being ingested by the engine and if there is a leak and extra air is getting in it makes a mess of your car. My MAP sensor in a Buick failed under loading like hitting a hill with a trailer behind you. At first it would miss a bit here and then it started to get worse so I popped another MAP on and that problem left me.
Check your O2 as I am suspicious it is slowed down a bit causing the problems in the transitions like coming to idle after running at speed. If you have time check your CTS for accuracy as that can add on to other problems.
Hello again rusty76!
Some of us gap our plugs at 60-65 to use the high powered ignition for the best effect. My ignition system on my C3 "burns" plugs if the gap is too small. With my compression and HOT spark I run a bigger gap than normal. I think a lot of people don't even check the spark plugs gap anymore, they assume it comes all set. Set your plug's gap and then put anti-seize on their threads and install them. I spent hours with a test bench testing spark plugs and was amazed at some of the differences. I used an Older MSD ignition and mounted the spark plug for observing it and taking pictures of the spark. I found some Bosch Fusion Spark plugs and WOW, that is a spark. No other plug came close but the cost of 8 of the Fusion plugs was expensive so I to have my old AC Delco spark plugs in there instead. When the MSD system in my car fires you can hear the spark as it sounds like a spot welder with the multiple sparks up to 3k rpm.
Be careful though as there is too much of a good thing. I used a Hot coil setup on my Wife's Chevy pick up and it started eating distributor caps every six to nine months. Carbon tracking occurs in the ionized air in the cap with the voltages the coil made. Removed coil and the problem disappeared.
Best regards,
Chris
How old is the oxygen sensor in your Corvette? The older oxygen sensors get slower in their response time and their signal weakens until they finally just fail. If your O2 is older than a couple years or has some miles on it you might consider replacing the O2. The performance of an O2 deteriorates and so does the car's performance and mileage. An older O2 is not able to handle high speeds and fast changes as well.
The sputtering under load has me curious, how do you mean sputtering, Bucking, missing, surging? MAP sensors measure the volume of air being ingested by the engine and if there is a leak and extra air is getting in it makes a mess of your car. My MAP sensor in a Buick failed under loading like hitting a hill with a trailer behind you. At first it would miss a bit here and then it started to get worse so I popped another MAP on and that problem left me.
Check your O2 as I am suspicious it is slowed down a bit causing the problems in the transitions like coming to idle after running at speed. If you have time check your CTS for accuracy as that can add on to other problems.
Hello again rusty76!
Some of us gap our plugs at 60-65 to use the high powered ignition for the best effect. My ignition system on my C3 "burns" plugs if the gap is too small. With my compression and HOT spark I run a bigger gap than normal. I think a lot of people don't even check the spark plugs gap anymore, they assume it comes all set. Set your plug's gap and then put anti-seize on their threads and install them. I spent hours with a test bench testing spark plugs and was amazed at some of the differences. I used an Older MSD ignition and mounted the spark plug for observing it and taking pictures of the spark. I found some Bosch Fusion Spark plugs and WOW, that is a spark. No other plug came close but the cost of 8 of the Fusion plugs was expensive so I to have my old AC Delco spark plugs in there instead. When the MSD system in my car fires you can hear the spark as it sounds like a spot welder with the multiple sparks up to 3k rpm.
Be careful though as there is too much of a good thing. I used a Hot coil setup on my Wife's Chevy pick up and it started eating distributor caps every six to nine months. Carbon tracking occurs in the ionized air in the cap with the voltages the coil made. Removed coil and the problem disappeared.
Best regards,
Chris
Racer
Joined: Feb 2017
Posts: 388
Likes: 54
From: Sparta New Jersey
Thanks Chris for you comment on my plug issue. I considered the possibility that the 65 gap might be appropriate to the plug but decided to go with the stock setting as I'm trying to eliminate variables.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Just a suggestion
I chased a hesitation problem for a long time on my 94, check everything all looked good. In the end it was the EGR valve. It did not leak, it pass all the tests on and off the car that are on the internet , books and manuals.
However there is an internal check valve that was bad which caused the problem. Nobody really addressed a test for this and it was the problem. I came up with a test for this and it worked. I wrote a thread on it and if I can find it I will post it.
I chased a hesitation problem for a long time on my 94, check everything all looked good. In the end it was the EGR valve. It did not leak, it pass all the tests on and off the car that are on the internet , books and manuals.
However there is an internal check valve that was bad which caused the problem. Nobody really addressed a test for this and it was the problem. I came up with a test for this and it worked. I wrote a thread on it and if I can find it I will post it.
