HELP Fuel Related? Engine surges randomly, stutters when stomp on pedal, more....

[TammyLS]

Several symptoms, I believe are all related. I have an idea or two what it could be, but insight would be great..... Thanks in advance.

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It used to be that when I got low on gas and stomped on it it would cut out on me. Then I got this wierd symptom of it accelerating all on its own to the point I had to pull over and shut it off (automatic). That happened about 4-5 times in the last 6 months. Reved to 5 and would not go down. I shut it off and was fine, then ran like a rocket. Now it periodically runs like a champ, and other times just ok. I know my baby like the back of my hand, something is wrong. Within the last couple of weeks now I've noticed at idle it surges slightly. A couple times when tank had at least a half it died on me after I started it and acted like it was going to die on me at a "coast". Also, when I stomp on it, it "chokes" on me and seems to "cut out" or acting like it does when I run out of gas (yes I have done that to my poor car). Has these symptoms on a full tank as well. Thanks for help.

 

[vetteboy86]

Welcome to the Corvette Action Center!!

Sounds like you may have a few issues. Have you done any fuel pressure verification?

I can personally say that if my fuel guage shows 1/4 and I'm try some spirited driving, my motor will become fuel starved. I know there has been discussion about this, and how the tank is designed to prevent this. I don't run mine below a 1/4 and have a good idea of when the problem will occur so I avoid it.

 

[djsroknrol]

Sounds like a plugged inline fuel filter or plugged pickup screen....

 

[TammyLS]

I have filled the tank full and still does the same thing :confused

 

[TammyLS]

I wll try a fuel filter. I've also read alot about the fuel pump. Periodically I do hear it whine when I start it up, but figure that is normal. I am not a techy at all and don't have the where with all to hook up guages and all that fun stuff. I do have a mechanic but would like to steer him in a direction at least... Thanks

 

[Jeb]

I wll try a fuel filter. I've also read alot about the fuel pump. Periodically I do hear it whine when I start it up, but figure that is normal. I am not a techy at all and don't have the where with all to hook up guages and all that fun stuff. I do have a mechanic but would like to steer him in a direction at least... Thanks

If it were me, I'd just tell your mechanic what the car is doing let him figure it out. By "steering" him, you are telling him to do something which may or may not be necessary.

Having said that, I cannot see how a fuel filter or pump related problem would cause the car to accelerate to the point where you must turn off the key to make it stop. Surging, yes. Stalling, yes, burping, yes. But there isn't anyway that I know of that a bad fuel filter or pump would cause what you have described.

 

[Jeb]

Welcome to the Corvette Action Center!!

Sounds like you may have a few issues. Have you done any fuel pressure verification?

I can personally say that if my fuel guage shows 1/4 and I'm try some spirited driving, my motor will become fuel starved. I know there has been discussion about this, and how the tank is designed to prevent this. I don't run mine below a 1/4 and have a good idea of when the problem will occur so I avoid it.

Running it lower than 1/4 will also shorten the life of the fuel pump since it is cooled by the fuel around it and if there isn't any fuel, it'll run hotter than it likes.

 

[LLC5]

Several symptoms, I believe are all related. I have an idea or two what it could be, but insight would be great..... Thanks in advance.

It used to be that when I got low on gas and stomped on it it would cut out on me. Then I got this wierd symptom of it accelerating all on its own to the point I had to pull over and shut it off (automatic). That happened about 4-5 times in the last 6 months. Reved to 5 and would not go down. I shut it off and was fine, then ran like a rocket. Now it periodically runs like a champ, and other times just ok. I know my baby like the back of my hand, something is wrong. Within the last couple of weeks now I've noticed at idle it surges slightly. A couple times when tank had at least a half it died on me after I started it and acted like it was going to die on me at a "coast". Also, when I stomp on it, it "chokes" on me and seems to "cut out" or acting like it does when I run out of gas (yes I have done that to my poor car). Has these symptoms on a full tank as well. Thanks for help.

You might have multiple problems, but I would take a very close look inside your throttle body and make sure that it is not carboned up. Check for any stored codes in your ECU also, if there are any they can steer you in the right direction. Good luck with it.

 

[TammyLS]

Thanks. I probably have a couple issues.. Thank you very much.

