Surging i have a 98 honda civic hx A.T. that surges from 500 rmp to 300 when i put it in gear and turn the ac on. in park or neutral that car idles fine at about 750. could u help me out asap

Did you change fuel and air filter,put fuel cleaner good one.

which engine, options there are many.???
cant fix any engine, until you know what it there.
a civic not Tacoma. as posted.
see end for engines ????

surge 101 (running gasoline?)
it caused by 2 things. (and lots of reasons)
1: engine running lean. all engines lean surge. fix that first.
hint use a scan tool see live data........?????
2: ISC system is faulting, the idle speed controller can fail for #1
or for itself. (it can stick) clean in.


wiki list of engines. (which one???????????????)_
The sixth generation featured engine options were available along with their first Natural Gas Powered Civic, the GX. From 1996-2000 the Civic was sold under the CX, DX, EX, EXR, HX, LX, and for Canada, SE, and Si trims; all base models were made with 1.6L engines. The EX-CX are all SOHC (Honda D engine). The CX, DX, and LX all have D16y7 non-VTEC engines; whereas the EX has a D16y8 VTEC, and the HX has D16y5 VTEC-E. The USDM Si and Canadian SiR came with a DOHC (B16A2 VTEC). The first civic SI coupe EM1 was introduced in 1999 until 2000. Europe saw a DOHC 1.6 VTI hatch and sedan and a DOHC 1.8VTI engine was available for the Domani related five-door liftback and esta
end quote.
I CAN NOT GUESS>!!!

Idle fluctuations are usually caused by a vacuum leak.

where do i change my fuse or light volve in honda accord 1999 signal light don't work

On the throttle body, that's the part where the throttle cable goes on, will be a screw. might have a plastic cap covering it, remove cap, and with screw driver turn screw in there to where it will idle where you want it, that the idle mixture screw.

The surging is related to your Idle Air Control Valve (IACV), it adjusts idle based on coolant temperature, your coolant could be low or your IACV could be bad.

Possibly a Throttle position sensor. If it surges in park and it won't idle correctly this could be a solution.

That is normal, in park or neutral there is no resistance on the engine when you put it in gear there is resistance because the car wants to move. Also when you turn on the ac that turns on the compressor that is run off the belts of the engine so it puts more resistance on the engine. Low idle is not a problem unless the engine dies.

Have you install a timing belt recently? If you get it off a tooth it will idle high and surge

Check the throttle sensor and MASS air flow sensor. Throttle sensor cheap check first. MASS nice penny.