bigtimemcc Posted July 11, 2007 Share Posted July 11, 2007 Hey guys, my 93 has been running BAD and I dont know what else to do. Have checked, clean, replaced almost everything on this rig and nothing helps. It gets way too much fuel, black sut out the tail pipe, and about 10 mpg. Idles at about 700 when its cold and about 200 when its warm, but always burning rich no matter what temp. So, I would like to, if possible, put a carburetor on this bad boy and do away with the efi altogether. I heard they put carbs on non US versions, will I be able to convert mine? Where to get one? Any advice would be a big help. Been working at this thing trying to get it running right for months, should I just trash it or what? Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 Have you run codes? Checked cam timing? Replaced the oxygen sensor? Replaced the coolant temp sensor? Checked the fuel pressure regulator? To convert to carb, you would need to find a carb manifold and a carb from overseas. It probably wouldn't solve your problem anyway. And you wouldn't pass emissions any more. And your power would go down. And your maintenance needs would go up. And your fuel economy would get worse. Etc., etc., etc. "I want to convert to carb because I can't get it to run right" is, well, stupid. Fuel injection is *easy* once you grasp the logic; the computer can help you diagnose, and it's usually something simple that you can figure out and fix in under an hour (with access to a parts store). Why not post everything you've checked and how you've checked it, and we can see what you skipped and what else you can do? Diagnosing these things is easy - if you know what you're doing (people here do) and have manuals or proper documentation (people here do)! Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 11, 2007 Author Share Posted July 11, 2007 Ok, I replaced the tps, maf (twice), temp sensor, o2 sensor, fuel pessure regulator (twice), cleaned and wiggled every plug under the hood, ran the codes (comes back 12 for maf every time). MAF - since the computer spit out 12 everytime, I replaced the maf 2 times, and then figured maybe wire was broke or bad connection. To test this out, I simply unplugged the maf while running and it would run much much worse, plug it back in and it would go back to "normal". The truck has been underwater at some point, before I owned it. So I figure whatever can go wrong has or will. The carb seems like the easy fix. Fuel economy? Cant get any worse than it is now. Plus it would be easy to adjust. When I replaced the regulator the 2nd time I noticed that the rubber fuel return line had a kink in it, so I put a shorter hose to fix that problem. It did make it run "better" but not a total fix. Also, while it is idling, I can squeeze the fuel feed line almost shut and it will idle up and run GREAT. Untill you give it some throttle and it will die as it then is starved for fuel. I saw a site that sells a tbi intake converted to run a holley carb. I could put a 2 barrel on it be just fine. It said the intake would fit VG30 motor, that is what i have isnt it? Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 (edited) MAF - since the computer spit out 12 everytime, I replaced the maf 2 times, and then figured maybe wire was broke or bad connection. To test this out, I simply unplugged the maf while running and it would run much much worse, plug it back in and it would go back to "normal". Also, while it is idling, I can squeeze the fuel feed line almost shut and it will idle up and run GREAT. Untill you give it some throttle and it will die as it then is starved for fuel. I saw a site that sells a tbi intake converted to run a holley carb. I could put a 2 barrel on it be just fine. It said the intake would fit VG30 motor, that is what i have isnt it? All it takes is one of the MAF lines to go off and it will run poorly. The MAF isn't an all-or-nothing proposition. It will still try to pass some information on to the computer, and the computer will attempt to run on what information it does get. If I had to guess, I'd said the air temp sensor line is trashed. I bet the computer isn't seeing anything on that line. Take a multimeter and ring out the harness between the MAF plug and the ECU plug. You should be able to find the broken (or high resistance) line that way. Shouldn't take more than about an hour to fix - assuming you cleaned the connectors. Also, did you check the vacuum level at the fuel pressure regulator? Insufficient vacuum would cause rich running. Edited July 11, 2007 by GhostPath Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 11, 2007 Author Share Posted July 11, 2007 (edited) If I had to guess, I'd said the air temp sensor line is trashed. I bet the computer isn't seeing anything on that line. Take a multimeter and ring out the harness between the MAF plug and the ECU plug. You should be able to find the broken (or high resistance) line that way. Shouldn't take more than about an hour to fix - assuming you cleaned the connectors. That sounds like a good idea. Wouldnt happen to know which pins in the ECU plug match the MAF do you, or know where this info could be found? I havent been able to find a wiring breakdown of this rig, or a vacuum diagram. Sure would like to get my hands on that stuff... It does have plenty of vacuum at the regulator. It actually runs better with that line off, primarily because the extra air lets