CO_pathfinder Posted November 23, 2014 Share Posted November 23, 2014 I'm really making this thread to confirm that my list of things to check is complete and covers all of the most likely reasons why my truck is misfiring randomly, and why the tailpipe is black as tar (misfire and richness combined) Real quick background on my issue: The truck runs mostly fine. It ALWAYS starts within a half crank to 1, and doesn't have any issue starting. When its cold, it properly high-idles until op temps are reached, then it drops down to 740-780, where it will slightly oscillate back and forth. As far as I know, this is not a problem. There is a random misfire both when the truck is cold and when it is warmed up. Its audible and can barely be felt while in the truck. The truck smells like total gasoline when its started up and is cold outside, but the smell mostly goes away once warmed up. The truck doesn't smell awfully rich while running when warmed up, but the fact that the tailpipe, and all associated holes in my exhaust, are blacked by some serious soot leads me to think that my truck is running slightly rich, in addition to the fuel going through my exhaust because of the missing. Mode 1 diagnostic (checking the o2) reads no issue, and flashes about 1/sec. Mode 2 diagnostic (fuel/air mix) flashes only the green light, which means that the ECU is reading >5% rich. Mode 3 diagnostic (codes) gives me "55," all clear, which is weird because I should be getting a 63-68 or a 71, because the truck is audibly misfiring. When driving, I can't feel the misfiring at all, unless a slight (and slow) pulsation in the pedal at high RPM is what I would feel with a random misfire. Changed the timing belt about a month ago, and it might be off a tooth, because when I snap the throttle 2-3k, it hesitates a little. Above 3k, it doesn't hesitate at all. From a stop, if I don't work the throttle and clutch right, it dips pretty low and almost doesn't go, then picks up and takes off as usual. As far as gas mileage after the swap, I haven't really noticed a decrease, but then again my gas mileage never really was predictable to begin with. The misfire was there before I changed the timing belt, as was the black tailpipe. The vehicle did pass emissions back in June. It goes in order of a combination of cost-minded stuff and easiness. 1. Check ECU codes 2. Replace cap, rotor and wires 3. Wiggle wires for MAF, TPS 3. Check and regap plugs; replace if necessary 4. Check O2 sensor resistance (anybody got a link for how to do so?) 5. Confirm ignition timing with timing light; fix if necessary 6. Scratch head a little if not yet fixed 7. Re-do my timing belt 8. etc etc Let me know if I'm missing anything, or if there are things about what I've said that might tip you off to another, less common issue. Link to comment Share on other sites More sharing options...
gv280z Posted November 24, 2014 Share Posted November 24, 2014 pvc, egr, fuel filter, seafoam / injector cleaner, hook up a donor ecu from a known good running similar year model and engine d21 / wd21, you might have a failing ecu, also there is a delicate little "timing disc" (for lack of a better term) contained beneath a plastic protective "plate" inside your distributor underneath the rotor, make sure that little disc is clean of any foreign debris, dirt / dust, I've got a feeling it works similar to the way a laser reads the microscopic pits and blanks that work like binary code in a cd while it's spinning inside a cd-rom drive. Also you might have a bad throttle position sensor. Unhook it, spray some electrical contact cleaner on the contacts in the harness and re-connect. Oh yeah, vacuum lines, check those too. Are you saying you did a vg33 swap and that's the engine that's running bad? Link to comment Share on other sites More sharing options...
CO_pathfinder Posted November 24, 2014 Author Share Posted November 24, 2014 (edited) Are you saying you did a vg33 swap and that's the engine that's running bad? Not to be rude, but I feel like you just threw literally every result that comes up when you search "misfire" at me. No, I haven't done a VG33 swap, and I didn't mention anything that might even remotely allude to that lol. hook up a donor ecu from a known good running similar year model and engine d21 / wd21, you might have a failing ecu, Quite a jump there... What would lead you to believe that I have a failing ECU, esp. considering that the truck starts fine, the gas mileage is fine, and the truck only has 80k on it? also there is a delicate little "timing disc" (for lack of a better term) contained beneath a plastic protective "plate" inside your distributor underneath the rotor, make sure that little disc is clean of any foreign debris, dirt / dust This I can understand as a possibility. I'll look into it, though IIRC my distributor has never been touched before. pvc, egr, fuel filter, seafoam / injector cleaner, I feel like a fuel filter is a stretch for a misfire and richness issue, but ok.... I've never heard of an EGR going bad before the truck hits at least 150k, but again, I suppose I can check that, if it hasn't been resolved by one of the more likely things that should be on the list above it haha. Also you might have a bad throttle position sensor. Unhook it, spray some electrical contact cleaner on the contacts in the harness and re-connect This I can certainly do. While I don't really see how a loosely connected TPS would cause my listed issues, I don't see anything wrong with trying. Care to elaborate on this? Edited November 24, 2014 by CO_pathfinder Link to comment Share on other sites More sharing options...
