rocky_mtn_a4 Posted February 20, 2011 Share Posted February 20, 2011 Ok so a little background info first...Truck broke down on me coming home from work, turned out to be the rotor. Replaced it, truck started hiccuping around 2500 rpms...done the distributor cap, fuel filter, used EGR valve cleaned real well from the junk yard, a couple new vacuum lines, new coil wire...problem is it runs fine when its cold, but once it warms up it starts running like crap anything above idle. Idle's fine, just once you hit 2500 rpms it starts bouncing the tach around and smells like gas profusely. If you lay on the throttle heavily while its hiccuping, it'll backfire loud as heck out of the airbox...any advice? No CEL...yea I thought that was weird too. It's actually a friend of mines truck and it's sitting in my driveway this weekend and I'd love to get it on its way. I have my own issues to deal with. =) Anyhow, I'm going to double check his work tomorrow with the fuel filter, check for vacuum leaks and whatnot. The fuel smell is whats tripping me out. That and the bouncing RPM's w/ backfire through the airbox. Has me perplexed. At first I thought it could be ignition, but how would engine temperature affect that? So I moved on to fuel or vacuum. It's almost exactly like it's running on 5 cyl. rather than 6. I'll check wires and plugs tomorrow as well. Link to comment Share on other sites More sharing options...
adamzan Posted February 20, 2011 Share Posted February 20, 2011 Sounds like your o2 sensor is gone. I had the same problem and it didn't put a CEL on. Either the o2 sensor or the coolant temp sensor. If you look in the garage section there will be a how to on how to check the codes even if the CEL isn't on there may be a code stored. It can't hurt to check. Also download the factory service manual it will give you resistance values for the sensors. Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 20, 2011 Author Share Posted February 20, 2011 Sounds like your o2 sensor is gone. I had the same problem and it didn't put a CEL on. Either the o2 sensor or the coolant temp sensor. If you look in the garage section there will be a how to on how to check the codes even if the CEL isn't on there may be a code stored. It can't hurt to check. Also download the factory service manual it will give you resistance values for the sensors. Right on...yea I'll download that as soon as I get home from the hospital. I'm visiting my son and the hospital WIFI wont allow downloads. As for the CEL, I'm sure the FSM says, but I was curious at the moment if this is one of those vehicles that the CEL can be checked without diagnostic software or hardware? Like my Honda flashed the CEL for certain codes a certain amount of times, so no OBD was needed. If so, whats this process? Again I'm sure the manual says, but I can't download it at the moment. Thanks a bunch. Link to comment Share on other sites More sharing options...
adamzan Posted February 20, 2011 Share Posted February 20, 2011 You don't need to have any sort of scanner. Here is how to do it. http://www.nissanpathfinders.net/forum/index.php?showtopic=21 Link to comment Share on other sites More sharing options...
Tungsten Posted February 20, 2011 Share Posted February 20, 2011 yep i remember when my o2 sensor failed and the ecu was also sensing a knock, the truck ran like a pile of @!*% Link to comment Share on other sites More sharing options...
aranay Posted February 20, 2011 Share Posted February 20, 2011 It's really hard to remote-diagnose these kind of problems but I would bet a least a couple of bucks that it's your coil. Have a look at the coil pack and see if there's any brownish goo starting to leak from it (might not be leaking but could still be bad) I'm not sure on the p-finder but the old dodge 318 coil is similar to a ballast in a fluorescent light fixture. Someone on here may be able to advise you as to the best way to check/test it. Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 20, 2011 Author Share Posted February 20, 2011 (edited) Well...checked the codes, all I get is 55, No malfunction. Checked plugs for fouling or gap issues, all good, checked timing, all good. Cleaned MAFS...no change. It's only when its warm. Sprayed all the vacuum areas and intake area with carb cleaner trying to get it to cough, no dice. Once it hits 3250-3500 rpms now its just backfiring loud as all get out through the intake/airbox. Would low fuel pressure cause this? He said he took it to the mechanic a couple weeks back and they said his fuel pressure wasn't exactly where it was supposed to be. I checked most the injector o-rings and they all look ok. No fuel leaks anywhere I can find. My fuel pressure gauge has a quick connect fitting for mopars, so I can't use it on this truck...Also, there's a noticable exhaust leak coming from the manifold area, not sure if this is playing a part. Edited February 20, 2011 by rocky_mtn_a4 Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 20, 2011 Author Share Posted February 20, 2011 (edited) Quick update, I am now getting a 1 red and 2 greens indication of MAFS failure...I dont believe I was diagnosing it properly before...I'm sure I am now. Could this cause said problems? Still plan on doing the O2 sensor test and live diagnostics momentarily... Edited February 20, 2011 by rocky_mtn_a4 Link to comment Share on other sites More sharing options...
