I have a 2004 Trailblazer EXT with 148000 miles on it. I have had an issue with power loss from the engine, it starts and idles great, but when driving it, it will go down the road, but it struggles to go. Around 20 to 30 miles per hour it has its most problems, but I can floor the gas pedal and it will eventually get up to speed. I have had it to the dealer and they have done the following, replaced the catalytic converter, replaced muffler, cleaned throttle body, and induction flush. I have personally changed spark plugs, fuel filter, air filter, CPAS, and I have cleaned the throttle body several times. The dealership is done with it, they don't know what is wrong with it and don't want to look at it anymore. I can fix it, if I know what is wrong with it, but at this point I have no idea what could be wrong with it. I asked the dealership to check the catalytic converter again and they act like they don't want to. This is my wife's vehicle and I really need to get this repaired, I would greatly appreciate any help.
Loss of engine power
- Thread starter rrpeace
- Start date
What are the compression numbers? Long and short term fuel trims? Fuel pressure regulator OK? Fuel pressure and flow good?
The dealer changed parts with zero guarantee that they had properly diagnosed the problem? Goons.
The dealer changed parts with zero guarantee that they had properly diagnosed the problem? Goons.
I used the AC Delco plugs 41-103. They replaced the front 02 sensor when they replaced the catalytic converter. The transmission, I have never done anything with, other than had it flushed once, the dealer told me not to change the filter and fluid because of the high mileage. I have not done a compression test or fuel pressure test, I don't have the tools for that. The engine does rev up but I will have to see about it roaring, I have replaced the fan clutch a few years ago. I don't know how to check fuel trims or the fuel pressure regulator, any help on how to do that would be great. Is it common for problems with compression on the trailblazers?
Wooluf1952
Member
Welcome In case you haven't heard:
http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/
Just so we're all on the same page: When you say the dealer and you cleaned the t-body, it was actually removed from the engine and both sides were cleaned?
IllogicTC
Member
- Dec 30, 2013
- 3,452
What I find strange is the guy goes back because he wants this fixed, and they're like "Oh, more money? Nah bro, we already got this stack over here. We're good."The_Roadie said:
Very un-dealer-like!Fuel trims can be checked with a scanner unit. Specifically, one at least a step or two above the "it gives you a code number" basic readers. If you have an Android phone, a popular choice among forum-goers is to buy a $20 ELM327 Bluetooth adapter and get the Torque Pro app for a whole $5. Gives a pretty full-featured scanner for a total cost of $25 and a little bit of setup time.
If you don't have an Android device, you could consider buying an actual scanner, but they can be pretty pricey. I have the Actron CP9575 (sold at Advance Auto and likely other parts stores), it gives code read and reset, emissions status, and some basic live data (fuel trims included) and this set me back $100. Either with this or the Android-based Torque Pro app, you'll find the investment a smart one in the long run as not only will it work with cars at least for the foreseeable future, but all your buddies probably wouldn't mind paying a couple bucks or a beer for you to bring it over and help them read their code.
How does the temperature gauge look? Does it climb up to and stay at the 210 mark or is it consistently under? If it stays low you could be having a thermostat issue which can end up eating up catalytic converters, fuel economy, and build up some nasty carbon deposits within the engine.
I may have a friend that has a code reader that may show me that data, I will ask tomorrow. My temperature gauge has always been a little under 210, I have replaced the thermostat and temperature sensor about a year ago, ac delco, purchased at the dealer and it still is just under 210.
KNBlazer
Member
- Feb 8, 2012
- 811
Get a code reader and see if your timing is advancing as you accelerate... even though you have a new CAT, your other exhaust components could be plugged...try removing O2 sensor and taking it for a drive....
Oh and let us know which dealer you went to, thus helping other members avoid going there...
Oh and let us know which dealer you went to, thus helping other members avoid going there...
