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Discussion Starter #1
:bonk: I've searched the site extensively, Completed all suggestions/recommendations. Big issue is when driving under mild load conditions. i.e. cruise on flat roads, slight exceleration, or sometimes just idle, the TB has a sluggish feeling and a deffinate lug or vibration felt throughout the vehicle. I've check/verified fuel pressures/volume; vacuum pressures/holds; all compression checks, fuel filters, fuel injector cleaners, Throttle body removed cleaned twice, checked/ohmd all sensors and removed those temperature reliant--tested on stove. Although no codes present, changed 02 sensor--#1. Changed plugs, regapped after a couple hundred miles/OEM plugs Both times the plugs looked great--light tan. Checked Motor mounts by putting in Drive/reverse and monitored engine rock. Checked for debris in drive train, along mounts, drive shafts, rear end. Changed trans filter/fluid. Trans shifts fine, just thought I would freshen up the fluid for the torque converter--no change. I have had three different thermostats in it. I read that even 20 degrees low will effect engine operation. The second one read the same temps as the 1st. So, I changed it out again, with a different brand--same numbers. 170-200. Fan clutch looks ok, no sounds or excessive play. I'm sure I'm forgetting some things too.

I can only explain the feeling as like being in too high of a gear for the conditions. Like I was lugging it. this is more prevelant at lower speeds. 40-55. Above that it isn't noticable. As I stated, torque converter and tranny is shifting and locking and unlocking fine. RPM's are similar to others on the site. shifts are smooth.

I have the 3:43 gears. I've had it since it was a yr old. I have taken OBD II numbers at 8 different times including cold hot, idle under load,

I'm looking for someone who can interpret numbers from the code reader, and give me a little guidance. I'll appreciate any experiences or knowledge to be passed on.. James
 

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Discussion Starter #2
additional information

:crazy:

I just wanted to add that there is no change in rpm while lugging/driving, but the RPM needle does drop slightly during the idle problems. Also changed the Camshaft sensor, and the actuator. Again no change in symptoms.

Anyone have an Idea or different approach...
 

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2004 gmc
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Boy you've done the right stuff in my mind so far. I'm not an exhaust expert, but I've heard something like this blamed on a clogged cat. How many miles on it, and was there any history of issues that could have clogged the cat?

Air filter OK?
 

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Discussion Starter #4
Thanks for the note back. I've changed the Air Breather. I haven't gone towards the CAT side of the house because CATS usually have a problem under exhaust flow situations. Just a little throttle and mine takes off with no problems -- especially above 4,000 rpm. And it winds up really well. It's all stock, but I've always liked the power. Wish it was a little lower in the RPM range, but I'm waiting to get this problem fixed before I go with a PCMfourless upgrade. I herd about them through this site.

Do you know anyone on the site that can read some numbers from the live feed read out of the OBD II scanner?

Thanks again, James
 

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2003 chevy trailblazer_ls
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You have not said how long you have had the TB. If this is a new problem and the TB has been fine for years I would lean towards the CAT. If you just aquired the TB then you might have a normal running TB. Mine has always been fast off the line and then the acc. slows a little until 4K then it takes off again. (Power band thingy) Got the tune and it is faster overall.
 

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Discussion Starter #6
I bought the TB in 2003 one yr old. My ex has had it for the last couple of years. I got it back about three months ago. A little run down, I had to fix a bunch of things. This is a new condition. The power, and the power band is the same. It's just when I'm cruising it has a sluggish feel, and a groan, like a vibration. Not loud, you know when your driving a stick shift and you put into the next gear a little too soon. you get that lugging feeling and sound? It's not as bad as that situation, but it's the only way I can descripe it. Plus when you come to a stop, in drive, sometimes it has a little rough idle. Like it's idling too low, and things begin to vibrate a bit. I've run the OBD II and after it's warmed up, it idles from 605 to 635 over 8 readings. Most of the time, it sits and idles beautiful--barely hear it running. But, sometimes it bounces around 200-300 rpm and when it drops down, its noticable. Gas mileage is in the 17's, not city but suburban driving. It used to get 18-19 under the same conditions. I check (manually, no onboard system) every tank.