Thread Starter
Heel & Toe
Joined: Oct 2017
Posts: 19
Likes: 2
I will try the fuel injector cleaner and replace the fuel filter. The car starts right up and idles just fine .
I back out of the driveway and start down the road. Thats where the sputtering starts. It usually lasts a minute or so. It seems like its going to stall but doesn't
After that minute or so the car runs fine the rest of the day and sometimes the next day. One minute of frustration. No lights come on nothing to indicate whats wrong
I back out of the driveway and start down the road. Thats where the sputtering starts. It usually lasts a minute or so. It seems like its going to stall but doesn't
After that minute or so the car runs fine the rest of the day and sometimes the next day. One minute of frustration. No lights come on nothing to indicate whats wrong
Team Owner
Joined: Jul 2004
Posts: 28,330
Likes: 3,245
From: Hartford WI
Have you tried seeing what the fuel pressure is at key on engine off? It should spike up and hold. After that, I'd like to see what the WOT pressure is. It might be ok at idle but not with a load.
How is the spark quality? Plugs and wires known good or look good?
Got a scanner to see what the ECM thinks the coolant temp is vs what it really is?
I don't think it is injectors but if you suspect it, since they are so old, send them off to FIC for cleaning and testing. Ask him to specifically include a "Before and After" so you can see if that was really the issue.
How is the spark quality? Plugs and wires known good or look good?
Got a scanner to see what the ECM thinks the coolant temp is vs what it really is?
I don't think it is injectors but if you suspect it, since they are so old, send them off to FIC for cleaning and testing. Ask him to specifically include a "Before and After" so you can see if that was really the issue.
Safety Car
Joined: May 2001
Posts: 4,720
Likes: 1,625
From: Fairfax Virginia
Hello aklim, et al
I looked into the cleaning and flow testing and FIC wants $15 per injector just to test it and another $25 per injector to clean them. That is a lot of money to spend on a suspect injector problem. You could buy a brand new matched set for less than the services listed earlier. I guess my $25 bottle of B&G 44K is not so bad after all. IT works and its is only $25to clean the fuel system thoroughly. It has never failed to improve the performance of any car I have used it in.
You are right to suggest testing the strength of the Spark. I keep opening the gap on my tester to see where the coil starts to have trouble, it gives me an idea of how strong the ignition system is. I would also use the gap tester at each spark plug to be sure it is not a wire causing the intermittent miss.
Does the problem start when the Corvette is transitioning from Open loop to Closed Loop?
Does it smooth out after a couple minutes and work fine from then on?
The reason the car takes a few seconds longer to start after a few days is that the Car needs to prime the fuel system prior to cranking the engine. That is normal. How long it takes your engine to catch on and run normally is another story.
Are their any details you might have forgotten? The more you give us the better we can help you. Put as much data about your car on the Profile Page so we know what we are working with. Knowing where you are would also be helpful as some of us have scanners and can help you where you live.
As always I wish you the very best in getting this Corvette back on it's best behavior again!
Best regards,
Chris
I looked into the cleaning and flow testing and FIC wants $15 per injector just to test it and another $25 per injector to clean them. That is a lot of money to spend on a suspect injector problem. You could buy a brand new matched set for less than the services listed earlier. I guess my $25 bottle of B&G 44K is not so bad after all. IT works and its is only $25to clean the fuel system thoroughly. It has never failed to improve the performance of any car I have used it in.
You are right to suggest testing the strength of the Spark. I keep opening the gap on my tester to see where the coil starts to have trouble, it gives me an idea of how strong the ignition system is. I would also use the gap tester at each spark plug to be sure it is not a wire causing the intermittent miss.
Does the problem start when the Corvette is transitioning from Open loop to Closed Loop?
Does it smooth out after a couple minutes and work fine from then on?
The reason the car takes a few seconds longer to start after a few days is that the Car needs to prime the fuel system prior to cranking the engine. That is normal. How long it takes your engine to catch on and run normally is another story.
Are their any details you might have forgotten? The more you give us the better we can help you. Put as much data about your car on the Profile Page so we know what we are working with. Knowing where you are would also be helpful as some of us have scanners and can help you where you live.
As always I wish you the very best in getting this Corvette back on it's best behavior again!
Best regards,
Chris
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Team Owner
Joined: Jul 2004
Posts: 28,330
Likes: 3,245
From: Hartford WI
Hello aklim, et al
I looked into the cleaning and flow testing and FIC wants $15 per injector just to test it and another $25 per injector to clean them. That is a lot of money to spend on a suspect injector problem. You could buy a brand new matched set for less than the services listed earlier.
