Possible vacuum problems, please help
07-07-2002, 07:10 PM
#1
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Possible vacuum problems, please help
Does anyone know if their is a specified vacuum under throttle, or just at idle, and what is it? I'm getting 22psi at idle, which is in specs, and my idle varies at different throttle levels, but is usually around 5 psi of vacuum at mid throttle. Reason I'm asking is that Ive been having some problems with my FPR, which started a couple days after I installed it, and I think it is a defective FPR, but I can't find anything wrong with it. Its vacuum controlled, so I'm trying to figure out if my vacuum is in specs or not. Thanks in advance. 
07-07-2002, 11:30 PM
#5
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First three days, car ran PERFECT, felt even stronger than before, I think because I wasn't running a little rich anymore. Then, on the fourth day, while going uphill, I started getting about a 5psi fluctuation. Checked all my vacuum lines and even replaced a few, still won't stay steady. Got a vacuum tester, checked my vacuum, 22in-hg, fuel pressure still fluctuates. Took my FPR apart, could not find any problems with it, so I replaced the return port. Still fluctuates. Hooked up the Vacuum gauge and drove the car around. Fuel pressure fluctuates while vacuum remains steady. Only thing I can think of is FPR is bad, but I can't figure out why, the FPR doesn't have that many parts to it. AT WOT, fuel pressure stays steady, when I first start up my car, it stays steady, as soon as I start driving it at part throttle, it fluctuates. It's SOOOO frustrating!!!
Originally posted by Chunger
Why do you think you have a problem? Are your vacuum readings different than before? Are you having A/F problems?
Why do you think you have a problem? Are your vacuum readings different than before? Are you having A/F problems?
07-07-2002, 11:44 PM
#6
Originally posted by mtrai760
First three days, car ran PERFECT, felt even stronger than before, I think because I wasn't running a little rich anymore. Then, on the fourth day, while going uphill, I started getting about a 5psi fluctuation. Checked all my vacuum lines and even replaced a few, still won't stay steady. Got a vacuum tester, checked my vacuum, 22in-hg, fuel pressure still fluctuates. Took my FPR apart, could not find any problems with it, so I replaced the return port. Still fluctuates. Hooked up the Vacuum gauge and drove the car around. Fuel pressure fluctuates while vacuum remains steady. Only thing I can think of is FPR is bad, but I can't figure out why, the FPR doesn't have that many parts to it. AT WOT, fuel pressure stays steady, when I first start up my car, it stays steady, as soon as I start driving it at part throttle, it fluctuates. It's SOOOO frustrating!!!
First three days, car ran PERFECT, felt even stronger than before, I think because I wasn't running a little rich anymore. Then, on the fourth day, while going uphill, I started getting about a 5psi fluctuation. Checked all my vacuum lines and even replaced a few, still won't stay steady. Got a vacuum tester, checked my vacuum, 22in-hg, fuel pressure still fluctuates. Took my FPR apart, could not find any problems with it, so I replaced the return port. Still fluctuates. Hooked up the Vacuum gauge and drove the car around. Fuel pressure fluctuates while vacuum remains steady. Only thing I can think of is FPR is bad, but I can't figure out why, the FPR doesn't have that many parts to it. AT WOT, fuel pressure stays steady, when I first start up my car, it stays steady, as soon as I start driving it at part throttle, it fluctuates. It's SOOOO frustrating!!!
07-07-2002, 11:46 PM
#7
Originally posted by mtrai760
First three days, car ran PERFECT, felt even stronger than before, I think because I wasn't running a little rich anymore. Then, on the fourth day, while going uphill, I started getting about a 5psi fluctuation. Checked all my vacuum lines and even replaced a few, still won't stay steady. Got a vacuum tester, checked my vacuum, 22in-hg, fuel pressure still fluctuates. Took my FPR apart, could not find any problems with it, so I replaced the return port. Still fluctuates. Hooked up the Vacuum gauge and drove the car around. Fuel pressure fluctuates while vacuum remains steady. Only thing I can think of is FPR is bad, but I can't figure out why, the FPR doesn't have that many parts to it. AT WOT, fuel pressure stays steady, when I first start up my car, it stays steady, as soon as I start driving it at part throttle, it fluctuates. It's SOOOO frustrating!!!
