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Idle probs, running rich, mutiple codes


AZJOE
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Hey everyone, my 94 Pathfinder is about to drive me nuts. It started about a year ago stalling at stops and turns and I got codes for Idle Air control valve. I had a guy replace it and it worked for a few months, then started again. So I took it to a dealership and they did the same job again and cleaned the ports behind the IAC and it worked for several more months. (they also replaced the knock sensor at the same time).Then this winter I parked it for 3 months and didn't drive it. When I started it I could tell the heater blower was making noise and didn't blow air, so pulled it and it had a mouse nest in it. Cleaned it out and started it again and all of a sudden the engine ran horrible with black smoke coming out and I got codes for fuel injector leak and fuel injector circuit. Had it towed to a repair facility and it started running fine and they couldn't see any obvious problems with it (like wires chewed by mice). Took it home and soon afterwards started stalling at stops again. took it to a dealership for repairs and they changed plugs, plug wires, cap and rotor and claimed the platinum plugs I put in it were too hot and melted the cap and rotor. Well, all these items were replaced only a year ago, and maybe 5,000 miles. I think the tech was just throwing parts at it and hoping we'd get lucky. The plugs were very black showing a rich mixture. Anyway, it didn't make any difference. Took it back, they said it's the Mass Airflow sensor, so I installed a new one, it didn't make any difference.

 

I'm getting the following codes now. 45 injector leak, 51 injector circuit. I had the injectors cleaned at Sears not long ago. Where would you suggest I start checking for problems? One place checked injector harness on the three that are visible and couldn't find anything wrong. Any suggestions where to start? I'm not much of a mechanic anymore, but hire a guy who is very good and reasonable in price. He just is not good at diagnostics and doesn't have any of the testing computers for newer cars. If I tell him what to check or replace, he'll do it and do it right.

 

Eventually I suppose it will get fixed, as I've durn near replaced everything! OX sensor, EGR, now MAF, IAC. Any suggestions, anyone?

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Has anyone checked the condition of the Fuel Pressure Regulator on the back of the intake? Is the vacuum line into it new? Are all the vacuum lines new? The only other things I can think of is a leaking intake gasket or intake boot. Anyone else?

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The IAC valve has a controller. There is a test in the manual. Not saying that is the problem. Something to check.

 

Have you added an additional ground to the maf? It may not fix it but a good thing to do.

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Has anyone checked the condition of the Fuel Pressure Regulator on the back of the intake? Is the vacuum line into it new? Are all the vacuum lines new? The only other things I can think of is a leaking intake gasket or intake boot. Anyone else?

We have not checked fuel pressure regulator and am not sure how to check it. However, at this point I'm considering having the intake taken off again and having the intake harnesses and injectors check under the intake, so that would be the time to check it.

Vacuum lines have not been replaced, but I suppose it wouldn't cost much to do that also. I don't think that is the current problem though, as it's intermittent. Most the time it runs and idles great.

Thanks for your input!

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The IAC valve has a controller. There is a test in the manual. Not saying that is the problem. Something to check.

 

Have you added an additional ground to the maf? It may not fix it but a good thing to do.

I'm not sure here that controller is, but your comments before. After the IAC posts were cleaned in June, it ran great until the incident this winter.

I will have my mechanic install and extra ground wire also.

Could you send me a link to the service manual please? I know it's here somewhere but was unable to find and download it. I know if would e more helpful than the commercial manual I have.

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I'm just wondering if it would be beneficial to remove the intake and replace all 6 of the fuel injector harnesses and also replace the rubber O rings on all the injectors? (not talking too much money here) Of the 3 harnesses visible, some have cracked plastic where they attach. And since I have an injector leak code, wouldn't replacing the O rings possible help that situation? And I suppose my mechanic could also inspect the injectors at he same time and possibly see any that need replacement.

Just guessing here. I'm a carb man with experience from the 70's and no nothing about injectors.

