I have been trying to find a problem with my 1998 corvette, but cannot find anything. I got it checked on a tech II and nothing came up. Basically the problem is: When I start the car cold, in the morning it has a little trouble starting, but than runs fine. Its when I stop for short periods of time, lets say hour and try to start it, it will start okay, but will sputter and almost stall (or stall sometimes) I go to take off and the car lerchs and jumps, but than i push the clutch in, give it gas take off hard and it will be fine. I already put a new fuel filter in, and run some fuel system cleaner through it.

 

check your fuel pressure. 42-45psi. connect your guage to the fuel rail.

 

Theres a couple of things to check;

1- First, remove the air filter assembly and check the filter and the housing. Make sure there is nothing out of the ordinary wrong there.
I had a K&N filter in my 98 with a CUT stock housing. Worked great,,,,,,until it rained. The filter got soaked and it went down below freezing the next day. The filter frozen SOLID! Car would hardly run!

You cant take anything for granted!

2- The connections between the MAF and the throttle body MUST be made up properly and AIR TIGHT. Make sure that there is a complete and tight seal at every joint. The plastic air duct (air bridge assy) that sits on the radiator shroud is known well for deforming and leaking air.

3- While the the air filter assy is out, "CLEAN THE THROTTLE BODY" and CLEAN THE MAF. They sell MAF cleaning spray but, I have had good success with brake parts cleaner. Spray the cleaner in the MAF (do not touch the small wires or sensors inside the MAF) and flush out the dirt. Let her dry out until the cleaner evaporates.

4- Use the same cleaner for the TB. Push the blade open, spray the cleaner in and wipe the housing and blade with a rag. Let it flop shut. It will NOT shut all the way! Thats NORMAL!

5- Check all the vacuum lines and MAKE SURE that there not loose, deteriorated or cracked. Especially the PCV line. Its also well known to crack and rub through! BIG AIR LEAK!

 

I checked the fuel pressure at the rail, and it seems even higher than that, more like 58 or so. Even when the car is sputtering and dying the fuel pressure holds around 58.

 

That is the correct pressure. The 42-45 psi posted by aquaholic is wrong.

 

So in that case its not the fuel pump? I am following Bill's procedure, I found one little hose that was cracked up I hope thats it. We will see though it should only be another half hour to put it back together, Ill be back on after a short test drive.

 

I followed Bill's procedure, cleaned MAF and TB put it all back together, cleared all the codes. Had a hard time starting, but that maybe because I took of the fuel pressure gauge, and all the built up gas was released. Anyway start it, take it for a cruise. Runs nice!! I let it sit for twenty min or so. The car starts no problems but after a few moments the idle drops really low and the car starts sputtering. Any ideas, some kind of throttle problems??

 

any ideas?

 

its 55-61. i looked it up in the service manual.

 

TAC module?

 

Any air getting into the engine without going through the MAF will cause problems. Make sure you have no loose intake or throttle body bolts, no loose clamps or hoses. no more cracked hoses etc.

 

Hello, here it what I found causing issues on another 98. Note the 98 has a fuel pressure reg that is vented to the engine air inlet. when the reg starts to leak, fuel runs down the vent line into the intake and causes the enging to run rough intermitantly.

Pull the line off the reg and check it for fuel (see pic) if there is fuel at line, then this is the problem.

Hope this is helpful.

 

And 58 psi is nominal.

BTW, good idea there 69.

 

Do I test this with the engine running? Also where that hose (in the photo) goes into the intake tube it seems that its not a really tight seal, it just kind of pop in; could that be the problem?

 

What is the TAC module and how can I test it?

 

If you don't have any codes I would not worry about it. Most people get codes when the TAC is failing, and you have not reported any.

If you have PCM codes, post them up.

I'm assuming you have checked wires and plugs.

Remove the fuel rail covers and wiggle test the MAF and injector wiring while the car is idling.

 

Hello, with the enging off, not running, pull the line off the pres reg and check it for fuel drip or fuel in the line. the line just pops in the inlet.

K

 

As for the fuel pressure reg. It is not leaking.

 

I dropped my car off at the local Chevy dealer today. They said they cannot pin point the problem, however for $975 they will replace the oil pressure sensor, map sensor, and one o2 sensor. He said however he cannot gaureentee it will work. I am def not paying a thousand, for something that "might" fix the problem. When the parts wont cost me nearly that much.

 

RUN FORREST,,,,,RUN!!!!!!!!!!! That is BS Dont go back there!

Try this:

The wiring harness on top of the engine drivers side runs down to the back of the engine. There is a metal bracket that it bends around. That bracket can and sometimes chafffes the wires and causes driveability issues. Check that harness and the wires in it. Look for chaffed worn wires.

Like FRCTony recommended, check and wiggle the wires in other places.

Theres one more thing that can cause weird issues. The Ignition switch. If the key isnt fully in the RUN position, it can cause simular issues. You car is 10 years old. I recommend that you read my post on ignition switch reapir and cleaning and eliminate that as a possibility. Best part about it,,,,,,ITS FREE!