 

[catbert]

Replace the filters and clean the throttle body with CRC spray throttle body cleaner. Don't use anything else - the are very fragile. C are about 50/50 this will clear it up.

 

[John Robinson]

Sounds Familiar

Long story short it sounds like what I went through earlier this year on my 93. Here are some things to look at

1. The grounds all need to be cleaned that is a part of the problem
2. Check the wires in the TPS connector. They may be broken.
3. Pull the codes (they will tell us a lot )
4. Yes as mentioned by others the Fuel pump, The fuel pump pick up screen, and the fuel filter.
5. The O2 sensor

I found all of these things were contributing to my problems.

But before any of that is done pull the codes and let us know what they are. From them we can collectively offer solutions that might not cost you an arm and a leg.

Another question I have for you is have you noticed a dramatic drop in Fuel mileage. The reason I ask is in my case I went from 17 MPG town to 12 MPG or less and on the road from 26 to 27 MPG to 19 or 20 MPG.

 

[boomdriver]

maybe several things...

vac leak in/at the intake.

TPS gone wild.. (pg-13 rated version) boo

fuel regulator defect internally

Injector leaking down too much fuel or sticking open or shorting open

Timing control module

IAC valve open or stuck open / damaged

This is a MAP system right? Not a MAF to measure airflow.
Either way it sounds like its not adjusting fuel to whatever air gets metered.
Of course a fuel filter could be the cause of everything...

 

[Hib Halverson]

First thing to do...before you drive the car any more...is find out why the throttle is sticking. That you had to pull over and shut off the engine indicates an unsafe condition.

I'd check the entire accelerator linkage/cable from the pedal on the floor all the way to the throttle body. Also you may want to perform the accelerator cable adjustment procedure listed in the Service Manual.

Inspect the throttle body itself to make sure the throttle plates are not sticking or binding as they operate.

I suspect the problem is not fuel supply, however, if the fuel filter has not been changed in the last 3 years, I'd change it.

It sounds like this is more of an idle stability and/or throttle response problem.

Is the check engine light on or has it been on and gone off recently? If so, what codes were set?

Has the TPS been adjusted per the FSM?

Has the main engine controls ground (near the oil filter) been checked for corrosion and/or tightness?

Has the engine been checked for a vacuum leak?

 

[John Robinson]

Update to previous post

The reason I asked about the fuel mileage is because when I changed the O2 sensor it went back up to what it was before. So if you do have a code 64 that indicates that you have a lean right bank O2 sensor signal to the ECM

A lean engine will not have any power. It may rev to the red line but it will probably act as if it is holding back and may even stumble during acceleration.

As for the TPS I had one go bad and it made the engine run over 2000RPM. The codes for it I l think are 21 or 22 but in my case I did not get a code from the TPS failure. So I agree you should have the TPS checked out for proper operation

 

[Schrade]

Running it lower than 1/4 will also shorten the life of the fuel pump since it is cooled by the fuel around it and if there isn't any fuel, it'll run hotter than it likes.

Yup. Times get tight, and the fuel tank stays near empty. The fuel keeps the pump cool...

2. Check the wires in the TPS connector. They may be broken.
.

I say TPS fault, or carbon fouling in TB butterfly. That will cause rpm's to stay improperly high...



Whatever you decide, when you go to the mechanic, you don't have to know squat really, but you just think critically about what he tells you, i. e., "The MAF circuit has a fault; I can replace the MAF sensor for $315, and that will probably fix it".

And he replaces it, clears the computer, you drive away cold motor, no code check, and think it's fixed. First time it goes closed loop/warmed up, you get MAF circuit problem again. Wasted $315...

How to prevent this? Ask him why he said "probably", and then get him to SHOW you, with a test, why he wants to do any thing in particular.

Wannabe mechanics love to do UPnP repairs with your wallet.

(UPnP = universal plug-n-PRAY)

 

[vetteboy86]

All good suggestions. I think the most important is to figure out why the throttle is sticking first. This represents a major safety concern. I would get in the car, and press the accelerator and notice how it returns. Does it return to the normal position freely?

Eliminate any mechanical issues first as these will be the easiest to diagnose.