running a little rough

[RF600]

The hose for the fuel pressure regulator has been changed.

 

The new intake boot was actually nicer than I expected. It did fix the whistle. The problem still remains.

 

I think I finally found out what the issue is. After putting on the new intake tube, it was still running rough. I reved the engine up by hand and noticed a pretty bad exhaust manifold leak on the passenger side. I had not heard the leak before. With hearing about all of the issues of studs breaking, I'm a bit worried. That and I have a bit over 300k, I'm not expecting things to go very well. The check engine light actually came on, O2 sensor. Since the O2 is brand new and with the exhaust leak, I'm pretty sure that's what caused the check engine light to come on.

 

Do these manifold have a tendency to warp? I have a sander that will fit the manifold to flatten it out. It's just a long process making a cast manifold flat again.

[adamzan]

On my first wd21, I was able to just replace the studs and put the manifold back on, it seemed flat enough when I put a straight edge against it. The studs were known to break on their own, not from taking them off (that's just an old car problem as I'm sure you know lol). Being in california you probably have a lot less corrosion than us.

 

What brand of o2 sensor is it? I have had them bad out of the box/shortly after replacing before. Also check that you haven't melted the wires of it against the exhaust... Been there too.

[RF600]

4 hours ago, adamzan said:

On my first wd21, I was able to just replace the studs and put the manifold back on, it seemed flat enough when I put a straight edge against it. The studs were known to break on their own, not from taking them off (that's just an old car problem as I'm sure you know lol). Being in california you probably have a lot less corrosion than us.

 

What brand of o2 sensor is it? I have had them bad out of the box/shortly after replacing before. Also check that you haven't melted the wires of it against the exhaust... Been there too.

The manifold is warped. I haven’t measured it, but it looks like around 1/8” or so. It’s at the front of the manifold. I don’t think it’s going to want to bend that much going back together. The middle and the back are flat. I have a belt sander but I can’t find any sanding belts that are the right size. If I can find the right size, it’s the wrong material. It’s going to take me for ever to make it flat with the belt I have now. I was wanting to get this finished this weekend. That’s not going to happen. 
 

I only had to drill and resize one hole. It was the very front. Thankfully it was the easier one to get to without having to get an extra long drill bit. 
 

We don’t have the corrosion out here compared to others. I can’t imagine having to deal with that. 
 

The O2 was a Bosch, I think. I made sure to keep the wires away from things. 

[RF600]

I surfaced the manifold. Installed the gasket and the ring at the end of the manifold. Started it up, there was a leak. After a few choice words were said, the ring at the end of the manifold was leaking. So I get to go back to the parts store and buy the flange gasket I just returned. it's supposed to rain for the next 3 days. What's another few days with it being down?

[adamzan]

Mine's been down for almost 2 years at this point but I feel your pain. I hate working on exhaust so much!

[RF600]

It's not really any better. I can start it up cold and it jumps to high idle like it should. After a short time if stumbles and acts like it doesn't want to run properly. It won't die, but it acts like it wants to. 

 

Putting the ECU into mode 2, after it's warmed up, both lights come on. They will stay on for about 20 seconds and go off for 4 seconds then come back on. It continues to do that. The exhaust doesn't smell right. If I understand the manual right, that means it's between 5% lean and 5% rich. I don't think that it blinks enough to consider normal operation? Can anyone verify how the lights are suppose to blink for normal operation?

 

The only thing I haven't done is to remove the injector clips one at a time and see if that does anything. As most of us know, you can't get to the inside bank to remove the clips without removing the plenum, making jumper harnesses and putting the plenum back on. At this point I think I need to try that? I don't really know what else to do. 

[adamzan]

I can go fire mine up and check after work this week. If someone else can't. @Slartibartfast still uses his as a DD so he might get to it quicker.

[RF600]

10 hours ago, adamzan said:

I can go fire mine up and check after work this week. If someone else can't. @Slartibartfast still uses his as a DD so he might get to it quicker.

