I have 2000 civic ex with a b18c motor swap. In the summer and warmer weather car runs fine. In the colder weather car feels like it is surging. At low and high rpm it fine but under normal driving it feels like it is running out of gas. At a stop line the ideal goes up and sometimes it drops to like 400 500 rpm. Any ideas what it cold be.
Thanks in advance

 

Dang no help yet

 

Check the TPS sensor? I've been having a similar problem and the TPS was mentioned as a possible culprit.

 

Is the CEL ON?

What do you mean by normal driving versus low and high rpm?

When were the plugs, plug wires, cap, and rotor last replaced? You may want to inspect them. Is the ignition timing set to spec?

Regarding the low and surging idle, have you tried cleaning the IACV on the throttle body? You should also bleed the cooling system of possible trapped air and carefully look for intake air and vacuum leaks.

 

The cel is not on it does come on every once in awhile in the summer when it is not acting up. Tune up was about 6 months ago and as far as I know the Timing is set right I never touched it. And i have cleaned the IACV

 

Jump the service connector to see what code(s) are stored in the ECU.

Try bleeding the cooling system of possible trapped air and looking for a vacuum leak.

 

but why would it only act up when it is below 40 degrees out

 

There is a sensor on top of the intake what sensor is that its right above the iacv

 

One explanation would be that heat causes expansion while cold causes contraction. Contraction might be allowing for a vaccum/intak air leak or causing some component to malfunction.

What CEL codes do you retrieve when the service connector is jumped?

 

i got code 43

 

I replaced fuel pump and filter it did not help. I notice when I put the lights on the idle goes down or roll down my window could it be the altenator going out and that is why it happens when it is cold out?

 

If you changed your pump & filter and made no difference you may try harness connections for idle air control, manifold absolute pressure. Perhaps the fuel rails themselves may need to be purged. Although if the cold temperature makes this problems worse it could be a fault in the distributer or ignition coil or spark plugs and/or wiring. Check all your harness connections first, it is possible you may have a malfunctioning sensor that hasn't quite failed completely and the ECU is not picking up on it.

 

there is a sensor that goes to the manifold there is no wiring going to it what sensor is it

 

um ok hold on i may have the schematic for that car or engine um you said engine swap so I am assuming the fuel injector assembly was changed also right?

 

I am not sure I bought the car and did not it had one done until later so I am not sure

 

ok I looked up the wiring connections for the swap on engine and what I am seeing is that what I had already suggested check however the EGR system may need purging as well. Is it possible the fuel might be contaminated or bad grounding wires to the fuel pump itself. Evap canister also may need to be purged. These are my best guesses for now. I will try to help you further if you discover any new information

Before I forget - if possible try to make the car have the malfunction again and do your best to make note of everything and anything you notice even if it seems trivial. It may give clues as to where to look for the origin of this issue...

 

have you checking the idle adjustment screw???has it ever been adjusted??

 

I have never adjusted it

 

i would rec checking the adjustment by turning the screw all the way in and backing it out like 1 1/2 to 2 full turns out i believe that should be good enough. or just try turn the screw in 1/4 turn at a time and recheck the idle.

 

The car idles fine expect when it acts up but other then that it is fine

 

can you post a pic of the sensor that has no connector on it??

 

Yes i can it goes on the top of the manifold on the ps right above the iacv it has two prongs it looks like