Fluctuating Temp Guage & RPM Surging
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Teching In
Joined: Jul 2004
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From: Bristol, Rhode Island
Fluctuating Temp Guage & RPM Surging I have been having an on going problem for a few months with my 99 Z28. The problem is very intermitten but very annoying none the less. While driving the temp guage becomes very erratic, jumping from cold to hot and everywhere in between. While the temp guage is going crazy the RPMs will either surge up to 2000 RPMs higher than where it should be or the engine just starts bogging, almost choking. When I am stopped at a traffic light the same thing will happen with surging RPMs or the car will all out stall. As I said this problem is very erratic, sometimes I am able go three days with no problems and then some days its just awful. Through my research I have replaced the following and nothing has helped: MAF Sensor, IAC Motor, TPS Sensor, PCV Valve, and EGR Valve. I also verified that there is no blockage in the PCV tubing assembly and I have cleaned the throttle body thoroughly. Please give me your thoughts. Perhaps Air Pump or O2 Sensors??? If any part of this is confusing I can try to be more clear in my explanation. Thanks Guys
10 Second Club
Joined: Jul 2004
Posts: 156
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From: San jose
i am having almost that same exact problem but my is my mph and temp gauge & fuel gauge my mph just starts tweeking when i am driving it will go up and down then g back to its original speed.And my temp&and gas gauge drop to empty or 0 for a feew minutes then go back to normal.i wished we could get this problem fixed. 
Launching!
Joined: Mar 2003
Posts: 293
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From: TX.
Originally Posted by DAM1999Z28
I have been having an on going problem for a few months with my 99 Z28. The problem is very intermitten but very annoying none the less. While driving the temp guage becomes very erratic, jumping from cold to hot and everywhere in between. While the temp guage is going crazy the RPMs will either surge up to 2000 RPMs higher than where it should be or the engine just starts bogging, almost choking. When I am stopped at a traffic light the same thing will happen with surging RPMs or the car will all out stall. As I said this problem is very erratic, sometimes I am able go three days with no problems and then some days its just awful. Through my research I have replaced the following and nothing has helped: MAF Sensor, IAC Motor, TPS Sensor, PCV Valve, and EGR Valve. I also verified that there is no blockage in the PCV tubing assembly and I have cleaned the throttle body thoroughly. Please give me your thoughts. Perhaps Air Pump or O2 Sensors??? If any part of this is confusing I can try to be more clear in my explanation. Thanks Guys
the pcm adjusts fuel and timing by recieving signals from the IAT, ECT, MAF, MAP, CKP, CMP, and O2 sensors.
hope that helps.
Thread Starter
Teching In
Joined: Jul 2004
Posts: 7
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From: Bristol, Rhode Island
Thank you for the input guys. I did however replace my ECT sensor in summer 2003. I replaced it due to the fact that I snapped it clean off while changing my spark plugs (that was not a fun job). Perhaps the ECT sensor that I bought is a dud. I am at the point know where I will replace whatever part that I need to. I am so sick of the damn surging RPMs and erratic temp guage. I really don't want to get rid of my f-body but if I cannot nail down this problem then I might have to. As for you SnakeEater my fuel guage has also danced around but now its mostly the temp guage that does along with surging RPMs.
Launching!
Joined: Mar 2003
Posts: 293
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From: TX.
Originally Posted by 8-Pack
Check your grounds if you havent already
all of the grounds, and the terminals on the battery.
good luck man.
dont worry, you will fix it.