First three days, car ran PERFECT, felt even stronger than before, I think because I wasn't running a little rich anymore. Then, on the fourth day, while going uphill, I started getting about a 5psi fluctuation. Checked all my vacuum lines and even replaced a few, still won't stay steady. Got a vacuum tester, checked my vacuum, 22in-hg, fuel pressure still fluctuates. Took my FPR apart, could not find any problems with it, so I replaced the return port. Still fluctuates. Hooked up the Vacuum gauge and drove the car around. Fuel pressure fluctuates while vacuum remains steady. Only thing I can think of is FPR is bad, but I can't figure out why, the FPR doesn't have that many parts to it. AT WOT, fuel pressure stays steady, when I first start up my car, it stays steady, as soon as I start driving it at part throttle, it fluctuates. It's SOOOO frustrating!!!
07-07-2002, 11:49 PM
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I did disconnect it when I pulled the TB off to change the FPR, but I haven't touched it since, and I don't think it would make a difference, I thought Fuel pressure was controlled by vacuum, not by the ECU? I'll pull codes tomorrow and see if it tells me anything...
Originally posted by emax95
By any chance did you touch your MAFS in the last few days? Just a idea since it can make a lot of weird things happen.
By any chance did you touch your MAFS in the last few days? Just a idea since it can make a lot of weird things happen.
07-07-2002, 11:53 PM
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I KNOW I installed everything correctly. Ive been going over the dang installation for the past 8 months prior to installation... I also had 1/2 tank during the fluctuations... I really wish I lived close to someone that had a aftermarket FPR, I already spent $150 on the AEM, if I can't get this figured out tomorrow, I'm gonna send Thomas $$$ for a SARD...
Originally posted by Chunger
Hmmm.. sounds like you covered everything... It may be the FPR. You weren't low on gas during these incidents of psi fluctuation? Just a shot in the dark. Too bad you aren't local to me... i would've lent you mine.
Hmmm.. sounds like you covered everything... It may be the FPR. You weren't low on gas during these incidents of psi fluctuation? Just a shot in the dark. Too bad you aren't local to me... i would've lent you mine.
07-08-2002, 09:54 AM
#11
Originally posted by mtrai760
I did disconnect it when I pulled the TB off to change the FPR, but I haven't touched it since, and I don't think it would make a difference, I thought Fuel pressure was controlled by vacuum, not by the ECU? I'll pull codes tomorrow and see if it tells me anything...
I did disconnect it when I pulled the TB off to change the FPR, but I haven't touched it since, and I don't think it would make a difference, I thought Fuel pressure was controlled by vacuum, not by the ECU? I'll pull codes tomorrow and see if it tells me anything...
07-08-2002, 12:55 PM
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Well I just pulled my codes= 0505, everything normal I was actually hoping for a code, that way I would know how to fix the problem. As I understand it, fuel pressure is controlled by vacuum, the MAF tells the ECU how much air is flowing through, which in turn controls how long the injectors stay open for. The less vacuum, the more your fuel pressure rises, that way under throttle you get a rise because your vacuum goes down to about 5in-hg, and if your boosted or run a dry nitrous kit, your FP really goes up...
I was actually hoping for a code, that way I would know how to fix the problem. As I understand it, fuel pressure is controlled by vacuum, the MAF tells the ECU how much air is flowing through, which in turn controls how long the injectors stay open for. The less vacuum, the more your fuel pressure rises, that way under throttle you get a rise because your vacuum goes down to about 5in-hg, and if your boosted or run a dry nitrous kit, your FP really goes up...
Originally posted by emax95
I thought the MAFS told the ECU the amount of air flow which is traveling through air filte/TB? Then the ECU send's out fuel pressure accordingly. When my MAFS went out on my I30 my car ran super rich and the idle use to pulsate up and down because the car was running so rich. The only time the car ran right was when I first started it up when the engine was cold.
I thought the MAFS told the ECU the amount of air flow which is traveling through air filte/TB? Then the ECU send's out fuel pressure accordingly. When my MAFS went out on my I30 my car ran super rich and the idle use to pulsate up and down because the car was running so rich. The only time the car ran right was when I first started it up when the engine was cold.
07-08-2002, 01:58 PM
#14
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Fuel pressure is only controlled by the FPR. If your vacuum reading is steady then it's the AEM for sure. It's either a poor design, defective or the spring is too soft to control that much psi.
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