Hesitation, lack of power under moderate throttle
#13
04-13-2011 | 02:39 PM
Junior Member
Joined: Apr 2011
Posts: 3
Have Had back to dealer twice and they tell me that this is normal. I drive my freind h2 suv with the same exact driveline and it runs like a raped ape. The dealer said that there were no codes and "what did i want them to do?, just start changing parts?" I said well it is still under warranty. Well if you find out what is wrong with yours please post, I will keep tring to work with the dealer and see if they will fix. If I do find out, Will relay the info to you.
#14
06-04-2011 | 10:46 PM
Thread Starter
|
Member
Joined: Jun 2010
Posts: 38
From: Saint John, NB, Canada
Been busy working on my car, so haven't really played with the truck. I have changed the fuel sending unit as it was leaking, and it still didn't change anything.
So, FWIW, fuel pressure with the key on, engine off and the fuel pump commanded on with a scan tool, the fuel pressure should be 55-62 psi. We played around with the adjustment screw on the regulator, and we have it around that area, but the truck still works the same.
The thing that was bugging me was that it only runs 8 degrees of total timing(under power) with no knock retard registering. Then it hit me all of a sudden, I bet someone had a supercharger on it at one point, but when they removed it, they didn't revert the ECM tune to stock. It all makes sense now!
I then took my 03 Escalade out and datalogged it. It never sees less than 24 degrees of total timing.
My next step is to see if my friend can flash it back to stock with his TechII or I may just buy HP tuners and put a performance tune to it. (plus I can do the vette and escalade)
Good times..
So, FWIW, fuel pressure with the key on, engine off and the fuel pump commanded on with a scan tool, the fuel pressure should be 55-62 psi. We played around with the adjustment screw on the regulator, and we have it around that area, but the truck still works the same.
The thing that was bugging me was that it only runs 8 degrees of total timing(under power) with no knock retard registering. Then it hit me all of a sudden, I bet someone had a supercharger on it at one point, but when they removed it, they didn't revert the ECM tune to stock. It all makes sense now!
I then took my 03 Escalade out and datalogged it. It never sees less than 24 degrees of total timing.
My next step is to see if my friend can flash it back to stock with his TechII or I may just buy HP tuners and put a performance tune to it. (plus I can do the vette and escalade)
Good times..
#15
06-08-2011 | 08:36 PM
Thread Starter
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Member
Joined: Jun 2010
Posts: 38
From: Saint John, NB, Canada
So, my buddy was able to flash my PCM to stock, but that didn't change anything. We messed around some more, but couldn't figure what the problem was.
Next thing you know, he is taking a napkin out of the glove box, and says he wants to try something. He took my air filter off (it has a CAI) and positions the napkin over a portion of the MAF honeycomb. We take off, and it's doggy as hell, but it comes out of it and pulls hard. Timing was great, right around 25 degrees.. Exciting, but we were like WTF? We took some tape and positioned the right amount in the middle of the MAF to give the best driveability until I sort it out.
Best we can figure is that it is the CAI that is to blame. I have decided to purchase HP Tuners and change the tune to compensate for it.
If I had the stock air box and such, I would switch it back, but it was like this when I bought it.
Next thing you know, he is taking a napkin out of the glove box, and says he wants to try something. He took my air filter off (it has a CAI) and positions the napkin over a portion of the MAF honeycomb. We take off, and it's doggy as hell, but it comes out of it and pulls hard. Timing was great, right around 25 degrees.. Exciting, but we were like WTF? We took some tape and positioned the right amount in the middle of the MAF to give the best driveability until I sort it out.
Best we can figure is that it is the CAI that is to blame. I have decided to purchase HP Tuners and change the tune to compensate for it.
If I had the stock air box and such, I would switch it back, but it was like this when I bought it.
#16
06-08-2011 | 08:57 PM
Senior Member
Joined: Feb 2009
Posts: 148
From: Santa Fe, NM
I'm not surprised, I had to retune mine as well after I installed the CAI.
If you want the factory airbox and such PM me i'm sure we can work something out. Its simply taking up room in my garage at the moment.
If you want the factory airbox and such PM me i'm sure we can work something out. Its simply taking up room in my garage at the moment.
