Starting problem.

[Paul Higg]

Now that the heat of the summer is here in Atlanta (80's) I have noticed it is getting harder to start the car. It seems as if it is not getting enough gas when cranking. If I press on the gas pedal it will start. Any ideas?

LT1

90,000 miles.

 

[Tuna]

Cleaning the throttle body might help.

The IAC (Idle Air Control) may be sooted up and interferring with the flow when trying to start.

 

[Paul Higg]

Thanks Tuna, can't I get at it when I remove the plenum and the duct? I think it looks like a twin tube with a split in the middle? It is metal right? I will look it up.

Thanks again.

 

[Tuna]

The C4 throttle body has twin throats and butterflys and the IAC air flow is between them. Take the air bridge (duct from the air cleaner to the TB) loose and spray the TB with throttle body cleaner and wipe off the soot that drips out. The see if that helps.

Forgot to ask, is it hard to start when the motor is cold or hot or both?

 

[minifridge1138]

When was the last time you replace the fuel filter?
Cleaning out the carbon build up is a good idea anyway at 90K miles.

Also, before you start it, turn the key to "ON" 3 times. You should hear the fuel pump buzz each time. This will pressurize the system.

If you turn the key directly to "START" you'll start cranking the motor as the fuel system is trying to pressurize and it will take longer to start.


Good LUCK!

 

[Paul Higg]

THAT'S what I noticed! I will try that. Thanks for the advice.

Paul

 

[Paul Higg]

Just hot.

 

[gmjunkie]

Just hot.

Paul,Check the temp sending unit!(On the front of the water pump!!) These will sometimes develop a loose or corroded connection and give the ECM a False reading, or just get out of range!!Can cause Hard start Hot,or cause problems starting Cold!!(Just Depends!!):W:W"Rascal Rascal 99" called me a couple weeks ago while he was on the road going to Bowling Green after he did his Opti because his car was acting strange and not running quite right!!I told him to check that sensor and he found he had accidentally broken the plastic on the sensor putting the belt on and it wasn't getting a good connection!! He changed out the sensor in a NAPA Parking lot and ALL is well now!!

 

[Tuna]

I had a '96 LT4 that was hard to start when hot. Turned out that the fuel pressure was bleeding off too quickly due to a check valve in the tank. Seems that LT1/4's like a good residual fuel pressure to start when hot.

Put a fuel pressure gauge on it and see if it holds pressure after shut down. If not, suspect a sticking injector or a back check valve.

I agree with junk also. The temp sending unit on my '92 broke recently and gave me problems. The housing seems to get real brittle as they age and easy to crack or brake. If the connection is loose there, it can cause all sorts of problems with running and starting. I noticed the digital temp readings changing randomly when it was loose. It may set service engine soon lights also.

 

[gmjunkie]

I agree with junk also. The temp sending unit on my '92 broke recently and gave me problems. The housing seems to get real brittle as they age and easy to crack or brake. If the connection is loose there, it can cause all sorts of problems with running and starting. I noticed the digital temp readings changing randomly when it was loose. It may set service engine soon lights also.

I remember that!!

http://www.corvetteactioncenter.com/forums/showpost.php?p=869699&postcount=10

http://www.corvetteactioncenter.com/forums/showpost.php?p=869926&postcount=13

 

[Paul Higg]

Paul,Check the temp sending unit!(On the front of the water pump!!) These will sometimes develop a loose or corroded connection and give the ECM a False reading, or just get out of range!!Can cause Hard start Hot,or cause problems starting Cold!!(Just Depends!!):W:W"Rascal Rascal 99" called me a couple weeks ago while he was on the road going to Bowling Green after he did his Opti because his car was acting strange and not running quite right!!I told him to check that sensor and he found he had accidentally broken the plastic on the sensor putting the belt on and it wasn't getting a good connection!! He changed out the sensor in a NAPA Parking lot and ALL is well now!!

Junk, I just replaced it a month or so ago when I removed the radiator for cleaning. I am getting good temp readings too. No codes when I jump 4-12 but I do not have an ODB I tester with the adapter.

 

[Paul Higg]

I had a '96 LT4 that was hard to start when hot. Turned out that the fuel pressure was bleeding off too quickly due to a check valve in the tank. Seems that LT1/4's like a good residual fuel pressure to start when hot.

Put a fuel pressure gauge on it and see if it holds pressure after shut down. If not, suspect a sticking injector or a back check valve.

I agree with junk also. The temp sending unit on my '92 broke recently and gave me problems. The housing seems to get real brittle as they age and easy to crack or brake. If the connection is loose there, it can cause all sorts of problems with running and starting. I noticed the digital temp readings changing randomly when it was loose. It may set service engine soon lights also.

Okay, I haven't looked at the FSM yet but what kind of tools do I need to do this? What is the pressure gauge and where can I get one? Are they expensive? Is it difficult to replace a bad check valve?

 

[gmjunkie]

Junk, I just replaced it a month or so ago when I removed the radiator for cleaning. I am getting good temp readings too. No codes when I jump 4-12 but I do not have an ODB I tester with the adapter.