gv280z Posted November 24, 2014 Share Posted November 24, 2014 I've never done a search for "misfire" so I don't know what comes up. Everything I told you came straight from me thinking about things that could possibly be causing your problems. I mentioned a swap because I mis-read you had mentioned doing a timing belt swap, and I thought you meant engine swap. Failing ecu? It seems to me that they can halfway fail, have some circuits go bad and still manage to start and run the vehicle. I don't really understand it, it's just a notion, you know? Maybe someone else can explain it better. Fuel filter is easy to do and bad dirty fuel could certainly affect the way the engine runs if the gas is so dirty it's almost not even combustible, it may cause mis-firing symptoms. EGR valve, I don't really know why I said this other than the fact that it's an integral component of the systems that run your engine and you hadn't already mentioned it. About the throttle position sensor, I never said anything about it being loose, It may be bad or just have dirty contacts and not making a good connection. If it were malfunctioning, the ecu would never really know how much gas to send to the engine for it to run correctly. Anyway I'm just a 39 year old dumbass that's owned about 20 cars over the last 24 years and read everything automotive that I can get my hands on, you know it's not like I've picked anything up along the way, I'm just throwing random bs at you so I can feel like I have something important to say. I'm sure the others can give you some good solid, helpful information. Good Luck. Link to comment Share on other sites More sharing options...
CO_pathfinder Posted November 24, 2014 Author Share Posted November 24, 2014 I've never done a search for "misfire" so I don't know what comes up. Everything I told you came straight from me thinking about things that could possibly be causing your problems. I mentioned a swap because I mis-read you had mentioned doing a timing belt swap, and I thought you meant engine swap. Failing ecu? It seems to me that they can halfway fail, have some circuits go bad and still manage to start and run the vehicle. I don't really understand it, it's just a notion, you know? Maybe someone else can explain it better. Fuel filter is easy to do and bad dirty fuel could certainly affect the way the engine runs if the gas is so dirty it's almost not even combustible, it may cause mis-firing symptoms. EGR valve, I don't really know why I said this other than the fact that it's an integral component of the systems that run your engine and you hadn't already mentioned it. About the throttle position sensor, I never said anything about it being loose, It may be bad or just have dirty contacts and not making a good connection. If it were malfunctioning, the ecu would never really know how much gas to send to the engine for it to run correctly. Anyway I'm just a 39 year old dumbass that's owned about 20 cars over the last 24 years and read everything automotive that I can get my hands on, you know it's not like I've picked anything up along the way, I'm just throwing random bs at you so I can feel like I have something important to say. I'm sure the others can give you some good solid, helpful information. Good Luck. I'm not bashing man. I'll take anything I can get. It just threw me when you said engine swap, ya know? Now I know why you did and its understandable. I think we can both agree that there are a lot of people here that sometimes don't know what they are talking about. I'm sorry for the misunderstanding. I changed the fuel filter this morning, no noticeable change in misfire frequency or smoothness. I'll be checking the dizzy laser-like thing hopefully tomorrow if this damn white stuff stops falling from the sky. Link to comment Share on other sites More sharing options...
RF600 Posted November 30, 2014 Share Posted November 30, 2014 How many miles do you have on the O2 sensor? O2's can get slow as they age. Even if it shows good you might consider changing it. If you get too much fuel into the cat it can plug it. Plugged exhaust is not good. Link to comment Share on other sites More sharing options...
CO_pathfinder Posted November 30, 2014 Author Share Posted November 30, 2014 The truck's only got 80k now, so I'm assuming the o2 only has 80k as well. Link to comment Share on other sites More sharing options...
RF600 Posted November 30, 2014 Share Posted November 30, 2014 If I remember right O2's are supposed to be changed out at about 100k. It wouldn't hurt to change it. I was still getting good fuel mileage on my rig with a bad O2. Link to comment Share on other sites More sharing options...
CO_pathfinder Posted November 30, 2014 Author Share Posted November 30, 2014 If I remember right O2's are supposed to be changed out at about 100k. It wouldn't hurt to change it. I was still getting good fuel mileage on my rig with a bad O2. I'm thinking then that that's part of it. I still get between 15 and 18, running rich, misfiring, and with timing that feels slightly off. Its a miracle. Going to try to see if I can get a few hours together soon, before finals, so that I can diagnose and hopefully resolve this misfire issue. Link to comment Share on other sites More sharing options...
adamzan Posted November 30, 2014 Share Posted November 30, 2014 If the o2 sensor is original, change it. 1 Link to comment Share on other sites More sharing options...
CO_pathfinder Posted December 1, 2014 Author Share Posted December 1, 2014 If the o2 sensor is original, change it. Okey dokey. Is it cool to just get one from my local parts store? Link to comment Share on other sites More sharing options...
adamzan Posted December 1, 2014 Share Posted December 1, 2014 Yes. Link to comment Share on other sites More sharing options...