I guess my $25 bottle of B&G 44K is not so bad after all. IT works and its is only $25to clean the fuel system thoroughly. It has never failed to improve the performance of any car I have used it in.
I looked into the cleaning and flow testing and FIC wants $15 per injector just to test it and another $25 per injector to clean them. That is a lot of money to spend on a suspect injector problem. You could buy a brand new matched set for less than the services listed earlier.
I guess my $25 bottle of B&G 44K is not so bad after all. IT works and its is only $25to clean the fuel system thoroughly. It has never failed to improve the performance of any car I have used it in.
THE SERVICE INCLUDES:
1) Injectors are externally cleaned, visual inspected
2) We test injectors for resistance, shorts, and current draw.
3) We perform leak test, spray pattern, and flow rate testing on one of our 5 ASNU flow bench. All data is recorded and sent to you.
4) Remove filter baskets, o-rings, and pintle caps. Metal injectors are bead blasted to remove old paint and rust from the injector body.
5) The injectors are placed in a heated ultrasonic bath to insure that the injector is free of dirt and contaminants that could hinder the rest of the process.
6) The injectors are now put into another ultrasonic system while they are pulsed allowing the ultrasonic energy to dislodge any particles and build-up inside the injectors.
7) The injectors are now back flowed to remove all debris, etc.
8) The injectors are now returned to the flow bench for retesting of all functions. The data from this test is returned to you in detail with your injectors.
9) The injectors are now refinished with high temp paint. the stainless steel injectors are polished to a high finish.
10) One of our techs. now reassembles the injector, using all new parts.
11) The injectors are then vac sealed and packaged for shipment along with the old parts.
2) We test injectors for resistance, shorts, and current draw.
3) We perform leak test, spray pattern, and flow rate testing on one of our 5 ASNU flow bench. All data is recorded and sent to you.
4) Remove filter baskets, o-rings, and pintle caps. Metal injectors are bead blasted to remove old paint and rust from the injector body.
5) The injectors are placed in a heated ultrasonic bath to insure that the injector is free of dirt and contaminants that could hinder the rest of the process.
6) The injectors are now put into another ultrasonic system while they are pulsed allowing the ultrasonic energy to dislodge any particles and build-up inside the injectors.
7) The injectors are now back flowed to remove all debris, etc.
8) The injectors are now returned to the flow bench for retesting of all functions. The data from this test is returned to you in detail with your injectors.
9) The injectors are now refinished with high temp paint. the stainless steel injectors are polished to a high finish.
10) One of our techs. now reassembles the injector, using all new parts.
11) The injectors are then vac sealed and packaged for shipment along with the old parts.
Where did you get $40 per?
I'm sure you THINK it works as well as you say based on some butt dyno data. I have verified Jon's work with a flow bench to see if he fudged some numbers for me. Can you say you have flow benched them before and after? Have you done all that is listed in the above quote? How did you determine "thoroughly" besides "it feels better"? How did you know what it was before and what it is after? Like I said, before I sent it to him, I tested it on a flow bench at the tech college. After, I flowed it again and compared it to the data he sent of what was before and after to verify if he is honest. Also, doing it a few times helps me determine at what interval there is build up and how far I feel comfortable with the build up.
Last edited by aklim; Sep 11, 2019 at 02:30 PM.
Safety Car
Joined: May 2001
Posts: 4,720
Likes: 1,625
From: Fairfax Virginia
Hello there aklim, First- I am NOT trying to bait you or make you angry. If I have I apologize for having done so!!
I looked up what was charged for cleaning and testing services and those are the numbers I found.
No I don't have a flow station for testing fuel injectors at my home. I do know a little about how to recognize a problem with an injector's spray pattern and have tested them myself at home on occasion. I used to work with diesel Engines and their mechanical injectors but these electronic fuel injectors are over my head "so to speak".
I am glad that FIC is honest, I have never double checked someones work like that but then I don't have the equipment or knowledge. I have seen the tests done with various cleaning agents used in fuel injectors. Some things work, some thing don't.
Check out this list.
I will admit I made a mistake, The site I got my prices from was not FIC but instead FIC the Fuel Injection Clinic.
Here is the page I got the numbers from. http://fuelinjectorclinic.com/fuel-injector-cleaning and the other page http://fuelinjectorclinic.com/flow-testing
I sincerely apologize to anyone offended by my mistake. I have heard nothing but praise for Jon and his Fuel Injector Connection business.
I looked up what was charged for cleaning and testing services and those are the numbers I found.
