Just bought a 96 Ford 4.9L started up ran fine. I knew it was a project when I bought it, the guy said it only needed cats drove fine for about 50 miles then threw the codes p1131 p1151 p1507 rough idle, won't throttle, bogs down when I try to give it gas. If I rev it while starting it will rev fine but if I let off it goes back to rough idle can't throttle.
Anyone had this issue or have any suggestions? I bought an IAC anyways. I don't want to just throw parts if it's something else. I am replacing the o2 sensors.
thanks.

 

Welcome to the site!

Given the codes apparently came on all at once, would look for something else being the true cause, with the codes of the oxygen sensors and the IAC just being the results of that cause.

Wondering whether something happened to the fuel system, may check the fuel pressure while running, at the rail - thinking along the lines of a plugged filter or pickup screen, or maybe even the fuel pump losing its do-right???

Suggest you have the right idea - test and troubleshoot before replacing. IMO, blind replacements eat a hole in the wallet fast, quick, and in a hurry, as well as risking installation of a bad-out-of-the-box part so to add another problem to the pile.

Good luck, and keep us posted.

 

Don't change ANY parts until one fails a published test. Neither the IAC nor the HEGOs affect the throttle function, and replacement HEGOs are not likely to be as good as originals. Get a digital multimeter, and TEST things. Even a $15 one will work fine, but a $30-90 one might be a better investment.

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The Haynes manual explains how to test nearly everything on the truck, and there aren't many things to test on these antiques. Follow the links on this page:

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This page shows most of them:

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Well I tested all the sensors under the hood that I could find everything is getting power but not sure if they're working correctly. I can't find much in the Haynes manual about this problem. I haven't tested the fuel pump yet, only had a short time while the baby took a nap.
the fuel filter looks new, also where is the tank selector valve reservoir at? I've read a little about it but can't find it. To switch fuel tanks doesn't work and I can't find the reservoir, I see a couple lines hanging from the rear in front of the rear tank.
Thanks.

 

...but you didn't list them, or post pics of each one so we'd know what you've done.Then you DIDN'T test any of them.Don't look for this problem - look for how to test the sensors & actuators. But it's easier to find them in the links I posted above.There isn't one, so don't worry about it....but you didn't post pics of them.

 

So if there is no valve reservoir does the switch just supply power to the pumps and it switches that way? Is there no return lines? Overflow? Just curious as to what I've been reading thanks.
Yeah sorry I don't have a lot of time, baby was taking a nap only could get out and test a few things. I just tested the MAF sensor by unplugging it and running, the truck idled better and was able to rev up without it bogging down. I'm guessing that's my cause, I'll swap that part out run it and see if I can get it to throw codes again.
Is there anything that can make those go bad so I know what to look for? It was getting about 12v so I figured that was ok.

 

Read this page:

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Unplugging things is NOT testing. Guessing is expensive & usually a waste of time & money. No, they don't usually go bad until someone messes with them. DO NOT discard or trade in any original parts that have NOT tested bad - you'll probably need them soon.

 

Thanks for that link I'll read into it. Here's a picture of the lines I said were disconnected.

 

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Ok finally was able to test the fuel rail pressure, I was getting about 39 PSI and holding would drop a couple PSI when I revved it. Note I wouldn't get any pressure with the engine off. Once started it built pressure. Moved it forward about 5ft pressure dropped to about 10 rough idle I relieved the rest with the gauge and it died.
​​​​​​Now before condemning the fuel pump, could the regulator or anything else have a play in this?