93 pathy rough idle (codes)

[savePF]

Hey there everyone,

Just dropped in here and need help.m

My 93 Pathfinder has a low, rough idle and dies when I give it gas to drive it.

 

I pulled three codes that are-

Mass air flow sensor

Leaky injector

Knock sensor.

 

So far I have cleaned the MAF, replaced the air filter while I discovered a rodents nest resulting in a chewed filter and that felt like liner material.

 

The MAF is the original 32 year factory unit so?

Any direction as to next steps is appreciated.

 

Thanks

 

[Slartibartfast]

 

The mouse nest may have something to do with the MAF code. Mine came with a rat's nest in the air box (same as yours, the blighter ate both the air filter and that little pad whatsit), and a MAF code. The nest had been sucked up against the screen on the MAF. I suspect the code was due to the computer not believing how little air the MAF was reporting getting past the rat's nest, but I cleaned the MAF while I was in there just in case it had a bit of rat's nest stuck to it. (Use a cleaner that doesn't leave a residue, and be very careful not to damage the filaments.) I cleaned it up, cleared the code, and have not seen that code since.

 

These also commonly have issues with the connector for the MAF sensor. Mine acted up for years (surging/stalling at idle when warm, and a little stumble just off idle) until I replaced the connector. It never coded for that, annoyingly.

 

The injector leak code means it can't get the mixture to lean out. This may or may not be due to an injector issue. Check the condition of the spark plugs. Look for one that's much darker than the rest, or wet with fuel. If they all look about the same, I would address the MAF issue, clear the codes, and see if the stumbling persists and/or the injector leak code returns. If it comes back, something else (possibly the coolant temp sensor) could be throwing the mixture rich.

 

The knock sensor code is likely unrelated. Mine ran normally when it had that code. The code is for a problem with the sensor (mine had drifted out of spec) or the wiring (mice love nesting under intake manifolds). AFAIK it does not throw the code for actual knocking or pinging--it just quietly retards the timing.

[adamzan]

As Slart said, the KS code can be ignored for now, it's not your issue (though if you end up pulling the intake to do the injectors you could change it). Check your injectors they should all be around 14ohms if the are healthy. If the MAF is setting a code it could be bad or it could be the wiring. But like previously mentioned it was a notorious issue on these, but speaking from experience when the wiring has issues, it will usually stall unless you hold the throttle down slightly.

[savePF]

WOW!

Thanks for all the feedback. I have since discovered that I was not operating the ECM correctly. 

Since learning how to read codes correctly all I get is a 55....no codes.

I have since replaced the PC and it's hose since it broke in half as I pulled it off.

 

I  tested the MAF and the TBS which were both good. The vehicle has sat for over a year and the engine bay is pretty caked . I have also since  noticed three vacuum lines on the EGR and air intake hose so I will replace those. The EGR is the factory original so I can't imagine it still working well.

 

I believe I will address all those, then the spark plugs. 

 

[adamzan]

You say it dies if you give it gas to drive, is it an auto or manual? Does it die even when giving throttle in neutral?

 

The ECM in this isn't that sensitive so it has to be pretty "wrong" for it to pick something up. Sadly that means drivability issues can be tough to pinpoint. But I would start with all the hoses and doing a clean up. Cap and rotor look good too?

[savePF]

Thanks for the input.

So,

It starts up, idles to 900 a little rough, stays there for a minute then drops to 400-500 and is very rough. After replacing the EGR ,PCV It will now keep running and not die when in park (auto) but is a bit rough. 

 

I have replaced three VAC hoses as well . I am hosing it down with non solvent engine bay cleaner to give it a good bath.

 

I pulled three plugs and one was fine, one black, dry and one black oily. I have ordered new  plugs as my locals don't  stock the NGK BRK5EGP's (7090) that are in it.

 

Checking the cap and rotary as well.

 

 

 

[savePF]

So,

I thoroughly cleaned the engine bay.....WOW! Now I can actually see what I am working on.

 

I checked the cap and rotor,,...........horrible!

Rotor heavily pitted , black.

Cap contacts look like someone poured acid on them as they are super pitted, malformed, etc.

 

I ordered both from Nissan and they are actually only a few bucks more than the off brands.

 

Putting all in on Friday. Will post the results

[Slartibartfast]

New cap and rotor can't hurt! And yeah, always nicer to work on stuff that doesn't look like it just came out of a hole in the ground.

 

Oily/black plugs aren't a good sign. Black could be injector issues. Oily... hopefully it's just wet with fuel (leaky injector or plug not firing), but if it's actually oil, that could be rings or valve stem seals. Does it smoke?

