Hello, I have a 2000 Trans Am 6-speed. Since about 3-4 weeks ago, it has experienced a sudden drop in power and acceleration and nobody around here can seem to figure it out.

It's a full bolt-on, cam only, 9" rear car. I've run a best of 12.6 in it, but that was a year and a half ago, when the car didn't have as much done.

About a month ago I had my mechanic install a TNT F2 nitrous kit with all the accessories. Everything was wired and ran correctly and it is a good looking kit. At that time, he also re-tuned my car with LS1Edit because it had been running very rich.

The nitrous never seemed to work right from the beginning. Testing it at the shop, everything was working correctly, the WOT switch was hitting, fuel was being let in, nitrous was coming out, etc. On the street, though, it never really seemed to hit hard at all on a 100 shot. As much as he tried, the mechanic could not figure it out. It felt to me like it hit a little, but definitely nothing like a 100 shot.

At that time, the car was still fairly quick off the nitrous - probably something around a 12.0 car. Since about three weeks ago, though, the car has experienced a significant drop in power - it feels like I'm back to a 14 second car . Under normal driving, it will hesitate at times under normal throttle. This is hard to explain without actually driving the car, but it feels almost like a misfire, and does it through all six gears at seemingly random times. When you're pushing the gas pedal down, once in a while it will "blip" back really quickly for a fraction of a second, like the car is having trouble running.

It doesn't seem to do this under WOT, but I'm fairly sure whatever is affecting it under normal throttle is also affecting it under WOT because the car is much, much slower. 5-10 different people have told me this while driving around, you can really feel that it has lost power. It sounds the same, it revs up the same, there are no SES codes, but it just no longer has that "pull you back into your seat" power.

The reason I'm posting this in the Fueling section is because it might be a problem with my fuel system. Ever since the nitrous install, and for a couple months before, the car has been running pretty rich and wasting a lot of fuel. My mechanic has been working on it and tuning it, but without a wideband it is hard to adjust(I'm getting a wideband within the next two weeks.) On Thursday my mechanic swapped the plugs and we could see that the old TR-6 plugs were pretty worn out. It ran a little better with the new plugs, but still had all the same old problems.

This leads to the question - what could the other possible causes of this be? My mechanic's current guess is that it's my O2 sensors. They might have been fouled from all of this rich air/fuel driving from the past couple months, in addition to the nitrous. I cannot think of anything else it would be, does anyone have any opinions or advice? Thanks.

 

how many miles is on the car? I would try changing the fuel filter you would be surprised!!

 

60k on the car. The fuel filter only has about 5,000 miles on it, but I am going to try replacing that as well.

 

it could be o2's but they will ussually throw a code when they go out or aren't reading well. i don't know about your weather in ohio but my car has the same problem in the same time frame, it's going back on the dyno in another week or so to see if the tune has been thrown off do to the sudden change in the weather (which is what i believe happened). it was first brought to my attention when my friend told me i was throwing out smoke between shifts during WOT. I'll let you know how it goes

 

I replaced the o2 sensors and that did not fix it. We ghetto-rigged a fuel pressure gauge to the car and found out that under wide-open throttle the fuel pressure was dropping very, very low(15-20psi). My mechanic decided the only thing left was the fuel pump, so we took out my 6 month old Walbro 255lph fuel pump and replaced it with another identical one, and voila - it ran great again n/a. The fuel pressure was back to normal. It still is not feeling much like a 100 shot at all when the nitrous is used though. I'm not sure what could be causing that, but I have ordered a wideband gauge, fuel pressure gauge, and nitrous pressure gauge which will go in next week and hopefully then we can begin to find the problems

 

Do you have a bottle heater? What is your bottle pressure when you spray it? You'd be surprised at what incorrect bottle pressure can make a car feel like. I think it should be required or included in all N2O kits...

 

Is it possible that the nitrous and fuel is pointed the wrong direction and spraying on the maf?

 

I do have a bottle heater. I have tried the nitrous at 850psi, 900psi, 950psi, 1000psi, and 1050psi and it has not been significant at any of those.

As to the question about the nozzles being pointed the wrong way, I just went outside and double checked everything and it is all perfectly aligned.

 

Get an NOS kit and be done with it. A plate kit would do wonders for ya.

We picked up I believe it was 158 HP at the tires on a 98 camaro ss on a 150 shot. It's in GMHTP magazine, Jan or Feb I believe.

 

Well, I think your on the right track. It does sound like a fuel delivery problem. I went through this same thing on mine while running a 150 shot. How much fuel pressure are you running now with the new fuel pump? I added an inline pump on mine and the fuel pressure went from 40 psi to 60 psi. My nitrous dyno numbers jumped from 450 rwhp to 527 rwhp. BIG difference. I'd say if your not running at least 60 psi you need to do something different.

Also, if you have a fuel pressure safety switch in your nitrous circuit, then that also could be the reason your not feeling the nitrous. It simply does not have enough fuel pressure to activate the circuit. Your mechanic should have installed this. If not, I would find a new mechanic.

PS - I wouldn't rule out a new fuel filter.

 

Hey I thought of something else:


Are your solenoids even coming on? They way you can test them is to set your rpm window switch (if you have one) down to something very low like 500 rpm. Make sure your nitrous bottle is CLOSED. Then start the car and reach over with your finger and activate the WOT switch (don't worry, it won't bite). If you hear a loud *click*, then your solenoids are working. If not then do this:

By-pass fuel pressure safety switch temporarily and see if it works this time. If it does, you are not getting enough fuel pressure. Be sure to hook your fuel pressure safety switch back up.

 

Yes, the solenoids are on. We have already done this test.

I don't have a fuel pressure safety switch installed because they seem to cause more trouble than they prevent. I don't think it's my mechanic's fault, it was more of a mutual agreement not to use a FPSS.

The fuel filter has been replaced and is about a week old. My fuel pressure gauge should be coming early next week and that will help with diagnosing the problem. Thanks for the current help though.

 

Well I've honestly never heard that one before. Its just a switch activated by your fuel pressure that breaks the circuit if theres not enough fuel pressure. It only costs about $25 and is a no-brainer to install. $25 is alot cheaper and less hassle than replacing your engine.

I've never ever had a problem with mine and would remove my entire nitrous system before I would run it without a FPPS or an RPM window switch.

No offense, but if it is your mechanic telling you all this I would not only find a new mechanic I would shoot your old one

Good luck to you buddy

 

Do you have a purge on the nitrous kit? A nitrous filter? What about the screen in the noids? I'd get your NA problems ironed out for sure before getting into the nitrous but those are all things to look at.

 

I agree... Basics FIRST!!
As for the "mechanic".. WHY would a sure enough tuner/mechanic, NOT have a FP gauge in his toolbox??
That's a basic, basic tool for working on EFI applications.
Like others have mentioned... Find a new mechanic.

 

The way you have the bottle mounted affects a lot. I had mine in the hump between the 2 back seats and the way it mounts it sat flat and the siphon tube was not sucking up hardly any nitrous at all but everything still worked and checked out. Confused me for a while and then I felt stupid when I realized.

 

Hook up a vacuum guage to the engine to make sure its not hurt.