TugboatTony Posted October 6, 2011 Share Posted October 6, 2011 Hello all! I'm new here and although very experienced pullin' wrenches, new to my Pathy. ( '95 SE 3.0 Auto) I just bought this truck from my uncle in law for 500 bucks and I love it!! Besides the typical erratic tach, it's practically immaculate body/frame/interior wise but it's causing me some serious problems. After just replacing broken manifold studs, the whole exhaust system (including the O2 sensor, a COMPLETE engine tune up and a bottle of trans tune. It's still having a severe hesitation problem under load. As stupid as it sounds I cant tell whether its a fuel issue or auto trans issue. - Could anyone tell me what the fuel pressure is supposed to be? - I've heard these transmissions go in the worst way, I've been scared to give it a full flush/filter change as in past experiences this made the situation worse. Much appreciated!! Link to comment Share on other sites More sharing options...
Towncivilian Posted October 6, 2011 Share Posted October 6, 2011 Have you changed the fuel filter? A flush on high mileage transmissions without previous service is often questioned, but unless the transmission is already slipping, etc then it's generally safe. A "flush" today is nothing more than using the transmission's own pump to exchange all of the fluid. To be safe, you can do a pan drop to change the in-pan filter/strainer and then do several drain & fills within a week or two to exchange most of the transmission fluid if you are still hesitant about a flush. Link to comment Share on other sites More sharing options...
sewebster Posted October 6, 2011 Share Posted October 6, 2011 The proper fuel pressure is listed in the factory service manual, which you can download. The link is posted in a sticky this garage section. Link to comment Share on other sites More sharing options...
TugboatTony Posted October 6, 2011 Author Share Posted October 6, 2011 Have you changed the fuel filter? A flush on high mileage transmissions without previous service is often questioned, but unless the transmission is already slipping, etc then it's generally safe. A "flush" today is nothing more than using the transmission's own pump to exchange all of the fluid. To be safe, you can do a pan drop to change the in-pan filter/strainer and then do several drain & fills within a week or two to exchange most of the transmission fluid if you are still hesitant about a flush. I have, I've replaced every filter except for the trans filter. I've replaced the cap, rotor, plugs, wires, air filter oil & filter. It seems to run great while idling and even driving it without any major load but as soon as i go up a hill or put my foot into it, the whole truck shakes and shutters.........this is where i'm stuck, the fuel pump is working fine BUT I cant tell if its pushing the volume of fuel it needs. Being a low pressure pump it could be that or.....does this sound like a transmission thing? I might just bite the bullet and do a flush , crossing my fingers thats all it needs. Link to comment Share on other sites More sharing options...
RJSquirrel Posted October 6, 2011 Share Posted October 6, 2011 (edited) Hesistation is probably not the tranny. It will shift slow, then funny, and then reverse will go out. I'd check for water in fuel or bad/loose ignition wires? Are the plugs properly gapped? Distributor Cap/Rotor?( I know you said you did complete tuneup) Is ignition timing properly set?(Too much advance or faulty knock sensor) Worn bushing in Distributor can cause issues also, but doesn't sound like your issue(check last) Coolant in oil?(head gasket?) Any codes from ECM? Carbon in the intake? (Seafoam or Chevron Techron fuel injector cleaner) Loose/Dirty battery contacts? There is an issue with faulty grounding on the MAF sensor that can cause misfire issues. There are some threads detailing the correct fix. I believe there is even a factory part that addresses the TSB on this... BTW Erratic tach is a grounding problem or bad solder joints in gauge cluster... Edited October 6, 2011 by RJSquirrel Link to comment Share on other sites More sharing options...
TugboatTony Posted October 6, 2011 Author Share Posted October 6, 2011 The proper fuel pressure is listed in the factory service manual, which you can download. The link is posted in a sticky this garage section. Thats great, Thanx! Link to comment Share on other sites More sharing options...
TugboatTony Posted October 6, 2011 Author Share Posted October 6, 2011 Hesistation is probably not the tranny. It will shift slow, then funny, and then reverse will go out. I'd check for water in fuel or bad/loose ignition wires? Are the plugs properly gapped? Distributor Cap/Rotor?( I know you said you did complete tuneup) Is ignition timing properly set?(Too much advance or faulty knock sensor) Worn bushing in Distributor can cause issues also, but doesn't sound like your issue(check last) Coolant in oil?(head gasket?) Any codes from ECM? Carbon in the intake? (Seafoam or Exxon Techron fuel injector cleaner) Loose/Dirty battery contacts? There is an issue with faulty grounding on the MAF sensor that can cause misfire issues. There are some threads detailing the correct fix. I believe there is even a factory part that addresses the TSB on this... BTW Erratic tach is a grounding problem or bad solder joints in gauge cluster... The trans is shifting slow but i thought this just might be due the the age and mileage (240k) It does act up from time to time but yet again i figured this might be due to the age. I still have reverse, the OD and cruise control both work great. The ignition components are all tight as I've been checking and re checking everything. battery terminals are clean and tight. The timing is good and the oil is clean. Good compression in all 6 holes. I've topped it up with premium fuel and added seafoam fuel treatment (used seafoam in the trans too). Link to comment Share on other sites More sharing options...
