Power Loss Issue Can Anyone Voice An Opinion

[Juiced_97Cobra]

Hey guys I just picked up a 93 Cobra from my dad and drove the car home an hr away and seemed fine but never nailed it though at anytime. I took the h-pipe and cat back off and installed a new off road x and flowmaster cat back. Car idles fine but seems as if it has a miss as I take off and when I smash the gas in 3rd gear or so at 2500-3500 rpms the car loses all power like car has died until I let off the gas then it will smooth out. Car has a 306,vortech s trim,twisted wedge aluminum heads ect ect. Also has an external t-rex pump. It has a fuel pressure gauge on the pillar and it reads right around the 30 marker at idle. Car revs fine when sitting still no missing just seems to be under a load. Also no check engine light on either. Any thoughts what it might be or I can try? I do know he has hardly ever drove the car in the 4yrs he owned it. I did fill up with premium gas and added a bottle of water remover and lucas fuel cleaner. Car has been inside at all times. Thanks!!

 

[kcp203]

Start with cleaning the MAF sensor (this is #1 because it won't cost anything to try). I have had MAF related issues when running a new K&N filter, as sometimes the oil on the filter seems to foul the sensor wire.

If that doesn't do it, try changing out the coil. Also check your plug boots for cracks. This sounds like an ignition issue under load.

 

[richstang]

This sounds very familiar. A buddy of mine just picked up a very low mile '92 SAAC convertible with similar issues. Initially he checked the wires and plugs. He found one slightly loose plug and a very loose wire. Even after that fix the car ran rough at wide open throttle. Then he replaced the coil and it seemed to solve the issue.

 

[Juiced_97Cobra]

Thanks guys. Dad said he messed with the boost retard knob he thought. Again this car has sat for a long time only getting started and moved around once in a while. He has the boost retard knob set on 2. It's a 0-3 setting.

 

[WillyB93]

I would lean toward the Ignition Control Module, how modified is the car? If you have a supercharger on the car, with the timing and boost retarder set wrong and causing it to loose power also.

 

[Juiced_97Cobra]

Motor is a 306 vortec s trim twisted wedge aluminum heads msd box ported stock intake t-rex external pump, 65mm tb and 70mm maf,full exhaust ect ect. I have been reading up on it as much as possible and a lot of people saying that the knob being set up on two maybe the whole issue. Some saying try 1/2-1 range and that may cure it.

 

[Juiced_97Cobra]

I adjusted the knob tonight down to 1/2 and drove it and worked my way back up to almost 2 and the car had no changes. I was watching the fuel gauge on the pillar and as I hit the gas and it stalls out the pressure drops down in the 20's. At idle it's 30 don't believe at any given time I seen the gauge get over 34ish.

 

[kcp203]

I'm still leaning toward an ignition issue, not fuel system. Either the coil, MSD box, or bad main ground. If not that, then vacuum leak, although that would most likely throw a code, usually showing a lean mix.

 

[walt460]

FB should be 39 psi.

 

[kcp203]

FB should be 39 psi.

You're right. I wasn't paying attention. (plus I've spent most of my time the last few years working on my old, carbureted mustangs and don't have to pay much attention to fuel pressure). However, 30 psi doesn't seem that out of the ordinary for the car at idle if vacuum is hooked up to the regulator. I may be wrong, but I think 39 psi is with vacuum unhooked from the regulator and plugged.

As for fuel system, what FP regulator are you using? You also don't say what cam you have, as that will affect vacuum and FP drop under load that you see at the gauge.

I've never run a supercharged car, so someone else here has to chime in if they think it is SC related.

 

[Juiced_97Cobra]

Well guys I got it figured out. There was a custom stereo system in the hatch and I had pulled it all out and I guess I cut the ground wire to the external t rex pump. I seen the relay itself was grounded so I assumed that was how it was grounded and the other ground wire coming from pump didn't need grounded too. Luckilyi had the schematic with all the records that came with car

 

[kcp203]

Glad you found it. Electrical/ground issues are the worst things to track down.