Wants to stall under throttle at first start up
#1
Wants to stall under throttle at first start up
New to the forum, trying to figure out my issue. The Blazer will fire right up and rev fine, as soon as you put it into gear and give it throttle, it wants to stall out. It will sputter down the road and does this a few times, by the time I get 100' down the road and stop, it wont do it again until the next start up. Seems worse when it is not at operating temps but has done it at normal temp as well but only after restarting the engine. It has 126k on the clock.
I have had the spider injectors replaced and some vacuum lines repaired at a shop. I have replaced the MAF, EGR, PCV, O2 sensor # 3, a few more vacuum lines, fuel filter,air filter, fuel pump, plugs, wires, rotor, cap and gas cap. Can't get the fuel pressure over 50psi. and the vacuum is around 20.
I do have a P0171 & P0174 code that I assume is related? Any help would be appreciated. This is my sons first car and I'm having trouble getting it on the road.
I have had the spider injectors replaced and some vacuum lines repaired at a shop. I have replaced the MAF, EGR, PCV, O2 sensor # 3, a few more vacuum lines, fuel filter,air filter, fuel pump, plugs, wires, rotor, cap and gas cap. Can't get the fuel pressure over 50psi. and the vacuum is around 20.
I do have a P0171 & P0174 code that I assume is related? Any help would be appreciated. This is my sons first car and I'm having trouble getting it on the road.
Last edited by ajfetterman; 10-19-2018 at 01:20 PM.
#2
What year? What actually is the fuel pressure?
A good start is to get the OBD scanner and check the fuel trims on both banks. Definitely cheaper and faster than replacing everything around.
EDIT: Oh, the codes are for lean mixture, but I'd get a scanner to get some live data.
A good start is to get the OBD scanner and check the fuel trims on both banks. Definitely cheaper and faster than replacing everything around.
EDIT: Oh, the codes are for lean mixture, but I'd get a scanner to get some live data.
Last edited by Mike.308; 10-19-2018 at 02:39 PM.
#8
So whats wrong? Either an actual lean or rich condition exists or a sensor is hosed and is presenting improper data to the PCM. Which is it? That's the $64,000 question. You either have a failed sensor(s) or you were running lean and the computer is adding fuel to keep the emissions low by keeping the air fuel mixture at 14.7:1 or stoichiometry. The most common causes of running lean are a vacuum leak (hoses, intake manifold, intake after the MAF) or a bad MAF sensor. Clean the MAF sensor if you haven't already, look for any cracked hoses or other evidence of a vacuum leak and then give us fuel trim numbers at idle, 1500, and 2500 - both banks, all 4 numbers including sign/polarity. If trims get better with RPM then we suspect a vacuum leak. Well get ya right eventually but bare with us, sometimes its obvious and sometimes its not so easy.
George
Last edited by GeorgeLG; 10-19-2018 at 09:30 PM.
#9
That is a good idea to follow. If - in your condition - it is possible to increase the RPMs on idle up to - let's say 3k RPMS and lookup the trims value it may help a lot. If the fuel trims are getting better it is likely the vacuum leak. If they don't - it could be an issue with fuel injection.
An important information could be when/how that all happened.
An important information could be when/how that all happened.
#10
Wow that is a lot of info.
Thank you guys, I will get some live data at higher rpm and see what that provides.
I thought I have replaced all of the vacuum hoses but not 100% certain. 4x4 engages if that means anything. I’m also going to check fuel pressure at the filter. My fuel pressure does not hold with engine off, key on. It will spike to 60-65 or so then drop pretty much immediately.
Thank you guys, I will get some live data at higher rpm and see what that provides.
I thought I have replaced all of the vacuum hoses but not 100% certain. 4x4 engages if that means anything. I’m also going to check fuel pressure at the filter. My fuel pressure does not hold with engine off, key on. It will spike to 60-65 or so then drop pretty much immediately.