Alright guys this is for my friend. He has a 2000 F150 Lariat, 5.4 V8, two wheel drive extended cab. Its just over 119000 miles and his dad borrowed it the other day to haul some mail three ours away. The truck was waaaay overloaded and his dad brought it back with that darn skip around 40-50 mph that iv searched is really common. You know where it kind of lurches, or bucks, also i came back with the SES light on. (of course his dad is blaming it on him when he babies his truck, honestly i have never seen a 21 year old drive so carefully. Daddys got shallow pockets) ANYWAYS everyone says, maybe torque converter hesitation i think, or a coil or something similar. The big thing is that they all say CHECK THE LIGHT GET IT TESTED. We would absolutely love to get it tested. Unfortunately he has always had a slight problem with the wiring in the truck, its not a huge issue. The problem is that if the steering column isnt all the way up his turn signals do not work. ( would aggrivate the mess out of me but he lives with it) reguardless apperantly its worse than we thought because both auto zone (bunch of fools, ill explain further later) and good year said theres no power to the diagnostic port. So apperantly the wiring issue is related is all that i can think of. But about the auto zone light. Dude said that "nah man thats not you CEL thats your SES, that means you like need an oil change or something, here try a new gas cap" i was like, Kyle.....were leaving this place. Guy doesnt know jack s**t lol. Sorry guys for the profanity. We appreciate any help in any way at all. I myself drive a miata, so i hope yall dont get as bashful as they do when you search, missed a post, and the post something that already has a thread. Anywho, thanks!

 

Try driving it with it out of overdrive and see if that clears it up. IIRC there is a situation with EGR at that point that send things lean and will cause misfires that will make it buck like that.....tranny is fine...it's the misfire that makes it act up. Someone smarter will chime in on the EGR issue....I don't recall the whole deal.

 

cool thanks. so if it goes away with overdrive off then its the egr of is that only if it 're occurs.

 

EGR problems usually don't cause any bucking or lurching. It sounds like a bad coil to me. The problem with the turn signals is the connector shell at the switch. The locking tabs for the wires break off and the wire comes out of the connector. The no power to the diagnostic port is a blown cigarette lighter fuse.

 

If you have a weak coil or plug or wire, would it likely show up in that 45 mph range when the EGR opens which makes it lean and the RPM's are very low in OD? Seems to me there was a big thread on that with guys pulling the torque converters and all kinds of stuff, when it actually was an engine miss they were feeling...

 

You got it. When you are cruising in OD and EGR is flowing the air/fuel mix is lean and timing is advanced plus load is high because of the low engine RPM vs MPH. A weak coil will fail to fire in those conditions or a worn spark plug can cause the spark to travel on the outside of the plug between the plug and boot. Electricity will always take the easiest path to ground.

 

Thanks for the confirmation...I knew it was something like that.

 

So is the CEL light on or not ? If you can get a code read, that would narrow down a LOT OF GUESSING.

 

fixed the reason it couldn't pull the code. cigar lighter fuse was blow. anyways the stored code was 0125. coolent temp sensor. its my understanding the truck does not actually have this but auto zone sold it to me anyways?? this is stupid. thermostat cause those symptoms? the dash temp is where is should be sitting.

 

P0125 is telling you that it takes too long for the engine to come up to temp and therefore will not enter closed loop fuel control early on.

Could be the stat. Maybe the ECT or CHT senors are out inacurate. Are you low on coolant?

 

Here is some help on the 125 code.
From a cold start the computer starts a count-down timer to make sure the CHT sensor senses at least 175 degrees within a set amount of time.
When the timer times out and the CHT does not read 175+, the code is set.
Usually it is the thermostat stuck open.
If the coolant is too cold the the fuel control won't go into closed loop.
The engine runs overly rich, may idle rough and fuel mileage suffers and you get very little heat from the heater..
Good luck.

 

do I have to drain the coolent to replace the tstat. I used to have a Cherokee and caught hell trying to keep air out of that system and it overheating. now I know how to turn a wrench just i know certain vehicles are different and I dont have enough experience first hand to know everything about it. and I would like to know due to this being my friends truck, if I screw something up his parents will be up my ****. naturally change it when its cold, just need to know will I have to drain and bleed the coolent system. thanks

 

You can drain about a gallon, maybe less from the radiator, but don't drain it dry. As long as the level is below the thermostat you are good. I usually take out maybe half a gallon and loosen the housing. If it wants to weep out I drain it down some more. When you fill it back up, fill it slowly. Usually there isn't an air pocket issue by just taking some from the radiator and putting it back....."usually"...

 

alright then. we'll Give it a shot next payday. I appreciate the help. btw is there a special drain plug or do I just pop off the lower rad hose. and any advice on how to bleed it if we do get and air pocket in it?

 

I would not disturb the hose. There is a drain **** on the radiator. It is on the bottom corner on the passenger side of the radiator. You will see a large white nylon nut with a small hose nipple on it. Put a piece of tubing on the nipple and run that to a container. Loosen the nylon nut and turn it till coolant runs out the tubing. If you get nothing snug it down and reopen it a few times....maybe gunk has settled in the petcock. IIRC the nut is 19MM... maybe 21 MM...Treat that nut like a lady....it is just nylon and if you heave ho it to tighten it...she will snap. I just slowly fill it back up, start it with the cap off till it is hot and all is flowing good, shut it down and put the cap on. Check the level when cool and add if needed. Do a search on rad. fill here at the site....topic has all kinds of threads...good luck..