Edited April 3 by Slartibartfast

[savePF]

9 hours ago, Slartibartfast said:

New cap and rotor can't hurt! And yeah, always nicer to work on stuff that doesn't look like it just came out of a hole in the ground.

 

Oily/black plugs aren't a good sign. Black could be injector issues. Oily... hopefully it's just wet with fuel (leaky injector or plug not firing), but if it's actually oil, that could be rings or valve stem seals. Does it smoke?

No smoke at all!

[savePF]

Ok,

So I changed the plugs, cap, rotor.......no change.

When changing the plugs on the left side where the the are clearly visible I pulled out a piece of vacuum hose . It was and end that was cracked all around whatever it plugged onto and the other end was rotted off . It might be nothing or a clue about a vacuum hose that is disconnected?

 

I am getting closer to that point of frustration of dropping it with my mechanic but I don't want give up.

 

I have the two new sensors for the coolant/engine temp that both screw into piece connected to the upper rad hose. I read that these can effect idle?

 

[adamzan]

Not that it will make a difference in your issue, but BRK5EGP is not the OE plug, BRK6EY is. The ones you have are platinum and 1 heat range hotter than stock. Probably fine but watch out for pre detonation under load.

 

The hose that came off, was it at the back? There is a short vacuum line on the back of the intake that goes to the fuel pressure regulator. That is commonly knocked off when doing plugs/wires.

 

Only the 2 wire sensor affects how it runs, the single wire sensor is just for the gauge. It still sounds like you have a vacuum leak somewhere though. Try spraying the intake down with brake cleaner or something flammable while it idles, if there is a leak you will hear it change speed.

Edited April 6 by adamzan

[savePF]

12 minutes ago, adamzan said:

Not that it will make a difference in your issue, but BRK5EGP is not the OE plug, BRK6EY is. The ones you have are platinum and 1 heat range hotter than stock. Probably fine but watch out for pre detonation under load.

 

The hose that came off, was it at the back? There is a short vacuum line on the back of the intake that goes to the fuel pressure regulator. That is commonly knocked off when doing plugs/wires.

 

Only the 2 wire sensor affects how it runs, the single wire sensor is just for the gauge. It still sounds like you have a vacuum leak somewhere though. Try spraying the intake down with brake cleaner or something flammable while it idles, if there is a leak you will hear it change speed.

OH,

I thought the lower the number (5 vs. 6 ) was a hotter plug?  I just used the same ones on the last mechanic tune up 11 years ago.

 

Both sensors are krusty and have worn wires .

 

I DID check the fuel pressure regulator vacuum hose and it's solid.

 

I will use the spray trick to see if/where their may be a leak.

 

Thanks a bunch.

 

 

 

 

[savePF]

Just now, savePF said:

OH,

I thought the lower the number (5 vs. 6 ) was a hotter plug?  I just used the same ones on the last mechanic tune up 11 years ago.

 

Both sensors are krusty and have worn wires .

 

I DID check the fuel pressure regulator vacuum hose and it's solid.

 

I will use the spray trick to see if/where their may be a leak.

 

Thanks a bunch.

 

 

 

 

Cancel my last about the plug heat range

[adamzan]

No problem. One more thing, if it runs better when cold but once it gets some temp into it, runs poorly, check the o2 sensor, you can just unplug it from that tree of plugs on the passenger fender. I have had more than a few of them cause odd running issues over the years.

[savePF]

2 hours ago, adamzan said:

No problem. One more thing, if it runs better when cold but once it gets some temp into it, runs poorly, check the o2 sensor, you can just unplug it from that tree of plugs on the passenger fender. I have had more than a few of them cause odd running issues over the years.

Will do ,

Thanks

[savePF]

3 hours ago, savePF said:

Will do ,

Thanks

I tried the 02 sensor. No change.

Just sprayed all of the vacuum hoses....nothing. 

As of right now. It starts , idles and most of the time it doesn't die.

 

I have not tested/replaced the IAC which, unless I am missing something (certainly possible) is about the only thing left except the coil?

 

Just so I can rule these out for sure, how do I test the TBS and MAF?

[savePF]

Just now, savePF said:

I tried the 02 sensor. No change.

Just sprayed all of the vacuum hoses....nothing. 

As of right now. It starts , idles and most of the time it doesn't die.

 

I have not tested/replaced the IAC which, unless I am missing something (certainly possible) is about the only thing left except the coil?

 

Just so I can rule these out for sure, how do I test the TBS and MAF?

Starts, idles a little  rough and stumbles a bit when accelerating.

I have not actually driven it as my tags have lapsed as I can't pass smog so I can't get it registered.

 

I don't know if a good freeway run wouldn't help as it has been sitting for 1-1/2 years.

 

If so , I can have someone follow me so the CHP doesn't see my tag.