My parents both own F-150’s (4.6). My Dad’s is a 2001 and Mom’s is an 02.
Dad changed the thermostat on his truck and when he got done, the truck was running very rough and the CEL was on. (He spilled quite a lot of antifreeze over the engine). The engine runs at an idle and the RPM’s will come up as long as it is in park but it barely hauls itself on the road, especially up hill. You can hold it clear to the floor and there is nothing there. It will go 55 MPH but only if you gradually increase the speed. He assumed that it was wet so he took it for a drive, thinking it would dry itself off. He took the truck to a local garage and had the codes read. They told him that the mass air flow sensor was faulty. He swapped MAF sensors with Mom to test it before he purchased one. His still ran bad and hers still ran good. He took it to another garage and was told that the rear O2 sensors were both bad. He replaced both of them and the fuel filter. The fuel pressure is 38 pounds at an idle and underway and doesn’t fluctuate. Another mechanic told him that the EGR valve was the culprit. A new EGR and a new vacuum hose didn’t make any difference. The truck was running perfect before he changed the thermostat. It has 125,000 miles. Mom consistently gets 22 MPG with her truck but Dad can only get about 16 with his. Any ideas???

 

Dan, it's hard to say what happened during the cooling system service except dad was a bit sloppy at doing the work.
Need to know what codes are present if any to even begin to be of help.
Commment, questions;
Is the mass air meter connector hooked up?
Is the air tube assembly fully on at the throttle body and mass air meter. NO Air leaks into the air tube at any point?
Is the Throttle position sensor pluged in?
Any coolant in the spark plug wells?
.
It's hard to tell what may have happend not being able to look at it myself.
I'm sure the issue is simple once it is discovered.
One thing for sure, all the shops you had it to didn't do a very good job of it.
You almost have to go over everything to find it.
Good luck.

 

Thanks for the reply. I've called my Dad and passed on the tips. I will let you know what the outcome is.

 

I have observed in the past that when anti-freeze is spilled it wont evaporate like plain water does.In essence,it will just stay in place where it lands until diluted with water,or wiped up.
Heat may help the evaporation process,but not that much.
While I dont usually recommend this,perhaps the Dad needs to get some engine cleaner,and spray down the engine.rinse all the nastys off,and let it dry before driving.Just be sure the engine isnt hot,and do NOT use a pressure washer.

 

We have cleaned and dried the engine very thoroughly, including all electrical connections. We took each one apart and made sure that it was clean and dry. (we used compressed air and a clean rag) We swapped the entire breather/intake hose from the throttle body to the air cleaner with the other truck. His still doesn't run and hers still does. I used to run a Crown Vic that had traction assist. Dad's truck acts for all the world like the traction assist activated, but it doesn't have traction assist. It starts and idles fine and, as long as you don't try to go uphill, it will go about 30 MPH with no problems. You can nurse it along a little at a time and get 55 MPH out of it, as long as you don't give it too much. If you try to accelerate too much there is nothing there. The engine just doesn't respond. As long as the engine is not under a load or is just idling, it runs OK. We will probably have to take it to the dealer.

 

Well,Im at a loss.If it was running fine prior to the thermostat change,and you have cleaned,and dried all the components...well I just dont know.
Considering your issues,it sounds like a plugged converter,but if thats the case,its purely coincedental,and thermostat change had nothing to do with it.
I will be interested to know what the dealership finds.
Good luck my friend.

 

I'd bet on a couple fouled plugs. But at this point any thing could of gone. May very well in the end be a bad cat.

 

One of the mechanics did that it might be a plugged converter but he didnt know how to test it and my Dad wasnt willing to buy one just to try it. It was bad enough buying two O2 sensors and an EGR valve. I'll let you know what the dealer finds out.

 

I have seen mechanics test a cat with a temp probe.This may well be "old school" now,but if the truck is put on a lift...running...the inlet temp should be close to the outlet.If its not,there is a restriction.
As I stated earlier,old school.....been a lot of years since ive seen the "procedure" in action

 

It ended up being three weak coils, all on the drivers side. Apparently the problem was coincidental to the thermostat change. The dealer also told us that one of the new after market O2 sensors was not working properly. None of the mechanics that he had taken it to previously said anything about weak coils. The truck also had an exhaust leak. (My Dad is hard of hearing) That leak was on the manifold end of the tube going to the EGR valve. We ordered a new tube and will replace the faulty O2 sensor. When asked why the local mechanics missed the diagnosis, the shop foreman said that their scanning computer costs $15,000.00, does only Ford products and gets updated with new information daily via the Internet. Thanks for all of the replies.

 

Just my thoughts on your bad running engine. While it's nice to claim the best equipment did the job, it was probably a mechanic that did a somewhat better job of diagnostic's than the previous mechanic.

While the coils may have been a little weak, unless a crack in them was causing a short when wet from antifreeze I would suspect the problem really was the sparkplug to coil boots were old and not sealing properly allowing some coolant into the sparkplug well. Bluegrass mentioned coolant in plug wells earlier. Most people will change plugs and coils but forget the boots deform internally from heat over time and don't seal quite as well as they should when used again. Most also forget to use dielectric grease just inside the boot where the boot sits on the plus porcilin. I also use it lightly where the coil snaps into the boot.

 

Actually if you got any antifreeze around the spark plug wells it was the reason for your issues, if you pulled the COPS out as well as the spark plugs and cleaned everything while applying dialetic grease in the appropriate fitting that would have solved the problem. Most likely NOT three "weak" COPS, just moisture getting in the way where it shouldn't have.

 

We removed the plugs and COP's that had gotten wet (only two) and dried them with compressed air. The plug boots were inspected and none were cracked. All of the other wire connections that had gotten wet were also disconnected, dried with compressed air and re-connected. I am as confused as everyone else, but replacing the three coils seems to have fixed the problem.

 

I have a question if you don't mind.

I was wondering about this before I get into the work of changing plugs etc.

On the temp tester, can I use a inferred one or will that just rad the metals heat across the pip and not be able to differentiate between either side.

Thanks,
Jim


I did post on this topic, see below if needed:https://www.ford-trucks.com/forums/9...l#post10136286

 

Jim, I would think that any of the new infrared temp detectors would work.Just be sure the range goes relatively high.The boss has one,and it shines a laser dot on the surface to be tested.Seems to work well,but he only uses it on A/C registers at work.