PFFlier Posted June 6, 2014 Share Posted June 6, 2014 One day a month or two ago my 91 Pathfinder (VG30E with only about 85K miles) started up rough and when running it in neutral or under load it seemed to miss worst between 1200 and 1500 RPM's. So about 3 weeks ago I finally had time to work on it so I started with the usual suspects, replacing the plugs, cap, rotor, PCV valve and when that didn't do it, the fuel filter and ran some seafoam through the intake and the gas tank. Still running the same, I took it to my son in laws who has a 92 like mine and we started swapping out things trying to isolate the problem, the plug wires, coil, MAF, TPS. Still running the same. By the way, his ran great. This led me to suspect plugged or bad injectors so I listened to the ones I could get to, 1, 3, 5, and 2 and they sounded fine. After talking to a mechanic he thought I was on the right track so I removed the injectors and took them to him. There was quite a bit of crud that came out of the fuel rail when I removed the first injector which happened to be #4. He didn't have an adaptor for that style injector to do a flow test but he put power to them and they all started clicking, checked them with an ohm meter and all read about 11.6 ohms except one which read 126 ohms so I replaced it and had him clean the rest. I bought new o rings and put the injectors back in, replace a couple. Funny thing was, when I checked them at home the bad one read about 16 ohms vs 11.6 or so. Maybe something is loose inside and moving around changing the impedance. Anyway I replaced it. I also had found a wire going to the #4 injector that had the insulation chewed off of part of the wire but there were no shorts. I bought some liquid electrical tape and put a couple coats on it before assembly. After putting it all back together I started it up and it ran perfect. Took it for a test drive a couple miles and it was fine. The next day I took it about 20 miles with mixed driving and it seemed cured (although it did seem to have to crank longer that usual before starting. Then yesterday I started it after about 5 seconds of cranking and ran like crap. It seems to idle fine at about 750 or 800 and pretty smooth but as soon as I bring the R's up it misses badly. Drives worse than before. Runs bad hot and cold and in between. I'm wondering if the longer cranking is a result of a weak fuel pump??? By the way, before doing the injectors I ran the computer (mode 1, 2, 3 and 4) diagnostics and everything read normal. I couldn't find a Schrader valve to use for testing the fuel pressure. I could use some help figuring this one out. Any ideas on what could be the culprit? ECM? Link to comment Share on other sites More sharing options...
PFFlier Posted June 6, 2014 Author Share Posted June 6, 2014 Pulled the plugs again to see what they look like. 1, 3, and 5 look fine, maybe a bit lean. 2, 4, and 6 are fouled with only about 30 or 40 miles on them. The previous plugs looked good before I changed them. Anyone know why bank 2 would misfire? It only has a single coil and control module as far as I can tell. Link to comment Share on other sites More sharing options...
Slartibartfast Posted June 8, 2014 Share Posted June 8, 2014 I wish I had a good explanation for that. My first thought was coolant temp sensor, but yours acts up cold, and the CTS crops up more when the engine's warmed up. All I can think of is some issue with an electrical ground increasing resistance in one bank's injector circuit, causing a lean condition. The computer sees a lean burn on the O2 sensor and adds fuel trying to even out the mix, making the one side run rich. This probably isn't a good explanation, since injectors aren't linear AFAIK, they're either on or they're off. Maybe not a ground, but I'll bet there's something restricting fuel to one side, and I'd be surprised if it was the computer. Link to comment Share on other sites More sharing options...
Kingman Posted June 8, 2014 Share Posted June 8, 2014 Not linear themselves, but the computer controls how long they are open for which is how the AFR is controlled. Have you checked the timing belt? If the one cam slipped a tooth that'll happen. Link to comment Share on other sites More sharing options...
Slartibartfast Posted June 8, 2014 Share Posted June 8, 2014 ^^ A slipped T-belt makes a lot more sense than my theory. Link to comment Share on other sites More sharing options...
Precise1 Posted June 9, 2014 Share Posted June 9, 2014 Agreed, I can't think of any reason why one bank runs richer than the other (especially to foul the plugs) other than if one of the cross over tubes was clogged and one side had pressure/the other starved, but that is unlikely, especially since you had the rails off. B Link to comment Share on other sites More sharing options...