I should have the code reader this coming Monday, I will check the things that have been suggested to check out. The dealer I went to is Tim Short in Winchester KY, I can't complain a great deal, they have treated me right in the way of cost. They have done a lot of the checking and troubleshooting and not charged me for it, because they could not guarantee it to be fixed, I just don't understand why the attitude of not wanting to work on it and saying, "I don't know". As for me when I am working on anything that I have a hard time figuring out, I can't rest until I find out why and get it fixed. Thanks so much for all of the input so far, I will update the post with the information when I can get it. If anyone thinks of anything else that I may have missed or not checked, please let me know and I will be glad to check it out, I want this fixed!
The dealer isn't being paid for diagnosing, it seems - and I can understand why they don't get obsessed about working for free on a vehicle that's being a pain in the butt.
IllogicTC
Member
- Dec 30, 2013
- 3,452
Double-edge sword. On the one hand, they aren't getting paid for diagnosing and therefore don't want to sink tons of man-hours into it, which is understandable. On the other hand, they have this deal where diagnosis is free, and to the customer it's seen as a very nice touch and they expect something more than a bunch of "I dunno." Also understandable. Really ought to change their policy.The_Roadie said:
Okay, I don't have a way to monitor the values while driving, because I don't have anyone to drive for me and won't have until this Thursday, but I do have some values at idle.
Mill Status Off
ABSLT TPS % 13.3
ENG SPEED RPM 608
CALC LOAD % 32.5
MAP KPA 36
COOLANT TEMP 195
IAT TEMP 100 with arrow pointing down
IGN ADVANCE DE 12.5
ST FTRM1 % .7
LT FTRM1 % -9.2
VEH SPEED MPH 0
FUEL SYS 1 CLSD
FUEL SYS 2 N/A
O2S11 V 0.830
ST FTRM11 % -1.0 with arrow pointing down
02S12 S 0.775
MIL DIST mi 0
OBD2 STAT CA/US
This is the data so far, I don't know what the values should be but hopefully you all do!
KNBlazer, I did see the timing advancing when the engine is reved up at idle, or I suppose it is, it changes but the number appeared to be getting larger during acceleration. I have not removed the O2 sensor and drove it yet, but I will give it a try when I can. Thanks for all of the input, hopefully this information will help.
Mill Status Off
ABSLT TPS % 13.3
ENG SPEED RPM 608
CALC LOAD % 32.5
MAP KPA 36
COOLANT TEMP 195
IAT TEMP 100 with arrow pointing down
IGN ADVANCE DE 12.5
ST FTRM1 % .7
LT FTRM1 % -9.2
VEH SPEED MPH 0
FUEL SYS 1 CLSD
FUEL SYS 2 N/A
O2S11 V 0.830
ST FTRM11 % -1.0 with arrow pointing down
02S12 S 0.775
MIL DIST mi 0
OBD2 STAT CA/US
This is the data so far, I don't know what the values should be but hopefully you all do!
KNBlazer, I did see the timing advancing when the engine is reved up at idle, or I suppose it is, it changes but the number appeared to be getting larger during acceleration. I have not removed the O2 sensor and drove it yet, but I will give it a try when I can. Thanks for all of the input, hopefully this information will help.
I started the engine and let it run for a while and watched the rpm gauge then I put the gas peddle to the floor and it will only go to 3000 rpm. I connected the code reader again and noticed the reading on the throttle position sensor was 28.6 % with it just idling. I shut the engine off and put the peddle to the floor and it only reads 87%. I have a 2004 truck and I connected the code reader to it and it shows 99.9% with the peddle to the floor. What do you guys think?
gmcman
Member
- Dec 12, 2011
- 4,656
When in Park the engine will only rev to 3-4K. Engaging the trans at high RPM's will generally tear up the sunshell in these transmissions. This is common in alot of GM vehicles in regards to high revs when not in gear.
With the engine off, remove the intake hose to the TB and have someone watch the butterfly while you fully depress the accelerator pedal with the key ON, engine OFF. Does it eventually fully open? I believe it should.
With the engine off, remove the intake hose to the TB and have someone watch the butterfly while you fully depress the accelerator pedal with the key ON, engine OFF. Does it eventually fully open? I believe it should.
Pretty sure 87% is correct for fully open on these engines.
The thing I am wondering about is the fuel trims. It is pulling out almost 10% fuel which is a lot even if it isn't enough to throw a code.
