94T/A5.7LT1

iTrader: (1)

ok so my car is a DD and usually in the morning or first start up of the day the car will start then stumble and die, the second time i go to start it starts but i have to give it gas. Also sometimes when i drive i will shut the car off and then when i go to drive it again it would run like ****, the car hesitates and bogs when accelerating then after stomping on the gas and just trying to get up to speed the car will just like kick in and the performance is back. Then the car will run fine, All this just started happening in about a week or two. Car ran great before that. So today i went down changed the fuel filter, PCV valve, put some sea foam in the gas, and shot some deep creap down the manifold. I put NGK tr55 plugs, MSD wires, and MSD coil a couple of months ago so those are still new. Any other suggestions that could be the problem? My dad said its possible that the fuel pump is going bad and i was thinking maybe it could be the opti as well. Thanks

venomhp

iTrader: (13)

are you throwing any codes? could be the o2 sensors, could be the fuel regulator, one or more of your injectors could be stuck open/closed...just some ideas. normally when the fuel pump goes out it just goes out.

94T/A5.7LT1

iTrader: (1)

i was thinking the the o2 sensor but there are no codes. well if its a fuel regulator might as well put in an adjustable. The regulator is located in the back of the fuel rails correct? How do you get the fuel lines off of the fuel rail?

tasilver

iTrader: (2)

Use some MAF cleaner. You be amazed at the amount of problems a dirty one will cause. Do you run a K&N filter and if so Have you cleaned it, If you use to much oil it will make you MAF go to crap until it the MAF is cleaned.

Mine did the same thing, bog and you have to mash the gas then it would kick in. I thought my fuel filter was bad too. The reason the car kicks in with WOT is because the pcm does not use the MAF at WOT. With everthing else you have done your car should run great if the MAF was the problem.

Spink

iTrader: (1)

+1

The o2 will only affect the car after it goes into closed loop once it's warm so that can't be it.

94T/A5.7LT1

iTrader: (1)

alright ill check kragens and autozone tomorrow for it. Also i was thinking could a bad opti cap and rotor cause that problem? The car has 129000 miles on it and i have never touched the opti.

wssix99

iTrader: (5)

I had the same problem. The car threw no codes - it was a fouled MAF sensor. Cleaning the MAF took care of the issue.

94T/A5.7LT1

iTrader: (1)

ok cleaned the MAF but i still get the hesitating just not as bad before. Still have the start then die problem on first start up but im pretty sure that just because its cold outside. Im going to try replacing the fuel pressure regulator first and if the problem still happens im going to check the opti, check to see if the cap has any cracks in it then replace. Anything else i should check before i start taking things off just to get to the opti?

wssix99

iTrader: (5)

Have you changed your fuel filter recently?

94T/A5.7LT1

iTrader: (1)

yes i changed it couple of days ago along with the pcv valve. It was doing it last night again and i noticed it only did it in gear, so is it possible for the trans or rear end could be going out? when i through it in neutral it reved up fine with no hesitation.

wssix99

iTrader: (5)

When I had the problem on my '99 LS1, it did the same. No problems in neutral - I only got the hesitation when the engine was under load.

If your first MAF cleaning showed tangible results, you may give it another cleaning. (GM and K&N have a nasty debate on the issue. GM says the problem is cause by oiled air filters and K&N says its silicone leaking out of the sensor. I would think that oil would be easier to get off than the later.)

For a second cleaning, you may try disassembling the housing (so you can get closer to the sensor) and looking at it under a magnifying glass. If there is contamination, you should be able to see it or some associated discoloration. Taking the sensor out of the housing should also allow you to get a better shot at it with the cleaner. (If you do this, you need to do so with great care as the sensor is fragile and its not supposed to be touched.) I ended up rubbing mine down very gently with a Q-Tip and didn't seem to hurt anything, but maybe I got lucky...

If you have access to a scanning tool, like AutoTap, you could also check your air flow readings and other sensor voltages and compare them to other cars that are running well.

94T/A5.7LT1

iTrader: (1)

okay so i cleaned my MAF 3 times already and i still have the problem. It only does it for a couple of minutes and then it runs fine, does it when its cold and warmed up. Now i have noticed that since i have an autometer A/F gauge (not wideband since they didnt make one in the cobalt series at the time) That it goes all crazy or just doesnt read at all, if its possible for the sensor to start to go bad or maybe my ses light just didnt go off for some reason? Now i am able to read the computer and when i use the datamaster program it shows that its running a little lean all the time, so could i have a fuel pressure regulator starting to go out as well? Also it does not show any codes.

94T/A5.7LT1

iTrader: (1)

anyone?