My 2002 Chevy blazer keeps trying to kill me

Power/Fuel
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1

My 2002 Chevy blazer stalls and tries to die when I accelerate gently.

This is recently become a thing and it’s mostly only noticeable when driving in the city and making frequent slow starts in traffic. When trying to accelerate gently, say 1500 RPM, the engine has very little power, will hang the RPM around 1200, and sometimes make a gurgling shag noise and try to die.

Problem only occurs when I’m being gentle on the gas – if I take my foot off and then give her the beans and I’ll hop up to 2000 RPM and accelerate with no problems, except for the problem that I only have 10 feet of space until I rear end the guy in front of me and I am flooring it just to keep the engine running.

It’s got a P1875, P0171, and P0174 code, but those are 4wd electrical and very common lean fuel codes. I’d suspect a fuel pump if it didn’t work fine when floored?

200,000 miles, what do?

2

Find and fix the cause of the lean fuel codes. That is what is causing your stumble and lack of power.

Look for vacuum leaks, look for a split in the inlet hose between the MAF and throttle body. Check the fuel pressure at idle and while accelerating.

6 Likes
3

Thanks for the reply!

When you say stumble, you mean the hang at 1200-1500 rpm? It feels like a CPU speed governor is kicking on; there’s no lack of power when floored.

Thanks for the checklist on where leaks could be; I’ll report back after looking. How/where can I look for vacuum leaks?

4

What you described is what I would call a lean stumble. There is no CPU governor. Find and fix your lean condition.

First hook a vacuum gauge to one of the several small hoses attached to your intake manifold between the throttle plates and engine. If any of them crumble in your hands… there’s your problem. Start the engine and read the vacuum gauge. It should read about 18 to 21 in/hg and be steady.

Anyplace the manifold attaches the throttle body or engine, there may be a vacuum leak.

4 Likes
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Shop says no vacuum leaks in engine; fuel pressure 55psi; MAF sensor reading good. Recommend replacing both pre-cat O2 sensors, am I chasing a dragon?

6

Does 55 psi fuel rail pressure meet the manufacturer’s spec? fuel injection requires the fuel rail pressure be correct, otherwise it will never work. Has your shop tried using ether spray to find an unmetered pathway into the engine? Have they checked for a sticking throttle valve? I’d be disinclined to replace o2 sensors unless there was clear evidence of a problem. I’ve had sort of similar symptoms on my Corolla, caused by slightly clogged fuel injectors and a mis-adjusted throttle position sensor.

7

So if you’ve taken it to a shop, why are you here asking us how to fix it?

Since you have codes what does your shop say when they can’t make the codes clear and the car run properly? You don’t need us, you need a better shop.

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Maybe I do need a better shop; I said I’d come back with test results so that’s what I did.

Seems like we all agree an o2 sensor is a waste of time; any other ideas before we throw the book at it?

9

If one of the upstream oxygen sensors is producing a false rich signal, the computer will lean the fuel delivery. This can cause a bad hesitation when accelerating.

Disconnect the oxygen sensors and drive the vehicle, see if the engine runs better.

1 Like
10

If a shop is reputable then they will stand behind there work, and if they say it needs o2 sensors and you agree to the repairs but it does fix it then they should not charge you due to there misdiagnosis… If they are not willing to stand behind there work then you need a shop that will…

11

if you have a 4.8L. 5.3L, 5.7L, or a 6.0L engine, then your fuel pressure at 55psi is below the spec of 60-66psi.
I’d start by verifying that the fuel pressure regulator isn’t leaking down pressure, and if it is fine, then check fuel filter (heck, i’d just replace it to make sure it isn’t an issue.)
If issue still persists, then it might be time to start eyeballing a new fuel pump. Failing fuel pumps are a common issues on these vehicles.

You should probably start by finding a better shop first, though.

12

With the more comprehensive diagnostic analyzers, the O2 sensors can be tested in situ.