I just recently purchased a 2000 accord ex about 5 weeks ago and i need help solving some of the big issues that have since occurred with it. Its a 4 cylinder automatic with 155k miles on it. upon purchase the car ran strong with no signs of any issues whatsoever despite having the CEL light on. we checked the codes and found out that they were caused by a transmission issue and EGR flow. we did a transmission flush and that fixed one problem. We cleaned the EGR valve but it didnt erase the code. After all this my father used the car to go to work to save some gas. The car still ran strong and was very fuel efficient like all hondas. The problems started appearing about 2 weeks ago they are...

overheating
the car started overheating about 2 weeks ago. The first time it happened we pulled over and let the car cool. when we got home we inspected the hoses for any leaks but there werent any. The coolant was completely empty. We added more coolant and checked the wiring on the fans. One of the wires was a bit loose so we wrapped it in electrical tape to make sure it didnt move around. we then checked to see if the fans worked with the ac on and off. They did work fine and the car seemed to be working fine but the problem arose again. this time when it overheated i noticed that the temperature seems to fluctuate whenever it gets hot. also the car remains at a good temperature when cruising and seems to overheat in an instant. I do live in texas and it is very hot here right now so maybe that could be affecting the car as well seeing as not only my car had overheating issues that same week but also my dads 06 mustang and my moms 01 sequoia. the guys at the local shop said it was because of the heat messing with the cooling hoses.

fuel efficiency
whenever my dad drove the car to work the car was being very fuel efficient getting somewhere above 24 mpg. this past week the car is getting an almost unbelievable 10mpg! i double checked my calculations and refilled the gas tank to make sure the gas needle was reading correctly. i traveled 80 miles on a half tank of gas. i did a little research and think it might have something to do with the oxygen sensor but then again i dont know that much about cars. i am wondering if its the sensor that needs replacing or if its something else. this is a complete mystery to me and i am baffled as to how it can happen. I do drive the car like a normal person and dont abuse it so it cant be my driving style.

EGR valve
i took the time to clean the EGR valve once i got the p0401 code but it seems to not have made a single bit of difference despite previously being pretty clogged up. i am wondering if i may have to buy a new EGR valve or get the entire engine cleaned inside. could it be possible for me to do the cleaning on the engine to save money? how hard is it to do a job like that? i have seen videos of it being done online but you never really know until you try yourself.

Like i said before i do not have a vast knowledge of car mechanics but i am willing to try any sugggestions. i am a college kid so any money saving options are welcome . if you need anymore information i will try and get it for you. i will check again to see if the cooling fans are working properly whenever i have some free time. thank you for reading this incredibly long post and thank you for your time. websites like this and helpful people like you are awesome!

note: i will not be able to reply during labor day weekend as my family and i are taking a trip to the lake but i will reply as soon as possible.

 

My best guess is you are loosing coolant into the engine some way. Look at your spark plugs, see what color they are and if there is any build up on the electrodes. The fluctuation, does it seem to coincide with speed? Like stepping ont he gas the temp drops down, but foot off the gas or stop and the temp flies up to out of range? This is a sign of not enough coolant in the system. At low RPM the water pump can't move fluid, it needs more RPM to get the suction to pull from the radiator if it is low.

The coolant burning could cause the EGR valve to be dirty.

Now, if you see it in the plugs, then the chances are probably decent you have a bad head gasket.

My opinion anyway.

 

1. Overheating issue. Is the coolant level still low? So it is not overheating when cruising; but, at idle? When it is overheating, have you checked if the radiator fan is on? If your cooling system is functioning properly, you shouldn't be overheating even in Texas heat.

2. Fuel efficiency. Correct way to calculate average mpg, is to fill up tank all the way, reset trip meter. On next fill up of tank all the way, divide trip mileage by number of gallons to refill. Repeat as needed.

However, even eyeballing and having the gas gauge drop approximately half while only going 80 miles is telling something is wrong.

3. P0401 is usually clogged EGR ports. For your 2000 4 cylinder, refer to this link for cleaning the EGR port:

honda-tech.com/showthread.php?t=2691467

 

Update: checked the coolant level and it had lowered after the overheating. it didnt completely empty but it had lowered significantly. You could still see the coolant flow through the radiator cap. after filling it up again i took it for a drive to check the if the fans were working right. they werent but just touching the connecting switch for the fans made them turn on so i guess i need a new switch. hopefully that takes care of my overheating issue. there doesnt seem to be any leaks coming from the hoses but i will keep checking up on them. the temperature fluctuations did seem to occur with speed as the car normally overheated during stop and go traffic and at idle hence why i think the fan switch might be the culprit. one of the things i noticed though is that the radiator seems to be a little dirty around the radiator cap and also inside the coolant tank. could this also be affecting my cooling system? What would be the proper way to clean something like that?

As for the fuel efficiency i measured it using trip miles and the regular odometer. i traveled 87.4 miles on almost exactly a half tank of gas. i also filled my car up to make sure i the gas needle was working. like i said this baffles me since it seems to have happened from one day to the next.my dad drove the car for a week and got good mpg then the car was left in the garage for a week. this is when i drove the car and noticed i was getting the awful fuel efficiency. my dad drives around 60 miles to get to and from work and he only had to fill up the car once in one week of driving it for five days to work. I havent had time to check the spark plugs but i will as soon as i get out of class.

Note: the car when purchased started up easily. right know it still starts up instantly but it sort of has a small stutter in the beginning. the engine is still running smoothly so the stutter only happens when you start the car and that only happens every once in a while. thank you so far for all your help.

 

Really need to look into cleaning the egr ports, is this a 4 or 6-I might have missed it.

Sounds like there is a coolant leak, need to find the source. Some places (autozone, ect) rent testers-you get your money back. Get one and see if the system holds pressure, while you have the tester on there look for leaks.

MPG by the gauge can be hard. Best method, fill it up, set the trip, drive for a few days, fill it back up. Divide the miles driven by the gallons needed to fill it back up.-EDIT: I now see Redbull-1 already had this.

 

well i fixed the overheating issue or at least it appears to have been fixed so one problem is fixed. i plan to clean the ports soon after looking at a few how to's and diagrams i dont think it will be too much of a problem. As for the fuel efficiency its still awful but i guess im going to go to a local shop and have it checked out properly. thanks for all the help!