94 Civic VX stutters

[Egghead]

New to this forum and i am not familiar with the best etiquette here so i will just be blunt to the point.

1994 Civic VX California model. The car will stutter, when doing light acceleration around 1500 to 2000 rpm. It also does that when out of gear and i tried to slowly raise the rpm to between 1500 to 2000 rpm. And it only does this after the car is fully warmed up. If i apply harder acceleration or accelerate beyond 2000 rpm or so, the stuttering goes away. Car idles pretty steadily between 600 to 800 rpm. When i turn on/off the AC, the idle adjusts accordingly. Changed everything from the spark plugs to the wires to a brand new distributor, including cap and rotor. Finally i suspected it was the egr valve. I unplugged the vacuum hose and the car runs fine like good old days.

I took it to a mechanic and he tested my egr valve with a vacuum pump and gauge. There is vacuum from the hose and it varies when applying throttle. He then hook up the pump to the egr valve and applied vacuum. The car started to choke, ran rough and almost stalled when he pumped the vacuum pump. Therefore, he said my engine vacuum looks normal and the egr valve is not stuck closed/opened. His conclusion is my egr valve most likely has a bad spring as it is over sensitive to the vacuum and opens too much, too early, letting too much exhaust gas recirculating, thus causing the stutter. When i accelerate hard or pass 2000 rpm, the engine with the o2 sensor is compensating with full vacuum.

Does this make sense? I don't mind getting a new egr valve but since it is not a cheap part, i want some reassurance and second opinions. Furthermore, where can i get a replacement egr valve for best price. I have checked online and they are not widely available. At least Autozone, Pepboys and O'Reiley don't carry them. The few places i found do not specify VX + CA and have the vacuum line pointing up in their pictures. Mine has the vacuum line going sideways. I look at the position and if the vacuum line goes up, it will possibly hit the throttle wire right behind it.

Please help. Thanks.

 

[HeX]

Remove then thoroughly clean the EGR valve internals using carb cleaner. Honda EGRs are the best route. Search through online dealer stores like HondaPartsNow.com.

What brand of spark plugs & wires are you using?

 

[Egghead]

Remove then thoroughly clean the EGR valve internals using carb cleaner. Honda EGRs are the best route. Search through online dealer stores like HondaPartsNow.com.

What brand of spark plugs & wires are you using?

I did ask about cleaning the egr valve but mechanic disagreed. He said the valve is opening and closing with the vacuum pump, so it is not stuck and no point cleaning. He contends that the spring may have gotten weakened over time and is opening too much with the vacuum so the egr valve needs to be replaced. Cleaning egr valve will not fix the spring problem. Does the spring in an egr valve really go bad?

Obviously the car runs fine when the vacuum hose is disconnected, meaning egr valve closed all the time. My question is whether the diagnosis is correct. If the spring is bad and valve opens too much when only little vacuum, causing large amount of exhaust recirculation, does that really cause the engine to stutter? Then when i hard accelerate or go into higher rpm, high vacuum kicks in and valve fully opens anyways so everything operates normal. Does that sound right?

I will search hondapartsnow to see what i find.

I use ngk spark plugs and wires. The VX is as bone stock as you can find with a 22 years old car. I literally have no upgrades on any components. Even the original Honda cassette radio is there.

 

[HeX]

Im no expert in this but Ive never heard of an EGR valve being "too open". By my understanding, a faulty spring could not allow it to shut enough when needed. I would contest the possibility that gunk could impede it from shutting or moving correctly as well. Therefore, if its truly the spring the cleaning it wouldnt hurt but could improve it so its worth the shot.

I was curious of the cost of your EGR valve and found that it seems to be discontinued by Honda, so cleaning it may have to be your next choice. If that changes nothing then you may need to consider finding a machinist that could open it up and replace the spring. Make sure to hunt for aftermarket or used parts anyways and search elsewhere online with the part number.

 

[Egghead]

So out of the blue i just wanted to try this because egr is part of the whole emission system. I played all 4 permutations between the o2 sensor and egr valve.

1. o2 sensor connected/ egr valve vacuum hose connected. Described symtoms.
2. o2 sensor disconnected / egr hose connected. Described symtoms.
3. o2 sensor connected / egr hose disconnected. Car runs fine.
4. o2 sensor disconnected / egr hose disconnected. Car runs fine.

Therefore, only thing that makes the ok/not ok difference is whether the egr valve vacuum hose being disconnected or connected. Keep in mind in all 4 cases, the car idles fine with not stalling, no high rpm, no fluctuating. Steady between 600 - 800 rpm. I am not sure if symptoms are similar when you have bad o2 sensor and good egr valve.

I don't think the egr is stuck opened or closed. If stuck opened, my idle will be rough, bouncing and may be car stalling. If stuck closed, it should not matter if i have the vacuum hose connected or disconnected. In terms of a faulty spring, i guess there are 2 ways they can be faulty. The spring is stuck compressed, thus not providing the length at full release. This will cause a stuck open. 2nd way is when the spring loses its spring tension. You need less force to compress the spring but the spring will still release back to original height. This will provide a close when no vacuum exists. However, when only little vacuum comes, as in light acceleration, since the spring loses the tension, the small vacuum opens up the valve too much. This is how my mechanic explained it.

Then the egr valve is either "too open" (spring loosening and opens too much with small vacuum) or "too close" (like sticky and not opening enough when vacuum comes). Assuming there is a thing called "too open", will both too little recirculation or too much recirculation cause the same stuttering symptom?

 

[Jonathan62019]

Can do what i do on all my cars/trucks I delete the egr by using a plate to block it off. I have over 30 cars at my house split between me and my uncle. Everyone has the egr delete, with zero problems or cel.

 

[Egghead]

Can do what i do on all my cars/trucks I delete the egr by using a plate to block it off. I have over 30 cars at my house split between me and my uncle. Everyone has the egr delete, with zero problems or cel.

I can do that as a temporary solution only. I am in California and will need to pass the smog test in a few months to renew my registration. If I get pulled over on spot emission checkpoints by the CHP, I will get a ticket also.

 

[Jonathan62019]

Oh man. That sucks. :/

 

[Egghead]

So i have pulled the egr valve and cleaned it. Inspected hoses with no blocking. I can even feel the vacuum from the hose to the egr valve. I have also put in a new o2 sensor. Still having the same issue.

What should i try or look at next? The only thing that can make the car run fine is unplugging the hose to the egr valve to keep it shut. No CEL. I don't believe i have a clogged cat because with or without the hose connected to the egr valve, i can rev/run the engine up to the redline.

 

[Egghead]

Yes. If i disconnect the o2 sensor, the CEL comes on. If i pull the VSS, the CEL comes on also.