Hesitation on acceleration

[Erik the Awful]

If you haven't done a complete tune up in a while, start with that. Plugs, wires, cap, rotor, air filter, and fuel filter. That's not throwing parts at it, that's maintenance. Beyond that, sensors, EGR valve, etc. is throwing parts at it and you should use diagnosis to determine problems with them.

 

[Schurkey]

If you haven't done a complete tune up in a while,

Define "a while".

start with that. Plugs, wires, cap, rotor, air filter, and fuel filter. That's not throwing parts at it, that's maintenance.

Maybe. I still test plug wires, I inspect plugs. I use compressed air to blow dirt out of air filters at least once, and sometimes more often. I've been known to back-flush fuel filters that aren't actually plugged, but have some debris in them, and put them back in.

Throwing stuff away that's provably NOT at the end of it's service life is kinda silly. The original spark plugs in my '03 Trailblazer came out at 90K miles, and looked so perfect I tightened the gaps about two thousandths, added some anti-seize to the threads, and put them back in. The set of new plugs I'd bought went on my parts-shelf; they weren't installed until 160+ thousand miles. I never thought I'd get 160K out of spark plugs...but I did, with no codes, no hesitation, no misfire.

'Course, this does depend on a person's ability to estimate a part's service life with some degree of accuracy.

IBeyond that, sensors, EGR valve, etc. is throwing parts at it and you should use diagnosis to determine problems with them.

 

[Erik the Awful]

Define "a while".

Can you remember when you last performed a full tune-up? Have you bought and aged out underwear since then? Time for another tune-up.

 

[Nw2000]

Can you remember when you last performed a full tune-up? Have you bought and aged out underwear since then? Time for another tune-up.

I did a tune up whenever I bought the truck about 11-12k miles ago then swapped the engine from a 305 to a 350. Swapped chips and injectors. It seems to run a lot better on startup then once it warms up it seems to dull out on power. It still has go for the most part when it’s not being jerky but when it starts up it has enough power that I have to watch myself from squealing the tires then it just mellows out once it’s warmed up.

 

[PlayingWithTBI]

Yeah it’s odd like I’ll be accelerating and it’ll seem like it’s lacking power then when it shifts to next gear it feels like it should and it’s really unpredictable.sometimes it runs fine sometimes it doesn’t

It sounds like your fuel pump, suction sock, and/or fuel filter are suspect. When you're accelerating it lacks power then shifts and you get more power, you mat be losing fuel pressure and going lean. It would be easy to tell with a scanner, given your O2 sensor is working properly. Get a pressure gauge and see what you have before throwing more stuff at it. Pressure s/b 9-13 PSI, according to GM but, 11 -13 is optimal. Less than that can give you hard starts when warm and a lean condition when jacking with the skinny pedal.

Or your timing is off and too far retarded. You can try advancing it ~4* +/- BTDC with the Black/Tan EST wire disconnected, see if it helps.

 

[Nw2000]

It sounds like your fuel pump, suction sock, and/or fuel filter are suspect. When you're accelerating it lacks power then shifts and you get more power, you mat be losing fuel pressure and going lean. It would be easy to tell with a scanner, given your O2 sensor is working properly. Get a pressure gauge and see what you have before throwing more stuff at it. Pressure s/b 9-13 PSI, according to GM but, 11 -13 is optimal. Less than that can give you hard starts when warm and a lean condition when jacking with the skinny pedal.

Or your timing is off and too far retarded. You can try advancing it ~4* +/- BTDC with the Black/Tan EST wire disconnected, see if it helps.

I’ll take a look at fuel pressure as it does wanna be a little moody on warm starts. This may be unrelated but I was driving it home earlier from work and as it was cooler later in the day it seemed not to be as gutless. Not sure if this is relevant but the truck does have headers and it does increase the temps in the engine bay perhaps that could be it or at least a contributing factor? I got header wrap it’s just a matter of getting around to putting it on lol.

 

[SUBURBAN5]

I’ll take a look at fuel pressure as it does wanna be a little moody on warm starts. This may be unrelated but I was driving it home earlier from work and as it was cooler later in the day it seemed not to be as gutless. Not sure if this is relevant but the truck does have headers and it does increase the temps in the engine bay perhaps that could be it or at least a contributing factor? I got header wrap it’s just a matter of getting around to putting it on lol.

I would put it on asap... I'm gonna go back to my stock manifolds. Headers do tend to make it hotter under there.

 

[Nw2000]

I would put it on asap... I'm gonna go back to my stock manifolds. Headers do tend to make it hotter under there.

Definitely planning on it soon. Would’ve stuck with stock manifolds but the ones I had were worn out and went for headers since they price wasn’t all that different and I do plan on getting the exhaust upgraded as time and money permits.

 

[PlayingWithTBI]

Headers do tend to make it hotter under there.

Yeah, more so when sitting at a light, not so much when hauling ass down the road, LOL. However, since we don't have a MAF or IAT you will have different AFRs in summer and winter. IMHO headers still give you better performance given the engine breathes better from intake down.

 

[SUBURBAN5]

Dumb question.. how do you know if your manifold are bad or worn? My were fine til I got the motor swapped. Been in the garage since collecting Webb's and dust...