Welcome Visitor! Please take a few seconds and fletcher969
Well-Known Member
Ok, I've been having some issues with my truck this week. It seems to know when to know when I've set aside time for some professional studies. Anyway, a little history in case it's relevant. See signature and title for basic info.
I've had a very slight off-idle hesitation after WOT is reached for several months. New plugs and plug wires 4 months ago didn't change anything. Other than that...no issues with the engine...runs and sounds smooth. The other day, however, I went to start it, and it died a couple seconds afterwards. I could only keep it running worked the RPMs up to around 1700-2000, and warmed it up, after which it would operate normally most of the time except for some occasional off-idle stumbling and loping. I cleaned the MAF and IAC...no change. Checked for (obvious) vacuum leaks, zipped my throttle peddle, checked plug and other wires, cleaned contacts on sensors, adjusted the throttle adjustment screw, etc. I did notice the results of unplugging the MAF were inconsistent. Sometimes it would cause the idle to surge/get better, other times it would get worse, other times it would just die. With the IAC...idle just gets worse if unplugged, and eventually dies, both before and after I cleaned it. Ultimately I narrowed the problem down primarily to the MAF, and replaced it...which cleared the problem. I ran it for 10-15 miles afterward, and it ran like it did before the MAF failed, slight hesitation and all. I was happy.
This morning, I started the truck up, and it ran fine. I decided to change my fuel filter shortly thereafter, because it needed it, and it might have been part of the slight hesitation issue. I changed it, cleared the PCM (so it would relearn), and after the fuel re-fed, it started stumbling badly, and also did so when I hit the throttle. This continued, though it eventually idled normally after it warmed up, but stumbled badly if I hit the throttle. Subsequent restarts during the next half hour or so resulted in the same. I wanted to know if it would do the same thing driving around, so I went for a drive. Surprisingly, it drove very nicely! No stumble, and it even had a little more spunk (which I noticed immediately while idling backwards in reverse...more "push"), and slightly less off-idle hesitation at stop signs (almost gone, but nooooot quite). I got back home, turned it off for and let it sit for about 10 minutes, and started it back up. It started and idled normally (whereas before it stumbled immediately), but it still stumbles with throttle input. NO CEL activity at all.
Ok...the fuel filter is installed correctly, so this must have to do with more fuel pressure being available, because I suspect the old filter was nearly clogged...it drained almost-black gasoline. So I'm deducing when I hit the throttle, more fuel is available more quickly, and I'm guessing whatever controls the air intake or spark? isn't able to keep up during or off of idle (just backyard guessing). IAC? I did read another thread wherein somebody said the "plunger" moves freely inside. While cleaning mine, I noticed it moved, but freely would be a stretch. I could move it with a screwdriver, but whatever position I placed it, it would remain (i.e. if I opened it, it remained open, and I would have to physically close it myself, and vice versa).
Anyway...I'm leaning towards an IAC replacement, but I thought I'd toss the above info at you guys to see if there is a favorable consensus, or something that steers me in a different direction...or maybe I just missed something.
Thanks guys!
Dave
I've had a very slight off-idle hesitation after WOT is reached for several months. New plugs and plug wires 4 months ago didn't change anything. Other than that...no issues with the engine...runs and sounds smooth. The other day, however, I went to start it, and it died a couple seconds afterwards. I could only keep it running worked the RPMs up to around 1700-2000, and warmed it up, after which it would operate normally most of the time except for some occasional off-idle stumbling and loping. I cleaned the MAF and IAC...no change. Checked for (obvious) vacuum leaks, zipped my throttle peddle, checked plug and other wires, cleaned contacts on sensors, adjusted the throttle adjustment screw, etc. I did notice the results of unplugging the MAF were inconsistent. Sometimes it would cause the idle to surge/get better, other times it would get worse, other times it would just die. With the IAC...idle just gets worse if unplugged, and eventually dies, both before and after I cleaned it. Ultimately I narrowed the problem down primarily to the MAF, and replaced it...which cleared the problem. I ran it for 10-15 miles afterward, and it ran like it did before the MAF failed, slight hesitation and all. I was happy.
This morning, I started the truck up, and it ran fine. I decided to change my fuel filter shortly thereafter, because it needed it, and it might have been part of the slight hesitation issue. I changed it, cleared the PCM (so it would relearn), and after the fuel re-fed, it started stumbling badly, and also did so when I hit the throttle. This continued, though it eventually idled normally after it warmed up, but stumbled badly if I hit the throttle. Subsequent restarts during the next half hour or so resulted in the same. I wanted to know if it would do the same thing driving around, so I went for a drive. Surprisingly, it drove very nicely! No stumble, and it even had a little more spunk (which I noticed immediately while idling backwards in reverse...more "push"), and slightly less off-idle hesitation at stop signs (almost gone, but nooooot quite). I got back home, turned it off for and let it sit for about 10 minutes, and started it back up. It started and idled normally (whereas before it stumbled immediately), but it still stumbles with throttle input. NO CEL activity at all.
Ok...the fuel filter is installed correctly, so this must have to do with more fuel pressure being available, because I suspect the old filter was nearly clogged...it drained almost-black gasoline. So I'm deducing when I hit the throttle, more fuel is available more quickly, and I'm guessing whatever controls the air intake or spark? isn't able to keep up during or off of idle (just backyard guessing). IAC? I did read another thread wherein somebody said the "plunger" moves freely inside. While cleaning mine, I noticed it moved, but freely would be a stretch. I could move it with a screwdriver, but whatever position I placed it, it would remain (i.e. if I opened it, it remained open, and I would have to physically close it myself, and vice versa).
Anyway...I'm leaning towards an IAC replacement, but I thought I'd toss the above info at you guys to see if there is a favorable consensus, or something that steers me in a different direction...or maybe I just missed something.
Thanks guys!
Dave