the engine idle higher. I drove it with the line on and the line off, and there was no difference. Edited July 11, 2007 by bigtimemcc Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 (edited) That sounds like a good idea. Wouldnt happen to know which pins in the ECU plug match the MAF do you, or know where this info could be found? I havent been able to find a wiring breakdown of this rig, or a vacuum diagram. Sure would like to get my hands on that stuff... It does have plenty of vacuum at the regulator. It actually runs better with that line off, primarily because the extra air lets the engine idle higher. I drove it with the line on and the line off, and there was no difference. If you look at the top of this forum, you will see a link entitled "Pathfinder Service Manuals." http://www.nissanpathfinders.net/forum/index.php?showtopic=9692 Follow the info there. Download the service manual for the 94 Pathfinder, and then open the "EC" section. Check out pages 8, 9 and 10. All the information you need is in there as there were no significant changes in the engine controls from 92-95 (if not further back to when they pitched TBI). Edited July 11, 2007 by GhostPath Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 11, 2007 Author Share Posted July 11, 2007 (edited) OK, I checked to continuity of all 3 wires on the maf sensor plug to the ecu. I have good continuity on all 3. The ecu still throws code 12 for MAF, and I am at a loss for what to do. Maybe the ECU is bad? The rig was under water at one point, so is it possible that the ECU got fried when it got wet? I dont know if it even is the original ECU, because this is how I got it, previous owner could have had it replaced. Is there any way to check the ECU to make sure it is operating correctly? As a side thought, if I junk the MFI and go for a carb set up, would I need to find a distributor to match? All carbed vehicles I have ever had always had a vacuum advance on the distributor to advance the timing with the engine speed. What do you think? Edited July 11, 2007 by bigtimemcc Link to comment Share on other sites More sharing options...
mws Posted July 11, 2007 Share Posted July 11, 2007 Good luck with the diagnostics. I am sure you can find it and fix it. I understand your frustration, but giving up and putting on a carb will really be a sad compromise.... You will need to change the fuel delivery system (much lower pressure), customize your own linkage, possibly have to tweak some sensors to get the ECU to still provide proper spark curve, etc. And then when it's all done, you are stuck with a carb and all the compromises that come with that. Heat soak problems, poor fuel economy, fuel delivery compromises, etc. Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 11, 2007 Author Share Posted July 11, 2007 Good luck with the diagnostics. I am sure you can find it and fix it. I am glad someone is optimistic, cuz I definately am not. I have spend hours and hours all to no avail. And nobody I talk to has a clue what it could be. I have tried every suggestion given from every shop mechanic to shade tree mechanic. GRRRRRRRRR!!! Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 (edited) OK, I checked to continuity of all 3 wires on the maf sensor plug to the ecu. I have good continuity on all 3. The ecu still throws code 12 for MAF, and I am at a loss for what to do. Maybe the ECU is bad? The rig was under water at one point, so is it possible that the ECU got fried when it got wet? I dont know if it even is the original ECU, because this is how I got it, previous owner could have had it replaced. Is there any way to check the ECU to make sure it is operating correctly? As a side thought, if I junk the MFI and go for a carb set up, would I need to find a distributor to match? All carbed vehicles I have ever had always had a vacuum advance on the distributor to advance the timing with the engine speed. What do you think? Yup, it's quite possible that your ECU got shorted out or damaged while under water. The easiest way to check it is to swap out with another ECU from a known working truck. Where are you located? And, yes, you would need to find a distributor and ignition system if you converted, as ECCS relies on the EFI ECU to work. I am glad someone is optimistic, cuz I definately am not. I have spend hours and hours all to no avail. And nobody I talk to has a clue what it could be. I have tried every suggestion given from every shop mechanic to shade tree mechanic. GRRRRRRRRR!!! It really isn't that hard. It's a lot harder to, say, choose the appropriate jets and needles for a carb. And you've just about eliminated the wiring harness as a culprit. The ECU is the next thing to check. How much resistance did you note between the MAF and ECU connectors? Edited July 11, 2007 by GhostPath Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 11, 2007 Author Share Posted July 11, 2007 (edited) Yup, it's quite possible that your ECU got shorted out or damaged while under water. The easiest way to check it is to swap out with another ECU from a known working truck. Where are you located? And, yes, you would need to find a distributor and ignition system if you converted, as ECCS relies on the EFI ECU to work. I live near Little Rock, Arkansas. I have checked every junk yard, feild, and back yard in this whole state. I think I may have found one about 400 miles away. They wanted $60 plus shipping