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2G Won't rev past 5000 rpm and backfires

Michael Gomes

Probationary Member
17
0
Dec 28, 2018
Riverbank, California
I'm hoping someone can help me to speed up the diagnosis on what's going on with my car. First off I have a 99 GST. 5 speed. 114,000 miles. I had been having some issues with the car surging at WOT. I had just about fixed that then all of a sudden it got worse. I'd have to baby the throttle go go through the power band without it hiccuping. Today when I was about home it felt funny in a different way, I popped it in neutral and floored it. It would get to 5000 rpm and that's it. And when it hit 5000 rpm if hear a slight backfire two mild sounding pops. My plug wires are old along with my ignition coils. Any ideas?
 

Vegas Smith

Proven Member
4,343
2,166
Dec 2, 2002
Houston, Texas
It sounds to me like an idle position switch issue. I know the 2g has it built into the tps so maybe there is an issue with the tps or connector. Do you have a way to log?
 

Murdertalon

Proven Member
372
62
Jul 7, 2016
East side, Washington
Also do a compression test, and check codes. If your car is running too rich it might cause symptoms like this. Mine runs too rich and burns a little oil so it has random hangs in throttle response. My way to fix it is send it until the engine explodes and rebuild. If I get a couple more years out of this engine it will be worth it, still pulls strong but I'm pretty sure I have low compression.
 

mooserage

Probationary Member
11
5
Dec 28, 2006
Seattle, Washington
Just a thought, but does the car have a chip with a stutterbox set to 5000rpm? The clutch pedal signal may be out and causing it to think the clutch pedal is constantly pressed. I'd only check this if the 5000rpm hold is really consistent.

It sounds like there are other issues as well, but this may be one.
 

Michael Gomes

Probationary Member
17
0
Dec 28, 2018
Riverbank, California
No I have no way to log and also don't have a stutterbox. I replaced the spark plug wires and that helped a lot. One of the two screws on my TPS wasn't tight. Also replaced a couple little hoses one that is attached to the wastegate and the other little hose coming off the compressor side of the turbo. ( They both are attached to a T. ) Cleaned my blow off valve, Turbo inlet, and some piping. Running a lot better now. But I'm still going to baby it until I'm done replacing a few more parts. I want to get it 100 % restored to stock spec before I start to have the real fun of modifying .
 

Michael Gomes

Probationary Member
17
0
Dec 28, 2018
Riverbank, California
Thanks for all of the good advice. And thanks also for taking the time to respond to this. I appreciate it
 

greddy_1700

Proven Member
956
41
Aug 27, 2006
Regina, SK_Canada
Old wires can do that for sure. My car would bog hard around 5k, changed the wires and it went away.
 

Michael Gomes

Probationary Member
17
0
Dec 28, 2018
Riverbank, California
Why would you put it in neutral and floor it? :idontknow:, do you want a hole in your engine block?
I only popped it in neutral and floored it because while I was driving it seems like it wouldn't even get up to three or four thousand if I had to guess so Poppin it neutral allowed me to find out how high would go there is a rev limiter right so there is no real danger of throwing a rod or anything like that unless I was just to keep my foot down
 

camocorvette

Proven Member
64
21
Aug 5, 2012
Spanaway, Washington
Check the knock sensor on the back of the motor, if its fried (black tar types stuff oozing on sensor) that can cause similar problems. Check the tps position with a voltmeter. Are you on SD or MAF? Either one with a bad maf or omni sensor could cause issues.

What's your spark plug gap? Boost level?
 
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