Why did you change it,was it not working right?? Just because it's New don't mean it's Not bad!!(Specially if it's a Aftermarket!!) It has 2 circuits in it,1 for the Digital Gage and 1 for the ECM to run the fuel injection and other systems!! There is another Temp sensor between #6 and #8 on the right head that go's to the ECM that controls the Cooling Fans and the Analog Gage,But I don't think it could be the problem!! I've had allot of problems with Aftermarket Senors!! TPS,Temp,O2 Sensors,Crank and Cam Sensors,Pick Up Coils and Other Electronics I replace with 100% GM!! The job don't pay worth a damn the second time around!! I've found the Aftermarket stuff is sometimes out of range NEW!!(And won't necessarily trip the light!)

 

[Paul Higg]

I replaced it with GM Junk. I had to replace it because some bonehead before me broke off the plastic housing where the plug connects. Really, it was working fine and reads fine. I replaced it several months ago and it was fine. This starting problem is only a few days old and only due to the heat outside. It starts fine cold in my garage.

 

[gmjunkie]

I replaced it with GM Junk. I had to replace it because some bonehead before me broke off the plastic housing where the plug connects. Really, it was working fine and reads fine. I replaced it several months ago and it was fine. This starting problem is only a few days old and only due to the heat outside. It starts fine cold in my garage.

Man,I wish you were closer!! I was down to Villa Rica a couple weeks ago to Repossess a car!!(Almost got Cut!!hnoes)
Try un-plugging the sensor and plugging it back in a couple times,maybe it has a little corrosion from dangling in front of the engine for a while,also you might go to Advance or Auto Zone and see if they have a Loner Fuel Pressure gage,I'd hate to see you have to buy one for no more than you'd use it!!(Schrader Valve is between 6 & 8 injectors on the bottom of the fuel rail!) Tuna's right these cars (LT1's & LT4's) Like Good fuel pressure!! 42-48 lbs,If it drops much below 38-40 good and warm that may be the problem at warm start!! You might even see if they would put your car on there scanner and see whats happening,Problem with that most of the guys there won't know what there looking at in Data mode!!

Another thing you might check is the EGR valve if it's leaking a little or has a small piece of carbon in it,it could cause it to take a little longer to start Hot in Closed Loop. Remove it and hold with the pintail at the bottom and squirt some WD-40 or some sort of penetrating oil in the Big hole(Yours I think is a little rectangular!!) If it leaks out of the pintail,It's Leaking!! Either it has a small piece of carbon stuck in it or the seat is eroded!! I'm able to clean them most of the time with carburetor cleaner and put them back on!! I usually replace them back with 2 gaskets with a Stainless Screen sandwiched between the two gaskets at the bigger hole!!This will help from getting a chunk of carbon in the pintail,Breaks larger pieces up small enough to go through the pintail with out getting caught!! (The one in the photos below is off a 4.3 V6 but work on the same principle it's just electronic instead of vacuum!!) It's "Junk"!!:ugh:ugh:ugh

You may see a little seepage around the pintail but not enough to run out!! If it runs out like this one does,It's Leaking!!!


I had a 93 a few weeks ago that was a real hair puller,wouldn't set a Code,Bubba had been hacking wires,corroded connections and splices in harness every where,No Codes stored,in Data mode scanner said Quad-Driver "Fault" 2 and 3 I couldn't get it to run long enough to see what it was doing!! But He's Cruising Now!!!

 

[Paul Higg]

No corrosion on plug.

Called Auto Zone and others, no one is allowed to read the OBD I plugs anymore, don't know why. They were told by their managers to remove all the adapters and just read OBD II's now. Pissed me off.

Fuel pressure gauge, never used one before buy I am sure I could learn. Need guidance.

I can look in the FSM to find out how to remove the EGR valve but in a nutshell, do I have to tear half the engine apart? (Seems like you have to for EVERYTHING on this car).

I save your post and photos Junk. I REALLY appreciate your help.

One more question, in a previous post someone said to clean the throttle body. Well, several months ago when I removed the radiator for cleaning it looked shiny and new. Does that mean anything or how should I clean it and with what brand of cleaner?

 

[gmjunkie]

Fuel pressure gauge, never used one before buy I am sure I could learn. Need guidance.

Nothing to it!!

I can look in the FSM to find out how to remove the EGR valve but in a nutshell, do I have to tear half the engine apart? (Seems like you have to for EVERYTHING on this car).

No it's Easy on yours!! The thing below the Fuel Pressure regulator with the green Dot!! 2 nuts and a vacuum line!!

One more question, in a previous post someone said to clean the throttle body. Well, several months ago when I removed the radiator for cleaning it looked shiny and new. Does that mean anything or how should I clean it and with what brand of cleaner?

I'd remove the IAC valve,Hold OPEN the throttle plates and spray away!!Also spray in the IAC opening and the Valve pintail itself!!! Use any Sensor Safe Carb,Throttle Body or Air Intake Cleaner!! (Gunk,K&W,Carb Medic,as long as it's Sensor Safe!!)When you open it and Look down it's throat,You'll see Black Crud I'm sure!!!

 

[Paul Higg]

Okay Junk, you're AMAZING. Now that I know where the EGR is and it looks easy to remove, how do I get at the IAC valve? Please forgive my stupid questions but I really need to learn this engine.

 

[gmjunkie]

Okay Junk, you're AMAZING. Now that I know where the EGR is and it looks easy to remove, how do I get at the IAC valve? Please forgive my stupid questions but I really need to learn this engine.

It's right below the TPS!!

 

[Toms007]

I learn so much stuff reading these posts! Junkie, you da man! I may take mine apart, just to get ahead of the game.