Recently the old boye has been having an occasional rough start up or lumpy idle. It never happens when cold, only when we do something like... drive to the grocery store, let it sit, come back, and then it'll kind of choke as it's starting. Not always, but sometimes. It will also occasionally idle kind of rough at a light. It's not consistent though. Sometimes it's as smooth as glass, sometimes it has what feels like a slight hesitation. Almost like a misfire but I'm not getting any misfire codes.

Sparkies, wires and coil packs are new. Battery new (and verified it's fully charged before posting this). O2 sensors are new. I've never replaced the fuel pump or injectors, but *do* always run either Chevron or Costco 91, point being, I'm not skimping on bad gas so the fuel system should be pretty OK. He just ticked over 210K miles. It's pretty much one of the most well sorted Discos out there, except for this small occasional issue.

It's coming up because this morning we dropped the toddler off at preschool, spent probably 5 minutes doing that whole process, and then when I went to start the Disco it behaved as if the battery was low. It would still crank. After three attempts it finally started but felt like it was choking down a mouthful of bread while doing so. On the drive back home it ran smooth as ever, no rough idling.

Oh and the starter was recently replaced, not that it has any symptoms of a bad starter, but figured it was worth mentioning.

ANYYyyyywayyy... I'm suspecting a fuel related issue since air and spark are all sorted. Between injectors and fuel pump I'd suspect the latter first, but wanted to run it across you all first.

 

As if the battery was dead?? No crank whatsoever? That's not a fuel pump. Maybe clean the terminals and ground points and see what happens?

 

I guess not dead…more low. It would crank. Should’ve clarified. Edited.

 

Maybe some diag. Monitor live data O2 sensors and fuel trims, especially during times of trouble. Measure fuel pressure at idle and throttle open. Try carb cleaner for IACV and throttle body/plate and anything related to crankcase ventilation.

 

Alrighty, hooked up a fuel pressure test and it's pretty much holding steady at 52psi on a cold start. I did two tests, one at stone cold start, which is this video below. You can see when I purge fuel, it recovers quickly.


I waited about five minutes, engine warm, etc, and then did another test (next video, below) and the recovery after purging fuel was much longer. Not sure if that's a gauge issue, as I couldn't hear the engine stuttering or anything when the gauge read very low numbers for a moment.

Good news though is that it’s holding 52psi after shutdown.

 

My fuel pump was already bad when I got my D2 at 129k miles. It would always take 2 tries to start when engine was cold. That stopped completely after replacing it.

 

There is another thread going you should read, if you have not, about this, suggestions include unplugging MAF, etc.

sounds like a similar issue potentially.

 

Related but unproductive to your issue question: where did you hook up to get the reading? Did it just create a loop in the system to show pressure? This looks like a tool I’d like to have.

 

Take a look at that video I linked and I start by showing the fuel rail inspection port I connected to

 

Yeah I saw that part, but I must not have looked close enough. Thanks, though, I’ll check it out just so I know where to look.