hesitation surging stalling no codes. 05 i6

sh4d0w1021

Original poster
Member
Apr 18, 2013
6
for about a week my trailblazer has been stalling surging hesitating and just feels bogged down, i have changed the o2 because it had a p0130 and that light went off, i did a reset of the pcm and no luck. it sounds like i have a slight manifold leak but not loud or anything, it has 80000 miles, i did a tune up at 77000 along with cleaning the throttle body. i at first got a defective denzo o2 and have since replaced it with an acdelco oe o2. what other systems can make the the vehicle act this way? i have torque pro for android, is there any systems i should be watching? thank you for any help
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
What's a "tune up" anymore? Plugs plus O2 sensor? Are you running Delco 41-103?

Clogged cat, poorly operating CPAS that hasn't thrown a code yet, vacuum leak or MAP sensor problem. Have you used Torque to check fuel trims?
 

sh4d0w1021

Original poster
Member
Apr 18, 2013
6
the roadie said:
What's a "tune up" anymore? Plugs plus O2 sensor? Are you running Delco 41-103?

Clogged cat, poorly operating CPAS that hasn't thrown a code yet, vacuum leak or MAP sensor problem. Have you used Torque to check fuel trims?

The tune up was acdelco 41-103s, air filter, oil change, cleaned throttle body, greased all grease fittings, checked diff fluids. the long term fuel trim is consistently negative between -3 and -12
 

signalnc

Member
Dec 28, 2012
249
I found this answer online for negative fuel trim:

Check for air leaks in the Air Induction system (e.g., in the intake manifold)
Check for air leaks in the exhaust manifold and in the exhaust pipesFuel control sensor is out of calibration (ECT, IAT, MAF, MAP)
HO2S has failed (it may be contaminated with fuel, silicone or water)
Low fuel pressure (fuel filter clogged, pressure regulator failure)
One or more injectors restricted or pressure regulator has failed
Vacuum hose is disconnected, broken, leaking or loose

I would suspect you manifold leak is upsetting you map sensor and the computer is trying to adjust to compensate. since you think you have a manifold leak i would suspect that, but would not rule out doing a fuel pressure test and a vacuum test.
 

sh4d0w1021

Original poster
Member
Apr 18, 2013
6
so i decided to go ahead and change the exhaust manifold after work, i broke 1 bolt off in the head (thankfully just one). i cleaned the throttle body and did a relearn. the hesitation/surge/stall seems to be fixed. the ltft is still -12 on idle but +/- 3 on acceleration. i did see the thermostat is running cold (183). could a cold thermostat cause -ltft? thanks everyone for all the help.
 

signalnc

Member
Dec 28, 2012
249
running at lower temps will cause it to run rich and burn more fuel, also significantly reducing the life of the catalytic converter. the vehicle needs to run at 210.
Not sure how it will affect fuel trim, but suspect it would. Running at low temperature means the vehicle is in "start up" mode. It sends more fuel to try and get the temps up to 210. If it never reaches 210, then it is constantly stuck in that mode of trying.
 

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