for it, or I could get mine rebuilt for $300. The bad part is that it is year and model specific. Can only be from a 93 automatic trans 4x4. Havent found one yet. You ever heard of testing the ECU, is it possible? I used a multimeter to check it, the kind with a needle. I used the ohm setting, with no continuity there is infinite ohms, with continuity there is 0 ohms. It buried the needle to 0 ohms on all 3 wires. Edited July 11, 2007 by bigtimemcc Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 I live near Little Rock, Arkansas. I have checked every junk yard, feild, and back yard in this whole state. I think I may have found one about 400 miles away. They wanted $60 plus shipping for it, or I could get mine rebuilt for $300. The bad part is that it is year and model specific. Can only be from a 93 automatic trans 4x4. Havent found one yet. You ever heard of testing the ECU, is it possible? Testing it is possible, but I think only Nissan dealers can do it. Your ECU isn't actually year/model specific. The part number is, but you can use the ECU from any other 49-state automatic V6 Pathfinder from 90-95. There will be some small fuel mapping changes, but your truck will run properly. Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 11, 2007 Author Share Posted July 11, 2007 Testing it is possible, but I think only Nissan dealers can do it. Your ECU isn't actually year/model specific. The part number is, but you can use the ECU from any other 49-state automatic V6 Pathfinder from 90-95. There will be some small fuel mapping changes, but your truck will run properly. I have another computer that I tried, but it would not hardly run at all with it hooked up. All the parts stores I have called and the salvage yards have told me that it had to be the same as what is in it now. Some other years can swap out with one another, but not the 93. Why, you got one in yer back pocket? (hopefully) Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 I have another computer that I tried, but it would not hardly run at all with it hooked up. All the parts stores I have called and the salvage yards have told me that it had to be the same as what is in it now. Some other years can swap out with one another, but not the 93. Why, you got one in yer back pocket? (hopefully) You can't use some of the older computers, because they used TBI instead of MPFI. Here are some options. eBay is your friend: http://cgi.ebay.com/ebaymotors/1992-Pathfi...sspagenameZWD1V http://cgi.ebay.com/ebaymotors/Nissan-Path...sspagenameZWDVW Link to comment Share on other sites More sharing options...
94extreme Posted July 11, 2007 Share Posted July 11, 2007 yeah. make sure the one you get is for a setup like yours. the main differnce is in TBI and MPFI like ghost here is advising. as to the carb idea: seems all the reasons against it have already been spelled out. you wouldn't need to necessarily change the intake manifold but you'd have to fins a carb that'd fit the "seat." fuel pump pressure would probably one of the main things you'd have to deal with besides the ECU starving for input. i'm sure it's doable but i can't recall anyone doing it. rich condition: one of your sensors or the ECU are reading something wrong or not reading.. seems like you checked most of them. your timing is correct? did the truck always do this since you've owned it? if not, when did it happen? did you service anything about that time? Link to comment Share on other sites More sharing options...
Simon Posted July 11, 2007 Share Posted July 11, 2007 If it's always done this, and you know it's been swamped....is it possible that the PO put in a higher flow rate fuel pump, causing your issue? If it's getting too much fuel, and squeezing off the lines seems to help, I'd give that a look. Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 If it's always done this, and you know it's been swamped....is it possible that the PO put in a higher flow rate fuel pump, causing your issue? If it's getting too much fuel, and squeezing off the lines seems to help, I'd give that a look. Even if the PO had installed a Walbro 255 or similar, the fuel pressure regulator would be able to bleed it off to standard operating pressures. The other thing is that the ECU would be throwing "overrich" or "oxygen sensor failure" codes, not "MAF failure". Link to comment Share on other sites More sharing options...
Simon Posted July 11, 2007 Share Posted July 11, 2007 Good point GhostPath. I had overlooked the Pressure regulator. Link to comment Share on other sites More sharing options...
88pathoffroad Posted July 11, 2007 Share Posted July 11, 2007 I'd say that if it has been underwater it needs to have the the relays in the interior kick panels and the ECU connectors inside under the carpet examined for corrosion, the grounds all need to be removed, cleaned and re-bolted, and it wouldn't hurt to remove the top cover of the ECU to examine the motherboard for corrosion. The spare ECU you got could be bad also, you never can tell. Oh, and do NOT attempt to ohm out pins on the ECU, your voltmeter can damage it if you get the right pins shorted or run even a small amount of voltage through them. I'm sorry you're having such a terrible time trying to get it to run right, but if it's been dunked there are a LOT of things that could be wrong with it. How deep was it sunk? Any ideas? Link to comment Share on other sites More sharing options...
