94 Stang Power Loss Problems

94cobraslow

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Jun 18, 2015
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ok im new to this forum!!!!!


i have a 94 cobra 120k on it
having a problem its losing power/ slugs down/ no power at time!


im check the tps voltage and adjusted it! was at 1.024v adj down to.980v
cleaned the mafs
car has or h-pipe so know its not cat problem
has code 181 189 136 172 lean codes
checked fuel pressure and this where i think my problems at but want some input on what other ppl think!
key on engine off fuel pressure read 36psi. engine running 35psi. pull the vacuum hose off regulator jumps to 40psi sound good right? but when u open the throttle or increase rpms the fuel pressure drops to 25to 28 psi!!
so iwas thinking this is a bad fuel pressure regulator or pump what do yall think?
 
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key on engine off fuel pressure read 36psi. engine running 35psi. pull the vacuum hose off regulator jumps to 40psi sound good right? but when u open the throttle or increase rpms the fuel pressure drops to 25to 28 psi!!
so iwas thinking this is a bad fuel pressure regulator or pump what do yall think?

Most likely the pump. While it's over kill for your application I would still get a Walbro GSS340 255 lph fuel pump. About $100. Because these systems return excess fuel back to the tank the high flow rate isn't an issue.
 
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hey toyman just looking at mod list how do u like the kb blower? and and how must is a full set up? I was thinking about one get the kb blower for this one! but I have had the vortec v2 on my last 5.0 and it work nice to!
 
I wouldn't suspect the regulator because it's doing what it's supposed to do at idle. Probably a fuel flow problem, I'd start with the filter and then the pump (checking the electrical connectors while you're at it). It's possible the restriction from the previously backwards filter wiped out the pump, but it wouldn't have harmed the regulator. Or the pump is just old and worn, or the sock is gummed up if it ever sat a while. If you do get Walbro (good pumps) be sure to get genuine Walbro, a lot of knock-offs on eBay.
 
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ok had some problems with parts!!! was sent the wrong parts!! but i did install my areomotive adj regulator and my volt gauge, wideband gauge and fuel pressure gauge! hose was bad on the fuel pressure gauge so wait on new pressure hose for the gauge and still waiting of the pump first one was wrong!!!

ok here the ques? i adj the fuel presssure up to 40psi at idle but when i rev it it still drops to 30psi!!!! the wideband say the car goes lean as soon as u touch the gas!!
so when i get the pump in and put in!

IF IT DOES THE SAME THING WHAT ELSE COULD IT BE?
 
I usually hope it's not the pump too (it's a bit of a hassle), but there's little reason to suspect that it'll do the same thing after you put the new one in. At least it's still working so you won't have to change it with a full tank of gas. In fact, if you're able, drain / run out the gas before you start. That way you can ensure that you have fresh fuel. I had to replace my dad's fuel pump on his '96 with <2k total miles on it because it sat in the garage for too many years with the same tank of gas, varnish will clog up the filter sock pretty quickly. Change the pump, use a new sock, check your electrical connections for corrosion / melting and replace if needed, and I think you'll be just fine. Our fuel systems aren't that complicated. As long as the pump is in good condition (including the sock) and it's getting full electrical power, you'll easily get your 40psi at any rpm. The only other thing it would possibly be would be a kinked or damaged fuel line. Unless you have reason to suspect your line has been crushed (an accident or a poorly placed jack) it's very unlikely.
 
ok got the pump put in today pressure sit at 40psi and goes up on the rev now! haven't drove it yet to see if it gain power back! but I got one for yall some ppl shouldn't work on car! Start this hole thing out with the previous owner put the fuel filter in backwards and when I drop the tank today someone has put a walbro pump in but the fun part was when they put that pump in they broke thrle original filler tube grommet off and never got it out of the tank and it end up sucked up in to the pump
 
Sounds like you'll be good to go. Just an FYI, the fuel pressure should be set to around 39 psi with the vacuum line disconnected from the regulator. Then, when you put the line back on, it should drop to somewhere below 35 psi. When you rev, it should head back towards 39. If you're set to 40 psi at idle with the vacuum line connected, you might find you're running too rich.
 
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Ok put the new pump in adj the fuel to spec ! Was good for 3 days know the we start but wont rev up an no power! Pulled plug out and the tip is blue so I know it running lean as hell! SoS I'm going to recheck the fuel pressure to make sure the new pump didn't go out! Does anyone think the dizzy could cause this problem? I put a new one in 6 month ago because it failed or could the maf cause this? Im to the put a hammer sound good lol
 
Definitely re-check pressure, pull codes if any. If you find that is good, then disconnect battery and leave disconnected for at least 15 minutes. This will reset the computer's fuel adjustments. Then, see if you're good again for a few days.

If you find that's the case, your O2 sensors may be reporting a rich condition, causing the computer to lean things out over time. This could mean a problem O2 sensor, or even a leaky fuel injector (causing a legitimate rich condition as detected by the O2 sensor). O2 sensors I typically replace at mileage intervals preventatively. It's possible they got somewhat baked by the previous lean condition, this is tough to diagnose without a scope / datalog. To diagnose a faulty injector, you can pull all of the plugs to see if they're all equally running hot. You could also run a cylinder balance test.

Over-advanced ignition can cause the plugs to run hot too, along with pinging. I don't think a faulty distributor would cause that, but it could be that your timing needs to be re-checked. MAF should throw a code if out of range, and of course does impact fuel and timing. I'd test it before considering replacement, as they are kind of pricey to guess at.
 
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ok when i was on lunch took a quick look at it and fuel pressure setting at 38 key on engine off- key on engine running 38- when i can get it to rev fuel jumps about 10psi and returns to 38 to40 psi so pressure wise i thinking im good!! but i did back fire trying to rev in the intake so im thinking the dizzy out or timing! someone correct me if im wrong but doesn't the hell effect sensor on dizzy tell the injector when to fire? wait on my buddy to bring his nood set so i can check for injector pulses and still no codes so im going to try and disconnect the the battery and see if anything change to!