97, 5.7 has light throttle miss city and highway

[340doc]

My 97 pickup 5.7 has a light throttle miss around town and seems to be missing steadlily at highway speeds. If I give it more gas it goes away and no missing under WOT. It seems to be at a low rpm, I can drive around it by giving more or less gas and it goes away.Heres what I"ve done so far...Cap,rotor,wires.plugs.fuel filter. all delco. Also replaced fuel pressure regulator. Fuel pump is a little down on pressure, about 50 at idle and drops alittle when on the throttle also does not hold pressure when key is cut bleeding off I guess. should I drop the tank or look somwhere else? No engine light on. THANKS!!!

[jimbo543]

was the exact same problem there before you replaced the parts
sounds like spark plug bad/cracked, or plug wire loose/bad

[jdfenske]

i agree with jimbo.

from my experience i always replace one part at a time. not all of them. if the problem gets fixed, i don't know what really fixed it if i replaced a bunch at once. and rarely will anyone take the parts back off and see what it was.

[340doc]

Thanks for the repleys, I got the truck about a month ago and it had this problem, I thought a good tune up would fix it. I thought maybe a bad plug too so I changed them again, no difference. plug wire connections are tight and no visible arching at night. the truck idles perfect and I cant get it to act up by loading the motor on the brake or free reving it. weird. I was talking to a guy at work and he thought it might be in the fuel injection system under the top half of the intake but why would'ent it act up all the time if it was that. I dont want to rule out something simpler first. THANKS!

[WisconsinHick]

First off I would check the gaps on your plugs make sure they are to spec. Second the injectors wont act up when free reving it because it is pushing more fuel through. After checking the plug gaps I would go get some HEET to remove any maybe water in your tank and also add some sea foam in too this will take care of cleaning the injectors if there is a problem. My brother is a GM mechanic and I have had this problem before and he told me run the truck down under a half tank put that stuff in and hammer on the throttle so the sea foam can go through the injectors at full force. Its just as good as paying god knows how much for an injector cleaning at a shop. Best of luck.

[340doc]

Thanks, I got the seafoam in it now, I dont know what to think. I had a guy tell me it might be the transmission, locking and unlocking or something like that. The weird part is you can free rev it all day and load it on the brake and its smooth, it seems I have to be driving before it does it. Maybe he's right.

[98k1500]

mine is doing the same kind of thing look at the "engine or tranny" thread... it is the same thing that i have been trying to explain to an extent...

[stumpuller454]

my truck used to have a weird short hesitation a low throttle accel cleaned my mass air flow sensor and it was fixed! my k&n must have gummed it up!

[340doc]

Thanks I"ll check that out, forget the trans, this morning I was able to rev it up real slow in park and when I got above 2000 rpm I felt the roughness very slight, I guess its just more violent when I"m driving. Its still not throwing a code. Any ideas???

[340doc]

Oh yeah how do I get to the engine and tranny thread?