TrailChaser Posted July 25, 2010 Share Posted July 25, 2010 How is it that my engine is starting and running backwards???? I just confirmed that is did indeed start and run backwards.(while I yelled kill it..kill it!!!) It was doing the stutter start and then it stopped and WENT BACKWARDS all three belts "exhaust" cloud from the snorkel everything went the opposite direction than it was going when the starter was spinning it. How is this possible? Can a clogged cat make an engine run backwards due to extreme back pressure forcing the pistons the wrong way? PS: This is not a joke. I'm 100% dead serious about everything here and desperately need some solid advice. Should I just cut the cat off and see how she runs? Link to comment Share on other sites More sharing options...
Tungsten Posted July 26, 2010 Share Posted July 26, 2010 So if you put the truck in forward gear, does it drive in reverse? Link to comment Share on other sites More sharing options...
Mr.510 Posted July 26, 2010 Share Posted July 26, 2010 I've seen this happen a couple times on older Datsuns but am surprised that an injected Pathy engine could run backwards for any length of time. Some old L-series four cylinders will 'diesel' (run backwards with no ignition spark) all day long after the ignition is turned off if you don't let the clutch out in gear to stop the crankshaft. I let an old POS L16 'diesel' for 20 minutes once to prove it was possible. The times that I've seen it happen at startup a backfire into the intake due to a serious electrical miss caused the engine to reverse direction just as the starter disengaged. I don't *think* any amount of exhaust back pressure would be a contributing factor. Do you have the firing order mixed up? If the plug wires are scrambled or you have cross-firing between two wires (or inside the distributor cap) that could be a factor. Does it start and run backwards consistently? Link to comment Share on other sites More sharing options...
Mr.510 Posted July 26, 2010 Share Posted July 26, 2010 I just read your other thread. EGR and PCV will have zero effect on something like this. You've got a major ignition timing issue. Whether it's the ECU, crank angle sensor, cross-firing, or the firing order is scrambled you have to be getting spark to the wrong plug at exactly the right time (piston near BDC) for this to happen. You probably get a 'chuff' noise in the intake just as the starter disengages. This is a cylinder firing near Bottom Dead Center while the intake valve is still open. You aren't, by chance, running it with just a flex plate without a transmission bolted up are you? A lack of flywheel inertia can contribute to a problem like this as it takes much less energy to reverse the direction the crank is rotating. Racing engines with very light rotating assemblies are highly prone to 'dieseling' at shutdown due to low rotational inertia. Link to comment Share on other sites More sharing options...
TrailChaser Posted July 26, 2010 Author Share Posted July 26, 2010 Thanks for the reply, and I like your website. I've suspected timing, but when it cranks it runs really good until it reaches operating temps. I discovered the power steering pump pressure sensor was broken off, and I know it has something to do with the idle. I think when it's running backwards it's reburning the fuel that was in the exhaust system. Do you think the ECU could just be on the fritz and about to go out? How bad is it for an engine to run backwards for about 4-5seconds? Link to comment Share on other sites More sharing options...
MY1PATH Posted July 26, 2010 Share Posted July 26, 2010 haha almost all our gound equipment @ work diesels when you shut it off. the colder it is the longer it does so and you can't leave it till its off. I sivered next to compessor unit waiting for it to finally die for Idono how long (prolly over 30~45 min) and I think it was like -5 out. 1 Link to comment Share on other sites More sharing options...
Mr.510 Posted July 26, 2010 Share Posted July 26, 2010 Thanks for the reply, and I like your website. I've suspected timing, but when it cranks it runs really good until it reaches operating temps. I discovered the power steering pump pressure sensor was broken off, and I know it has something to do with the idle. I think when it's running backwards it's reburning the fuel that was in the exhaust system. Do you think the ECU could just be on the fritz and about to go out? How bad is it for an engine to run backwards for about 4-5seconds? My first guess would be the ECU is going haywire. It could also be the crank angle sensor in the distributor but I personally have only known them work perfectly or not at all. The fact that it runs decent until it warms up makes me think ECU or coil. A bad coil isn't likely to make a cylinder get a spark at the wrong time and make it start backwards though. If it consistently starts backwards my guess is 99% it's the ECU. No other component could screw up consistently enough to make that happen! The power steering pressure switch or idle kickup won't have an effect on any of this. On running backwards, if the ignition is 'on' the injectors are spraying fresh fuel onto the intake valves regardless of which direction the crank is turning. The ECU has no way to know the crank is turning the wrong way so it goes about business as usual. The tach probably works too. Even with the intake and exhaust valve's functions reversed (as you described exhaust out the snorkel) some of the fresh fuel sprayed at the intake valves is going to dribble into the cylinders and keep it running. It takes barely more than a little vapor to keep an engine running poorly at a few hundred rpm. I would not let it run backwards very long as it will have little or no oil pressure. Soot will foul up the air flow meter in short order as well. Link to comment Share on other sites More sharing options...