 

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Most likely you need new fuel injectors. The best way to test/check is to measure the injector resistance at each one. You are looking for about 12 and 1/2 ohms per injector. Measure through the harness connectors on passenger valve cover, if they are not all close and equal then removing the upper intake and inspecting the connection at each injector is necessary, look for green corrosion. If ok remeasure resistance at each individual injector to confirm. Best to do the first check cold and then when engine is at operating temp. If for example five injectors are at 11.7 ohms and one is at 36.4 ohms then you have isolated the problem. Of course make sure no vacuum leaks, mass air flow sensor not contaminated with air filter oil(K&N), fuel pressure regulator hose at rear of intake is ok, etc.

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Maybe I'll just replace all of them. One repair facility I took it to checked resistance on the 3 injectors that are accessible. They said, #1-12 ohms, #3-27 ohms and #5-10 ohms. And they also said specifications is 10 - 17 ohms, so maybe they should have replaced #3 for starters?

Ok, well I'm getting some good information from everyone and sure do appreciate it. Considering what the dealership has been charging me for labor and parts and NOT fixing the problem, I'm inclined to just replace everything that might be related to it and save money in the long run. Thanks for your input.

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The FSM is available for download through nicoclub, the link to them is in a pinned thread at the top of the Garage section. The EC section (Engine Control) has a pretty good diagnostic section, so I recommend just going through it enough to familiarize yourself. Also EC-137 states that the values for the injector should be 10-14 ohms, so that #3 injector is suspect for sure. Another trick would be to run it briefly, then pull the plugs and inspect them. Any plug with a leaking injector should be darker or wet with gas.

 

If the injector connectors are cracked, you have to determine if the injectors are getting a good and consistent signal.

 

 

I'm just wondering if it would be beneficial to remove the intake and replace all 6 of the fuel injector harnesses and also replace the rubber O rings on all the injectors? (not talking too much money here) Of the 3 harnesses visible, some have cracked plastic where they attach. And since I have an injector leak code, wouldn't replacing the O rings possible help that situation? And I suppose my mechanic could also inspect the injectors at he same time and possibly see any that need replacement.

Just guessing here. I'm a carb man with experience from the 70's and no nothing about injectors.

 

Start on the bank that the injectors are easy to get to. Always replace the O-rings if you remove/replace an injector, wet them with gas prior to installation for a little lubrication. It is more likely that any leakage is through the injector, not the O-rings.

I'd just start by replacing #3 first rather than replacing all 6. I bought a set of used injectors/fuel rails when one failed on our 1999.0, and only replaced the faulty #1. That was years ago, and still no issues with any of the others (and I have spares now).

Also, injectors are color coded (a dab of paint should be visible when you remove the harness connector). Conventional wisdom is to match colors to ensure the same spray pattern, etc. Maybe ask here/in the classifieds section to see if anyone has any spare injectors (once you know you color); I have personally sent a couple out to people.

 

B

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The FSM is available for download through nicoclub, the link to them is in a pinned thread at the top of the Garage section. The EC section (Engine Control) has a pretty good diagnostic section, so I recommend just going through it enough to familiarize yourself. Also EC-137 states that the values for the injector should be 10-14 ohms, so that #3 injector is suspect for sure. Another trick would be to run it briefly, then pull the plugs and inspect them. Any plug with a leaking injector should be darker or wet with gas.

 

If the injector connectors are cracked, you have to determine if the injectors are getting a good and consistent signal.

 

 

Start on the bank that the injectors are easy to get to. Always replace the O-rings if you remove/replace an injector, wet them with gas prior to installation for a little lubrication. It is more likely that any leakage is through the injector, not the O-rings.

I'd just start by replacing #3 first rather than replacing all 6. I bought a set of used injectors/fuel rails when one failed on our 1999.0, and only replaced the faulty #1. That was years ago, and still no issues with any of the others (and I have spares now).

Also, injectors are color coded (a dab of paint should be visible when you remove the harness connector). Conventional wisdom is to match colors to ensure the same spray pattern, etc. Maybe ask here/in the classifieds section to see if anyone has any spare injectors (once you know you color); I have personally sent a couple out to people.