#19
06-14-2011 | 09:19 PM
Thread Starter
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Member
Joined: Jun 2010
Posts: 38
From: Saint John, NB, Canada
Alright! My cable came in the mail today. First thing I did, was make 2 datalogs of the Hummer, then I made 2 similar datalogs of the Escalade. My main concern was that my timing was in the crapper, and when I compared the two logs, I found that the Hummer MAF was flowing 25% more than the Escalade.
It's not really flowing 25% more air, but the CAI is throwing the calibration of the MAF off, so all I did was scale the main MAF Calibration table down by 25%. This will put me back into the "sweet" spot of the timing map.
Soo, I did 6 logs with this new file burned to the turck, and it seems to be working great! I got home and compared it to the Escalade files, and the timing is good and O2's are around .850 volts at WOT. I also noticed that in my original Hummer logs, the O2's were showing .900+ volts, so the CAI was affecting the AFR too, but not to the extreme that it had on timing.
Anyway, that is my rambling for now.
It's not really flowing 25% more air, but the CAI is throwing the calibration of the MAF off, so all I did was scale the main MAF Calibration table down by 25%. This will put me back into the "sweet" spot of the timing map.
Soo, I did 6 logs with this new file burned to the turck, and it seems to be working great! I got home and compared it to the Escalade files, and the timing is good and O2's are around .850 volts at WOT. I also noticed that in my original Hummer logs, the O2's were showing .900+ volts, so the CAI was affecting the AFR too, but not to the extreme that it had on timing.
Anyway, that is my rambling for now.
#20
07-03-2011 | 06:55 AM
Junior Member
Joined: Jun 2011
Posts: 4
help My 2003 is doing the same thing
So, I've been having a problem where part throttle driving is absolutely horrible. Cruising around town, half throttle will bog, but as you let up on the gas, it picks up. It would seem after 3300 rpm, it picks right up and works well. I put a new MAF on it which helped some throttle response, but the issue still remains.
I put a techII on it and it shows the MAF stop at 120g/s and continuing to press the throttle down doesn't change the value and it works bad. Once it hits a higher TP angle and/or 3300rpm+, the MAF jumps to 2XXg/s and works great. When it works good, the O2's are around .850 volts, but under bad working conditions the O2's are cycling, but it's too hard to tell where they are at.
It seems when the truck is in open loop, there is something maybe pulling fuel from the system? Once the truck goes into closed loop (heavy accel), everything seems peachy. Timing is also around 4* advance when working bad, but no timing retard being recorded.
I can't pull the data logs off the TechII to review them. No codes in the system. I did check the fuel pressure while running, and it was close to the numbers I found, but I'm not sure if they are right or not. Can someone verify the fuel pressure at idle?
Any thoughts would be appreciated, I'm at a loss.
I put a techII on it and it shows the MAF stop at 120g/s and continuing to press the throttle down doesn't change the value and it works bad. Once it hits a higher TP angle and/or 3300rpm+, the MAF jumps to 2XXg/s and works great. When it works good, the O2's are around .850 volts, but under bad working conditions the O2's are cycling, but it's too hard to tell where they are at.
It seems when the truck is in open loop, there is something maybe pulling fuel from the system? Once the truck goes into closed loop (heavy accel), everything seems peachy. Timing is also around 4* advance when working bad, but no timing retard being recorded.
I can't pull the data logs off the TechII to review them. No codes in the system. I did check the fuel pressure while running, and it was close to the numbers I found, but I'm not sure if they are right or not. Can someone verify the fuel pressure at idle?
Any thoughts would be appreciated, I'm at a loss.
Installed a new feul filter and it still works the same.
The tech II doesn't show A/F, especially since there isn't an A/F sensor in the system. (2 front o2 and 2 rear o2 sensors) They cycle so fast I can't even get an average. If I could pull the logs off, I could step through it and see, and also possibly graph it.
The o2's stop cycling when it goes into closed look (aka wot or above 3500) and sit at .850 volts which is perfect under power.
The tech II doesn't show A/F, especially since there isn't an A/F sensor in the system. (2 front o2 and 2 rear o2 sensors) They cycle so fast I can't even get an average. If I could pull the logs off, I could step through it and see, and also possibly graph it.
The o2's stop cycling when it goes into closed look (aka wot or above 3500) and sit at .850 volts which is perfect under power.