silverton Posted July 26, 2010 Share Posted July 26, 2010 I want a video of this! Link to comment Share on other sites More sharing options...
TrailChaser Posted July 26, 2010 Author Share Posted July 26, 2010 I just took a few videos, and I'm uploading one of them to youtube right now. it'll still be processing for the next few minutes. In that video it's trying to start up backwards after being started forward, but it's not running backward like it was yesterday.(Yesterday it fully started backwards) I got it started and drove it around for about 15mins or so. It's not having the idle issue anymore and runs good while it's running. When I kill it it dies like it's suppose to, but then it doesn't start again unless I pull start it.(starter is turning the engine fine and IMO plenty fast enough) I'm thinking of doing the unthinkable.... Taking to a mechanic and paying out the nose for a diagnosis. Only $60 for an hour!!! Link to comment Share on other sites More sharing options...
Cuong Nguyen Posted July 26, 2010 Share Posted July 26, 2010 Perhaps a bad starter or some crazy short to cause the starter to not disengage but run backwards? Mister510 is right about the ecu not knowing which way the crank is turning. Link to comment Share on other sites More sharing options...
TrailChaser Posted July 26, 2010 Author Share Posted July 26, 2010 Hey Cuong, It's been a while since I seen/heard from you. I hope you're doing well. The starter seems to be fine. It's held up to lots of abuse in the last few days of turning the engine over trying to find the gremlin. I uploaded another video of it starting. The backward video was shot just before the video of it cranking up. I killed it and recranked it a few times then when for a drive to warm it up. After warming up it wouldn't start back up. In the video of it actually starting you can tell that it's struggling instead of just firing right up like it normally does. (same as the one I already posted in my last post) Link to comment Share on other sites More sharing options...
Slashjt Posted July 26, 2010 Share Posted July 26, 2010 wow that's crazy.. I've never seen something like that. Good luck with that Link to comment Share on other sites More sharing options...
jprater88 Posted July 27, 2010 Share Posted July 27, 2010 HMMMM this is extremely weird. and in all the years i have been a mechanic i have never seen this issue... but it seems like others have said it may be an ECU issue.... It seems as though it is having an issue of the ecu not knowing base timing on initial start up... notice how it stutters and hesitates on a regular start up for a brief moment... I have a question have you buried it in any mud or deep water lately.... or had any other odd occurrence that may not seem related to this issue... It may help to know what problems have happened lately to the vehicle and find the common item in them all... sorry if that was long winded but it will help me rap my head around the fact that a internal combustion engine just did that... Link to comment Share on other sites More sharing options...
TrailChaser Posted July 27, 2010 Author Share Posted July 27, 2010 After doing some research(googled "engine starting backwards") I found a few more cases were it has happened. I'm going to bite the bullet and go with the ignition module for $100 as that seems to be the best bet so far. I wish I knew someone around here that has a pathy I could just borrow the module from for a quick test. After you install one from an auto parts place there's no returning it. Link to comment Share on other sites More sharing options...
jprater88 Posted July 27, 2010 Share Posted July 27, 2010 man if i was back in texas i would let you borrow mine even though i dont know you from adam... i have other vehicles so it wouldnt be a problem.... but i am not there Link to comment Share on other sites More sharing options...
silverton Posted July 27, 2010 Share Posted July 27, 2010 anyone else notice the slight wobble in the crank pulley when it's cranking? Link to comment Share on other sites More sharing options...
tmoore4512 Posted July 27, 2010 Share Posted July 27, 2010 Dude that is pretty wild. Link to comment Share on other sites More sharing options...
