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Discussion Starter · #1 · (Edited)
I'm wondering if anyone has ever encountered this problem before and hoping the mods show up in my signature.

Sorry about the torque numbers, I don't have them. The tech removed my sct chip, and made a rip. The car made 310 rwhp. He then reinstalled the chip and made several a rip and got 270 rwhp. We noticed the air fuel mixture dancing around. Without any adjustments he makes another rip and the car makes 290. 12 rips in total, and the horsepower and air fuel mixture swing tremendously. I purchased the car with a trunk mount battery grounded to the bumper. I've since grounded the battery to the block with 1 ga, and the block to the chassis. The tech didn't want to even attempt a nitrous tune with the air fuel dancing around. He disabled several sensors during the rips to isolate the problem. There isn't any consistency. The car also makes peak power at 4600 rpm which isn't consistent with my cam specs. 310 rwhp doesn't seem good enough with my setup, especially on a dynojet. I may be lacking details someone would need to come to a conclusion. The inconsistency in horsepower and the powercurve don't seem right to me. Has anyone seen this before?
 

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I'm wondering if anyone has ever encountered this problem before and hoping the mods show up in my signature.

Sorry about the torque numbers, I don't have them. The tech removed my sct chip, and made a rip. The car made 310 rwhp. He then reinstalled the chip and made several a rip and got 270 rwhp. We noticed the air fuel mixture dancing around. Without any adjustments he makes another rip and the car makes 290. 12 rips in total, and the horsepower and air fuel mixture swing tremendously. I purchased the car with a trunk mount battery grounded to the bumper. I've since grounded the battery to the block with 1 ga, and the block to the chassis. The tech didn't want to even attempt a nitrous tune with the air fuel dancing around. He disabled several sensors during the rips to isolate the problem. There isn't any consistency. The car also makes peak power at 4600 rpm which isn't consistent with my cam specs. 310 rwhp doesn't seem good enough with my setup, especially on a dynojet. I may be lacking details someone would need to come to a conclusion. The inconsistency in horsepower and the powercurve don't seem right to me. Has anyone seen this before?

Did you check the fuel pressure with it running. You may have a bad regulator, bad fuel pump or a bad ground on the pump.
 

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Discussion Starter · #3 ·
Thanks for the response.I'm running 40 pounds right now. Tested the diagphram in the regulator. It's an aeromotive fuel pump and regulator with about 400 miles. The fuel pump is hooked to a toggle switch and grounded to the battery. I bought the car with the fuel pump on a toggle, don't see the point though. Since half of the harnesses on the car unplugged, I'm sure it will be fun tracing the problem if it is in fact a ground!
 

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Could be the tune or the chip is wonky. Was the 310 without the chip at least consistant? If everything is stable without the chip, I gotta suspect that is your problem.
 

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Discussion Starter · #5 ·
310 was without the chip. He didn't do a second rip without. If the dynojet is truly 12-15% higher than a mustang dyno, then my horespower isn't much more than stock! Since the dyno is 2 1/2 hours from my house, the chip may be worth a try. The tech says a car may lose 3-5 horsepower between rips due to heating, but 10-12% is unheard of. Does the chip control the amount of fuel being distributed, or injector pulse?
 

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I'm wondering if anyone has ever encountered this problem before and hoping the mods show up in my signature.

Sorry about the torque numbers, I don't have them. The tech removed my sct chip, and made a rip. The car made 310 rwhp. He then reinstalled the chip and made several a rip and got 270 rwhp. We noticed the air fuel mixture dancing around. Without any adjustments he makes another rip and the car makes 290. 12 rips in total, and the horsepower and air fuel mixture swing tremendously. I purchased the car with a trunk mount battery grounded to the bumper. I've since grounded the battery to the block with 1 ga, and the block to the chassis. The tech didn't want to even attempt a nitrous tune with the air fuel dancing around. He disabled several sensors during the rips to isolate the problem. There isn't any consistency. The car also makes peak power at 4600 rpm which isn't consistent with my cam specs. 310 rwhp doesn't seem good enough with my setup, especially on a dynojet. I may be lacking details someone would need to come to a conclusion. The inconsistency in horsepower and the powercurve don't seem right to me. Has anyone seen this before?
Aside other mechanical problems that may be causing the low rpms, looks like you may be getting ripped. If there's a problem in the ground circuits..... why doesn't it affect the system w/out the chip? All you have to do is run the KOEO/KOER self test routines and check if there is something causing failure codes to show up.... or a voltage drop test of the main ground circuits (including the EEC grounds) will help in ID'ing it as a possible ground problem.

