Engine holds at 3,100 RPM - First Post -

Fivestangs

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Hey everyone! First time poster here!

A friend of mine gave me this '96 GT. He has too many cars. Only thing was he'd pulled the heads. I had to put it back together! I'd done plenty of 302, 351W, 351C, and FE builds. I had never worked on a 4.6 before. I have an '03 Mach 1 but it is stock and low mileage.

Well I got it together and have been driving it as a daily driver for a few months now. Alternating between it and my '84 VW Rabbit. I began to notice that after about 15 miles it can no longer rev past 3,100 RPM if I floor it. It drives fine otherwise. Which is why I probably didn't notice it for so long. I usually have my "fun" the first few miles and then settle down the rest of the trip. Does anyone have any ideas? To help out I will list the few mods it has.

CAI
PI intake and cams
Shorty headers
BBK off-road H-pipe with a pair of Magnaflow high flow cats
10 series flowmasters
Steeda Under drive pulleys on crank and waterpump

It is a 5 speed.

It still has the 2.73 gears (UGH). That will change though!

When I got it.
96 GT (1).jpg

The heads were in the passenger seat!
96 GT (3).jpg

And here is when I got it running!
96 GT (2).jpg
I have since replaced the headlights.
 

Fivestangs

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Yes he is pretty cool! He mostly collects 68-71 Torinos and 67-70 mustangs. He had picked up three 69 Torinos and needed the parking spot!

It has three codes but from what I have read. They are emissions related and shouldn't cause this.

P0136
P1405
P1443

I can reset these codes and if I drive it "like a normal person" (as my wife says) they don't come back. That was how I passed emissions for the last time it was required. This issue doesn't go away with them though.

Other than this issue, the car runs and drives great! It really only shows up after about 15 miles. Even then it is only if I floor it. Otherwise you'd never know there was an issue. When I first noticed it I thought it was pulling timing. I switched to premium fuel made no difference. On the way home yesterday I floored it to see what would happen. It slowly revved up to 3,100 RPM and then it stayed there until I let off. After I couldn't find anyone mentioning something like this I decided to ask here.
 
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96blak54

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So no bogging, no change in engine noise like their is a struggle, doesnt matter what gear is used....3100rpm is it?
 

Fivestangs

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It feels like it's pulling timing, or like the traction control kicking in on my Mach 1. Only if I let off half way on the throttle it picks up some power but not all it normally has. The engine sounds fine. It just loses most of it's power and reaches a point at 3,100 RPM where it just will not rev any higher as long as it's floored. Again all of this starts happening after about 15 miles. It runs strong up to that point. It's not overheating, no pinging or any funny noises coming from anywhere.
 

evilcw311

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Put a meter on the tps and cycle it back and fourth while the car is cold. Then drive it around and when it starts acting up immediately pull in somewhere and meter it again while cycling it back and fourth. See if there is any changes.


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96blak54

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^
Where i was headed!

Meter the tps or try unplugging it, then go for a drive
 

Fivestangs

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I haven't had a chance to check the TPS. However, I have been doing more testing as I drive. I have found that it appears to be related to ambient temperatures. Below 80 degrees I never have an issue. It runs hard all the way to the redline no matter how far I go. Somewhere between 80 and 90 it starts to feel like it's pulling timing. Once it reaches the mid 90's it starts to do like I described in the initial post.

All this testing is done in first gear. With these 2.73 gears when I hit the redline in first I am already at 50 MPH. I would be breaking the speed limit everywhere there was one if I tried it beyond that!
 

evilcw311

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I haven't had a chance to check the TPS. However, I have been doing more testing as I drive. I have found that it appears to be related to ambient temperatures. Below 80 degrees I never have an issue. It runs hard all the way to the redline no matter how far I go. Somewhere between 80 and 90 it starts to feel like it's pulling timing. Once it reaches the mid 90's it starts to do like I described in the initial post.

All this testing is done in first gear. With these 2.73 gears when I hit the redline in first I am already at 50 MPH. I would be breaking the speed limit everywhere there was one if I tried it beyond that!

Very well be the iat then.


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Fivestangs

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Both sound like possible culprits.

The car was last tagged in '08 when I got it. I was afraid it would be like my '84 Rabbit convertible. I got it for $200. It was in great shape but it wasn't running. I ended up having to replace the fuel tank, pump, accumulator, a couple of injectors and the fuel filter! If I get off just replacing the fuel filter after as much time as this one sat I feel lucky!

The IAT looks to be the original. A replacement has been ordered and it would be a cheap fix if that is it.

Thank you all for your help and suggestions. I will report the results!
 

Paladin1001

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That is a really nice free car, most of the time free cars are turd bags. Either way you win in this scenario, congrats.
 

Fivestangs

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Thanks! Yes I couldn't pass it up! I figured even if it took what the Rabbit took to get running it was worth more than that. He even gave me a brand new timing set and gaskets. I chose to add the under drive pullies, PI cams, intake, shorty headers, off-road H with Magnaflow cats. I could have had less than $200 in it otherwise. I'm still only in it about $1,000 all together.

I think it may be the fuel filter clogged up as mentioned above causing these issues. I hope it is! It was running crappy again yesterday but was almost empty. I pulled in to a gas station and filled it up. When I left I found it to be running great again! My hope is that the filter is so clogged it is causing extra strain on the pump. Heating it up and making it less efficient. I will try to change the filter this weekend. I guess I will be driving the Rabbit all week if I don't. I'm not risking the pump until the filter is replaced.

Thanks again for all the help!
 

Fivestangs

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Well I am happy to report that OLD H2S appears to have had the answer! Not only do I no longer have the issue anymore, but the car feels much more powerful overall from start to stop! It feels like a different car!

Thank you all for reading this and offering advice! For a first time poster I could not have asked for more!

Likes all around!!!
 

evilcw311

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Well I am happy to report that OLD H2S appears to have had the answer! Not only do I no longer have the issue anymore, but the car feels much more powerful overall from start to stop! It feels like a different car!

Thank you all for reading this and offering advice! For a first time poster I could not have asked for more!

Likes all around!!!

Now it’s time to get a build thread going to keep track of this adventure!!!!!


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