[jadziasman]

My 92 VX has been acting up lately. I'm getting a hesitation issue right after it warms up, mostly in the morning after it has been off for 8 hours or more. Some days the behavior is worse than others. I might drive for up to 25 miles with the hesitation, sometimes it's only 10. Might be the gasoline I'm using. I was using Shell for about three years and did not have any issue while cruising at 70 mph but the idle was bad - misfiring like crazy. When I switched to Mobil in March this year, the idle is smooth but I get the strange hesitation (misfire?) at 65 to 70 mph - but not all the time.

There is currently no CEL on my 92 VX. It has at least 227K miles (was probably rolled back - quasi legal to do a roll back in Michigan for cars over 10years old).


While troubleshooting what can cause this, I found that the egr valve will not hold static vacuum with a hand vacuum pump (I would have expected a code 12 if the egr valve did not function correctly). As soon as I release the hand pump, air rushes back into the pump. It will only hold vacuum drawn from the running engine at 5 inches Hg at the EGR a idle. Is this normal? I have learned that in addition to ported egr valves, there are positive backpressure and negative backpressure egrs. I think that Honda might have used a negative backpressure egr but have been unable thus far to confirm this.

I put a vacuum gauge in the line from the egr solenoid valve to the egr valve and test drove it. I only get vacuum to the EGR valve at 3000 rpm or higher at a steady speed which is about 55 mph in third gear. That tells me everything is functional - the ECU is grounding the EGR solenoid when the conditions are right.

Thing is - I'm not sure if this is normal or not. I get no EGR vacuum when below 3000 rpm. That rules out 5th gear. Why would egr be needed only at 3000 rpm or greater? Does the VX engine cylinder temps stay low enough at cruising speed in 5th gear to not require egr?

Anyway, I'm looking for VX owners who can test the egr in their cars to see if they have the same symptoms. According to the helm manual, the egr valve is supposed to hold vacuum when running at idle. It does not say if the vacuum source is the engine or a hand vacuum pump like I have. My egr valve will maintain the engine vacuum - I switched to the evap purge solenoid out of the CVC valve to avoid the egr solenoid duty cycle. When I apply vacuum this way, the egr valve lifts and rpm drops - like it should.

Anyone willing to look at this? I'm mostly interested if someone else with a hand vacuum pump can see if the egr valve in their VX holds vacuum or not.
I'm having some difficulty understanding why the valve won't hold vacuum this way. What allows the air to return to the vacuum pump and zero the gauge?
Does the air escape through the diaphragm or the pintle shaft? Who knows.
I don't want to buy a new egr for $150 for no reason. Sometimes used egrs pop up on Ebay but none right now.