Car dying on declines?
Thread Starter
Teching In
Joined: Sep 2021
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Car dying on declines? I have a 2000 trans am m6 with heads cam intake bolt ons etc. Cam is a Thunder Racing RapTR cam. The car drives pretty good but when I am on a steepish decline whenever I put the clutch in or put it in neutral the RPMs drop below 500, oil pressure drops, voltage etc like its gonna die. On level ground it drives fine, just on declines. Any ideas as to what the problem could be? I'm not sure if it does it on inclines, as I haven't been to a spot where I have needed to come to a stop on an incline.
Sometimes on level ground it will drop to roughly 600rpm and jump back up but nothing major. Car idles 850-900rpm. I'm very new to the platform as I've only had the car for a couple weeks.
Any and all help appreciated!!
Sometimes on level ground it will drop to roughly 600rpm and jump back up but nothing major. Car idles 850-900rpm. I'm very new to the platform as I've only had the car for a couple weeks.
Any and all help appreciated!!
Thread Starter
Teching In
Joined: Sep 2021
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Oil pressure is fine until it gets like 3-400rpm so yeah I too believe it is due to it wanting to die.
Staging Lane
Joined: Dec 2011
Posts: 89
Likes: 16
From: Austin, Texas
Mine does the same thing but, lol, on flat ground. I noticed it on decel while keeping it in gear and letting the motor slow the car down, down to around 2500-2000rpm and then you hit the clutch and it acts exactly like yours does. I think that can be corrected in tuning though yeah? I'm H/C and have been wondering about it since it was tuned.
Maybe I am just old school, but it sounds like fueling issue, I would check fuel pump and make sure you are getting good pressure, fuel filters, and rail pressure. Just old school talking but it seems like a fuel supply issue.
If that is not it, I would look at MAF and 02 sensor readings...
If that is not it, I would look at MAF and 02 sensor readings...
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Thread Starter
Teching In
Joined: Sep 2021
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Mine does the same thing but, lol, on flat ground. I noticed it on decel while keeping it in gear and letting the motor slow the car down, down to around 2500-2000rpm and then you hit the clutch and it acts exactly like yours does. I think that can be corrected in tuning though yeah? I'm H/C and have been wondering about it since it was tuned.
If mine did it on flat ground I would definitely assume it was tune related. Honestly I have no clue though haha I'm too new to the platform.
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Verdad Gallardo Thread Starter
Teching In
Joined: Sep 2021
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Maybe I am just old school, but it sounds like fueling issue, I would check fuel pump and make sure you are getting good pressure, fuel filters, and rail pressure. Just old school talking but it seems like a fuel supply issue.
If that is not it, I would look at MAF and 02 sensor readings...
If that is not it, I would look at MAF and 02 sensor readings...
You’ll need to log with HPTuners or similar during this situation, to determine what’s going on. I’d say it’s a fueling (VE) issue, and can be fixed rather easily in the tune. Car is seeing more vacuum on the declines because engine is decelerating more, would be my guess.
You’ll need to log with HPTuners or similar during this situation, to determine what’s going on. I’d say it’s a fueling (VE) issue, and can be fixed rather easily in the tune. Car is seeing more vacuum on the declines because engine is decelerating more, would be my guess.
So, question for knowledge sake, I know I am a little more old school. Does this mean he could potentially have a vacuum leak, and this is why the car is having the decrease in vacuum pressure under decreased engine speed? So on top of logging, he would have to find the vacuum leak on the manifold? Sounds like something is leaking if he didn't have the issue before, but is now having vacuum issues now and the engine is stalling out. Just trying to learn and better understand.
The fact that the car is new to the OP only makes this harder to diagnose over the interwebs. We’re all just guessing without a tuning expert…which I am not…looking at logs of the car running through a bunch of different circumstances.
Sounds tune related to me. First of all, the car is idling too high for a 5.7 liter. That to me is a dead giveaway that tuning was poorly done, and someone just got it to run “good enough” and said goodbye. The intake sees very high vacuum when throttle body snaps shut, especially on a downhill where an engine will be decelerating harder (more rpm) than say flat ground. At lower rpm’s the intake won’t see as high a vacuum when throttle body snaps shut. This part of the fuel trims (map sensor is reading high vacuum) needs work especially with a cammed engine that has different valve events causing a difference in vacuum actually seen.
I appreciate you going through that and explaining it, that makes sense. Might have just been a start up tune / break in tune before going to dyno tuning then, or just a quick and dirty on the dyno where fuel and MAP hadn't been dialed in. Great information and thank you for sharing, the older I get the more I enjoy learning!
Thread Starter
Teching In
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I just got home from driving it for a bit. I was cruising for about an hour, ran perfectly fine. I headed over to the local performance shop, and when I turned on their road I noticed I was coasting 1k rpm but I couldn't hear the car. I pushed the clutch in, starts to die. I rev it up to keep it going, do it again, starts to die. Repeats it 3 or 4 times and when I pulled in, I just put it in neutral and it died. I hung out there for a couple hours, and when I got in it to leave, it started up just fine and drove great. Check engine light did come on though. Did a couple pulls and drove for about half an hour zero issues. Guys at the shop were unsure what it could be I'll probably have them look at it.
Any ideas at all? It's the strangest thing.
Note: the voltage, oil pressure, etc was fine
Any ideas at all? It's the strangest thing.
Note: the voltage, oil pressure, etc was fine
TECH Fanatic
Joined: Feb 2015
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Sounds like your having a problem now on level ground after heat soak? Connect a fuel pressure gauge so you can read in car. or... you could monitor short term fuel trims (STFT) to see what the computer is doing if you have scan tool with live data. If going positive, it's trying to add fuel to compensate for lack of (fuel pressure dropping, etc.) As 70velle mentioned, Do you have logging capabilities?
If you confirm fuel system issue, need to diagnose system to see where the problem is (pump, filter, regulator, injectors). Fuel cleaner likely not much help.
If you confirm fuel system issue, need to diagnose system to see where the problem is (pump, filter, regulator, injectors). Fuel cleaner likely not much help.