I would appreciate it.

 

I haven't checked the injectors yet as I have stated before. The fuel mileage isn't down, so I don't think they are an issue.

 

I suppose it's possible that the cam sensor is acting up. I guess I need to buy a timing light. 

[Slartibartfast]

EF&EC 26 of the '95 FSM says that in mode 2, at 2k rpm, no load, warm engine, the red and green lights should flash, together, more than five times in ten seconds. I don't know why they didn't list that spec in the description for the test modes. I don't know what to make of your twenty seconds on/four seconds off. Trying and failing to enter closed loop?

 

Are you checking at idle or at the 2k rpm spec'd? They don't stay in closed loop at idle, or at least mine doesn't. But I wouldn't expect that result at idle, either.

 

I've got some driving to do tomorrow anyway. I'll set it to mode 2 after and see what derblinkenlightzen have to say. 

 

On 4/13/2026 at 5:09 PM, RF600 said:

I can start it up cold and it jumps to high idle like it should. After a short time if stumbles and acts like it doesn't want to run properly.

 

I'm reminded of the usual failure symptoms of the distributors in these. Runs fine when it's cold, starts running like crap as it warms up. Ignition misfires could explain both the high hydrocarbon readings and the rough running. But from what I've read, those tend more towards stalling out and not running at all. Could be that the cold high idle is just masking whatever is wrong with yours, and that's why it gets worse as it warms up.

[RF600]

21 hours ago, Slartibartfast said:

EF&EC 26 of the '95 FSM says that in mode 2, at 2k rpm, no load, warm engine, the red and green lights should flash, together, more than five times in ten seconds. I don't know why they didn't list that spec in the description for the test modes. I don't know what to make of your twenty seconds on/four seconds off. Trying and failing to enter closed loop?

 

Are you checking at idle or at the 2k rpm spec'd? They don't stay in closed loop at idle, or at least mine doesn't. But I wouldn't expect that result at idle, either.

 

I've got some driving to do tomorrow anyway. I'll set it to mode 2 after and see what derblinkenlightzen have to say. 

 

 

I'm reminded of the usual failure symptoms of the distributors in these. Runs fine when it's cold, starts running like crap as it warms up. Ignition misfires could explain both the high hydrocarbon readings and the rough running. But from what I've read, those tend more towards stalling out and not running at all. Could be that the cold high idle is just masking whatever is wrong with yours, and that's why it gets worse as it warms up.

I was doing the test at idle. Maybe that's why it was doing what it was?

 

I started it up today and it didn't do the high cold idle. It went to running rough. The exhaust smells bad. That tells me the mixture is off. I did the mode 2 test again and ran the engine around 2k. I didn't count exactly the light interval, but it was blinking like it should. Mode 3 gives me a code 55. No surprise there.

 

I remember back when I first got my pathfinder there was a weird stutter around 2k rpm's. It turned out the cam sensor was acting up. New dizzy fixed the issue. I suppose the cam sensor could be acting up and causing the issue. I have not pulled the dizzy and checked to see if the injectors pulse like they are supposed to. The timing is good. I checked it. 

 

I do have another dizzy that I believe is good. I can swap that over and see what happens. I like having an older vehicle, but having an OBD2 vehicle would make this process a whole lot easier.

[Slartibartfast]

I ran mode 2 on mine today. Same as yours, both lights flash. So the computer thinks the mixture is okay, for whatever that's worth. 

 

And yeah, OBD1 is a pain.

[RF600]

21 hours ago, Slartibartfast said:

I ran mode 2 on mine today. Same as yours, both lights flash. So the computer thinks the mixture is okay, for whatever that's worth. 

 

And yeah, OBD1 is a pain.

Thank you.

[peejay76]

Have you done the Fuel Pressure Check?

[RF600]

2 hours ago, peejay76 said:

Have you done the Fuel Pressure Check?

Yes. It is in spec