 

B

Thanks for the info! I've downloaded the manual, so that will help a great deal.

If you buy remanufactured injectors, do you order them by the cylinder#? You are saying they are color coded is why ask.

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You are welcome, and... yes. :D

 

Sorry, not by cylinder number, all the injectors should be the same color. You'd want an injector for a 1994 Pathfinder VG30E, (blue, black, silver, etc) color code, regardless of what cylinder.

 

B

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If there's a big enough problem in the injector circuit to throw a code, start there. I seem to remember looking up that harness a while back and finding a plug that each injector's wires ran through, which could allow you to test under the intake without removing it. I don't think I looked up where that plug was, unfortunately.

 

Also, :clickdalink: for the manuals. The EF&EC section is your friend for troubleshooting, but the EL section will help you figure out where the wiring goes.

 

Checking individual plugs is a good idea. I'm not sure the resistance test alone will find an injector that's gummed open.

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The IAC valve has a controller. There is a test in the manual. Not saying that is the problem. Something to check.

 

Have you added an additional ground to the maf? It may not fix it but a good thing to do.

Do you mean to just get like a brass ground strap and connect it to the aluminum housing of the MAF, then the other end to the fender, or try to determine while wire in the harness is the ground and tap into that?

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The best way is to find the ground wire and tap into it; easy enough to do...

There was a thread very recently that detailed which wire, let me see if I can find it.

 

B

 

Sounds like it is the middle wire.

http://www.nissanpathfinders.net/forum/topic/39879-maf-ground/?hl=%2Bmaf+%2Bground

Edited by Precise1
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There is a ground on the core support on the drivers side. I put the ground there. My logic was, since there was an existing ground why not take advantage of it.

 

Tap into the correct wire on the maf. Run a new wire to a point on the chassis. I chose to use a heat shrink end connector. I also put a new connector on the maf. It is much easier to remove. No stupid clip to try and put back on. It is from Napa, EC173.

Edited by RF600
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There is a ground on the core support on the drivers side. I put the ground there. My logic was, since there was an existing ground why not take advantage of it.

 

Tap into the correct wire on the maf. Run a new wire to a point on the chassis. I chose to use a heat shrink end connector. I also put a new connector on the maf. It is much easier to remove. No stupid clip to try and put back on. It is from Napa, EC173.

Wasn't aware I could get that connector. Another guy tried 4 years ago and couldn't locate one. I got one ordered. Thanks. I noticed mine has a ground cable wrapped around the other 3 wires inside the plastic insulation. I wonder if it got pulled off at one point, like when I had the engine replaced? Tried to copy a pic in here of it but don't know how.

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  • 2 weeks later...

I'd like to thank everyone who responded with good suggestions of what to check and do. What I ended up doing was had my mechanic change all the injectors with rebuilt injectors, replace all the injector connectors with new ones, replace all vacuum lines, replace the fuel injector pressure regulator with a new one, and also got a new connector for the MAF sensor and directed him to install it with an auxiliary ground wire (this was the only thing that didn't happen; he replaced the connector on what I think is the throttle sensor that is 10 inches away from it and looks similar to it. Not a problem, I'll have him do that later).

 

Anyway, my wife drove it 25 miles home today and said it ran perfect, but the check engine came on just before getting home. I went out and started it and no light. Also drove it 10 miles and it ran perfect and no light.

 

Could someone tell me in a simplified manner how to clear it of all error codes it has stored? There's a bunch I there. I have the type of ECM under the passenger seat with a screw in it. I keep it turned all he way counterclockwise when I'm not trying to read codes, and turn it clockwise about half way to get it to start blinking out codes.

 

Seems I read somewhere you can disconnect the negative battery cable for 24 hours and that will do it. Is that right?

 

I'm planning to drive it to work over the next 2 weeks or so and see what happens, that's 85 miles per day, but need to clear out the old codes if it's still putting out codes to see what else might be wrong with it. I'm sure with all we did, something must have been fixed in the process. It sure seems to run nice now.

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