Something is making it run rich or think it is running rich and it's making the fuel trims go negative. If so you may have killed the cat again. Did the power come back for a little while after they changed the cat or did everything remain the same?
Maybe bad maf/map (but I think 36kpa is right for idle anyone else know for sure?), fuel pressure regulator or stuck/leaky injector? A miss could also make the PCM think the car is running rich because of the excess unburned fuel but I would think you would feel that our the dealership would have seen it on a scan.
Maybe try holding the revs in neutral at 2500 for a little while and see what readings you get.
Here is something I found on another site that may help you diagnose ii.
Originally Posted by Painless Performance Products
If you are experiencing overfueling when the engine is at idle here are several things that can be the cause.
Vacuum leaks. Any fuel injection system to utilizes a MAP sensor will run rich if a vacuum leak is present. The vacuum leak is seen as increased engine load the the ECM/PCM compensates for the engine load by increasing fuel delivery.
Bad HO2S sensor. HO2S sensors indicate to the ECM/PCM what the oxygen content the exhaust has. It uses this information to modify its fueling strategy in order to get as close as it can to its commanded air fuel ratio. A bad sensor, contaminated sensor or a sensor that the heater is not working properly can cause false readings which in turn sends to the ECM/PCM and incorrect Voltage signal. Scan tools will show codes for this issue.
Bad engine coolant temperature sensor. The ECM/PCM uses the ECT sensor to command open/close loop and also modify fueling strategies according to engine temperature. If the ECT has no signal most ECMs will command a very rich condition. Scan tools will show codes for this issue.
Leaking fuel injectors. Fuel injectors wear out, get stuck and dirty. Any fuel injector that does not close all the way will leak fuel into the intake manifold. This will cause a rich condition most noticeable at idle.
Leaking fuel regulator. Any fuel pressure regulator that uses a vacuum biased line from the intake manifold has the potential to leak fuel back into the intake manifold. This will usually only be noticeable at idle. If you suspect this just unplug the vacuum line from the biased port and plug it off. If the richness goes away, change the pressure regulator out with a new one.
High fuel pressure. Higher than required fuel pressure can cause a rich engine. Check to make sure you have the fuel pressure regulator set properly for your fuel injection system requirements. More pressure does not = better atomization and does not increase the injector volume output enough to warrant it. More pressure does = leaky injectors, broke injectors and shortened fuel pump life.
The thing I am wondering about is the fuel trims. It is pulling out almost 10% fuel which is a lot even if it isn't enough to throw a code.
Something is making it run rich or think it is running rich and it's making the fuel trims go negative. If so you may have killed the cat again. Did the power come back for a little while after they changed the cat or did everything remain the same?
Maybe bad maf/map (but I think 36kpa is right for idle anyone else know for sure?), fuel pressure regulator or stuck/leaky injector? A miss could also make the PCM think the car is running rich because of the excess unburned fuel but I would think you would feel that our the dealership would have seen it on a scan.
Maybe try holding the revs in neutral at 2500 for a little while and see what readings you get.
Here is something I found on another site that may help you diagnose ii.
Originally Posted by Painless Performance Products
If you are experiencing overfueling when the engine is at idle here are several things that can be the cause.
Vacuum leaks. Any fuel injection system to utilizes a MAP sensor will run rich if a vacuum leak is present. The vacuum leak is seen as increased engine load the the ECM/PCM compensates for the engine load by increasing fuel delivery.
Bad HO2S sensor. HO2S sensors indicate to the ECM/PCM what the oxygen content the exhaust has. It uses this information to modify its fueling strategy in order to get as close as it can to its commanded air fuel ratio. A bad sensor, contaminated sensor or a sensor that the heater is not working properly can cause false readings which in turn sends to the ECM/PCM and incorrect Voltage signal. Scan tools will show codes for this issue.
Bad engine coolant temperature sensor. The ECM/PCM uses the ECT sensor to command open/close loop and also modify fueling strategies according to engine temperature. If the ECT has no signal most ECMs will command a very rich condition. Scan tools will show codes for this issue.
