The fuel pump changing noise when you got the gas tank is a very good indication of a failed fuel pump. But if it was me I would still do what I could to narrow the diagnosis. Too many times I have replaced parts because I didn’t finish a diagnosis or did it wrong. Pressure gages aren’t horribly expensive. If you are going to do your own car repairs it is necessary to have tools for the job. If you do decide to pressure test it, the place to hook the gage is located on the fuel filter located under the car on drivers side near the gas tank. Pressure should read 50 - 57 psi with key on and also with engine running. Make sure all connectors are clean and connected good. Or just replace the pump. Good luck either way.
Does sound like a failing fuel pump. If it is, they usually don’t last too long before they fail completely - then you’ll know for certain. I imagine the squealing is the fuel pump binding (or something clogging it), trying to pump. Then you bump the tank and it jars the pump just enough to allow it to run under its own power. Good theory anyway.
If you do have to buy a pump later on, Rockauto and Amazon have decent prices. I believe you’re right in sticking with an AC Delco pump.
Also, I’m assuming this vehicle doesn’t have an external fuel filter, but has the filter as part of the pump assembly inside the tank, correct?
I had that squeek chirp noise for a coupe of years, it went away after the wheel bearing went out and was replaced.
Interesting. GM went to the in tank pump and strainer assembly in around 2004 for the half ton trucks, I believe. I assumed the trailblazer would be similar.
FWIW, seems to me there are more fuel pump problems on Chevy trucks than on any other vehicle I read about here. Even if it doesn’t solve the problem, a new one now might prevent that problem, so don’t feel too bad about the expenditure.
Unfortunately the site is incorrect about the '05. I’ve looked everywhere for it after seeing youtube repair videos give that range of years when showing a different year than the '05. Then in the comments a number of people say the '05 is in the tank. Is there someplace else to hook the gauge?
This sound is definitely not a wheel bearing on mine. Was happening while idle and I traced it to inside the tank.
Though, I also have a chirp coming from up front driver’s side but I’m pretty sure that’s the A/C clutch as it only happens while the A/C is on and it happens anytime I turn the A/C on/off. But I’ll deal with that later. It’s just one quick low level chirp every now and then.
Issue wasn’t really showing itself so I just kept driving it. I have the new pump but haven’t decided to put it in yet. Ordered it from Walmart so I can take it back if I don’t.
But today it did it twice (in the same place) and I was able to pay closer attention to what is happening so that I can describe it better. There’s a spot where I’m stopped and then turn left to go up a steady long incline. I can get up to 30-40 but then can’t get it to go any faster going up this incline. It will say steady at 30-40 but no matter how much more I press on the pedal, it doesn’t go faster. If I just go ahead and keep pushing it to the floor, the RPMs go up to 3k but I just keep going the same speed until the incline levels out.
So I think that’s why I was only noticing it sometimes on the way to/from work. Because I really have no reason to increase speed during any of the inclines. I can maintain speed fine even at 60 as long as I’m already going 60 once I hit the incline. But I had to make 2 supply runs at work today and hit this place where I’m going from stopped to uphill. It happened exactly the same both times and I’ll bet I can repeat it anytime I need to there.
So my question is, could still be a fuel delivery issue if the engine is reaching 3k but not going faster? Would RPMs increase if it’s not getting more fuel? What issues translate into more RPMs but not more speed? Anything other than transmission. If I have another damn transmission go out on a car I just bought, I’m never buying used again.
I’ve cleaned the throttle body. Sucked up 5oz of Seafoam into the brake booster then poured the rest into 4 gallons of gas. I didn’t think any of this would make a difference but figure I may as well try. It hasn’t made a difference.
I was wondering about maybe a cracked exhaust manifold but the bottom bolt on the shield rounded and is in too awkward of a place for me to do anything about it so I couldn’t get a look at the manifold. I plan on trying a smoke test.
I also plan on going to Harbor Freight and getting that gauge to do the back pressure test. My concern with that though is I need to take out the upstream O2 sensor and it’s in the manifold right above the bolt that was so corroded it rounded quit easily when I turned it. The higher up bolts came out fine. I don’t want to crack my manifold trying to test my cat. So I’m going to spray it and try a little force but if it doesn’t budge, I’ll just leave it alone.
If it passes all these tests then I’m going to look into the suggestion of rigging up a fuel pressure gauge I can see while driving over that problem area. But I’m not sure where I even hook the gauge up as the filter is in the tank.
I’m also considering just saying F it and driving it like this for as long as I can. Or until it throws a code and shows me some direction to where the issue is. It’s just not worth the money to take it somewhere and start having $500-1000 repairs done that may or may not fix it. I’ve been through that before and that’s what has made me want to learn to do my own repairs/maintenance when possible.
I think you are looking at a transmission issue. RPM increase no speed increase, I would chase that ghost first. How long since the last trans fluid and filter service?
Yeah, that’s what I was afraid of. I don’t remember the RPMs going up when this was happening before but it definitely was today. It tops out at just a little over 3k with my foot to the floor. Why doesn’t it go higher?