CO_pathfinder Posted December 1, 2014 Author Share Posted December 1, 2014 Danke. Will see how that changes things Link to comment Share on other sites More sharing options...
adamzan Posted December 1, 2014 Share Posted December 1, 2014 You can also unplug it and see if it drives better. It would still run rich though Link to comment Share on other sites More sharing options...
Precise1 Posted December 1, 2014 Share Posted December 1, 2014 You can also check the current at hot and cold to see if they are within spec first. I believe the acceptable range/test proceedure is stated in the FSM, but .1v cold and 1v hot comes to mind. B Link to comment Share on other sites More sharing options...
CO_pathfinder Posted December 1, 2014 Author Share Posted December 1, 2014 You can also check the current at hot and cold to see if they are within spec first. I believe the acceptable range/test proceedure is stated in the FSM, but .1v cold and 1v hot comes to mind. B That's the first step I need to take, because if I find that the o2 is in fact working, then I would have to look into replacing my ECM. Thank you both, B and Adam Link to comment Share on other sites More sharing options...
adamzan Posted December 1, 2014 Share Posted December 1, 2014 Replace the ecu? That's pretty extreme...they hardly ever fail and I would suspect a sensor way before that. Link to comment Share on other sites More sharing options...
CO_pathfinder Posted December 2, 2014 Author Share Posted December 2, 2014 Replace the ecu? That's pretty extreme...they hardly ever fail and I would suspect a sensor way before that. Haha oh I know, thats why I'm going to check and replace the o2 sensor first. Link to comment Share on other sites More sharing options...
adamzan Posted December 2, 2014 Share Posted December 2, 2014 What about your coolant temperature sensor? They are cheap but easy to check. What about your grounds? I was chasing a slight miss and found my main neg cable was loose where it contacts the body. It also solved about 10 other little issues. Any exhaust leaks? And did you ever check the ignition timing? Link to comment Share on other sites More sharing options...
CO_pathfinder Posted December 2, 2014 Author Share Posted December 2, 2014 I have crazy exhaust leaks.... The PO broke the tailpipe off trying to remove and replace the stock muffler, and so everything from the cat back is poorly welded together bits and pieces of new and old exhaust piping.. Need to get that fixed, just don't have any money for it.I checked the ignition timing a while ago, didn't seem to be off at all, but weirder things have happened. I'll check that this weekend.I really need to check my grounds. I know I've got one underneath the truck that frayed out, but I haven't really looked for any other spots.What kind of an effect would exhaust leaks cause? Link to comment Share on other sites More sharing options...
Bubbley11 Posted December 2, 2014 Share Posted December 2, 2014 Noise and poor o2 readings, depends on where the holes are. I just cut out the muffler and straight piped it with the cat. Seems to run better. Not noticeable mpg loss, except from me flooring it everywhere now, cause it sounds good. Link to comment Share on other sites More sharing options...
CO_pathfinder Posted December 3, 2014 Author Share Posted December 3, 2014 They really aren't holes so much as porous welds. I've never seen that much porosity in my life. all of the bad welds are after the cat, which is like a foot behind where it would be stock. Link to comment Share on other sites More sharing options...
RF600 Posted December 6, 2014 Share Posted December 6, 2014 If the welds were before the cat it would dilute the readings. Link to comment Share on other sites More sharing options...
adamzan Posted December 6, 2014 Share Posted December 6, 2014 Anything after the o2 sensor won't affect it. 1 Link to comment Share on other sites More sharing options...
CO_pathfinder Posted August 19, 2015 Author Share Posted August 19, 2015 Well, I've found time to revisit some of these issues tonight, and will continue to do so for the rest of the week before I go back to school. To revisit, my remaining symptoms are misfire (random but not "constant"), unsteady idle, and occasional high idle after warm-up. The truck no longer runs rich (thanks to NGK plug wires and a new fuel filter), but the truck does backfire/misfire heavily during geared deceleration when the engine speed is between 1800 and idle (750) rpm. Is this an indicator that it might be my IACV or another idle related sensor that is malfunctioning? I disconnected the following sensors individually... O2 - ran far richer and didn't solve misfire or unsteady idle. Coolant temp sensor - again, ran richer, maybe slightly smoother, but still with a misfire and unsteady idle. PCV - pinched the line, not sure how effectively I pinched it, but it didn't change the engine speed (FSM EF&EC-51) I want to see if the EGR valve is sticking or not next, but I really don't know how to tell. Also, noticed one of my injector screw-down things was cracked today.. could this be causing problems, as it appears that the injector isn't all the way in the hole now.. attached below are an audio-only video of my exhaust, and two pictures detailing what I mean about the injectors.. any help is welcome! http://tinypic.com/m/ivfy2o/3 cracked injector (cap)? You can see where it is cracked right in the middle of the picture. what it looks like in other cases, for reference Link to comment Share on other sites More sharing options...
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