My CRX once at operating temperature surges and misfires, when accelerating. Going up a hill it surges and misfires. Steady throttle it runs fine. At idle it hold a steady 700rpm and doesnt budge, yet you can hear a misfire out the tailpipe. When cold it runs like it should in close loop.

I have literally replaced everything it seems trying to fix this.

Things I have replaced:
-distributor
-MAP
-egr solenoid
-egr valve
-CVC
-Fuel pressure regulator
-fuel filter
-all vacuum lines
-plugs,wires
-TPS
-injectors
- 02 sensor twice....
I've done the EGR clean out as well (drill out the ports and clean). It did run better from doing that, as they were clogged something fierce. I've cleaned out the IAC thoroughly, as well as swapped it with a friends and it made no difference.

I've obtained multiple MAP sensors, egr solenoids, CVC's, and swapped them to make sure they weren't the culprit. It ran the same on all said sensors.

The timing belt is spot on. The solenoid fuse is intact and not blown.

I suspect the EGR is the culprit and have tested and retested the valve and solenoid. The valve actuates with vacuum ( both the old and new valve actuate). The solenoid click with 12 volts applied to it, and operates normally with vacuum.

Having said that, I wonder if the ECU( I think honda refers to them as ECM's) may be faulty in it's operation of the EGR circuit.

THOUGHTS? Any help is seriously appreciated.

 

When my tank is near empty I'm going to change the fuel pump. It has the signs of being weak....let's hope this is it!

 

No CEL?

Have you done a compression test?

 

youd get code 12 for the egr, ive seen the ecu's go out

 

I get the 12 code when I unhook the egr. I reconnect and clear the code and it never comes back.

I did a compression test: 168,168,165,159

I replaced the fuel pump and main relay, and neither made a difference.

What leads me to believe an ECM problem is that in closed loop(warm-up) it runs really well, with none of the surging that comes once it warms up. You'd think sensor but with all the ruling out and replacements of said sensors, it leads to the conclusion of the ECM itself. THOUGHTS?

Any conclusive tests on the ECM to validate?

 

Does the EGR valve hold vacuum?
Driveway test is to suck on vacuum tube hooked to the vacuum port.
If it holds (end of tube sticks to your tongue) for a period of time, then it's good.
If the vacuum bleeds off, then there is a leak in the EGR.
Or just buy a vacuum tool and test proper like.

One thing to note is that the vacuum pulled on the EGR does not occur until the solenoid pops.
So vacuum leak surging at idle even with the vacuum line to the EGR disconnected completely should not occur.
I don't think your prob is the EGR

 

I have the EXACT same issue with my '91 HF and I've done everything you've done except for the fuel pressure regulator and fuel pump. I've also changed out the coolant temperature sensor with no change. Also changed my O2 twice

One thing you didn't mention was the electrical timing (using a timing light), but I assume you checked it when you swapped out the distributor.

When you disconnect the EGR valve and the CEL comes on, does it run better? That is one of my main symptoms and I chalk it up to being forced into open loop. When that happens, my car runs perfect. What kind of mpg are you getting right now?

Btw, open loop is when the car is warming up, not the other way around. Closed loop means that the feedback system using the O2 sensor (and whatever other sensors?) is controlling the fuel (I'm pretty sure). I'm still not sure that if the CEL is on, that forces the car into open loop though.

I've just purchased a cheap ECU this week to rule that out also as you've suspected too. I'll let you know if I see any change with that.

 

I checked and adjusted my timing when I installed the new distributor.

Ya, i had that backwards open vs. closed loop.

It does run better with the egr disconnected, except for the pinging, but thats to be expected.

Did you try your ECU swap yet?


I tested the vacuum with a vacuum tool it holds the valve open indefinitely.

 

Nope, still haven't gotten the ECU. Hopefully I'll have it by the weekend.

A couple other things I tried that didn't make a difference but I figured I'd suggest anyway:

- Cleaning up the grounds and making sure the ground wires are ok.
- Valve lash adjustment

My problem with the car running better with the EGR disconnected is that I've done everything you've done to confirm the EGR is good, so why would disconnecting it make it run better? I have a brand new EGR valve, cleaned out the EGR ports, and swapped out the full "black box" on the firewall that contains the control solenoid. I've made sure the items hold vacuum that should and followed the test procedure in the shop manual.

The hesitation I get when accelerating is consistently at about 1800rpm and 2100 rpm only, which I've read is a symptom of the EGR. It's just so frustrating that every test and part swap shows that the EGR is good.

 

I seriously think we have the exact same problem...post as soon as you try out the ecu!

 

have you checked resistance and continuity in the egr wiring?

 

Funbus, I got the ECU in and there's no change.

 

Funbus, earlier you said your fuel pump "has signs of being weak." How did you come to that conclusion? If your fuel pressure was low before, is it good now that you replaced the fuel pump? I ask because I haven't really touched my fuel system besides changing the fuel filter until now.

I checked the fuel pressure at the fuel filter and it's at ~27psi with vacuum connected to the FPR and ~37psi with the vacuum disconnected...that's if my cheap Harbor Freight pressure tester is accurate. According to the honda shop manual, it should be between 40-50psi.

I was also digging through old posts here on HT and I read that when the EGR is blocked off (or disconnected in my case), the ECU goes into open loop and runs rich. So maybe when it's running rich, it's counteracting my low fuel pressure and actually performing normally.

Another symptom I have is that if the EGR is connected, when I let off the gas, the RPMs dip down fairly low, below 500rpms. It's almost like the throttle dashpot isn't reacting fast enough. I think that when the EGR is disconnected, I'm not seeing that. Have you noticed anything similar?

 

you'd still get a code if the computer is goin, it'd be code 1 i believe

 

Actually, I discovered it was faulty distributor.

Whats funny is that it was the third new distributor I had put in. Each time I would get the symptoms I've been dealing with, but this current distributor being the worst offender. Upon further investigation, I believe there's a short or faulty connection in the harness plug. The wiring plug on the new distributor was probably a good 1/8" taller than the original distributor. It ran decent when I put it in a month ago, but slowly began running worse and worse. I went back to my original distributor and the car runs almost perfect. I still a faint backfire/miss when cruising, but the improvement is huge. I've ordered the parts( new coil, module, pickup coil) to rebuild my original distributor and hopefully that will be the end of it.

I should add that I replaced the distributor to begin with to fix the slight miss at cruise.