higway speed miss, coolant leaks, flashing lights...lol

[sixfish]

:help: I feel like i'm losing my mind....lol... i gotta 97 tahoe, vortech 5.7, 4 wd, 115,000 miles. first off, I Noticed a couple months ago a hesitation while climbing a rather good sized hill on a nearby highway. seemed kinda odd but it went away after a few seconds so i thought nothing of it. noticed it a couple more times since then...and it's almost always after hard acceleration, usually at highway speeds (like passing). so first thing i did was change the plugs. a couple days later i noticed a coolant leak underneath the passenger side of the motor. dripping off the bellhousing and starter motor. so through asking guys at work and doing some online research I assumed it was the intake gaskets. (very common). anyways, while changing those out i got a sinking feeling as i lifted off the intake and noticed they were the same felpro gaskets i had just bought. it looked like someone had replaced them not that long ago. so sure enough, when i got her back together, it still leaked. i felt sick because i had just pulled half the motor apart for nothing. anyways, out of desperation i put some bars leak in the radiator and to my surprise the leak went away. it hasn't leaked for over a week now. but as i know this is only a temporary fix, i'm afraid i either have an external headgasket leak or bad freezeplugs. i can't tell where it was coming from. anyways, when i replaced the intake gaskets i went ahead and changed the plug wires too (figured i might as well). after i fired the engine up for the first time after replacing this stuff, the check engine light was on. engine was running smooth, no misses. went to autozone, had them read the codes and it came up as 2 misfire codes. they cleared them , i just pulled out of their drive and the check engine light came back on. i figured screw it...not messin with this anymore right now....next day after work i disconnected the battery, checked over all my work (spark plug wires, all my electrical connections on top of the motor, etc) hooked it back up, started it and the light came back on. disconnected the battery again, just on a hunch, climbed underneath and disconnected the crank sensor plug, blew in it a couple times and plugged it back in (this was one of the many things that had to be unhooked to change out the intake gaskets) hooked the battery back up, started it and and the light was off. just figured maybe i didn't have it plugged in all the way or something...cool. well it was good for about a week....well just the other day on the highway, the ses light came back on, this time it flashed several times before it stayed on solid. on the way home in the other direction i had to accelerate quickly to avoid on ramp traffic onto the highway and felt that old shaky hesitation again. it's there for about 10 or 15 seconds after mashing the gas pedal and then it smoothes back out....drove it later that evening and the light went out on it's own and hasn't been back on since (also haven't been on the highway since then either.) for the most part it starts, idles and city drives just fine. there are no noticeable misses or hesitations at all. i have had a couple times it wouldn't start on the first crank, but only a few. i did notice the fuel pump is getting louder and "whinier" i can hear it running when i stand at the back of the vehicle inside the tank while the engine is running. it was never this noticable before. i just feel like everything is falling apart at one time....lol.....oh yeah, forgot to mention i replaced the fuel filter too.....i think i can find the coolant leak its just a matter of pulling the inspection cover off the trans and seeing if i can't see more of what's going on, but for the whole engine light, lack of power at higwayspeeds misfire thing, in need of some advice.....ps....sorry this post is so stinkin' long...;o( thanks guys, any ideas would greatly be appreciated....

 

[Bigbill]

Check fuel pressure if its low you can get a hesitation especially at high way speeds also check the fuel filter again you could have flow but not forum and again at highway speeds it will be noticeable and not at all driving around town.

 

[sixfish]

thanks ;0)

I geuss i'll have to go get a fuel pressure gauge set tonight and check it out. Do you have any idea how long the system should hold pressure in the lines after the engine is off? The reason i ask this i had to remove the fuel lines from the intake manifold when i changed the intake gaskets. It was probably a couple hours after the engine had been ran. When i pressed in the relief valve on the fuel line to release the pressure before i removed it, i expected it to kinda spray out with some kind of force, but only a lttle bit of gas dribbled out, with basically no force behind it at all. Would this be considered normal? This is another reason i'm suspecting the fuel pressure maybe lower than it should be.....

