My 88 "Rosie" has been having problems for months. It hesitates, stalls, and sometimes backfires. This is an intermittent problem, though it is happening more often lately. I took it to local auto shop and their computer showed Rosie was throwing a misfire code as well as a lean code. I took it 3 months ago, and I took it last week, got the same codes. The lean code led me to check the fuel pressure. I did and while it should be healthy 48-55 psi, I got 48 for awhile then 15 PSI! Now I'm thinking fuel delivery. I started with the filter. Sure enough it was dirty. Weeks later, the problem persists. I replaced the fuel regulator (ok, mostly because it was cheaper than the replacing the fuel pump, which I really didn't want to have to do.) Still, no luck, so I finally caved and spent $200 and 12 hrs dropping the tank to replace the fuel pump. Guess, what? Still no dice. I'm still getting the hesitation and the misfiring. I haven't put the fuel pressure tester back on it (been busy) so I don't know if the pressure is still low or if these other things are even related.
I thought my logic was infallible. Let's face it, there's a finite number of parts that control fuel pressure. I'm running out of parts to replace. Where did I go wrong?
The only thing I can think of that could still do it is perhaps the fuel pump relay? I dunno. Would it work off and on or fail completely? I'd love to get some opinions on this.