car losing power at 4,000rpm
03-29-2009, 12:21 AM
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car losing power at 4,000rpm Hey, I just got my 98 Z28 put back together(new clutch and rebuilt tranny) and was test driving it when I go WOT it falls on it's face about 3,700-3,800 rpm and won't hardly turn up anymore. Its like it's running out of fuel. I put a new 255lph fuel pump in and new fuel filter. The car runs fine just cruising around and I can rev it up when it's sitting still only acts up when it has a load on it. could it be the fuel regulator going bad or an ignition problem? Any help would be great.
03-29-2009, 03:47 PM
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Hey, I just got my 98 Z28 put back together(new clutch and rebuilt tranny) and was test driving it when I go WOT it falls on it's face about 3,700-3,800 rpm and won't hardly turn up anymore. Its like it's running out of fuel. I put a new 255lph fuel pump in and new fuel filter. The car runs fine just cruising around and I can rev it up when it's sitting still only acts up when it has a load on it. could it be the fuel regulator going bad or an ignition problem? Any help would be great.
03-29-2009, 06:10 PM
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ok I took it to o'reillys and scanned it and both of the front o2's show low voltage. But the weird thing is they are both new. They have maybe 75 miles on them. I went ahead and picked up 2 more new ones but could there be a reason they went bad so soon? The car has ram air, lid, new mass air, motor out of 02 T/A with 241 heads, pace setter LT's, O/R y-pipe, stock exhaust with the muffler currently cut off I have a hooker Im going to weld back on.
03-30-2009, 08:39 PM
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Dude this is the EXACT problem I have I just got on here to check out. My car is losing power right about 3900RPM. At first I thought it was fuel pressure related and was acctually on the phone about to order a Walbro 255 when I figured I should at least test the fuel pressure first. It was right on. Finally after driving for ever it through two codes and they were the same as yours. Low voltage on sensor 1 bank 1 and 2. Same this I can rev it to redline and it runs perfectly until you go WOT and will hit 4000RPM and just start to slowly fall off untill you pul out of it. Mine came on out of nowhere. Just one day it started doing it. So it looks like we are in exactly the same boat. I'm going to dig into it more tomorrow but the O2 codes just arnt making sense.
03-30-2009, 10:18 PM
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Dude this is the EXACT problem I have I just got on here to check out. My car is losing power right about 3900RPM. At first I thought it was fuel pressure related and was acctually on the phone about to order a Walbro 255 when I figured I should at least test the fuel pressure first. It was right on. Finally after driving for ever it through two codes and they were the same as yours. Low voltage on sensor 1 bank 1 and 2. Same this I can rev it to redline and it runs perfectly until you go WOT and will hit 4000RPM and just start to slowly fall off untill you pul out of it. Mine came on out of nowhere. Just one day it started doing it. So it looks like we are in exactly the same boat. I'm going to dig into it more tomorrow but the O2 codes just arnt making sense.
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03-30-2009, 10:45 PM
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Haha, I was going to call you and ask you tomorrow. Good to see you're still up. I have a feeling that is the problem, not much else can come into play under only certain conditions like this. Like he said though we will let you know tomorrow what we come up with.
03-30-2009, 11:29 PM
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ok I went and got new o2's under warrantee and took it for a test drive just to find out that it is still doing the same thing. I cleared the codes so I guess I will drive it some more and read the coeds again and see what they say. I might just have to try a new MAF.
03-30-2009, 11:50 PM
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Well i might know both of yalls problems. I just got my first ls car (98 Trans am) and it was doing the same thing but when it hit 4,000 it would just cut out and i dont mean slowly. Turn you lights on and rev the car from idle, if it does it at 4,000 watch the dash (gauges and lights) and if they flicker it could be a bad ground. I just got car last week and the guy just put another motor in it. He told be there was some rigging i might want to check out. The ground on the back of the drivers head was cut and he used speaker wire and grounded it to the manifolds. On top of that, when they hooked the power wire back to the fuse box it was just strung across the car. When i started the car and went to check everything when i got it home it looked like the car was on fire from all of the sparks. Sorry this was so stretched out but check your grounds and hot wires. Got me know if you find anything.
03-31-2009, 12:51 PM
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Ok assuming it is the MAF. What do you guy's think we should do. Just get the 135 dollar reman from advance/autozone or is it worth it to drop some money on an aftermarket one and try and get some more power. I'm guessing just the reman. I've heard nothing but bad things about the SLP MAF but what about the Granatelli one. Or are none of them worth it?
03-31-2009, 02:45 PM
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I plan to later today, but if it is indeed the MAF I will need a new one. I'm just wondeirng if it is worth the money spent for a aftermarket one or just a autozone replacment for 135? Also should we run into any problem's being my car is a 98 and his is a 02?
03-31-2009, 05:41 PM
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my car did the same thing but only after I tried putting a ported throttle body from an 01 on my 98. Had to put mine back on. Guess the TPS didn't like that throttle body. I have heard a lot of stories with the 98's having weird computer related problems. Good luck.
03-31-2009, 08:01 PM
#19
This might sound stupid but check and make sure your getting WOT.
I did a tb swap on my car it was only seeing 60% throttle because the throttle blade cam is different. Mines an auto but would shift right @ 4k every time.
Just a thought.
I did a tb swap on my car it was only seeing 60% throttle because the throttle blade cam is different. Mines an auto but would shift right @ 4k every time.
Just a thought.
03-31-2009, 08:47 PM
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I will check to see if it's getting WOT. Does anyone know what voltage im suppose to get with my voltmeter if I turn the key on and open the throttle blade? Also can I just unplug my maf and see it it runs better or will that not work? Will it hurt anything?