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2002 Pontiac Grand Prix GTP
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Discussion Starter · #1 ·
So, as the title reads I just swapped my 2000 GTP motor into a 2002 GTP since my 2000 was rusted to hell and the transmission was failing. This 02 had a blown motor but a much better body and a working transmission. During the swap I went through a bunch of seals and gaskets such as head gaskets, valve seals, timing cover, oil pan, LIM, etc etc. Basically every gasket and seal I could think of. Been running and driving for a few days now, no leaks or anything like that aside from an exhaust leak at the rear manifold to downpipe. However, on the second day of driving it around I felt comfortable with getting on it a little bit, only went to about half throttle and I noticed it starting to buck and stumble a bit up high. Afterwards it started to stumble quite often. I did the fuel pump and filter already since they needed to get done anyways but still no change in that regard. It feels like it just trips on it's face trying to do pretty much anything. Starting from a stop I have to be real easy on it otherwise it just bucks hard and once it even stalled out. Even while just holding a steady speed it'll randomly start stumbling. Looking at fuel trims the short term was sitting at more or less -20 while cruising at 40mph. I know that's pretty rich and I could tell just from the smell but I can't figure out why it's running so damn rich. So far no codes other than EGR which doesn't exist on the engine anymore. I cleaned the IAC, replaced, PCV, MAF or TB shouldn't be dirty either. What's the deal here?
 

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It's odd that it'd be so rich. You might've popped a vacuum line or harness connection that's skewing your fueling somewhere? Is the cat in good shape (if present), especially after living thru a blown motor that might've puked things out?

Just take it easy/minimize running it until you dig around and come across something odd. If it's a stock-ish setup that you're monitoring closely, the list of options should stay short.
 

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Discussion Starter · #3 ·
It's odd that it'd be so rich. You might've popped a vacuum line or harness connection that's skewing your fueling somewhere? Is the cat in good shape (if present), especially after living thru a blown motor that might've puked things out?

Just take it easy/minimize running it until you dig around and come across something odd. If it's a stock-ish setup that you're monitoring closely, the list of options should stay short.
I've discovered after driving it a little bit while watching some readings. First O2 voltage was going absolutely ballistic on the graph.
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It should be oscillating between ~0.2 and 0.9 mV during normal driving, and steady up in the 0.85-0.95mV realm when you're in boost. Read up on the "narrow band O2 sensor" operations for this, and also how closed and open loop work in our older systems, if you can't get to sleep at night.

That said, what app/hardware are you using? ELM? Curious what else I could use thru my phone besides Torque & ChevroSys when I don't want to plug in the HPT.
 

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Discussion Starter · #5 ·
It should be oscillating between ~0.2 and 0.9 mV during normal driving, and steady up in the 0.85-0.95mV realm when you're in boost. Read up on the "narrow band O2 sensor" operations for this, and also how closed and open loop work in our older systems, if you can't get to sleep at night.

That said, what app/hardware are you using? ELM? Curious what else I could use thru my phone besides Torque & ChevroSys when I don't want to plug in the HPT.
I personally like Car Scanner Pro. It's pretty good st grabbing codes and you can easily see lots of sensor data with graphs and such. Very good for watching voltages, fuel trims, etc
 

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std resister core plug wires like to break internally and once they start having to jump the gap they chew themselves apart from the inside till you have near constant misfires as the spark tries to jump a half inch gap.

if the wires arent new and were twisted or bent/flexed heavily even after being on the engine for o nly a couple months could lead to an internal break, and that kind of misfire will give o2 readings like that
 

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Discussion Starter · #7 ·
It should be oscillating between ~0.2 and 0.9 mV during normal driving, and steady up in the 0.85-0.95mV realm when you're in boost. Read up on the "narrow band O2 sensor" operations for this, and also how closed and open loop work in our older systems, if you can't get to sleep at night.

That said, what app/hardware are you using? ELM? Curious what else I could use thru my phone besides Torque & ChevroSys when I don't want to plug in the HPT.
std resister core plug wires like to break internally and once they start having to jump the gap they chew themselves apart from the inside till you have near constant misfires as the spark tries to jump a half inch gap.

if the wires arent new and were twisted or bent/flexed heavily even after being on the engine for o nly a couple months could lead to an internal break, and that kind of misfire will give o2 readings like that
It doesn't feel like it's misfiring though is the thing. Even after a couple cycles I only have a pending cylinder 3 misfire which could be a result of what's going on with my mixture. Regardless it's still running SUPER rich.
 

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Discussion Starter · #8 ·
Fixed my exhaust leak, no change, tried a different PCM, no change, checked for vacuum leaks, no change. I'm running out options here.
 

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check the icm harness down near the ac compressor, ive had dozens of people end up with wires rubbed through on the ac pulley and intermittently shorting out the CKP/CMP signals to the icm

most people break the harness clip that holds it to the ac bracket and way from the belt and sometimes dont route it properly
 
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