Throttle body question

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big dady 65

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On the back of my 2001 5.4 Ltr throttle body sits a plug in sensor. The one closest to the fire wall What is the name of this sensor and what does she do.
 

tcwaltz

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Its the IAC. If your idle is crappy you can remove it and clean it. ALso check the vacuum hose that runs for it. Its one of the few things I didn't replace on my rebuild because it was working and just needed a little cleaning.
 
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big dady 65

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I wound up changing the IAC
After a smoke test I discovered it was leaking
I was hoping it would make my expy run better
But it hasn't
Thanks for your reply
I did a complete intake replacement
The truck now runs like she is a cylinder down
No codes in computer
So electrically all the coils are operational
I also did a cylinder balance test at around 1500 rpm but could not notice any significant deviance in motor function.
All injectors are operational
I put a long screw driver on each injector and heard the tapping sounds
So I'm still trumped
 

tcwaltz

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No coolant or anything down in a plug well right? What intake do you use? Did you swap to the Dorman intake or go back with a factory? I recently did and engine replacement and swapped everything while I was at it.
 
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big dady 65

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Yes I did use the Dorman intake replacement from Rock Auto for 149.99
I used compressed air to blow everything out prior to reinstalling everything. She fired right up but has a hesisitstion and stumbleds.
Very frustrating.
I did perform a smoke test on all vaccine lines and they were fine except for the IAC which I changed. But no better results from swap.
 

tcwaltz

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On the Dorman intake manifold there is a L vacuum port on the back that you install (photo below on the one I removed from my truck). There is an O ring in the bag you must use to seal that up or you will have a vacuum leak. Since this is an O ring sealing system you can't use any RTV on the seals. The one I took off the old motor was a Dorman and I didn't know it until I'd bought the replacment. The installer used RTV on the water jacket area and that is likely why it was leaking. Also need to make sure that you have a pretty clean and smooth surface to install it. If there is pitting on the head it can give you a faulty seal.

Since you replaced the intake, did you also replace the O rings on the fuel injectors? You'd likely be leaking fuel if the top ones are bad and vacuum if the bottoms are bad. You could have a bad fuel injector. You could do an OHM's test on each to see if you have one that is out of spec. When I had mine apart I actually cleaned and serviced the injectors replacing the O rings, pintle caps and internal filter. Also you are working in inch pounds on a lot of this. I had no torque wrench that would go low enough to use reliably (and couldn't find one in town) so I pretty much went snug on everything. Since I had a Dorman on mine when I bought it I have nothing to reference how it performed stock.

I completely cleaned my throttle body. It was in really nasty shape with the throttle plate sticking in the bore due to gum build up. Excessive carbon that took alot of soaking to clean. I replaced the TPS, cleaned and reused the IAC (mine was fine and pretty clean). I cleaned the MAF sensor with MAF sensor cleaner, new air filter. The other thing that I noticed due to the age of the truck was rotting vacuum lines which I replaced and made the engine idle smoother. The multi vacuum tap on the passenger side of the throttle body was fine. I found two separate pieces of rotted rubber tubing and different junctions. The worst was the piece running from where the T goes into the firewall for the AC controls and to the vacuum reservoir. The other which had some rub through was the large vacuum line from the top back to the vacuum valve deal on the firewall that runs down to the brake booster. I installed a new PCV valve and checked the vacuum line that runs from the port I was talking about needing an O ring to the PCV valve. Check that line because it could get rubbed through. One thing that was almost completely gone on mine was the small peice of hose between the plastic tube and the intake hose coming off the drivers side valve cover.

IMG_2911.JPG
 
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big dady 65

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That's a pretty thorough re build !!
The Dorman o ring I definitely put in I know that for a fact.
I would have to say by the way she is performing that I do have one or more bad injectors.
I'm probably going to buy new ones from Rock auto and try installing them.
One thing that I failed ho mention was that the exhaust had a peculiar smell. Never smelled this way prior to intake replacement Not a raw gas smell
Question On. My scanner in real time is there a way to check the cat converter from the 02 sensors in bank 1 and bank 2?
Meaning if the pressure is higher in front of the cat, the cat is bad. Too much back pressure ? That reading would b in volts like 0.something I'm assuming
Thanks
 

tcwaltz

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My understanding on the readings for cats is that the first reading should be pretty stable. The second reading is after the exhaust passes over the cats. Those numbers should be different. Can't really check pressure per say but you can see the readings coming off the o2 sensor which will adjust the fuel mixture. Also, before you assume the fuel injector is bad, it could just be dirty. Mine looked nasty.

With that said I ordered http://www.ebay.com/itm/200902231386?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I ohms tested each of the injectors and they were in limits. I got a syringe and pulled the plunger. Found one that the injector ends would fit in, super glued a stem from a can of carb cleaner in the other end. I got a momentary switch and made up a switch to turn the injector on and off. Held the injector in the end. Pressed a few squirts of carb cleaner into the injector to pressurize then popped the switch on and off to clean. Did this until I had a nice stream from the injectors. Afterward I painted them, cut off the old pintle caps, removed the internal filter with a #10 screw and a pair of pliers then put them all back together. So far so good.
 
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big dady 65

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Thanks for all your input
I appreciate it
As I gain another head of steam I'll let you know what I find out
Thanks again
 

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