PFFlier Posted June 9, 2014 Author Share Posted June 9, 2014 Slartibartfast mentioned a ground issue which brought to mind something I had meant to check.....those two ground wires on the front top of the engine connecting to the manifold collector, so I cleaned them up and reinstalled but it made no difference. I also took a closer look at the plugs in 2, 4 and 6. 2 is the worst and is all black with gas on it. 4 was better but not good and 6 was even better. I did a drop test unplugging the plug wires one at a time with the engine running. 2 made no change, 4 made a slight change and 6 made about a normal change like 1, 3 and 5. So I plugged a spark plug test light to plug wire 2, then 1 and they both lit up the same. Next I tried pulling plug 2 (the blackest one that made no change when unplugging during running) and plugged it into the plug wire and laid it on top of the engine, started it up and it had a nice bright bluish spark. Remember, this thing ran like a top for a day and a half after I put it back together before it suddenly the next day wouldn't run right. It puts out a lot of grayish smoke. I don't even want to drive it cause I don't want to mess up the O2 sensor or the cat any more. I did order a fuel pressure gauge kit that should me here in a few days. It is such a pain to take the fuel rail out that I think I will wait until I get the tester and eliminate the low fuel pressure possibility. As far as the suggestion of the T-belt sipping, it seams like all the plugs would miss equally and the drop test would have had different results. That's just my reasoning, I'm not saying that I'm right! Link to comment Share on other sites More sharing options...
PFFlier Posted June 9, 2014 Author Share Posted June 9, 2014 OK, here is another thing I thought of.......the only think I did between when it ran good and the next day when it ran bad was I washed it. I also washed the door to the gas cap and inside the door area which was crudded up with grimy dirt from years of not being cleaned. I was using water and a brush then rinsing it with a regular spray (not pressure washing). The cap was tight so I figured this was safe. I don't think this could have done any thing to the cap or got water in the tank but I thought I'd throw it out there for feedback. Link to comment Share on other sites More sharing options...
Terranovation Posted June 9, 2014 Share Posted June 9, 2014 You shouldn't have a problem with doing that, you wash that area when you do a regular wash on the outside with the flap closed although it might have been a better idea to be careful and clean inside that area with a quick spray of degreaser and wipe clean with paper towel, just to avoid any possible water entry. Anyway if you did get water in the fuel system you have a warning light for that to let you know to drain the fuel pump? I do on my '91. Link to comment Share on other sites More sharing options...
PFFlier Posted June 9, 2014 Author Share Posted June 9, 2014 Anyway if you did get water in the fuel system you have a warning light for that to let you know to drain the fuel pump? I do on my '91. Where is that warning light and what does it look like? Link to comment Share on other sites More sharing options...
Slartibartfast Posted June 9, 2014 Share Posted June 9, 2014 That's a diesel thing, gas models don't have them. Also, I'd be surprised if wet gas only screwed with the one side. Good reasoning on the t-belt, sounds like it's probably not your issue then. One thing that moisture does sometimes mess with, though, is the ignition. I would've expected it to dry out by now, but if the distributor cap is cracked, or the spark plug wires are shot, a little moisture could exacerbate arcing and lead to the plugs not firing. Non-firing plugs = dead cylinders = gas on the plugs. Link to comment Share on other sites More sharing options...
PFFlier Posted June 9, 2014 Author Share Posted June 9, 2014 One thing that moisture does sometimes mess with, though, is the ignition. I would've expected it to dry out by now, but if the distributor cap is cracked, or the spark plug wires are shot, a little moisture could exacerbate arcing and lead to the plugs not firing. Non-firing plugs = dead cylinders = gas on the plugs. I got no moisture under the hood between when it ran good and when it didn't (or any other time recently). Also, as I mentioned, the plug and cable spark strong when I pull the plug out. Plus I swapped plugs just in case and no change. I think I will do a compression test just for the heck of it. Link to comment Share on other sites More sharing options...
PFFlier Posted June 10, 2014 Author Share Posted June 10, 2014 I checked the compression and the cylinders were all about 175 except #2 (the bad one which was HIGHER!!! I did it 3 times on that cylinder and got readings of 185 210 and 200. Since that is the cylinder that was fouled the worst, it isn't because of low compression. I have one of those testers with the flexible hose about a foot long with the threaded brass end with a rubber o ring. They are difficult to make sure you are turning them to equal torque when it is down 10" inside the manifold collector, so that could account for some deviation. Still waiting for my fuel pressure gauge to arrive for more thorough testing of the fuel pump and fuel pressure regulator. Link to comment Share on other sites More sharing options...
Slartibartfast Posted June 10, 2014 Share Posted June 10, 2014 Maybe the #2 injector is leaking? Keep us posted, I'm interested to see what it turns out to be. Link to comment Share on other sites More sharing options...
