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Discussion Starter #1
Some background first. I have had an sc on my t100 with a 3.4 for over two years with no problems. Recently I decided to change the motor out (the original one had 300k on it) with a used one. I put the motor in with some JBA headers and the SC.

The problem: I cant get the truck to rev past 4500 rpm. Feels like its running out of gas or ??? Fuel filter has been replaced, no engine lights, runs smooth. The other odd thing is, is that in has absolutely no spark knock like it did with the original motor when it was under load at low rpm.


Any ideas?
 

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Mr.T said:
drabnor................I owe you a beer............Thats what it was.

Big thnx
sweet, glad it was that simple
 

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Do you have the URD Kit? My first instict would be to look at your fuel maps. You could be leaning out hard.

Could be your injectors, too.

A scan tool and the fuel maps is where I would start.
 

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so when you say it wont rev past 4500, does it physically not want to rev any faster or does it just rev like crap?

is this in neutral?

is it making any weird noises?

do you have any fuel mods?
 

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Humm what kind of shape is you CAT in? If it's plugged up and was toasted by the first engine, it's gonna choke the living shit out of the engine.

Do yourself a favor and get with URD this time around and do the fuel mods. Even if you do live at 5K feet. You should not have any knock.
If you still have access to the old engine, yank the heads and have a look around the valve seats. I'm betting that you're gonna find some cracks in the webs between the valves.
 

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Discussion Starter #14
So I had the sc on the old motor w/o any problems. No URD kit or other fuel mods. The new motor runs great/smooth with no odd noises. The weird thing is that with the original motor and sc I would have some pinging in lower rpm's under load. The pinging is non existent with this motor which leads me to believe that this is not a fueling problem. I'm starting to think that its an ignition problem maybe even the knock sensor is retarding the ignition too much.
 

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Discussion Starter #15
Dick Foster said:
Humm what kind of shape is you CAT in? If it's plugged up and was toasted by the first engine, it's gonna choke the living shit out of the engine.

Do yourself a favor and get with URD this time around and do the fuel mods. Even if you do live at 5K feet. You should not have any knock.
If you still have access to the old engine, yank the heads and have a look around the valve seats. I'm betting that you're gonna find some cracks in the webs between the valves.

I'm with you on that. I have a feeling the one of my heads is cracked on the old motor but hey it does have 300k on it
 

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Discussion Starter #16
SAR_Squid79 said:
Do you have the URD Kit? My first instict would be to look at your fuel maps. You could be leaning out hard.

Could be your injectors, too.

A scan tool and the fuel maps is where I would start.


I tried pulling codes w/o success.
 

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I'm gonna say the center jug in both heads are shot at least. The SC running the engine lean (knocking) does it, it's not the miles, it's the heat.
Just do the URD thing and you're new one will go the miles.
Did you send the SC to Magnuson and have them go through it? If you put that many miles on it, it was due.
At least you should have changed the oil in the nose drive. You can get the oil change kits at Buick dealerships or from Magnuson.
 

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Discussion Starter #18
Dick Foster said:
I'm gonna say the center jug in both heads are shot at least. The SC running the engine lean (knocking) does it, it's not the miles, it's the heat.
Just do the URD thing and you're new one will go the miles.
Did you send the SC to Magnuson and have them go through it? If you put that many miles on it, it was due.
At least you should have changed the oil in the nose drive. You can get the oil change kits at Buick dealerships or from Magnuson.

I plan on the urd kit and I will be changing the nosedrive oil soon ( sc has about 85k on it). I just want to get the truck back to baseline before I start throwing the urd kit in
 

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Mr.T said:
I tried pulling codes w/o success.
No - you need a SCAN TOOL - not a code reader.

An example of a scan tool is this:
http://www.shop.com/op/~AutoXray_OBD_II_Scanner_151_EZ_Scan_4000-prod-6998993-10019744?sourceid=3

It can tell you your exact fuel trims and o2 sensor readings in real time, and really help you nail down exactly where the problem is (or isn't).

With a scan tool, you'll be able to definitively tell whether you've got a problem with fuel delivery, vacuum or boost, or exhaust.
 
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