MY1PATH Posted July 27, 2010 Share Posted July 27, 2010 anyone else notice the slight wobble in the crank pulley when it's cranking? yep, our snouts are pretty long. the balancer starts doing its job better as you reach higher rpm so as long as you see it smooth out when you rev it your good. summit has aftermarket balancers from a company that just started diging up the nissan line of engines. Cost a pretty penny but they are built in a differant fassion that I bleive will reduce you low rpm wobbles if you are concerned about it. Lil heavier but the hieightned efficency is a must for big bores and strokers. Link to comment Share on other sites More sharing options...
Cuong Nguyen Posted July 27, 2010 Share Posted July 27, 2010 I'd let you borrow mine but my Pathfinder isn't here in Houston . What were you doing before you noticed something was wrong? Link to comment Share on other sites More sharing options...
TrailChaser Posted July 27, 2010 Author Share Posted July 27, 2010 Mine isn't either. I moved to Arkansas. It actually happened when I moved here. I had no problems loading it on the trailer to pull behind the U-haul. Maybe now the truck thinks it's a trailer queen and therefor not required to run right anymore. lol I think there may be a spare ignition modules in my parts box. I almost have enuff spare parts in that box to build a new pathy, or a space ship. Cuong, did you ever get that throttle cable situation figured out? I still have the one I gave you. Now that I'm living out in the sticks I can install one of those fancy GPS things for a speedo. I think/hope there is alot less crime around here compared to SW Houston. Link to comment Share on other sites More sharing options...
Precise1 Posted July 27, 2010 Share Posted July 27, 2010 After doing some research(googled "engine starting backwards") I found a few more cases were it has happened. I'm going to bite the bullet and go with the ignition module for $100 as that seems to be the best bet so far. I wish I knew someone around here that has a pathy I could just borrow the module from for a quick test. After you install one from an auto parts place there's no returning it. I'm willing to bet I have what you need on my parts pathy. I can pull it and ship it to you to test with. Let me know... B Link to comment Share on other sites More sharing options...
TrailChaser Posted July 27, 2010 Author Share Posted July 27, 2010 Thanks B, Cuong and jprater88, but I went to storage and found an ignition module that I took off my old parts pathy in the box full o' pathy stuff this morning.(I should make a list of everything in there.lol) That wasn't it. I also went ahead and bought a new rotor to replace the one I recently installed when I did the tune up a month or so ago. Neither had any effect on the problem. It's still doing the same thing. Maybe I'll replace the coil next. I'm feel like I'm just randomly replacing stuff at this point hoping that something will be the fix. I'm about to drill a big hole in the exhaust right before the cat... Then either way I'll be forced to install the now high flow cat I bought a few months ago.(exhaust work is a nightmare for me) Link to comment Share on other sites More sharing options...
Cuong Nguyen Posted July 27, 2010 Share Posted July 27, 2010 No kidding about SW Houston, I got my satellite radio and Zune stolen. Luckily I didn't have my radio deck installed at the time... I'm moving back to my Mom's for a bit next month.. You should try spinning the crank by hand. Maybe you can replicate the reverse rotation. I know the cam assemblies are under some tension when you do timing belt changes. remove all accessory belts? Link to comment Share on other sites More sharing options...
Precise1 Posted July 27, 2010 Share Posted July 27, 2010 You are welcome, just trying to help. I haven't offered up any advice because quite frankly, I haven't a clue about this one. I'm about to drill a big hole in the exhaust right before the cat... Rather than drill a hole, can't you just unbolt it after the crossover pipe?? You don't even have to drop it all the way, just give it a decent sized gap to fart through... B Link to comment Share on other sites More sharing options...
5523Pathfinder Posted July 27, 2010 Share Posted July 27, 2010 What about a fuel injector leaking? Im assuiming this happens when its hot(engine)? The fuel could be leaking into the cylinder and, if its hot enough, it may be combusting. All most the same thing as pinging. Try hooking up a fuel pressure tester and start it, then stop. Pressure should hold for quite some time. Just thought I would throw that out there.... Link to comment Share on other sites More sharing options...
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