adamzan Posted February 20, 2011 Share Posted February 20, 2011 Sounds like it could be the problem. Usually when a sensor is bad it will do it when warm because when the engine is cold the computer doesn't use the sensors for the mixture. Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 20, 2011 Author Share Posted February 20, 2011 (edited) Well I can't get the code to return after clearing it...now its definately saying 55 no malfunction. But still running like crap, it may have given me till 4000 rpm now before it starts sputtering. The mode 5 live diagnostics just made me more confused...I'm definately getting blinking on the green led, but picking out a pattern is impossible. If you rev it, it flashes pretty much constantly, if you let it idle, it pretty much stays solid green and stabilizes. I think I'm done with this thing, time to pass it on to someone else who knows more than me =). Edited February 20, 2011 by rocky_mtn_a4 Link to comment Share on other sites More sharing options...
Channel595 Posted February 21, 2011 Share Posted February 21, 2011 usually the backfire in the intake is a lean burn miss. if the exhaust leak is bad enough it could actually suck in air and trick the o2s into thinking the mixture is too lean and then make it too rich. fix the obvious problems first Link to comment Share on other sites More sharing options...
Channel595 Posted February 21, 2011 Share Posted February 21, 2011 also the timing pully on these can be installed incorrectly and be not on tdc... Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 22, 2011 Author Share Posted February 22, 2011 Can anyone tell me from experience if this model has the "fuel tank inspection cover" or does the tank need dropped to do the fuel pump? its the v6... Link to comment Share on other sites More sharing options...
sewebster Posted February 22, 2011 Share Posted February 22, 2011 Should be able to just remove the carpet and probably a panel in the back of the truck. Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 22, 2011 Author Share Posted February 22, 2011 Wow...wouldnt that be convenient...can I get a second more convincing opinion? I would check myself, but the truck isn't here at the moment, and the guy wants to know what I'd charge him to replace it for him. He's got the parts, I just don't know how much work I'm gettin myself into, or even what a shop would charge in labor. Link to comment Share on other sites More sharing options...
Dowser Posted February 22, 2011 Share Posted February 22, 2011 Yes it has an access hatch. just under the carpet in the rear. It has 4 bolts and gives you access directly over the sending unit. You can always go to a wrecker and find another Automatic Pathy years 90-95 and take the MAF and swap it. might be a cheaper route before handing off to someone that's gonna charge ya. Link to comment Share on other sites More sharing options...
rocky_mtn_a4 Posted February 22, 2011 Author Share Posted February 22, 2011 Yea I think you misunderstood, it's not my truck. I'm just working on it for my mother-in-laws friend. He already went and bought the fuel pump because he's going off what the tech at this shop told him. Heres a partial copy of his invoice. The tech told him his fuel pressure was 40% of normal and expected it to last no more than 3 months. Well since then he's went to Vegas and back. Now he wants me to install his fuel pump...I'm tryin to figure out how much to charge him....lol Link to comment Share on other sites More sharing options...
Dowser Posted February 22, 2011 Share Posted February 22, 2011 Ahhhh. I see. Well The fuel pump as you probably know then is inside the tank that you can get access to from the door hatch in the back of the vehicle. Just the trim by the hatch door needs to be removed to get the carpet up. I've heard that its rare that the Fuel pump goes on these vehicles but hey, if he's already picked up a fuel pump then by all means. I won't be able to help on job price quote though. Perhaps someone on here can chime in with a flat rate job time so you can see how long the dealer takes to do it and charge accordingly. Or just call a dealership and ask for the time on the job. Good luck with the install and solving the issues. Link to comment Share on other sites More sharing options...
sewebster Posted February 22, 2011 Share Posted February 22, 2011 Uhh, I'm confusd by those fuel pressure numbers. Isn't it supposed to be 36 psi with the regulator plugged in, and 43 with it unplugged? Link to comment Share on other sites More sharing options...
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