I noticed this issue about two days ago where there was a huge tone shift in how my Blazer feels while driving. It feels more sluggish, like maybe the brakes are dragging or maybe it's stuck in 4-Hi mode even though my dash says it's 2-Hi. I have noticed RPM wise that it's been working a little harder to get up to speed and I do feel myself pressing down on the throttle more to achieve the same rate of acceleration I've been accustom to. I'm typically under 2,000 RPM while driving at 60 MPH, but today my engine is running at about 2,100 while driving at 60 MPH, and it genuinely does feel like I'm dragging something. I just need some help brainstorming why the feel of the car would suddenly change after work when driving home one day. I will say this: the feel I'm getting now is the same feel I'm used to when I brake from high speeds (45+). That's why I think it's a dragging brake pad, but I'm not sure how to test it.

Or it could be something else cause I do have other minor issues going on:
- Currently giving error code P0171 and P0174. I believe this is the MAFS which I'm about to clean as of writing this. (Been driving around with this engine light on for about 2 weeks now.)
- Humming fuel pump which I believe needs to be replaced soon, but fuel pressure is fine at 54 PSI.
- Parking brake doesn't fully engage where the vehicle is still able to roll in reverse but won't roll forward.
- ABS light and Brake light always on the dash.

As far as the brakes go: I took the tires off and checked all the calipers and pads. I tapped them with a rubber mallet testing to loose parts, and the brakes disks themselves have no scarring so it's been braking clean. I'm very inexperienced at this so I'm not quite sure what to be looking for. It's it possible for one of the brake calipers to be constantly clapped down at all times? I checked the brakes as soon as I drove it home and I didn't smell anything burning or feel high heat radiating from them.

EDIT:
I'm also hearing some squealing while braking, but my pads don't need to be changed. Is that a sign of a loose component somewhere?

 

Sounds like what happened to mine back in November with the catalytic converter. Felt like something was dragging, no power, harsh shifts etc.

Remove an upstream 02 sensor and see if the problem still persists. It'll sound horrible, but at least it'll have full flow.

 

To check the brakes:

At around 5mph, take it out of gear and let it glide to a stop. Does it go to 0 mph slowly or does it seem to grab right at the end?

Jack up a given wheel, parking brake off, out of gear (careful, immobilize the truck under the other tires) and spin the tire. Is it fairly loose. Have someone hit and release the brakes while you move the tire back and forth. Does it grab hard and then release easily?

Are any of the rotors dark/dis colored from overheating? Does the truck shimmy during braking indicating a warped rotor from overheating? If you are squealing during braking with adequate pad material then that can be glazed/overheated pads against a smooth rotor.

What's happening with your fuel mileage?

What are your 4 fuel trim numbers at idle and again at 2500 rpm?

Did. Cleaning the MAF change anything?

p0171 and 0174 indicate that the engine is too lean. The main reasons for this are:

Bad/dirty MAF sensor giving and bad reading on incoming air volume
Vacuum leak
Poor fuel delivery
Bad O2 sensor
Wiring/connector problem
PCM fault


George

 

When this sluggish performance issue comes up, most jump on the engine performance and in a 13 + year old vehicle, there is a lot to look for. The 'off the wall' problems I wanted to bring up have already been mentioned in Post no. 1 and no. 2. 1./ Dragging rear caliper brakes. Look for stuck caliper pistons or frozen caliper pins. My 2003 had both! One problem on each side.
2./ Clogged catalytic converter. If this is the cause of the problem, please don't just replace the cat. converter and think you have solved the problem. Look for the cause of the cat. getting clogged in the first place.

 

Sluggish performance can be caused by a restricted exhaust which can be caused by a failed converter but then your codes should be rich, not lean as you have now. We need to get to the bottom of the lean codes because that can in time kill your converter. If you decide to check for a restricted exhaust you test for this by:

A back pressure gauge screwed into an O2 sensor port, or with a vacuum gauge at the intake manifold. I've never tried the open O2 port hole. I always use a back pressure gauge.