Leaking fuel injectors. Fuel injectors wear out, get stuck and dirty. Any fuel injector that does not close all the way will leak fuel into the intake manifold. This will cause a rich condition most noticeable at idle.
Leaking fuel regulator. Any fuel pressure regulator that uses a vacuum biased line from the intake manifold has the potential to leak fuel back into the intake manifold. This will usually only be noticeable at idle. If you suspect this just unplug the vacuum line from the biased port and plug it off. If the richness goes away, change the pressure regulator out with a new one.
High fuel pressure. Higher than required fuel pressure can cause a rich engine. Check to make sure you have the fuel pressure regulator set properly for your fuel injection system requirements. More pressure does not = better atomization and does not increase the injector volume output enough to warrant it. More pressure does = leaky injectors, broke injectors and shortened fuel pump life.
Okay, I had some time to watch the fuel trim some. I found that with it idling the LTFTRM was running about -7.7% and then I got the engine to 1500 rpm and it got closer to 0%, about -4%. When I got the engine up to 2500 rpm it went to -.5% after it ran at that rpm for a moment. The STFTRM was bouncing around really close to 0%. What does this mean, vacuum leak? I know nothing about fuel trim stuff.
I just looked and they replaced the O2 sensor on the back side of the converter not on the front side.
IllogicTC
Member
- Dec 30, 2013
- 3,452
The downstream sensor is used just to measure the cat's efficiency. If they didn't do the upstream that could be an issue.
Fuel trim percentages always fluctuate and as long as they stay within +/- 10% you should be okay generally. The O2S11 value on your scanner is for your upstream sensor, and the voltage should be bouncing between 0.1 and 0.9 or so volts at a relatively quick pace (generally once per second or more). If it's taking 2 or more seconds to transition states you may have a dying upstream sensor.
As for fuel trim values themselves: +X% means it's adding more fuel to the mix to match the air volume detected. -X% means its bringing the fuel amount down. A consistently high +% would mean an unmetered air leak, so your -% values seem to indicate your vacuum has no leaks.
Fuel trim percentages always fluctuate and as long as they stay within +/- 10% you should be okay generally. The O2S11 value on your scanner is for your upstream sensor, and the voltage should be bouncing between 0.1 and 0.9 or so volts at a relatively quick pace (generally once per second or more). If it's taking 2 or more seconds to transition states you may have a dying upstream sensor.
As for fuel trim values themselves: +X% means it's adding more fuel to the mix to match the air volume detected. -X% means its bringing the fuel amount down. A consistently high +% would mean an unmetered air leak, so your -% values seem to indicate your vacuum has no leaks.
Thanks so much for the reply! I just checked the O2S11 voltage and it is reading exactly as you said it should be between 0.1 and 0.9. Also today I rented a fuel pressure gauge and my fuel pressure was about 58 PSI. Any other thoughts?
Okay, I talked to the dealer and they looked at my trailblazer on and off for two days and could not find anything wrong. I decided to order the front O2 sensor and install it, that was a challenge, it would not come out! I ended up removing the heat shield to get the socket on there better and it came right off there. When I removed the heat shield I noticed there was a crack in my exhaust manifold. I drove the blazer after installing the O2 sensor for a short drive and it appears to be normal power with the engine now, but I can't drive it very long as the manifold is leaking pretty bad. My question is will the crack in the exhaust manifold cause it to not have power?
IllogicTC
Member
- Dec 30, 2013
- 3,452
It could, as the system expects good seals all the way around. This could either let exhaust out which could fudge the readings, or excess oxygen in via a sort of venturi effect which would again fudge the readings badly. It is good that you noticed this crack as you might be on the right path.rrpeace said:
KNBlazer, yes it is cracked by some numbers, I would post a picture, but I don't know how to get it on here! I plan on trying to find a exhaust manifold Monday, it will have to have it anyway, I just really hope and pray that this is my issue. I am SO ready for this to be fixed! I will let you all know how it goes, thanks so much for the replies, it really has been a tremendous help.