Precise1 Posted June 10, 2014 Share Posted June 10, 2014 I checked the compression and the cylinders were all about 175 except #2 (the bad one which was HIGHER!!! I did it 3 times on that cylinder and got readings of 185 210 and 200. Since that is the cylinder that was fouled the worst, it isn't because of low compression. I have one of those testers with the flexible hose about a foot long with the threaded brass end with a rubber o ring. They are difficult to make sure you are turning them to equal torque when it is down 10" inside the manifold collector, so that could account for some deviation. Still waiting for my fuel pressure gauge to arrive for more thorough testing of the fuel pump and fuel pressure regulator. Same one I have and yeah, I don't think it was meant for 10" deep plug wells. The compression is good enough, I'd rule that out, and I suspect that the timing belt should be ok as well. Check the wiring harness to the injectors on that side... B Link to comment Share on other sites More sharing options...
PeteyPathy Posted June 11, 2014 Share Posted June 11, 2014 (edited) Have you considered fuel pressure regulator? If it has failed on high side will over fuel, which accounts for fouling, if #2 is getting way too much fuel even with good spark won't fire right. Here is where my lack of knowledge shows, does fuel supply from pump feed in @ #2 if over pressure as it passes pressure will decrease down the line. Also is #2 the new injector? Possible they accidentally sold you wrong injector? Rx-7 uses higher flow version of same injectors as ours. Just a couple thoughts, i am inclined to over pressure, I'm assuming that when you found crap in fuel rail you removed and thoroughly cleaned ALL fuel lines from tank forward and replaced fuel filter. Blockage in fuel line before regulator would create high pressure infont of blockage normal or low pressure behind. This would account for rich on one side and lean on other. Edited June 11, 2014 by PeteyPathy Link to comment Share on other sites More sharing options...
PFFlier Posted June 11, 2014 Author Share Posted June 11, 2014 I have considered the fuel pressure regulator and plan on testing it and the fuel pump as soon as my fuel pressure test gauge kit arrives. All I know right now is the regulator doesn't seem to have a leaky diaphragm since there is no gas leaking out the vacuum connection when I pull it loose. I replaced the fuel filter before I resorted to removing the fuel rail, so no I didn't clean the lines before the filter, although I was able to blow through the old filter easily, indicating that it couldn't have been to bad. #6 is the new injector, so that isn't the issue either. As far as fuel line blockage, the fuel comes into injector 5, 3, 1, 2, 4 then 6. Since 1, 3 and 5 are clean and normal, 2 is black, 4 and 6 are better, but not as clean as bank 1, the statement about it being higher pressure before the blockage and lower ahead of it, doesn't make sense in my mind. I'm glad to know others are brainstorming this though! Link to comment Share on other sites More sharing options...
PFFlier Posted August 2, 2014 Author Share Posted August 2, 2014 (edited) OK. Here is the update on this saga. I took it to a mechanic to help pin point our diagnosis. He did the a compression test with plugs out, then put plug into adjacent cylinder of questionable #6 and the pressure went up 10 pounds so we figured the head gasket was going. Replaced head gasket, it ran great for a day or so then ran crappy again. Then it hydro locked when I was trying to start it and I knew it was probably a leaky injector. #2 had fuel in it. I took fuel rail off but left it hooked up to fuel lines, disconnected coil, then removed distributor, grounded its case, then slowly turned the distributor cam gear and observed injectors as their short little burst occurred in firing order. About the 4th time through the sequence #2 stuck on like it was peeing, even after forwarding to other cylinders, even after turning key off until all pressure was bled off of line. So I knew injector #2 needed replacing. When I removed the fuel rail to disassemble I noticed the vacuum tube to the fuel pressure regulator had fuel in it (it was dry earlier in this article) so I ordered one of those up at the tune of about $75.00. Now about 700 miles later it is still running like a top. Drove it around the Olympic Peninsula camping and it ran great. All's well that ends well! PS: that injector I replaced tested fine for resistance. Must have had a bad spring inside or something. Edited August 2, 2014 by PFFlier 1 Link to comment Share on other sites More sharing options...
Kingman Posted August 2, 2014 Share Posted August 2, 2014 Glad to got it fixed! Stick pintles do happen on occasion... Link to comment Share on other sites More sharing options...
Precise1 Posted August 2, 2014 Share Posted August 2, 2014 LOL English? Thank you for the update! I'm not sure about that mechanic, I wouldn't have pulled the head over 10lbs... Glad you finally got it sorted out, my own injector trouble took a lot of BS and time to identify as well. When they run, they run well, and otherwise they are a biatch. Still, I'll take it over carbs... B Link to comment Share on other sites More sharing options...
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