Hey Civic VX owners - I need your help - please test your egr valve

[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.

[jadziasman]

Nobody?

Oh well, I guess the behavior of my EGR valve will remain a mystery.

I won't change the EGR valve without knowing for certain it is bad. We don't test emissions in Michigan (yet).

[tim3058]

Hey man. I have the VX engine and a vacuum pump. Can't promise I'll be able to get to it anytime soon but once I get some other repairs done I might be able to try it out

[jadziasman]

Hello Tim, what's happening.

You might be able to try it out??.......That would be great.

Oh, and remember: next Friday... is Hawaiian shirt day. So, you know, if you want to, go ahead and wear a Hawaiian shirt and jeans.

Ahh, I'm also going to need you to go ahead and come in on Sunday, too. We've got some new people coming in and we... need to play catch-up. Thanks!

In case you forgot.........Bill Lumbergh.

[bhalseyp3]

Short Version- I believe the word you're looking for is "Quenching." Use NGK ZFR4F-11 Spark Plugs ONLY! Anything and Everything else is a problem particularly on the VX, which goes into Lean Burn Mode only after reaching Full operating Temperature, which you can't really tell from the gauge reading. The lean mixture is harder to ignite and “other” plugs don’t work well. If you're interested, the long version of this post details the problem.

[bhalseyp3]

Long Version- I believe the word you may be looking for is "Quenching"! I am an original owner of a VX and after replacing the O2, which only gave a CEL on deceleration I to also "changed the plugs", air filter etc, but started to experience some severe stuttering after reaching full operating temperature when the engine starts to use the O2 readings and go into lean burn. It was bad!! Thinking that perhaps the Non-OEM replacement O2 may be at fault after hearing that "the VX is picky about O2 Sensors" (actually it's an LAF in the 49 State Model 5-Wire) I nevertheless began to systematically eliminate all the other "Usual Suspects" to be sure. This included the EGR, EACV, Distributor, Vacuum Leak tests, MAP Sensor and the entire fuel system (including cleaning my injectors off car), Seafoam, draining the gas tank and trying Premium Grade Top Tier Gasoline. Everything checked out and there were no CELs! Some of this made some improvement, but the hesitation continued and at times it even seemed to be worse! But one day while on a test drive at the end of this month long odyssey I decided to drive a bit further and go to a Parts Store that carried NGK Plugs and got the Honda recommended ZFR4F-11 Plugs (NGK Stock #4043). This COMPLETELY solved the problem. You can go to the NGK site and read more about “Quenching.” But here’s what takes place on the VX. At full operating temperature it begins to consider the O2 data and goes from rich to lean burn particularly at under 2500. At under 2500 RPM only one intake valve fully opens (the other only partly opens to prevent a “gas puddle from forming” (ref. Honda Shop Manual). This lean air fuel mixture is much harder to ignite particularly under load and if not done properly it sets the O2 (LAF) and ECU into chaos. However, when the VTEC-E gets to around 2500 it goes into full 4-Valve Operation, with different Valve Timing and Lift and a Richer Fuel Mixture, all for sake of more power. At this point or before the engine is at full operating temperature and also running rich a non- NGK plug behaves better so the engine runs smoother. By the way, you can’t really tell full operating temperature from the gauge you have to drive about five miles even in hot weather. This was the best $8.00 I ever spent and ironically cheaper than the Platinum plugs that performed so badly. I’m also really glad that I didn’t throw a lot parts at it.