Still not runnin great

[nn2004]

This truck is killin me. I have unplugged all the sensors and driven it, as well as the EGR system, and it all still runs the same. I increased the idle even though I know you're not supposed to, and it runs a little better. It only stumbles when it hits around 500 RPMs at idle in gear. I increased its idle to 650 in gear, and it does it slightly less. I regapped all the plugs to .035 instead of the .040 that they were at, and it ran great, still does run better. But now it seems to be very hesitant to accelerate. When accelerating from a light, it tends to jump. It'll accelerate slightly, then be steady, and then 2 seconds later it'll start accelerating again, and it keeps going. When it is cold, it runs fine, but once it reaches around 180 degrees, it starts doing this. It has been starting fine in the morning now, oddly enough. The timing chain seems fine since there is no play in the rotor when I remove the cap. The plugs look great also. They are AC Delco CR43TS plugs. Hope those are the right ones. Injectors spray fine. Anything else I am missing here? My only next two thoughts are that the timing is actually off, or fuel pump is dying when it heats up. I dont think it is the fuel pump since it has been doing this hesitation since I bought it, and I drove it 150 mountainous miles a few weeks ago, and it did great. Any ideas anyone? Thanks in advance, and sorry to bother everyone again.

[cliffsta]

hmmm, im assuming you have new plug wires? mine acted alot like that a few weeks ago and it was a bad plug wire shorting out on the block. Tonight when its dark, drive around and warm it up to however hot it takes for the miss. Pop your hood, get a buddy to put it in drive and hold the brake and give it a little gas. Look around the block and see if you spot any blue sparks or light. Just throwing something out there, you might have already checked this, but i figured i'd try to help.
Good luck

[Grim Reaper]

Well the cold part cought my eye. It sounds like in open loop (basicly it's choke mode) it does ok but once it goes closed loop is when it has problem. That would indicate a possible mixture issue.

How old is the O2sensor? It is recomended that they be changed every 60k. If the engine burns oil it often takes the O2 out.

EGR is off in open loop but I see you have already done al ittle testing on it.

Check for vacuum leaks. My plastic lines on my 88 with only 83k are very brittle and had to be replaced where they had cracked and had vacuum leaks. The base gasket on the TBI unit is prone to failing as well. With the truck running shoot carb cleaner at the base of the TBI and if it is leaking you will get a idle change.

Also check the timing. You do know that to set the timing on these trucks there is a plug you have to undo. Its at the bulkhead conector under the booster. I think it's brown with white stripe. It will be sticking up with a plug that you can easily get at.

[nn2004]

Originally Posted by cliffsta

hmmm, im assuming you have new plug wires? mine acted alot like that a few weeks ago and it was a bad plug wire shorting out on the block. Tonight when its dark, drive around and warm it up to however hot it takes for the miss. Pop your hood, get a buddy to put it in drive and hold the brake and give it a little gas. Look around the block and see if you spot any blue sparks or light. Just throwing something out there, you might have already checked this, but i figured i'd try to help.
Good luck

Yup, sure enough was the wires. It has been stumbling since I bought it, and recently I spilled some water on the plug wires when doing a coolant temperature switch, so after that, it would try dying when climbing the mountainous hills here. Now, no stumble, no lag, just pure 350 ... plus all the emission regulation junk.. . Thanks for the advice.

[cliffsta]

Yee HAW i helped someone! Like i said, mine did the exact same thing, stumbling when you give it just a little gas. I bet you could here it popping? Mine made a ticking noise from the short.

[Russell]

When I first bought my truck, it was like a fireworks show under the hood, lol, I think I only had maybe 3 wires actually getting the spark down to the plug... New plug wires made a phenominal difference in the performance / driveablity / removal of exploding exhaust etc. 8 cylinders vs like 3 was quite nice

[nn2004]

Nope, actually I couldnt really hear or see it doing anything. The wires looked good physically, hence why I never replaced them. But now that I have replaced them, the problem has gone away, so something must have been wrong internally. I didnt know how old they were or if someone simply washed them off to look "new" when they sold me the truck, but I wouldnt doubt it. Well, at least now my truck does have a complete tune-up. The truck did have a very slight ticking noise, but when I reduced the spark plug gap to .035, it went away just like it did on my Toyota's 22R. If you want to hear a 22R sound like a lawnmower, leave the plugs at a .040 gap and let it run. .031 sounds a lot nicer at 55. I hear ya on how much nicer it is to have new wires. I think if the guy who sold my truck to me had put new wires on it before selling it, he would of been able to get more money for it for sure, but heck, I'm not complaining about the 1,500 I paid for it. It only has 138,000 thousand, with a clean, non-oil consuming 350, clean 700R4, and nice chrome rims. I've put about 500 in 31" tires and parts into it, and now it is totally worth it. It does impressive burn-outs when pressing the pedal to the floor so that some a-hole doesnt take your gas pump . But yet - I am used to inline 6 and 4 cylinders, it doesnt take much to impress me..