Low MPH need help w/ prognosis
12-07-2005, 01:04 AM
#1
TECH Enthusiast
Thread Starter
iTrader: (2)
Join Date: Jul 2005
Location: Dallas
Posts: 555
Likes: 0
Received 0 Likes
on
0 Posts
Low MPH need help w/ prognosis I have a 1999 Trans Am with a 6 speed. The car has 120,000 miles. the only mods are borla cat back, slp dif cover, and K&N filter.
I have been at the track a couple of times, and only seem to be able to acheive about 98 mph through the 1/4 traps. Now I know that my trap speed should be at least 102ish, and that the mph is a good indicator of HP.
The low end of the car <3000 rpm's still feels strong and performs adequetely off the line. But when the revs go above 3000 the car dosen't feel like it is pulling, and I have been pulled on by a basically stock mustang GT on the top end
.
So, I have come up with some possible problems:
1. Bad compression/ leak down.
2. worn valve spring(s).
3. I have the bosch 4+ platinum plugs, and some people have told me that they arent great for the LS1.
4. Something that is pulling timing out of the top end, I am having the ecu scanned next week to see if it is.
Any comments or suggestions are appreciated,
Josh
I have been at the track a couple of times, and only seem to be able to acheive about 98 mph through the 1/4 traps. Now I know that my trap speed should be at least 102ish, and that the mph is a good indicator of HP.
The low end of the car <3000 rpm's still feels strong and performs adequetely off the line. But when the revs go above 3000 the car dosen't feel like it is pulling, and I have been pulled on by a basically stock mustang GT on the top end
.So, I have come up with some possible problems:
1. Bad compression/ leak down.
2. worn valve spring(s).
3. I have the bosch 4+ platinum plugs, and some people have told me that they arent great for the LS1.
4. Something that is pulling timing out of the top end, I am having the ecu scanned next week to see if it is.
Any comments or suggestions are appreciated,
Josh
12-07-2005, 07:03 AM
#3
TECH Fanatic
Join Date: Jan 2002
Location: harrisburg, pa
Posts: 1,205
Likes: 0
Received 0 Likes
on
0 Posts
After you check all the basics...fuel filter, injection cleaner, plugs/wires, air filter...
how about bent push rods or broken rocker???? happens all the time
how about bent push rods or broken rocker???? happens all the time
12-07-2005, 01:25 PM
#4
TECH Resident
iTrader: (4)
Join Date: Nov 2004
Location: Nashville, TN
Posts: 879
Likes: 0
Received 0 Likes
on
0 Posts
Change the fuel filter and hook up a fuel pressure guage to the rail to see what the pressure is with the car running. It should be 58-60psi. If not, the fuel pump is going, and that could very easily be your problem, because the motor is running lean and lots of timing is being pulled up top. Unless you've mechanically overreved the engine by missing 3rd and hitting 1st instead, you probably don't have anything wrong internally. LS1's have a pretty good valvetrain.
Jason
Jason
12-07-2005, 03:24 PM
#7
TECH Fanatic
Join Date: Jan 2002
Location: harrisburg, pa
Posts: 1,205
Likes: 0
Received 0 Likes
on
0 Posts
id pull the valvecovers off and check the rockers/pushrods...after checking the fuel system...but if its not lean (plugs) and no knock..thats problably not the problem.
