1999 Suburban Hesitation/Power loss

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original_1999

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Hi, I have a 1999 Chevy Suburban K1500 with 92k miles. I am original owner. I have a recent issue where the the truck hesitates the first few minutes of driving. It is a bit hard to explain, it is not backfiring or running so poorly that it vibrates, but it has almost no acceleration. After the first few stop signs, it will accelerate better/normal for the rest of the drive. If I let it set 10-15 minutes, it exhibit the symptomns again, but not always. It always does this on first drive of the day.

A few times this happened where I pressed the gas pedal a signific ant amount and RPM's did not increase at all. I had to take foot off pedal and press a few times and the problem cured.

I wish I could explain better, the idle is fine, and nothing sounds siginificanlty odd when the problem happens...

What I know:

There have been no modifications to the vehicle.

Fuel pressure at idle is a little above 50 psi without disconnecting vaccum to regulator. It jumps to abve 60 when driving. It does not drop when the problem is occuring. And when I shut off engine, the pressure drops to about 58, then arouind 55 after a minute. After hours off, it is still above 30. I can get more accurate readings, I didnt tape gauge well enough to read easily while driving.

The air filter was replaced about 20k ago and appears clean.

Plugs were changed at 70k.

Fuel filter is original, as is ditributor cap and rotor. I have parts on the way for all of these. If this doesn't fix, not sure what to check next...

Thanks for any help!!!!
 
do you have a check engine light on? anything unusual about your engine temperature readings? could be the TPS, throttle position sensor.
 
No check engine light. Temperature is normal.

Thanks for suggestion on TPS. I will have to test it this weekend. I am hoping that is it, sure would be an easy fix...
 
no check engine light. the temperature is normal. I will have to test the TPS this weekend. Thanks for suggestion. It would be an easy fix...
 
Changed cap and rotor, also put in seafoam into gas.

The engine runs super smooth now, but the problem still exists. It feels like something is going on with the transmission. the engine doesn't rev like I would expect for a slip. From a stop, It is almost like it is starting in second gear then downshifts to 1st...and then runs ok. Always from a stop when it happens...

Guess I will poke around google for ideas related to transmission.
 
Have you ever changed the transmission fluid and filter? It's just like your engine and needs to be serviced every once in a while. That's one of the most commonly overlooked and neglected items in todays vehicles. Regular maintenance is the key to keeping one going for a couple hundred thousand miles or more.
 
I had a similar problem and it was the MAF sensor. I tried several new sensors from Autozone and the problem largely persisted. I had to use an AC Delco part from the dealer to eliminate the problem. The aftermarket replacement parts did not work correctly in my 1997 Suburban.
 
update. Transmisiion fluid was changed at 50k. I changed it and filter again. No change to symptoms. I check TPS and it was ok, I also took off EGR valve and it moved freely. I will try to figure out how to test mass flow sensor.

This is a second vehicle for me, and sometimes goes weeks without driving. I have been driving it daily for past several weeks and yhe symptoms have become very consistent:

First drive of the day it exhibits this problem. It will happen for first acceleration only. I have a stop sign less than 1/8 of a mile from my house. I accelerate to 30mph and it clears before it shifts into second. It will then drive normal until I shut the vehicle off. If it sits for more than 10 minutes, it does the same thing. Doesnt matter if I drive 1 mile and shut it off, or 20.

I will try to figure out how to test MAF sensor next....

Thanks for the inputs
 
Since you just enlightened us that it sits for weeks at a time, I'm going to suggest you get some dry gas or something similar to put in the gas tank. You might just get some Sta-Bil and add it. It almost sounds like you're getting moisture in the fuel system to me. BUT, I'm not a mechanic and don't claim to be.
 
I tested the tps per the same website referenced above. I tested when the engine was cold and after running for about a minute. My problem happens within the first minute of driving. I read .75V at throttle closed and smoothly rose to around 4.5.

I just tested the MAF sensor after running the engine 1 minute (and continued running for the test) and it checked out as well. I tested per the same website as the TPS test instructions.

As far as water in gas. I have been thru several tanks since problem started and have tried seafoam as well. 2 cans for about 30 gallons of fuel.

I do not know much about injectors, but to me it wouldnt seem likely for them to stick and free-up so consistently. I would think it would be more erratic.

I have never had a check engine light, but someone mentioned there might be codes that are being sent/stored that do not trip the CEL. Going to try to borrow a reader and see. Not sure what else to do for free at this point...
 
update:

Code reader showed no codes.

A mechanic friend drove and suspected plug wires. I changed plug wires, no change to problem....

I am going to pull plugs next and see if anything is to be learned...
 
Have you ever cleaned the throttle body?
 
I have not cleaned the throttle body. I did pull of the air intake and looked at it when I change cap and rotor. It looked brand new clean from what I could see.

I am guessing, but I suspect some type of injector problem... If I get that far in, I will certainly clean the throttle body...
 
Make sure you get some of the spray for throttle bodies. Regular carb cleaner has a harsher solvent that can dissolve the coating on your throttle body. I get mine at Walmart or any of the local parts stores. That would have been a good place to start, most likely.
 
I had a similar problem in my 2000 suburban 5.3L. I was using gas with 10% ethanol. I switched to straight gas, no ethanol, and after about 2 tanks the problem ceased and never returned. Hope it's that simple for you.
 
Has this problem ever been figured out im having this problem with my 99 suburban
 
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