No I don't have a flow station for testing fuel injectors at my home. I do know a little about how to recognize a problem with an injector's spray pattern and have tested them myself at home on occasion. I used to work with diesel Engines and their mechanical injectors but these electronic fuel injectors are over my head "so to speak".
I am glad that FIC is honest, I have never double checked someones work like that but then I don't have the equipment or knowledge. I have seen the tests done with various cleaning agents used in fuel injectors. Some things work, some thing don't.
Check out this list.
6 Best Fuel Injector(System) Cleaners
- Liqui Moly 2007 Jectron Gasoline Fuel Injection Cleaner.
- Lucas 10013 Fuel Treatment. ...
- BG 44K Fuel System Cleaner. ...
- Chevron 65740 Techron Concentrate Plus Fuel System Cleaner. ...
- Royal Purple 11754 Max-Clean Fuel Cleaner. ...
I will admit I made a mistake, The site I got my prices from was not FIC but instead FIC the Fuel Injection Clinic.
Here is the page I got the numbers from. http://fuelinjectorclinic.com/fuel-injector-cleaning and the other page http://fuelinjectorclinic.com/flow-testing
I sincerely apologize to anyone offended by my mistake. I have heard nothing but praise for Jon and his Fuel Injector Connection business.
Last edited by ctmccloskey; Sep 12, 2019 at 12:14 PM.
Team Owner
Joined: Jul 2004
Posts: 28,330
Likes: 3,245
From: Hartford WI
Hello there aklim, First- I am NOT trying to bait you or make you angry. If I have I apologize for having done so!!
No I don't have a flow station for testing fuel injectors at my home. I do know a little about how to recognize a problem with an injector's spray pattern and have tested them myself at home on occasion. I used to work with diesel Engines and their mechanical injectors but these electronic fuel injectors are over my head "so to speak".
I am glad that FIC is honest, I have never double checked someones work like that but then I don't have the equipment or knowledge. I have seen the tests done with various cleaning agents used in fuel injectors. Some things work, some thing don't.
6 Best Fuel Injector(System) Cleaners
I would myself try the B&G 44k first and then consider replacing the entire set with a new matched set. Then I would have a second set that I can have cleaned and ready for the next time as long as it costs less than the new set.
I will admit I made a mistake, The site I got my prices from was not FIC but instead FIC the Fuel Injection Clinic.
Here is the page I got the numbers from. http://fuelinjectorclinic.com/fuel-injector-cleaning and the other page http://fuelinjectorclinic.com/flow-testing
I sincerely apologize to anyone offended by my mistake. I have heard nothing but praise for Jon and his Fuel Injector Connection business.
No I don't have a flow station for testing fuel injectors at my home. I do know a little about how to recognize a problem with an injector's spray pattern and have tested them myself at home on occasion. I used to work with diesel Engines and their mechanical injectors but these electronic fuel injectors are over my head "so to speak".
I am glad that FIC is honest, I have never double checked someones work like that but then I don't have the equipment or knowledge. I have seen the tests done with various cleaning agents used in fuel injectors. Some things work, some thing don't.
6 Best Fuel Injector(System) Cleaners
I would myself try the B&G 44k first and then consider replacing the entire set with a new matched set. Then I would have a second set that I can have cleaned and ready for the next time as long as it costs less than the new set.
I will admit I made a mistake, The site I got my prices from was not FIC but instead FIC the Fuel Injection Clinic.
Here is the page I got the numbers from. http://fuelinjectorclinic.com/fuel-injector-cleaning and the other page http://fuelinjectorclinic.com/flow-testing
I sincerely apologize to anyone offended by my mistake. I have heard nothing but praise for Jon and his Fuel Injector Connection business.
Me neither but I did someone some favors so he let me use the one they have. For us, it would be cost prohibitive to own one unless we were doing commercial stuff.
Didn't Reagan quote the Russian proverb "Trust but verify"? I verify whenever possible. I have learned that people say many things, believe in few and do even fewer. As long as the tests come out good, I'm willing to extend the test interval a bit to build up confidence until they fail the test.
I don't know that the principles are much different, are they? I would assume spray pattern and volume but not totally sure.
I would love to see one efficacy test performed by an independent lab using commonly accepted testing methods. Automobileremedy has done an excellent job of using adjectives to describe something. Not sure how it came up with the answers but as my math teaches used to drill into our heads "No working, no credit".
If they are Multecs, it might not work out with the coils being fed additives.
I think what you got was a clean (which includes before and after testing) vs just testing. My guess is that $15 will turn to $25 if they discover a problem.
FOR NOW, at least, he is good.