What Now?

[riverposie]

I had a fuel pump put on by a ford dealer on my 1993 explorer with 170k on it...After $500.00 later, it worked fine..I noe have 300 miles on the new pump..I had no problems till yesterday..It was hot outside and i was running the A/C..i stopped for ice cream and left the engine run with the A/C on for about 20 minutes..The engine did not overheat...All of a sudden the CHECK ENGINE light came on and the engine started shaking and missind..i shut it off for a while..I re-started it and it jerked and bucked like it did when i had the fuel pump problem and the check engine light came on again...I waited and started it angai and drove it...it ran fine for about 4 miles and then it bucked and missed again...i again stopped and waited for an hour...then i re-started it again and it wirked fine....it has now bwwn 3 days and it works fine every day...can i trust it now or waht went on here ?

 

[MrShorty]

Pull the codes and see what code(s) is (are) stored in continuous memory.

 

[Opera House]

Could be the fuel pressure regulator. I had that problem when I replaced my pump. Some regulators have the spring off center and it wears the seat only on one side. The new pump with higher flow causes the valve to open more, slide to the side. and stick open. This happens mostly at high vacuum conditions (foot off the gas) when the valve opens the widest. Fuel pressures are normal except when the engine has a problem. One way to detect is to monitor fuel pump current. I couldn't figure this out for a long time until I cut open the old regulator.

Could also be a bad vacuum leak from one of the caps missing on the vacuum tree.

 

[riverposie]

cuts out ...on and off

Could be the fuel pressure regulator. I had that problem when I replaced my pump. Some regulators have the spring off center and it wears the seat only on one side. The new pump with higher flow causes the valve to open more, slide to the side. and stick open. This happens mostly at high vacuum conditions (foot off the gas) when the valve opens the widest. Fuel pressures are normal except when the engine has a problem. One way to detect is to monitor fuel pump current. I couldn't figure this out for a long time until I cut open the old regulator.

Could also be a bad vacuum leak from one of the caps missing on the vacuum tree.

would this cause the check engine light to come on? This happens constantly when the engine is at idle or slow driving....when i get up to about 55 the light goes out, but sometimes it comes on for a short while then too....the engine cuts out when i pull out from a stop..it bucks and jerks and thern it is o.k. for a while till i feed gas....tomorrow i am going to change thegas filter again..it was changed 3 weeks ago...the first one i changed was blocked solid..it had 10k on it....i am thinking that maybe this new one is blocked again....the dealer that put the new pump on said they got a lot of crap out of the tank...as much as they could....

 

[MrShorty]

A bad FPR can cause the check engine light to come on. Here's how it would work.
1) Valve slides to the side and sticks open as Opera House describes.
2) If pressure falls low enough, mixture goes lean. This condition is detected by the O2 sensor. The computer opens the injectors longer to try to compensate. If it's lean enough, long enough, the computer can't compensate, and the computer lights the CEL and sets an O2 sensor lean code in continuous memory.
The fault condition the Opera House describes won't always be extreme enough to light the CEL and set the code, but it could.
There are a myriad of other possible conditions that would also cause the CEL to come on. Whenever the CEL comes on like that, the computer should store a code in continuous memory. If you run the KOEO test, the second set of codes after the separator pulse is the continuous memory codes. Then you will know what fault your computer saw when it illuminated the CEL. You can also check for any hard faults (KOEO codes) or KOER codes that can help diagnose the problem.