I've had CAT's go out on me before. but not on the TB. When it goes out, it has a problem letting exhaust through. I've never had a problem on idle, only during excelleration or high exhaust requirement situations. And when mine went, they idled fine, but when I got into the throttle, the back pressure would build up. If it is plugging up during idle, surely it wouldn't be able to take full throttle--would it. Can the pressure blow by and temporarily open any obstruction? Most of the time I hear on the site about cats it's about doing down the road, like its building up pressure.
 

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For what its worth, mine is doing similar things. It is a tuning issue, and I'm sending my PCM back for a re-map after I make a couple of other changes.

I'd say that the shift points are set too low, that cam position is off a tad, and that the timing ramp isn't quite on spec for the mid-throttle tip in scenario.

Get on it, and it is a rocket, but just tipping it in a bit to pull a slight rise on the freeway without a shift and it bogs and dogs.
 

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Well Im surprised no one has mentioned a standard TrailVoy issue throttle body cleaning. Do it and report back, should help out your varying idle big time. Have you used and fuel system cleaner/seafoam through the brake booster lately? Its a good idea...:thumbsup:
 

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Discussion Starter #10
I've also put seafoam through the brake vacuum. You mentioned a tuning issue. I asked on another thread about getting the tune done. I asked if they could do a good tune without the vehicle on site. Never got a reply back. My Rpms run a little low most of the time. I thought timing may be off a little. Maybe advanced a little too much. Can PCMfourless correct these things without having the vehicle? How would they know what adjustments to make?

Without being familiar with the OBD numbers--I've been analyzing them anyway. I have a STFT Bank 1 number, LTFT Bank number 1 #, Bank 1 02S number. In addition I have a Bank 1 Sensor 1 STFT, and a Bank 1 Sensor 2 STFT. Out of all the numbers I ran, the STFT Sensor 2 number stays at 99%. I thought this was a constant, but Where is the Bank 1 Sensor 2 reading coming from.

All the other STFT's and LTFT numbers bounce around both + and - but stay within 5ish %. I'm taking a look at the 99% STFT Sensor 2 now. It's always the last number that shows up on the reader, and since it's always the same number i didnt' notice it until now. I was thinking the ideal was 100%, but maybe I need to understand it more? Any thoughts

These numbers were taken after 1hr run time:

numbers atg Idle numbers at 40 MPH

Load 26.9% 51%
Temp 201 174
STFT Bank 1 5.4% -5.4%
LTFT Bank 1 .7% 3.1%
Manifold Press 9.0" 15.6"
Eng RPM 614 1200
Ign Advance 15.5 deg 35.5
Speed 0 mph 41 mph
Intake Air Tmp 77 deg 78 deg
Throttle Pos 4.2% 19.5%
Bank 1 02S .095 v .140v
Bank 1 Sensor 1
STFT 4.6% .7%
Bank 1 Sensor 2
STFT 99% 99%
Bank 1 Sensor 02S
.815 v .660v


Does anyone see something out of line with these numbers?

I appreciate any experience with this.

James
 

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Discussion Starter #11
I've also put seafoam through the brake vacuum. You mentioned a tuning issue. I asked on another thread about getting the tune done. I asked if they could do a good tune without the vehicle on site. Never got a reply back. My Rpms run a little low most of the time. I thought timing may be off a little. Maybe advanced a little too much. Can PCMfourless correct these things without having the vehicle? How would they know what adjustments to make?

Without being familiar with the OBD numbers--I've been analyzing them anyway. I have a STFT Bank 1 number, LTFT Bank number 1 #, Bank 1 02S number. In addition I have a Bank 1 Sensor 1 STFT, and a Bank 1 Sensor 2 STFT. Out of all the numbers I ran, the STFT Sensor 2 number stays at 99%. I thought this was a constant, but Where is the Bank 1 Sensor 2 reading coming from.