 

[sixfish]

good fuel pressure

Bought and hooked up a pressure tester to the fuel line tonight and the pressure is right where it should be. At about 55psi at start up and idle and jumps up slightly to about 60psi when i give it a quick rev. No engine lights on right now and the guy at the auto store said he couldn't check any codes unless the light was on. Maybe i will just wait to see how things go and get it scanned if the light comes on again. Ordered a fuel pump anyways and will keep it on hand for the future....i know chevys are notorious for fuel pump failure anyways so it can't hurt to be prepaired.....just hate throwing parts and money at something and hoping it's the fix. Might be better off taking it to a professional shop if this problem continues cuz i'm running out of ideas. Also, don't know if this info helps but when i changed the plugs, even though the old ones were looking a bit old and tired, all 8 plugs looked pretty good as far as ignition, all uniform looking and no signs of problems, so i doubt this is an internal engine problem. No oil or gas mixing either and no signs of exhaust smoke either. It's just winter is right around the corner and here in michigan i don't want my vehicle breaking down....would like to figure this thing out....

 

[Erikmeister]

To be honest, go ahead and replace the fuel pump if you have it on order. From what it looks like (besides the coolant leak), the fuel pump should take care of your hesitation problem.

 

[sixfish]

mmmmm....

Thanks for the input, maybe i'll change the pump out.....are you speaking from experience? Have you had this problem or heard of it before? I have read on the net that it is possible for the pump to create enough pressure but still not supply enough volume.......i'm not sure. Any fuel pump problem i've had before with other vehicles, the things just died and would start at all, not something finicky like this. It's only "on demand" heavy throttle it acts up. Feels like it's loading up or starving for fuel or like the spark is breaking down. The wierd part is the misfire blinking ses light came on just cruising down the highway at 70, with no real "felt" misfire.

 

[samotahoe]

check to see if the fuel filter was installed the correct way. ive seen too many of these where the filter was installed backwards and the symptoms your describing normally happen highway speeds and/or higher RPM. it says flow on it with an arrow unerneath and that arrow needs to point towards the engine. i would double check that.

 

[sixfish]

thanks, but yeah

Thanks for the idea but yeah, the filter is in the correct position.....also, i had these symptoms before doing any repairs....thats why i did the filter change, plugs, wires etc....hoping it was just a simple maintenance thing......while i'm at it i think i'll replace the distributor cap and rotor this weekend too....might as well. It can't hurt. I just believe at this point it's beyond basic maintenance repair. The truck is running fine right now and still no lights, but once again i haven't done any highway driving either.....in the start up to idle to around 55mph range, you wouldn't know that there is an issue at all.....for some stinkin' reason it's that higher speed, needing some extra passing power range it stumbles....thanks for the thought though!

 

[sixfish]

just throwing this out there....

O.k. guys, just throwing this out there.....i know this comparison is two totally different vehicles, but......just for the heck of it i hooked my fuel pressure gauge up to my wife's 06 chevy uplander with the 3.5 liter...the fuel pressure sits at a dead steady 60 psi when the engine is running and the needle doesn't hardly move at all when the engine is revved, stays very constant.....hooked it back up to the tahoe and paid more attention to the needle and my fuel pressure is about 52 psi...so slightly lower than the recommended 55 to 60 psi. And as i stated before when revved, the pressure bounces back and forth about 5psi....bounces up and then back down......i know i'm kinda comparing apples and oranges here, but maybe not......i'm not a mechanic, but i am a body man and have done many automotive mechanical repairs in my lifetime....it's this electronic stuff that is always the hardest to figure out....lol.....not sure just how sensitive these fuel injection systems are....a 3psi out of specs could be nothing or it could be huge....i don't know.....do i want my fuel pressure to be more towards that 60psi number than being in the low 50's? My mechanical sense is telling me yes....and should the pressure really not fluctuate at all, and remain steady like it does on our van, regardless of idle or engine rev or whatever.....need your input guys ;0) thanks in advance!!! Just don't wanna pull the tank and change the pump and find nothing has changed.....lol.....cuz that's been my luck lately....lol