Fairly recently, my “service engine soon” light stayed on. The mechanic used his diagnostic tool, and said the air control pump motor was the problem. He replaced it. Two days later, the light went on again. I took it in, and his little computer reading device said that the idle was too high. He didn’t agree with it, and cleared the light. The light went on and off for a while, and the pattern seemed to be that if the tank was full of gas, the light was off. So I’ve tried to keep it near full. It got close to half empty yesterday, and the car shook when I started it, and I had a rough ride home from work. This morning I filled it up, and it seems a bit better now. Could it be gunk somewhere in the fuel pathways? If so, how much does it take to clean it all out? Or does it sound like something else? Thanks for your help.
Have a mechanic check the fuel pressure for a weak fuel pump.
If the fuel pump is weak, the level of gas in the gas tank can assist the weak fuel pump. This is called head pressure. When the tank is full the head pressure is at it’s greatest. As the level of gas in the gas tank decreases the head pressure decreases until it reaches a point where it no longer assists the weak fuel pump.
Also, if the fuel filter has never been replaced, you may want to consider that. A partially clogged fuel filter could cause the fuel pump to work harder and affect fuel pressure.
Thanks very much! I’ll check those out. By the way, how much money are we talking about in both cases? If it’s too much, how long can I simply try to keep the tank full?
Don’t know when it will fail completely, but checking fuel pressure should be fairly cheap.
If you open the gas cap when the tank is on the lower side, do you hear a whoosh of air being sucked in?
Thanks for the two new comments. I’m glad that checking fuel pressure should be fairly cheap. The mechanic I reached by phone two days ago said I need to let the gas get low so they can diagnose the problem better, so that will be a comforting thought while my car is shaking, rattling and rolling on low gas. I don’t remember any whooshing sound when I open the gas cap when the tank is on the lower side. I really appreciate everyone’s help so much!
It could be your EGR according to the Escort Fourm. Here is a great Escort EGR DIY link.
Thanks again, KN.
A really easy way to find out if it is an EGR valve problem is to just pull the vacuum line off of the valve. Plug the line (a golf tee is just the right size) and cap the port on the EGR (most anything will do). This WILL set a check engine light and WILL be bad for the engine over the long term. So this is temporary to see if the problem goes away. The EGR and vac line are clearly shown in that first pic of the thread knfenimore posted.
If this does get rid of the symptoms, don’t assume that you need a new EGR valve. It may instead be that you need a new vacuum solenoid (that’s where that vac line on the valve comes from). The DPFE sensors are also known to be a problem - but wouldn’t cause the kind of problem you are having.