car will rev past 4,000rpm but wont drive past 4,000 rpm - MustangForums.com



5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 06-11-2014, 10:00 AM   #1
BaltRavens
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Default car will rev past 4,000rpm but wont drive past 4,000 rpm

What are some possible problem areas? Its a 94 GT 5spd. At wide open throttle once you hit 3,800-4,000rpms its like its hits the rev limiter almost. The exhaust pops and crackles like crazy it sounds horrible. However sitting in the driveway idling I can floor it and it will bang off the rev limiter no problem.
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Old 06-11-2014, 11:26 AM   #2
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check it for codes first. Then the basics next, when was the last tune up? Check the distributor shaft they eat them also the pick up in the distributor goes bad often in those cars. Fuel pressure check.
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Old 06-11-2014, 12:08 PM   #3
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No codes being given. I have taken the car to 3 different shops and no one can make heads or tails out of the problem. They all have agreed its something electrical? The last guy I took the car to wanted a hefty price tag to fix the car. Couple grand to start... not something I am willing to pay. He even put the car on a dyno but apparently it didn't give him heads or tails of what the problem is exactly.

Saturday I have another mechanic who is going to look at it. I am just trying to get some ideas before I take the car to him and we work on it. The car starts and runs fine. It idles fine. Its just gets ti 3800ish RPMs and goes into a fit under wide open throttle.
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Old 06-11-2014, 01:02 PM   #4
88 orangepeel notch
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Maybe do a sweep test on the TPS, looking for a dead spot near WOT.
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Old 06-11-2014, 01:58 PM   #5
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Under load (when driving) the car will use way more fuel, have a bigger spark, and have higher timing than when just sitting and reving.

Could be a Coil, bad wires or a combo of both.
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Old 06-11-2014, 02:23 PM   #6
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Quote:
Originally Posted by Derf00 View Post
Under load (when driving) the car will use way more fuel, have a bigger spark, and have higher timing than when just sitting and reving.

Could be a Coil, bad wires or a combo of both.
This or something as simple as clogged fuel filter.
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Old 06-11-2014, 07:53 PM   #7
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check to see if spout connector fell out
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Old 06-18-2014, 08:53 AM   #8
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My buddy ran his car out of gas. He walked to the gas station, grabbed a gallon, and put it in the car. It would start and idle, but it would not drive or rev past a certain rpm. Long story short ...Running it out of gas caused the fuel pump to suck up junk from in the tank. He replaced the pump and filter, and all was good. Might be something you should look into.
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Old 06-18-2014, 08:38 PM   #9
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I'm having almost the same issues.. This is my story: Installed a 75mm TB, with my IAC and TPS now the cars bucking at around 2,100rpms under a load,and I can't accelerate passed that. Stalls a little while cold at the same rpms, and again around 4,000. I also replaced the TFI module with an accel tfi at the same time. I'm thinking either the TFI is bad or the TPS isn't setup right/is bad.

I also put in a new hypertech coil about 2 weeks ago.

I drove home from work pissed off and tired after dealing with adjusting the tps voltage to .98 with KOEO
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Old 06-22-2014, 01:05 PM   #10
BaltRavens
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I changed fuel filter. The only code thrown is code for o2 sensor but I replaced them and it didn't change... not sure whats up with that? I had a local performance shop look it over for vacuum leaks and set timing which they did and no leaks and time was good.

The car has 1.72RR(overkill imo) with GT40P heads. I am thinking when the guy installed these parts(guy I bought car from) he didn't install the valve upgrade kit for the bigger rockers. I ordered the upgrade kit from latemodel last week it should be here tomorrow. We will see if that helps the car out any.

I am at a pretty big loss mentally with the car I can't figure it out. I have replaced alot of sensors. I have had it to 3 mechanics who wasn't sure. I also had it to a dyno shop. The dyno shop wanted $2,000 for starters to fix the car but wouldn't give me heads or tails of whats actually wrong with the car... dyno shop wanted to start with new fuel rails, intake manifold, heads, injectors. It was more than I am willing to spend right now.

But for everyday driving the car runs fine its just underload it not at 100% power and like I said it hits its rev RPM limit at 3800-4100ish RPMs... It does search for idle a bit not bad. When you rev it to say 3k RPM. It will take a few seconds to descend back to idle RPM. It will search for idle RPM for about 3-4 seconds surging from 950 to 1300rpm.
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