Have I seen that before?..... yep, and different items were the ones that caused it...... only two were ground related, but the symptom was present with or w/out the chip installed.
 

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Discussion Starter · #7 ·
I will give that a try Joel. The car had trouble starting after it was warm, so the tech leaned it up some which has helped. I ran the car the other night, and flames shot from the exhaust when I speed shifted. I pulled the plugs, which are all brand new, and they looked super lean, except for # 6. #6 is filthy and black. I have an aeromotive pump with dual filters and about 500 miles. My guess is maybe it is stuck open. I'm going to move it to another cylinder to see if the problem follows the injector. The called JMS Chip who tuned the car and spoke with the tech about my findings and he feels this could certainly cause the problem, but would have gotten a false (lead or read I think) if a cylinder wasn't burning fuel. The whole setup has less than 500 miles on it, brand new MSD distributor. Since the dyno is 2 1/2 hours from where I live, I was also going to change the mass air meter, which is also new, to address the variation in air/fuel ratios when no adjustments were being made. Can open injector cause variations in a/f ratios when no adjustments were made. Since number 6 is the only black plug, I tend to shy away from the mass air meter. Your thoughts.
 

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moving the injector is a good idea. If you have a multimeter that has a "peak/valley hold" feature, you could monitor the voltage at an injector by piercing a wire whike doing a run to see what the voltage across an injector is during a run. If the return wire to the trunk battery is a restriction, it will show up at the injector as a lower applied voltage. The EEC has a function to correct for varying voltage to the injectors, but I'm not remembering what it's limitations are.
 

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Discussion Starter · #9 ·
thanks for the advice. If moving the injector doesn't work, I'm gonna try that also. It's a brand new MSD distributor and MSD wires, I wonder if a bad connection from the plug to the wire could cause this condition. I haven't tried it, but would the car barely idle on 7 cylinders. If that's the case, then moving the injector is the next logical step, then what you and Joel mentioned.
 

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Discussion Starter · #10 ·
thanks for the advice. If moving the injector doesn't work, I'm gonna try that also. It's a brand new MSD distributor and MSD wires, I wonder if a bad connection from the plug to the wire could cause this condition. I haven't tried it, but would the car barely idle on 7 cylinders. If that's the case, then moving the injector is the next logical step, then what you and Joel mentioned.
 

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Discussion Starter · #11 ·
I swapped #5 and #6 injectors, put a new clean plug in #6, drove the car about 20 miles, # 6 is still fouling out. Gonna swap the plug wires next to see if that could be causing the problem. Does anyone think this could be a valve issue. If the spark plug wire doesn't solve the issue, should I change the injector harness? Is there such a harness?
 

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I'd buy a cheap noid light to see if the injector harness for that cylinder is firing.

Valve issue don't normally result in rich conditions.
 

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Discussion Starter · #13 ·
thanks tmos, I'll give that a shot
 

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Discussion Starter · #14 ·
Tried the noid light, injector pulses like the others. I also put a new cap and rotor, swapped wires on 5 and 6, #6 continues to foul out. Put another ECM in the car and a fresh plug in 6, that cylinder still fouls out. Is the valve train the next step? I am wits end with this problem
 

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Check your fuel filter again just to be sure. You could have a tank full of rust.
My buddy has a vert with a carbed combo of a 306 w/185 heads, comp xe282hr /c-4. The car is a slug on the motor, but with a 200 shot it runs mid 10's.
 

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I'd be suspect of the rings at this point. Have you done a warm compression test ot leakdown?
 

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Discussion Starter · #17 ·
I haven't checked the filter. It's a brand new aeromotive sumped tank. Seems like a rusty tank wouldn't pick on #6 but I'm gonna chech anyway. TMOS, compression 198-202 in every cylinder. Leakdown next, valve stuck? I'm hoping it's in the valvetrain. Your thoughts?
 

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I don't see how a sticking valce would cause fouling, but if an intake guide where scored, that could put some oil in the cylinder
 

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Discussion Starter · #19 ·
Not sure if fouled is the best terminology, it's just a noticeably darker than the others, as if the fuel isn't burning all of the way. Do you know of a way to determine a 306 vs 347 without taking the motor apart, although it's an unrelated issue.
 
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