GhostPath Posted July 11, 2007 Share Posted July 11, 2007 I'd say that if it has been underwater it needs to have the the relays in the interior kick panels and the ECU connectors inside under the carpet examined for corrosion, the grounds all need to be removed, cleaned and re-bolted, and it wouldn't hurt to remove the top cover of the ECU to examine the motherboard for corrosion. The spare ECU you got could be bad also, you never can tell. Oh, and do NOT attempt to ohm out pins on the ECU, your voltmeter can damage it if you get the right pins shorted or run even a small amount of voltage through them. Seconded - I was telling him to check between the MAF wiring harness connector (not the MAF) and the ECU wiring harness connector (not on the actual ECU itself, the connector with all the wires going into it instead). Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 12, 2007 Author Share Posted July 12, 2007 Hey guys, I really appreciate all the support I am getting on here, REALLY. You guys know your stuff. I checked the resistance on everything I could find specs for and everything checks out. I called the STEALERSHIP and asked if they had a way to check the ECU, and they said the only way was to have one from a running donor swapped out to see if that fixed the problem. Oh yeah, I could buy a new one for $970 and he was just itching to order it for me. I went to car-parts.com and fount one 200 miles away having it shipped here in a few days. The ECU that is on it has salvage yard writing on it. I am sure it is not the original, but it also looks questionable. There is some corrosion around the hole where the LEDs are. While I'm waiting for the part.......off with the cat. Gonna let the bolts set with some penetrating oil on them for a day then hollow that thing out. I heard the junk inside was worth some big bucks. Funny how one mans pain is another mans treasure Thanks guys! Link to comment Share on other sites More sharing options...
GhostPath Posted July 12, 2007 Share Posted July 12, 2007 Hey guys, I really appreciate all the support I am getting on here, REALLY. You guys know your stuff. I checked the resistance on everything I could find specs for and everything checks out. I called the STEALERSHIP and asked if they had a way to check the ECU, and they said the only way was to have one from a running donor swapped out to see if that fixed the problem. Oh yeah, I could buy a new one for $970 and he was just itching to order it for me. I went to car-parts.com and fount one 200 miles away having it shipped here in a few days. The ECU that is on it has salvage yard writing on it. I am sure it is not the original, but it also looks questionable. There is some corrosion around the hole where the LEDs are. While I'm waiting for the part.......off with the cat. Gonna let the bolts set with some penetrating oil on them for a day then hollow that thing out. I heard the junk inside was worth some big bucks. Funny how one mans pain is another mans treasure Thanks guys! The junk inside, as you put it, is also worth 10 years and/or a $100,000 fine if you get caught. And, it's stupid - the difference between a straight pipe (or a hollowed out OEM cat) and a modern free-flow cat is less than ONE HORSEPOWER. Plus a replacement free-flow cat is less than $100 (this one is for 1990-1995): http://store.summitracing.com/partdetail.a...mp;autoview=sku Lets see. It's less than $100 to stay legal, less than 1 hp difference between legal and illegal, and it's 10/100 if you get caught, plus you won't pass a sniffer inspection at all. Personally, I don't think it's worth the risk. Back in ancient times (oh, say, when people used carbs), when there was no such thing as high-flow cats for affordable prices, yeah, it was worth it. Today? I would get the high-flow cat and install it. It's no longer worth the pain in the arse to NOT be legal, and there's no real power cost. Link to comment Share on other sites More sharing options...
bigtimemcc Posted July 12, 2007 Author Share Posted July 12, 2007 Lets see. It's less than $100 to stay legal, less than 1 hp difference between legal and illegal, and it's 10/100 if you get caught, plus you won't pass a sniffer inspection at all. Ah, maybe you're right. We dont have emissions tests here where we are so I am not worried there, but I may just get a high flow cat and off with muffler. Get rid of restriction and the cat will quiet it down enough for me. It's not so much the HP gain but mpg loss of the thing being on there. Link to comment Share on other sites More sharing options...
mws Posted July 12, 2007 Share Posted July 12, 2007 Fortunately for you, a properly sized cat won't cost you ANY mpg either! Link to comment Share on other sites More sharing options...
88pathoffroad Posted July 12, 2007 Share Posted July 12, 2007 Mine doesn't have a cat either, no emissions testing at all here. I welded a glasspack in it's place after the bolts and flanges got rusty. One drawback to hollowing out a cat is that it causes turbulence in the exhaust path which can hurt performance at lower RPM's, plus it rumbles more and might produce a bit of a resonant vibe through the floor. No biggie. Link to comment Share on other sites More sharing options...
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