TugboatTony Posted October 6, 2011 Author Share Posted October 6, 2011 I have, I've replaced every filter except for the trans filter. I've replaced the cap, rotor, plugs, wires, air filter oil & filter. It seems to run great while idling and even driving it without any major load but as soon as i go up a hill or put my foot into it, the whole truck shakes and shutters.........this is where i'm stuck, the fuel pump is working fine BUT I cant tell if its pushing the volume of fuel it needs. Being a low pressure pump it could be that or.....does this sound like a transmission thing? I might just bite the bullet and do a flush , crossing my fingers thats all it needs. Well............not a flush but a filter/fluid change. Link to comment Share on other sites More sharing options...
adamzan Posted October 6, 2011 Share Posted October 6, 2011 Check for vacuum leaks yet? What plugs did you use? Sometimes these trucks won't run right unless you use NGK plugs. Link to comment Share on other sites More sharing options...
TugboatTony Posted October 6, 2011 Author Share Posted October 6, 2011 Check for vacuum leaks yet? What plugs did you use? Sometimes these trucks won't run right unless you use NGK plugs. I've checked for vacuum leaks and used NGK plugs. ever heard of the pump not working while heading up a hill? Link to comment Share on other sites More sharing options...
adamzan Posted October 6, 2011 Share Posted October 6, 2011 Which pump? If the transmission was on its way out you would definitely notice it. Once it starts on these, it usually quits pretty fast. Try cleaning the MAF sensor (there is a how-to here) and checking the connections to it. Link to comment Share on other sites More sharing options...
TugboatTony Posted October 6, 2011 Author Share Posted October 6, 2011 Which pump? If the transmission was on its way out you would definitely notice it. Once it starts on these, it usually quits pretty fast. Try cleaning the MAF sensor (there is a how-to here) and checking the connections to it. I was wondering about the fuel pump, it does have a pretty loud 'hum' to it so could that mean a dirty sock? or is the hum pretty standard in pathfinders?I've filled it with premium fuel and filled it with a bottle of seafoam fuel treatment. I even took the new filter off and can blow through it pretty easily. The truck sat for a bit before i got it so maybe it'll take a bit to get the crappy gas and/or water out of the system. I will check the MAF sensor though. Appreciate the input mate! Link to comment Share on other sites More sharing options...
Towncivilian Posted October 6, 2011 Share Posted October 6, 2011 (edited) Don't use premium fuel in an engine that is not designed for it. Higher octane fuel is more difficult to ignite, and if an engine is designed for say 87 octane fuel, then it can't advance timing enough to compensate for the higher octane fuel, and performance and/or mileage will suffer. I'm assuming WD21s take 87 octane fuel, so use that only. Seafoam is a relatively harsh solvent, which is probably okay to use in gas, but I'd not use it in the crankcase since there is potential for large chunks of deposits to break loose and clog oil passages. I'd prefer to use Chevron Techron or Gumout w/ Regane as a fuel system cleaner as they both contain large amounts of poly-ether amines, which were developed by BMW and Chevron and are designed to not leave their own deposits after cleaning. Edited October 6, 2011 by Towncivilian Link to comment Share on other sites More sharing options...
adamzan Posted October 6, 2011 Share Posted October 6, 2011 I was wondering about the fuel pump, it does have a pretty loud 'hum' to it so could that mean a dirty sock? or is the hum pretty standard in pathfinders?I've filled it with premium fuel and filled it with a bottle of seafoam fuel treatment. I even took the new filter off and can blow through it pretty easily. The truck sat for a bit before i got it so maybe it'll take a bit to get the crappy gas and/or water out of the system. I will check the MAF sensor though. Appreciate the input mate! Mine has always made a humming/hissing noise at the back of the truck when running. I'm pretty sure it is normal as my old 93 did the same. If it has been sitting for a while I'd give it a chance to run for a little while. Don't use premium fuel in an engine that is not designed for it. Higher octane fuel is more difficult to ignite, and if an engine is designed for say 87 octane fuel, then it can't advance timing enough to compensate for the higher octane fuel, and performance and/or mileage will suffer. I'm assuming WD21s take 87 octane fuel, so use that only. Seafoam is a relatively harsh solvent, which is probably okay to use in gas, but I'd not use it in the crankcase since there is potential for large chunks of deposits to break loose and clog oil passages. I'd prefer to use Chevron Techron or Gumout w/ Regane as a fuel system cleaner as they both contain large amounts of poly-ether amines, which were developed by BMW and Chevron and are designed to not leave their own deposits after cleaning. I agree don't use premium it is a waste of money, you won't notice a difference. The only time I noticed a difference was with 89 octane and I only filled with that because the gas station ran out of regular and gave mid grade for the same price. If I could find Techron or Gumout here I would use it. Link to comment Share on other sites More sharing options...
Precise1 Posted October 7, 2011 Share Posted October 7, 2011 The trans is shifting slow but i thought this just might be due the the age and mileage (240k) It does act up from time to time but yet again i figured this might be due to the age. I still have reverse, the OD and cruise control both work great. The ignition components are all tight as I've been checking and re checking everything. battery terminals are clean and tight. The timing is good and the oil is clean. Good compression in all 6 holes. I've topped it up with premium fuel and added seafoam fuel treatment (used seafoam in the trans too). FYI the stock tranny cooler in the radiator is prone to clogging so many of us bypass it or install external filters. This may be why the tranny acts up occasionally, and is certainly worth considering and checking. Checking the ECU for codes, cleaning the MAF wires (and checking the connection, check the TPS for proper functioning. There is a temp sensor for the ECU that can send bad info also. You can download the factory service manual in the Garage section that will have all of this info... B Link to comment Share on other sites More sharing options...
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