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No (limited) Engine Power - Stumped Mechanic

15K views 27 replies 16 participants last post by  sugardaddy257 
#1 ·
My 2003 trailblazer with 95k miles has very limited engine power. The engine will not rev past 2800 RPM. The mechanic replaces the fan clutch already, checked out the catalytic converter and has done everything else he knows. He's been in business for 40+ years and I've never known him to be stumped on a vehicle. He has tried everything he knows. Anyone have any ideas?
 
#2 ·
I'm assuming that you mean it won't rev past 2800 RPM while driving, correct?

If you mean while in park, the rev limiter won't allow it to go much past that on purpose to limit engine damage from a "happy right foot".
 
#6 ·
Now THAT sounds like a bad fan clutch. I know you said you had it replaced, but that is EXACTLY what happened to mine....jet takeoff sound, and no power.
 
#5 ·
Well, I'm not the greatest on the "technical" parts of some of the stuff that comes up on this forum, but I wonder if your throttle body is opening all the way? It's "fly-by-wire" (no cables), but there must be a way to check it.

Hopefully some of the more knowledgeable members can chime in on this.
 
#8 ·
Was the fan clutch replacement a GM unit, or aftermarket? I replaced mine w/ a new GM unit at about 50,000 mi, and haven't had a problem since (142,000+ miles now). I've heard that aftermarket ones don't hold up.

Did you try resetting the PCM by disconnecting the battery for 30-45 min? Not sure that it will help, but you could give that a try.

Other than that, or the possible throttle body not working as I mentioned above, you've got me on this one....hope someone else has some ideas for you.
 
#9 ·
my first fan clutch died around 65k miles. the second one died around 95k (current mileage). The third one that was just put on was just put on and my car is still in the shop. All have been OEM. He thought for sure it was the fan clutch causing the loss of engine power but after switching it out for a new one, it was not. He test drove it afterwards to confirm.

Thanks for your help and ideas.
 
#11 ·
Im not sure what Reduced engine power is limited too (speed) (for those who have had it come on).
But next time you get in to your Trailvoy- turn the key- and make sure the REDUCED ENGINE POWER light comes on during the dash lights self test.
If it comes on, then the light is good. if it doesnt come one- then the bulb is burned out...

just a thought..:confused:
 
#12 ·
just got my car back..... here is what went down.... in order of events... mechanic is still confused but everything is running smoothly.

1- replaced fan clutch
2- test drove - results - still no engine power
3- pressure tested catalytic converter - checked out ok.
4- took apart some manifold where engine meets exhaust/catalyitc converter (i'm not technical so i could be describing this wrong)
5- test drove - car worked fine.
6- reassembled the thingy (<--- yes that is technical) taken apart in step 4 with the assumption that car would revert back to acting up with no engine power allowing him to further diagnose the problem
7- test drove car - car worked fine
8 - mechanic stumped - doesn't know why it works now, but it does.

anyone want to fill in the blanks
 
#13 ·
maybe your Accelerator position sensor is bad- it then triggers the reduced engine power, and lighting up the dash light....
does light work? yes then were still stumped... if no then thats the culprit.
some accelerator position sensors are know to act up- reduce power- and then magically start working again.
 
#14 ·
sounds like u were describing the EGR valve(i think)... what it does is puts some exhaust into the air mixture to reduce on polutants... i wish i would have seen this sooner... same thing happened on my dads truck except her was getting an error code with it... it turned out to be a problem with the EGR and the PCM... his EGR valve was stuck in the full open position acccording to the PCM when it was shut.. thus preventing any power cause it was thinkging it was getting to much exhaust into the mixture and running and less power to prevent damage...
 
#17 ·
Check fuel pressure? Mine died out like that, would run fine a day or so, then go out again. New fuel pump fixed it.

Also check ignition switch. Mine started fine, but switch was giving low volts.
 
#20 ·
My Envoy did the exact same thing. I took it to a dealer in SD and they did several things and at the end of the day, the car ran OK.

Then within a few days it got WORSE.

I took it to a dealer in MN and they correctly diagnosed a catalytic converter issue. They replaced it and it was immediately back to normal.

They suggested that on my trip to SD I was towing a trailer at high speeds and that over enough time it can melt the components of the Cat. The key was to do the pressure test while the vehicle was having issues. In SD, the mechanics had taken the exhaust apart which probably knocked some stuff around and masked the issue.

I repeat, my car was doing exactly what you describe and even got worse. On my way to the dealer it was so bad that it the vehicle would take about 30 seconds to accelerate to 30 mph. It was practically limping through the intersections. It was very bad. I had no idea a cat could do that.
 
#21 ·
thanks for the information work-n-show... i will keep that handy in case my car acts up again... it has been fine for 24hours now... an interesting comment you make is that you towed a trailer. i have also towed a few trailers on a 2 hour interstate drive within the past few months.... nothing extraordinarily heavy but still heavy enough to affect the drive, especially up and down West Virginia mountains. thanks again!
 
#22 ·
This same thing happened to me on my old 91 caprice classic. I was driving home from work one day and the car would not go above 30 mph or so. I almost didn't make it up one hill. I limped down the shoulder all the way to a gas station about 10 miles down the road all the while the car would not go over about 20 or 30mph also it was overheating due to me flooring it the whole way and the car not getting any air.

After I got to the gas station I called my step dad to come pick me up or follow me home. When he got there we took off and headed for home and the car ran fine. Just like the day it left the factory. My step dad thought I brought him out there for nothing.

Turned out to be a bad catalytic converter.
 
#23 ·
i know you said your guy pressure tested the cat converter .....but what about having him diconnect it then go drive it and see how it does. reason i say this is because we just had a 04 avalanch in here with the exact same problem after all the test we just decided to unhook the cats and guess what..it ran just fine although a little loud but hey found the problem. may wanna just give it a shot.
 
#25 ·
yes he did drive it with the cat converter disconnected and it ran fine....his thinking is that when he had it disconnected something that may have been stuck in the flow path may have gotten dislodged... b.c it ran fine once he reconnected everything... the only thing he ended up replacing was the fan clutch, which was definately going bad.
 
#26 ·
hey. ok check this out.
so i have been battling 2 weeks of work and a month of problems.

thought i cracked my exhaust manifold and i had a major lack of power.

turns out catalytic converter was clogged (apparently its supposed to have 1 pound of pressure (before cat) and mine was pushing 5 lbs.

clog caused my exhaust manifold gasket to blow, which melt my power steering return hose, and melted my a/c hose (cause the leak was in the very front). and to top it all off i had to replace a fan clutch haha. luckily i do all the work by myself (didnt diagnose the cat though, cause i dont have a scope)


to make a long story short, if you got major lack of power go have that catalyticc converter checked, cause it can take out a WHOLE lot of other stuff. parts cost me aprox $400 - $500 and if i didnt do my own work im sure it would have costed me about $2,000 - $4,000
 
#27 ·
i have a 2004 trailblazer and it is doing the same thing.when i try stepping on it it loses power and like it wants to stall.it also missing like the spark plugs are not firing but it dose lose power.please let me know if you found out the problem i have started with fuel filter it did not work.also it dose run good some times thank you
 
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