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Discussion Starter #1
My car has developed a problem, bad enough that I can't drive it. It started a couple weeks ago and has gotten progressively worse. Under load or not, if you ease in to the throttle it will run fine. But, if you blip the throttle or hold it wide open, it will miss out from 2,500 rpms to 4,000 rpms. Once you hit 4,000, it fires on all eight. There are no codes at all. Now I did have the injectors off of it this weekend, and I did see that on two of them, the pintle caps are broken. They are on oreder. Could they be the cause of this? Weak fuel pump maybe?
 

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we can't see how bad of a shape your injectors are. If the pintle caps that are broken are bad to the point where the Oring isn't sealing properly, that can easily be it. Don't diagnose until you have fixed mechanical problems first because you will likely waste your time.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Tackle things one step at a time. If there's something you know is busted, address it and see if it changes the situation. Troubleshooting 101: Don't change more than one thing at a time.
 

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Misfire at low RPM is almost always spark-related.

Look at the plugs, wires & coils.....


But you can try the pintle caps - let us know how that works out for you!
 

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Discussion Starter #6
I changed the caps. No change what so ever. I just put plugs and wires on 2 months ago. NGK's but Ibused Duralast wires. The car idles great, sounds great, until you try to go somewhere, the it just craps out.
 

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looks like the cold engine lockout for the heater too me. should be a small temp sensor in the coolant valley tube back their it connects too.

and a DPFE code from that intake is probably a plugged EGR tube or passage under the intake plenum. either that or a broken EGR tube. unfortunately the DPFE is on the back of the plenum under that EGR solinoid in the picture. pain to get too. same with the EGR and tube buried below all those hoses and stuff. 96+ intake swap FTW.
 

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Discussion Starter #12
I know where the dpfe sensor is. Looks like I will check into that tomorrow. I have the 3 dial hvac so that wire means nothing then. Thanks, I was racking my brain trying to figure out where that went.
 

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Discussion Starter #13
So today I have pulled the intake, cleaned the egr and passages, replaced all of the rubber vaccuum lines, installed new intake gaskets, and installed new wires. No change and I still have the code for the dpfe sensor.
 

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Discussion Starter #15
Now I've got codes for bank 1 and bank 2 too lean. I don't know what else I can change. I also put a new fuel filter on and tried an MAF off of my buddies T-bird.
 

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All those things you could have done wrong. It's just one of those things that since we can't see it, we kinda sorta have to take your word for it that you did do them correctly, but there is ALWAYS a chance that you messed up. Did you replace the DPFE hoses? Did you break any injector pintle caps/O-rings? How about the fuel pump strainer?
 

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Discussion Starter #17
I'm not a newb when it comes to working on cars. I replaced the broken pintle caps, intake gaskets, plug wires, and fuel filter. I also swapped out known good coil packs and MAF off of my buddies Tbird. No, I did not swap dpfe hoses, no one has them on stock. And I did not touch the fuel pump. Now I have codes telling me that I am running lean on both banks, I would think that would indicate a vaccuum leak at intake, or exhaust leaks, or maf is bad etc. All of those problems have been addressed. The only thing I have yet to do is to replace the O2 sensors and the fuel pump. Neither of which I reall want to do without being sure that,s what the problem is. Sometime this weekend I will get a fuel pressure test done.
 

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its real easy with that big heavy stupid 95 intake to get it slightly out of whack and not sealing right. i know getting mine off was a bear, i would never have imagined putting it back on afterwords. not when 96+ intake parts and pieces are still readily available. super easy swap too, especially if your using the NPI intake, and even with the PI just add RTV. :)

I've also herd people having issues with the felpro gaskets not sealing right probably from that vacuum channel for scavenging across all the intake ports. also check those big vacuum connections on the back of the intake. if one or both are not sealed properly they can cause a massive vacuum leak. i assume since you had the intake off you checked that they weren't soft, torn, or sucked closed.

and the DPFE might just be shot, or the hoses are plugged with gunk. try spraying them out with some carb cleaner or something before you go replacing them.

otherwise i know O'Reilly can order the hoses in different lengths. its got some sort of red rubber coating on the inside to resist heat so its not just your every day hose parts stores normally have in stock.
 

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Discussion Starter #19
I would have liked to do a PI intake swap, but there were none around here available. Even my buddies yard didn't have one, not to mention there are no newer cars to get the mn12 specific parts off of. I would have to drive about 3 hours to get everything. Its more cost effective to just fix what I have for now.
 

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i had a lean code on my car... along with a miss... The stock plastic airtube that goes from the filter box to the intake CRACKS around the seams. remove it, and hold it up to the sunlight while looking into the inlet/exit on the tube.... if you see light shining trough, that is your problem. Even a small crack can mess up these cars, Maf sensor doesent detect the extra air that is being sucked in after it. another Good way to test this is with a un lit propane torch and the car running.....
 
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