Tommy J

2004 Fx4 5.4 98k miles. I have been chasing this low idle for weeks and talked to an old mechanic of mine that asked his "Ford guy" about it and he said without hesitation that I fried my throttle body from disconnecting my battery to do other work. Im confused as to how this happens and if its legitimate before I go buying a new one. Before the low idle I changed the plugs,cops,injectors,cleaned the TB off of the truck, cleaned the Maf sensor,replaced fuel filter, air filter and FPDM. Never has thrown a code and I have tried the relearn which I get different oppinions on how to do or not. The symtoms are low idle(500 or below) with a little roughness periodectly while idling. It otherwise drives ok but does'nt seem to have the gusto it should. Never stalls and starts right up every morning however this past week after i have driven it for a while and park it, it has not started up on the first turn on a few occassions. I was thinking my fuel pump is going but don't have enough knowledge to confirm it. So... is the throttle body diagnosis common and how did I fry it? I"ve also removed the pcm to get to the plugs if that means anything. So if I needed a new battery at some point do I run the risk of frying my TB. It just does'nt make sense to me but Im just an average weekend mechanic.Thoughts?

jake_85

I would have to dissagree that disconnecting the battery would fry the tb. Have you checked the foam on the factory air filter tray?? It goes on the bottom back side of the face of the tray.

vintageman

I personally do not think that you fried your TB. I have disconnected my battery multiple times and never fried my TB. Worn out seals for vacuums or hoses will cause these problems, so will loose connections or missed connections. Go through and physically disconnect each of your injectors and reconnect them, same with the COPs, make sure that they click. When you cleaned your MAF and TB, what kind of cleaner did you use, was it TB cleaner or carb cleaner, carb cleaner is the wrong kind of cleaner. Did you let the MAF air dry?

izzysplace

I would say it is your Throttle position sensor. If you cleaned you throttle body with anything but Throttle body cleaner you most likely stripped off the coating on the butterfly. Was there any surging or the truck dying at stop signs?

Tommy J

Yes, it almost looks like its missing some, in other words it does'nt cover the whole side however this low idle only happened after the spark plug change

Tommy J

I cleaned the tb with tb cleaner and the maf with maf cleaner and let it dry at least an hour. It was idling low after the spark plug and coil change but before the new injectors. I've checked for vac leaks and disconnected and swapped the cops and the whole 9 yards, checked every injector and cop connection, unplugged while idling for change in idle etc. I don't understand the battery or pcm causing the frying except that it may have surged or something.... I don't know

Tommy J

I used TB cleaner. No surging or stalling at stops, just low idle. I was wondering why I'd have to replace the whole TB and not just the sensor but I have read some forums where other things show wear on the TB thus the whole thing needing replacing

Tommy J

Just to clarify symptoms. The truck never stalls. It has not started on a few occasions when driving for a while on the first try. Does'nt crank and crank, just sounds weird and does'nt start but starts immediately on the second try but has only done this a few times this week. Also when warmed up, when I start it, it idles normal for about 5 to 10 seconds and then drops down to 500 or so. While idling if I slowly press the gas it hits a shutter around 750-1000 and goes away above that and when I let off of the pedal it shudders again at those same spots on the way back down to 500

jake_85

Just for ****s n gigs, get some foam weather strip with the sticky back and replace it on the filter tray. It is a common problem.

Tommy J

Should the foam go around the entire edge or just the sides. What I have now is some original around the sides only and it looks kind of beat up plus the whole air induct piece coming from the fender into the housing is'nt such a great perfect fit but it was like that before this whole idle thing happened. This new symptom is more consistent now. After the truck is warm and I have driven it for a while, when I come back out to start it, it does'nt start on the first try but always starts on the second try. Is that fuel pump? and why after its warmed up? I don't have a schrader valve on the fuel rail so I have to check it through a scanner I guess but my older Actron does'nt seem to have the capabilities to check fuel pressure. I pulled the connector on my TPS while idling to see if it got better but opposite happened, it went crazy which to me means its working. I dont think its my TB like I was told but who knows. I don't know enough about technical symtoms to point me in the right direction. Its bad enough I changed the vct selonoids in the snow today. Thanks for your responses none the less