George

 

Hey guys!

Sorry I've been away from this topic for so long. Several things came up at work and I've been messing around with the fuel pump some. So, as it turns out the fuel pump was going bad so I changed it out. And to my surprise when I took the current one out, I discovered that the fuel pump had already been replaced (bought it used by owner). Note that this Blazer only has 120k miles on it, so I was expecting the OEM pump to still be there. Upon further inspection I recognized that the wrong fuel pump was put it. First off it was far too tall for my tank, and upon examining the specs, the pump I took out was mean't for the 4x4 4-door model, not my 4x4 2-door model. I squared that away with the proper fuel pump, reconnected the battery, and my engine codes for p0171 and p074 were gone. I haven't driven it far enough to see if they come back, but no more engine light so far.

The vehicle is still a bit sluggish than what I've been used to.

Following George's advice, I did a brake test in a vacant parking lot to see if the brakes suddenly grab it gliding from 5mph. I tested it in 2wd and 4wd -- smooth as butter. I no longer think the sluggishness is brake related. I did however noticed that my coolant reservoir has been loosing fluid, so I checked my radiator and discovered a black, gritty, sludge caked around the rad cap. I have no idea what it could be other than oil. It has no scent other than anti-freeze. I checked my oil (did an oil change about 2 weeks ago, actually) and it wasn't milky suggesting water has leaked into it. Maybe this is related to the sluggishness somehow(?)

Also George, no, cleaning the MAF sensor didn't resolve the sluggishness.

I haven't checked the catalytic converter yet or for restricted exhaust. Next on my list as soon as I solve this new coolant mystery.

 

 

It's inside the radiator cap, so something is swirling around with my engine coolant. The coolant coming out is a faded yellowish color. I have been mixing in a lot of tap water refilling the reservoir. I use the 50/50 mix, green coolant.

Also my engine codes came back today. p0171 and p0174.

 

The long life Dexa cool coolant used in these vehicles has a history of creating a nasty sludge from lack of maintainance, mixing coolants, sdditives, air in the system , overheating ... so this might be garden variety sludge. Drain, flush and refill with a universal coolant like Prestone may be in order. Someone here might be able to offer a good cleaning agent, I don't have any recent experience with that subject. There are other possibilites such as a blown headgasket which would also relate to your power issue. You can do a compression test, attach a pressure gauge to your radiator cap and look for pulsing, or test the coolant for acid (not as reliable). What are you fuel trims and gas mileage?

I would recheck your fuel pump pressures at key on and after the 15 min hold. Besides a new pump other issues can be restrictions, ground problens, wiring/connection problems. How did you connect the new pump? Did you check the ground at the pump? What voltage do you have at the pump?

Does the truck run better, worse or the same when it transitions from open to closed loop (need a scanner with live data)?

George

 

Dex Cool was generally introduced to GM cars and light trucks in 1996. This was touted as a long life i.e. 5 year or 100,000 mile coolant. Dex Cool was soon accused of causing a brown sludge in the cooling system. Some theories were it was not properly maintained. Others say it was mixed improperly with the old style 'green coolant' and that cause the sludge. Eventually there was a class action suit. If you have this brown sludge in your GM car or truck , use a flush like the Prestone flush. Flush it repeatedly and then use a 'new' Dex Cool version by Prestone or other major coolant manufacturer. That brown sludge is in not only the radiator, but the water pump. the reservoir, the heater core and hoses, the rad. hoses, the coolant passages in the engine block and anywhere the coolant has been pumped. Avoid the temptation to go back to the old green coolant because there could be remnants of the Dex Cool sludge lurking in the cooling system. You don't want to see the muddy brown sludge again. Right?
What was GM's response to the Dex Cool class action sludge issue? Some articles say the 'old GM aka prior to the GM bankruptcy' settled and paid up to $800.00. That may have paid for a new radiator and water pump, but what about those whose engines had intake manifolds gaskets destroyed by Dex Cool? GM 4.3L engine owners: does that sound familiar?