All the other STFT's and LTFT numbers bounce around both + and - but stay within 5ish %. I'm taking a look at the 99% STFT Sensor 2 now. It's always the last number that shows up on the reader, and since it's always the same number i didnt' notice it until now. I was thinking the ideal was 100%, but maybe I need to understand it more? Any thoughts

These numbers were taken after 1hr run time: The first number is at idle and the second number is at 41 mph it didn't post the way it was written, but I think you can understand it

numbers atg Idle numbers at 40 MPH

Load 26.9% , 51%
Temp 201 , 174
STFT Bank 1 5.4% , -5.4%
LTFT Bank 1 .7% , 3.1%
Manifold Press 9.0" , 15.6"
Eng RPM 614 , 1200
Ign Advance 15.5 deg , 35.5
Speed 0 mph , 41 mph
Intake Air Tmp 77 deg , 78 deg
Throttle Pos 4.2% , 19.5%
Bank 1 02S .095 v , .140v
Bank 1 Sensor 1
STFT 4.6% , .7%
Bank 1 Sensor 2
STFT 99% , 99%
Bank 1 Sensor 02S
.815 v , .660v


Does anyone see something out of line with these numbers?

I appreciate any experience with this.

James
 

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I'd like to see if bank 1 sensor 2 is actually responding to throttle input, or just reading 99% all the time. If it is reading 99% and not responding, that may be part of the problem, and the sensor should be replaced.

If it responds, then it may be reacting to another issue downstream.
 

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Discussion Starter #13
All the tests I've run, 12 or 15 live reads have always shown 99% on that sensor reading. Idle, cold, hot, under load. all the same.

what sensor is it. I don't have anything that tells me what bank one sensor 2 for the Fuel trim.

I never looked hard at that number until today. because it never changed, i thought 100% was good and 1% off would be ok. It reads that 99% even when the TB is running smooth as glass.
 

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Discussion Starter #14
For what its worth, mine is doing similar things. It is a tuning issue, and I'm sending my PCM back for a re-map after I make a couple of other changes.

I'd say that the shift points are set too low, that cam position is off a tad, and that the timing ramp isn't quite on spec for the mid-throttle tip in scenario.

Get on it, and it is a rocket, but just tipping it in a bit to pull a slight rise on the freeway without a shift and it bogs and dogs.
Sound like what I have. I dont even have to kick it down a gear, just a significant increase in throttle smooths everything out. But you didn't mention if you have the idle issue to.

Are those tune adjustments something the PCMforless can do, without hands on? The site talks pretty highly of them, at least the guys that follow instructions :) Is this new since you had your tune done? or has it been all along and just continued after your tune?

Thanks again for the feedback
 

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On mine, the way it reacts to this part throttle tip in has changed since I got the tune. The tune has made it better in every way -- smoother, WAY better throttle response, better shift points, etc., but I'm still not exactly happy with that mid-range point.

I'm sending my PCM back for a re-tune, and I'm also changing a couple of other compoents before I do (CAI, Vette servo, tire size). The good thing is that the good people at PCMfL will re-tune for $25, so I can afford to play around a bit.

There might not be much that can be done for this area -- it is a function of the gear selection in the transmission versus throttle position -- and with the OD and my tire size, I should be running 4:10 gears. That would cure most of these issues, I'm thinking, but I'm going to ask for a slightly different shift set point and perhaps just a tad richer fuel curve in that tip in spot to see what happens.

Oh, and just recently (especially after running a tank full of Thorton's gas -- stuff that I know is poor quality) I've seen some deterioration in idle quality also. I'm going to do the throttle body cleaning and Seafoam just to eliminate a dirty intake track from the equation. I'm also probably going to swap out my K&N filter for a True Flow setup.
 

