I have a 2007 Acura RDX with 155K miles. A few weeks ago the car stalled immediately after starting and left me stranded. It finally started normally after several hours of trying. I got a P0627 code (fuel pump open circuit) which I cleared and it hasn’t come back; however, the starting problem itself hasn’t gone away. Now when I start the car it sometimes runs for about half a second, almost stalls, and then runs fine. Most of the time it starts normally though. Also, when I lightly tap on the gas pedal at idle the engine stumbles slightly for a moment as if it’s about to stall.

This issue only occurs after the car has been driven for a while. Since the issue is intermittent I don’t know how to figure out what’s wrong with the car. I just replaced the fuel pump with a used one with 86K miles on it which didn’t help. What should I do?

 

since you replaced the fuel pump and it did not solve the problem, I would start looking at wiring.

Do you still get the Check engine light P0627 ?

 

The CEL still hasn’t come back. I also checked for pending DTCs and didn’t see any. Just changed the engine air filter today and didn’t notice a difference. Could a bad relay cause the idling issue?

 

It appears that two relays are directly linked to the P0627 code: "PGM-FI main relay 1" in the under-hood fuse box and "PGM-FI main relay 2" in the interior fuse box. I swapped relay 1 with an identical relay and nothing changed. I will replace relay 2 next.

The orange "Brake System" indicator has occasionally started illuminating when starting the vehicle. It turns off when I tap the brake pedal. Upon further investigation I found that the "Brake System" indicator relates to the electric vacuum pump which is part of the brake system. This pump also communicates with the PCM which controls fuel/emissions. Could the "Brake System" indicator somehow be related to the issues I've been having and could that provide a clue as to what needs repairing?

 

you're on to something!!!

a bad brake booster could cause a "stall", since it's using vacuum.

upon further reading/investigating, it seems as if this gen RDX has a problem with the brake booster pressure sensor.

https://acurazine.com/forums/1g-rdx-...sensor-712356/

 

Brake Vacuum Hose With Check Valve Replaced on my RDX, check yours for a leak. Brake/Clutch Switch Adjusted on my RDX, maybe you need to check that as well. Replaced Brake Light Switch on my RDX, could check that too.

 

Can a clogged air filter cause the fuel pump relay to hiccup and throw code p0627? Mine was filthy. After replacement and clearing codes, no problems starting and running better.

 

I would not worry about it unless it comes back. The newer electrics in these cars can throw any number of codes when battery dips low (constant cranking). Also heating of the fuel pump may cause it.

Did you pull the code with a honda based or honda intended scanner? That code may be confused from a different code that exists. If the car runs well then do not worry about it.

 

When the CEL occurred, the RDX hasn't been driven for 4 days. Doubtful it was a hot fuel pump. I used a Bluedriver Bluetooth scanner to read and clear the P0627 code. It works pretty well. It reads CELs and pretty much whatever the ECU has stored.