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Discussion Starter · #1 ·
He has at least a 50-60% loss of power. We use to race and it would be pretty even, sometimes I would win, sometimes he would...but now, I'm stomping him by 12-13 cars...its awful...lol...he got beat by a Dodge Nitro the other day, and I felt embarassed for him...lmao...back to the car, it seems to run perfect, no engine misses, but it has a hard time taching up...Any ideas as of what's wrong with it, would be nice...thanx guys...
 

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tranni or rear end are on there way out seems to me......

check his fluids levels for possible leaks. When my camaro's rear leaked i couldt accel for ****.

edit: Does he have catylytic converters? The could be backed up and no pressure is escaping
 

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Discussion Starter · #3 · (Edited)
He doesnt have cats...and we just changed his gear about 6 months ago to a 3.73 and changed his tranny too...but he did blow a hole in his intake about 3 months ago, and after we had it replaced, it just doesnt perform at all...
 

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Discussion Starter · #5 ·
I just posted on here that he doesnt have cats...awhile back though, we put turn-downs right out of his flows...but, I don't think it should make a difference...
 

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but he did blow a hole in his intake about 3 months ago, and after we had it replaced, it just doesnt perform at all...

This is the root of the problem, re-check your work. Sounds like a fuel/air mix problem
 

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i would take the intake off. put all rew gaskets in there and make sure it in 100% ok. a vac leak will kill your car
 

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+1. Recheck your manifold. New gaskets and I had to repleace the o-rings on the fuel injectors when I changed mine
 

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Discussion Starter · #12 ·
We have been playing around with his car and we re-shimmed the rear-end and it's not that...we raced the other day, my 08 Colorado (4cyl. 5spd...gas saver...lol) and I got him by a half a truck...we noticed that it just takes forever to tach up, but when we finally reach 5400-5500 rpm (our shift point) it still grabs pretty hard and even chirps in 4th...and for some reason it's strong until around 3000-3200 rpm and then it's like it falls on it's face...and then takes forever and a lifetime to tach up, over-exaggeration, but it does take a long time...and it's even starting to piss me off, partly cause I'm working on it and it's got me by the balls...any help, would be much appreciated...later guys...
 

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I would pull all plugs and inspect. They will tell you if it is rich or lean or good.
Lean can be caused by several things. Buy yourself a fuel pressure gauge. about 50-100 bucks at a hardware store. make sure you get one with a hose log enough to reach from the fuel rail to your windshield. fasten the gauge to a windshield wiper (I use tie-wraps). Road test it and record pressures under load. A 2000 4.6l mustang should have 30-45 psi under full load. If this checks out you have ruled out your fuel system (if all 8 injectors failed the same amount you might as well buy a lottery ticket). Next open the oil cap, if you can see vapour/smoke and there is alot of flow out you have excessive crankcase pressure which means blow-by which means base engine failure. If not inspect your MAF sensor. Check for contamination, a MAF sensor works by heating a wire and measuring the current required to keep it at a temperature. As the volume of air passing over it increases more current is req'd to keep it at that temperature this way it knows how much air is entering the engine. If there is contamination it can cause an insulation phenomenon which causes the engine too think there is less air entering the engine then there actually is which in turn causes lean fuel mixtures. The same will be caused by vacuum leaks or leaks in air inlet tubing after the maf. As all unmetered air will cause a lean condition. A little ether or propane or butane introduced to suspect leak areas will cause the engine to rev up and a vaccuum leak is confirmed. If it does not it can be ruled out. Don't try using brakeclean or wd40 because it only shows up on fuel trim pids not engine rpm as the IAC is duty cycled to maintain a preset rpm and adjusts to these less potent hydrocarbons. As for the MAF itself, unplug it and drive it. It will not idle well but the fuel trim tables it resorts to in failure mode gives as much power as stock (seat of the pants feel I'm sure it is different on the dyno but good enough for diagnostic purposes). Another possibility is a stuck egr valve (highly unlikelyto run good at idle). but it is a possibility. If you have a vaccuum leak it usually has a fluctuating-high idle. this is due to the maf sensing less air than it is actually getting so the engine runs lean then the 02 sensor senses this adds fuel then read rich and so on. If you have access to a dataloggind scan tool look at your fuel trims -short term or long term fuel trims beyond -10% mean running too rich and +short or long term running above 10 % mean running lean. If all this shows no fault disconnect the a/c compressor clutch. If the WOT cutout relay is faulty you will not get a/c cutout under WOT and lose approx 10-20 hp (this is also highly unlikely). If you are sure the clutch is good look for a dragging or stuck brake or e- brake.
Feel the wheels after a test drive, the one with the dragging brake will be very hot. If all this shows no fault change the plugs even if they look good. I had this exact concern 3 times could find nothing wrong, decided to change plugs cause they were out anyway and presto problem solved. I don't know why but, it fixed the problem. (all were aftermarket plugs). Also if you do suspect a vacuum leak and have access to a datastream capable scan tool
monitor your shortterm fuel trims and o2 sensors (11 and 21) while introducing a combustible to suspect vaccum leak area. If there is a small leak the fuel trims will go - (because the computer is taking away fuel) and 02 voltage will stop switching and stay high because of the combustible causing a rich condition. Hope this helps.
 

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check to make sure his intake manifold isn't cracked
 

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Also buy yourself a vacuum gauge and google poor engine vacuum info to find yourself all of the diagnostic capabilities of a vacuum gauge, and how to apply it to diagnosing base engine problems. BTW weak valve springs can cause problems at higher rpm.
 

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a cracked intake will show up on a vaccuum gauge (very slightly) and using the vaccuum leak test methods I explained earlier.
 

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a cracked intake will show up on a vaccuum gauge (very slightly) and using the vaccuum leak test methods I explained earlier.
didn't even read ur post. way to long and way to late
 

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Discussion Starter · #18 ·
I finally got the problem fixed...we bought a diablo programmer/code reader...and found out that the coils are weak/bad...thanks for the help guys...
 
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