Fluctuating RPM on a 90 honda accord LX. can i get a diagnosis from you guys?

Question

i cleaned my IAC valve and my air boost valve. It runs better but i still have low rpm when i first turn on the car; I need to accelerate for the rpm to go up to 1 thousand. It also goes down when i shift from first to reverse. Can any one give me an explination as to what might be causing this problem.

Answer 1

I have had the fuel pressure regulators stick and cause that problem with many FI cars. Before you go replacing the fuel pump, have that checked first and make sure the regulator is getting adequate vacuum. That is often a part that is overlooked and will cause you grief if not checked

Answer 2

This is the classic dying fuel pump as the pressures fluctuate so does the RPM's. It may even stall when you come to a stop at a stop light.

Before jumping into a fuel pump I'd clean the throttle body first and then see if this makes a big difference or no difference.

Good Luck!

P.S. If you do change the fuel pump you always run the new pump for a minute or two and then you relieve fuel pressure at the fuel rail again and then change the fuel filter. This gets any metal residue into the old filter and then you throw it away and install a new filter. No old metal residue in a new filter. The way the pumps work they have what look like roller bearings in them and these wear out and teeny tiny metal residues end up in the fuel filter. l

Answer 3

Replace the mass air flow sensor, the problem is the engine wants to die but the idol speed sensor wont let it. Every time the car tries to die the idol speed sensor revs the engine to keep it running This is your problem (its called searhing)

Answer 4

Have you tried adjusting the idle screw to raise the idle?
Check your timing as well.