I’m sure it’s never had a trans service. Just under 80k miles. Fluid level is good. Looks and smells ok. Aside from changing fluid/filter and solenoids, is there anything else I could do with the trans?
Can revving with no increase in speed be caused by something other than trans Could exhaust issue (cat restriction, manifold leak) cause that? Sometimes there’s also a low exhaust like rumble towards the mid-rear of the car while giving gas. It’s only when driving at faster speeds on the highway and it’s not super loud so I can’t really get a good feel for what it is. But hell, who knows how many simultaneous unrelated problems this vehicle has.
RPM increases without a corresponding increase in vehicle speed is a definite sign of an automatic transmission problem. That symptom is very unlikely to be related to an exhaust leak or obstruction.
It doesn’t mean the transmission is done-for though. It might just need some TLC, like a proper transmission service. And there are replaceable parts bolted to the outside of the transmission, or inside the transmission valve body that can fail and cause this, and sometimes some there’s an even simpler fix, like an adjustment. I’d start with a proper trans service. If that helps , but not 100%, do it again after driving 100 miles or so. After that you’ll need a transmission expert to diagnose what’s wrong. If they are experienced at diagnosing automatic transmissions, first they’ll take a test drive, next they’ll probably start the shop work by measuring transmission fluid pressures at various test ports.
Well, your first hunch was the cat converter is plugged. That could possibly keep the engine from reaching higher rpm’s. Low fuel pressure could cause that too. I think it would be best if you tested the exhaust back pressure and the fuel pressure (check fuel pressure at more than just idle). It might not be terribly expensive to have a shop do this for you rather than buying equipment. Pay them for diagnostics, then you do the repair yourself, if you want. I’ve done that several times.
Usually, a transmission problem won’t keep the engine from reaching higher rpm’s. With a trans problem, you reach really high rpm’s but you just don’t move much. In my experience, anyway.
If you floor it and it won’t go over 3k rpm, the transmission would not be my first guess…
The service I should be able to do myself. But will surely make a gian mess dropping the full pan. Guess I could look for a cheap pump. Is there a valve I should just replace on the blind while I’m in there? Is one more likely to be associated with the issue being only uphill?
That’s what has me split between all these possibilities. It revs and doesn’t increase speed but the RPMs top out at just over 3k with the foot to the floor. Could that happen with a bad fuel pump, though? The revving? Wouldn’t the RPM increase suggest it’s getting fuel to the engine but being bogged down by something else?
With so many possibilities now, I think I’ll have to just take it somewhere and see what they say. And like you said, if it’s a repair I can do, then I’ll do it myself. Problem is going to be finding a good place to take it. I’m not familiar with any (good places) and there’s a lot of poor quality work done around here (in general). I might just have to go to a dealer.
The experienced local mechanics in the area will know the best transmission shop in town. Ask around a few general repair shops, you’ll probably get the same answer.
Yes, I’d think low fuel pressure (clogged filter or weak pump) could allow the engine to rev to 3k rpm and not higher. I’d think all around performance would suffer if it’s a fuel delivery problem. I’m assuming it doesn’t accelerate as normal to that 3k rpm limit, but kind of struggles to get there.
It’s been driving fine for all other scenarios and usually stays at around 1500rpm going 50-60mph and then will go up to 2 or a little higher when I’m accelerating going uphill a little on the highway or need to speed up to pass someone, etc.
When I have it in neutral in my driveway and keep pressing on the pedal, it will continue to rev and get louder as the RPMs rise but then my foot hits the floor and it’s just above 3k. I’ve only held it there for a few seconds before letting back up but it never goes above that.
The issue when driving is only up a steady long incline where the speed tops out at 30-40mph and once it hits that, if I continue to press the pedal to try and get more speed, the rpms increase but my speed stays at 30-40. The RPMs advance with the pedal. If I let back up, they come down. If I floor it, then top out a little above 3k and the car just stills moves along a 30-40. I’d say the initial speed up from 0 to 30-40 is longer than I think it should be but maybe not and not something that really sticks out as an issue until I top out at 30-40. I believe the RPMs were steady increasing as I was going from 0 to 30-40 but I can’t specifically remember that.
Am I wrong in thinking that if the RPMs increase, then the fuel was delivered as the engine is turning. But then something is keeping it from translating that extra turning into extra speed?
That might be normal, as the transmission may be downshifting due to the uphill load on the engine. On many conventional automatics you can figure out if that’s happening by shifting out of D to a lower gear. My trucks has a 3 speed automatic. If nothing happen when I shift from D to 2, the transmission must have already shifted into that lower gear automatically, which is normal on steep uphills when pressing on the pedal…
Not going above 3k rpm sounds like a restriction to me. Either fuel is restricted, or the air getting out is restricted. I’ve been wrong before, of course. I’m assuming you’ve checked and made sure a rat hasn’t built a nest in the air box or the tube going to the throttle body or something goofy like that?
Transmission problems usually don’t show up as restricting rpm…