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Discussion Starter #16 (Edited)
Well, Alvin,

You have had a chance to look at this stuff..... what do ya think.. I've been asking questions that you should be able to answer... Can you program this thing or what.. I have a spread sheet with all the data pulled. :)
 

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Discussion Starter #17
Still Racking my brain

:crazy:Well, for anyone that may still be watching this thread; I've replaced Motor mounts with no change to the vibration. I really didn't expect much, but I thought I was feeling a little more vibration in the Drive position than in the Reverse. The rough Idle is still there, and gets worse when warmed up. If I turn the fan full on, or A/C it also seems to make it worse. Even with no AC if i turn the fan from high to low and back again it can almost stall the motor. I cleaned the throttle body twice--it's shining inside and out. I've run more numbers with the OBD and they seem to be all over the place. I was hoping that someone could help me with the Sensor #2, location or name of the sensor. It reads 99% under any condition.

Also, something that I found crazy. I finally had a chance to get it out on the highway. Made a trip to N. Corolina last week. I live in a suburban area and get 18 mpg normal driving. (I know it's good, no complaints there); But, straight highway driving only yielded 19-20. I tried 68-70 mph on a tank, 70-75 mph tank, cruise on one tank, cruise off one tank. 20 +/- 1 mpg. every tank. I even did a tank at near 80 mph all the time-19.5.

This makes me think that the timing is not adjusting properly. Wouldn't that make the idle run around on it, if the timing is a little off or fluctuating. It just doesn't make sense to me that flat lands of florida and the mountains of N. corolina should yield the same MPG.

I have a new set of Fuel injectors I'm going to put in tonight. I wish there was someone that would understand/interpret at the numbers from the OBD reader.

Does anyone out there know what Bank 1 Sensor 2 is?
 

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OP said: Throttle body removed cleaned twice
My bad....:x


Bank 1 Sensor 2 is the post cat sensor, with an inline motor setup and 1 common exhaust manifold (there are some inline motors with 6 manifolds...) the Bank 1 Sensor 1 is pre-cat and B1S2 is post cat. Not sure if changing it will yield a difference or not but might be worth it to change it out.

20mpg does seem a little low for a 2WD 3.42 geared I6, thats about if not slightly less than I got before tune, CAI, or exhaust in my 4WD 3.73 I6. Wish you were closer, could fire up EFILive and get some real datalogs for a better idea of whats happening.
 

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The power, and the power band is the same. It's just when I'm cruising it has a sluggish feel, and a groan, like a vibration. Not loud, you know when your driving a stick shift and you put into the next gear a little too soon. you get that lugging feeling and sound? It's not as bad as that situation, but it's the only way I can descripe it. Plus when you come to a stop, in drive, sometimes it has a little rough idle. Like it's idling too low, and things begin to vibrate a bit. I've run the OBD II and after it's warmed up, it idles from 605 to 635 over 8 readings. Most of the time, it sits and idles beautiful--barely hear it running. But, sometimes it bounces around 200-300 rpm and when it drops down, its noticable. Gas mileage is in the 17's, not city but suburban driving. It used to get 18-19 under the same conditions. I check (manually, no onboard system) every tank.

I've had CAT's go out on me before. but not on the TB. When it goes out, it has a problem letting exhaust through. I've never had a problem on idle, only during excelleration or high exhaust requirement situations. And when mine went, they idled fine, but when I got into the throttle, the back pressure would build up. If it is plugging up during idle, surely it wouldn't be able to take full throttle--would it. Can the pressure blow by and temporarily open any obstruction? Most of the time I hear on the site about cats it's about doing down the road, like its building up pressure.
Had a similar situation. Replaced the cat, igniton coils, spark plugs, efans, air filter, cleaned tb, oxygen sensors and nothing has changed. Did a change in the tune and solve the problem.

Try and get a tune and see if that solves your problem.
 

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Discussion Starter #20
I've just finished changing out the Fuel injectors. It's a little soon to tell, after having the Batt unhooked. It actually lost the little vibration and lugging, but the trans lock-up isn't kicking in like it was before. I'll run it a while and let the PCM settle back in and pass on the results. I'm not sure what would have changed the tranny shifting lockup charactoristics. It's cold here tonight compared to what's it's been. My RPM'a like to run a little lower than spec. 600-605. I'll pick that up with the tune when I get it. I'll keep you posted if the lock-up changes back. Thanks for the notes everyone.
 
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