BlazingTrails
Member
- Apr 27, 2014
- 19,409
This is the one I got it works great. You will probably have to drill and tap 1 or 2 bolts from the head. Buy all new bolts!!
http://www.ebay.com/itm/350976872986?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
http://www.ebay.com/itm/350976872986?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
BlazingTrails
Member
- Apr 27, 2014
- 19,409
March 8th, 3k miles. Perfect.KNBlazer said:
Edit: I also port matched mine, and it probably gets hotter than most because I frequently do wot pulls on a tune. And it is still perfect.
Pittdawg
Member
- Dec 5, 2011
- 538
I had a factory manifold extrude honed and ceramic coated after mine cracked...been good for about two years now (fingers crossed).
Btw, there was a recall on these manifolds, not sure if it's still in effect but GM ended up paying for my stock manifold and even the installation; I just had to shell out for the extrude honing and ceramic coating on my own.
Btw, there was a recall on these manifolds, not sure if it's still in effect but GM ended up paying for my stock manifold and even the installation; I just had to shell out for the extrude honing and ceramic coating on my own.
Okay, I have got the exhaust manifold off, but the very two bolts I did not want to be broke, was broke. I have the very first and very last bolt broke off in the head. Any ideas on how to get them out?
I gave the Roadiemobile to a trusted independent mechanic and told him to take his time - up to two weeks while I was on a business trip - and work on it a little bit at a time until his frustration level built up - then put it aside for the next time he had a time slot free. He had the special small right angle drill to do the job, and patience. You need a small right angle drill and stud extraction gadgets. Not a typical home DIY job.
BlazingTrails
Member
- Apr 27, 2014
- 19,409
Been there done that.
You will need a milwaukee M12 right angle drill + Battery
You will also need a 1/4" Drill bit. GET A GOOD ONE. (Rigid, Lennox, etc.)
Cut the bottom end of the drillbit down to where there is just enough of the shank to get a bite on it.
You'll need a 8mm x 1.25 Tap
(11) 8mm x 1.25 x 32-35mm length grade 8 or higher bolts
(11) Flat washers
Cutting oil/Tap Oil (use liberally)
I was able to drill and tap the bolt closest to the firewall with this combo.
run the tap gently in every hole to remove corrosion and blow them out with compressed air.
Use Anti seize compound on the threads of every bolt upon re-assembly.
Any question hmu
Edit: the factory bolts are very deep in the head, they are too small in diameter to get them out with an extractor. just drill straight into the old bolts 1" 1/4 deep and re-tap them.
see post 26 lol
From my phone lol
Thanks Blazing Trails, I had guessed that was my only option. I have a friend at work that has a right angle drill, I will borrow it tomorrow and get to drilling. I want to have it ready for when my new manifold gets here. Now I know what I have to do, I was just afraid of drilling and messing up the head, but it does make sense if you drill the same size hole to make new threads, it shouldn't be to big. How did you get a picture to go on this forum, I have tried with no luck.
Also, would I need to use softer bolts, the factory boost seam pretty soft! I was going to get factory bolts, would you recommend grade 8 instead?
Also, would I need to use softer bolts, the factory boost seam pretty soft! I was going to get factory bolts, would you recommend grade 8 instead?
BlazingTrails
Member
- Apr 27, 2014
- 19,409
I bought the OEM bolts from GM, because they have some dry antiseize compound pre-applied to the threads.
Hardened bolts would terrify me if THEY broke and I had to think about drilling them out. Sometimes a broken bolt acts as a mechanical fuse. Or the copper anti-seize could be the cure to broken bolts and GM was just being cheap to not use it in the factory.
Hardened bolts would terrify me if THEY broke and I had to think about drilling them out. Sometimes a broken bolt acts as a mechanical fuse. Or the copper anti-seize could be the cure to broken bolts and GM was just being cheap to not use it in the factory.
BlazingTrails
Member
- Apr 27, 2014
- 19,409
I have gotten the back one drilled out with the 1/4" bit, but the tap will not start in there, it seams to want to hang up and I am scared to put much pressure on the tap. Is there enough material around the bolt holes to go to the next size bolt? I just don't want a broken tap back there in that hole, you can't see what you are doing back there, boy in all of the places for the bolt to be broken!
BlazingTrails
Member
- Apr 27, 2014
- 19,409