My 93 civic 1.5 non-VTEC engine, will surge from 900-1500 RPMs precisely about every 2 seconds after it reaches warm up temp (fan starts ). The car runs great before it warms up and does not stall out, even during the surging.

1. New parts installed within the last 2 months include NGK plugs, PCV, main fuel relay, fuel pressure regulator, fuel filter, injector seals, Chevron Techron, Honda wires, cap and button, NAPA (auto store) igniter and coil. Swapped ECU with another exact unit, no change resulted.

2. My distributor is 2 yrs old.

3. I just changed my timing belt, water pump, tensioner, crank and cam seals.

4. Head gasket and bolts were changed to the newer type mentioned in this forum with part numbers (that was very helpful).

5. The belt was due for changing and the pump was leaking causing the belt to slip.

Any ideas would be greatly appreciated. Thanks:confused: :confused:

Honey, if you changed everything but the seat covers... I'd try and sell it before it dies. Seriously, have a good mechanic look at it and if he can't figure out why your race horse does this... then try and either 1. live with it if you can or 2. get a different car. Might be simple fix or it might be no fix.

You have done a lot of good things for your car. Here are some ideas concerning your present problem:

. Clean/replace the IAC Valve.
. Ensure vacuum hoses are tight.
. Check the Fast Idle Thermo Valve.
. Test the ignitor, even though it is new.
. Check the Oxygen Sensor and the Engine Coolant Temperature (ECT) Sensor. Both of these work together with the ECM to provide the right fuel mixture. Try replacing the Oxygen Sensor, with one made by Denso. It sounds like when it comes out of "open loop" mode problems begin. See if this helps:

https://www.askmehelpdesk.com/cars-t...tml#post223376

If the problem persists, test/replace the ECT Sensor.

I think this is a problem that would easily be solved with Honda's OBD test tools or test tools that use a laptop. Sensor values should easily show up if out of range.