PI Intake Progress

spitfirees20 said:

Finally got it working! My dad and I took off the plenum, and the bolt that I broke off had a little bit sticking out of the intake. Luckily, it was enough to grab with plyers and pull out, and it wasn't cross threaded at all, so we were able to just get another bolt and fix that. Also, the new gasket I had between the plenum and the intake manifold had a shred in it, (probably from me over tightening it ) so we fixed that also. We took off the fuel rail, cleaned all of the injectors and electrical connectors, and while we were at it replaced all of the spark plugs. Also, one vacuum line was old and ripping at the end, so for now we just cut the end off and put it back on, but I'm going to replace it. Runs like a champ now! Thanks for your help everybody.

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I'm not surprised the gasket and vacuum line were what were causing headaches. These 4.6's are real finicky if they are not asssembled perfectly. You should learn to use a torque wrench and look up the torque numbers in the owner's manual. BTW, how do you like the new power curve? How about your torque? My low-end torque decreased slightly but my power band is much better above 3000 rpm.

This type of experience will make you appreciate when things go right!!!

Glad to hear that its running good.

spitfirees20 said:

Finally got it working! My dad and I took off the plenum, and the bolt that I broke off had a little bit sticking out of the intake. Luckily, it was enough to grab with plyers and pull out, and it wasn't cross threaded at all, so we were able to just get another bolt and fix that. Also, the new gasket I had between the plenum and the intake manifold had a shred in it, (probably from me over tightening it ) so we fixed that also. We took off the fuel rail, cleaned all of the injectors and electrical connectors, and while we were at it replaced all of the spark plugs. Also, one vacuum line was old and ripping at the end, so for now we just cut the end off and put it back on, but I'm going to replace it. Runs like a champ now! Thanks for your help everybody.

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Glad you got it and that it was a minor fix. An important lesson I've learned working on cars over the years is to never overlook the simple answers...

Mel96GT said:

I'm not surprised the gasket and vacuum line were what were causing headaches. These 4.6's are real finicky if they are not asssembled perfectly. You should learn to use a torque wrench and look up the torque numbers in the owner's manual. BTW, how do you like the new power curve? How about your torque? My low-end torque decreased slightly but my power band is much better above 3000 rpm.

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it was not the gasket and vac line, that would not cause a misfire under load. it was probably the plugs or the connection to the plugs or dirt that got in the injectors.

most likely the plugs....

A intake leak would cause unmetered air to enter the intake this would cause a lean condition only near idle. once you get a load on it and vacuum drops then fuel trims would return to normal or near normal. The PCM adjusts for the lean condition and will add up to 25% to the fuel trims before it will trigger a p0171 and or a p0174 code. His vacuum leak was not that bad because he did not throw those codes and he did not have a surging idle.

If you have a scan tool with live data you can watch your long term fuel trims and if you see fuel trims near or at +25 at idle but then drop to near normal at higher RPM's or under load then you know it's a vacuum leak thats causing unmetered air to enter the intake.

I’m basically having this problem but not throwing any codes at all. I have a 96 GT that I did the PI intake swap onto non-PI heads. For the first 24 hours of driving I had zero problems and then suddenly after my 15th WOT run I had a misfire under kid. inconsistent as well. Here is a video

View: https://youtu.be/4-Sugrlh0JI


But anyway, I’ll probably have to take apart my fuel rail and clean it. If there are any thred people remember on fuel rails and injectors please post for me or link it

I did put all
new seals on my injectors and removed every injector from the fuel rail.

Maybe that’s where I messed up

I’m glad there was a good ending to this thred