makenzie71 Posted January 28, 2016 Share Posted January 28, 2016 I've had no problems until today. I go and fire the thing up and let her idle for a bit...I had just re-routed the circuit for the cooling fan and was testing it out to make sure it was working (previously the fan was just shorted to ground and on all the time)...before it even got to running temp it started running rough and stalled. I go and check things out...nothing obvious. FI light is on for the fuel injectors but it's been on since I built the buggy (I have not resolved to replace the injectors yet). I go to start it back up and she runs just fine for a minute...then rough and stalls. If she sits still for any length of time she starts right up and runs no problem, but only runs for a few minutes before stalling.Fuel pressure sits at 39psi at idle and never dips before 35 running. I changed the fuel filters. I changed the oil (because I was down there and couldn't remember when I'd done it last)...no water in the oil or steam in the exhaust, anyway, so at least that rules out a blown head gasket, and never overheated I cleaned the air filter and made sure the airbox was clean I checked to make sure that all four cylinders were, in fact, firing (check) What could I check next? I'd start taking those 12/13/14/15 error codes more seriously but the thing runs beautifully until it hits a certain point. I'm stumped. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 okay...so what happens after the engine warms up? What changes between warmup and cold? I'm convinced it has something to do with warmup. Link to comment Share on other sites More sharing options...
fstarocka01 Posted January 29, 2016 Share Posted January 29, 2016 Can't see what model this is.. Sure you didnt hook the choke cable on something while you were in there? Can you explain how the bike ran before and after, if reliably at all? Sent from my SM-G900M using Tapatalk Sounds like fuel delivery issue.. Somehow .. Sure filters are routed correct way .. And no airlock? Sent from my SM-G900M using Tapatalk Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 It's a fifth gen 800. Choke cable is disconnected.It ran beautifully. I've had no problems at all, always started right and ran smooth and fast. The only thing that's changed between running great and today is I moved a light bar and moved the ground for the fan from the frame back to the thermal switch.This is actually a vfr powered minibuggy. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 I want to add that, once symptoms start, it affects everything. Engine revs are lethargic, lots of misfiring and backfiring, and dying. Link to comment Share on other sites More sharing options...
Knight Posted January 29, 2016 Share Posted January 29, 2016 The ground relocation is a hint that it may be the potential building in a bad ground. Once both sides of the circuit are at the same voltage, the components being fed cannot work correctly. Check the relocated ground. As a test you could short the ground to the frame. If no then double check the condition of the wiring in that area, such as the supply side of the fan did not get shorted, etc. Before starting you could put an ammeter between the negative battery cable and the battery. The current should be 3mA (.03 A) or less. The ignition must be off when doing so. This tests for a short but only tests circuits that are live with the ignition off. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 I thought so as well, but even after moving it back to the frame the problem continues. I do know that it is definitely temperature related, though. Where is the block temperature sensor? To my knowledge the fan circuit is just a live 12v feed any time the key is on and what triggers the fan is a coolant temp sensor. The ECU shouldn't be seeing anything from it. I've had it disconnected before with no ill effect. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 Okay today I can say it's not even getting up to operating temps before acting up. Coolant hose on the pump side of the motor is cold, right side of the motor is hot. Nothing is flowing through the radiator. Can anyone tell me where the block temp sensor is? I don't have a dash so I can't see what the ECU sees as far as temps go. I need to be able to get to it and put a standalone probe in place. I would love to hear any other suggestions. Someone has suggested a vacuum leak or a clog. I will be going over my vac lines. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 Found the sensor. I disconnected it and started the engine up again and...same problem. After 13 minutes of idling it started stumbling and dying...and died. The coolant had only just started flowing through the radiator. So, I think that I can say it's not a matter of what the ECU is seeing from the sensor. It ran perfectly up to the point of stumbling...no fade. So I'm stuck looking for something else, I fear. I'm going to pull off that sensor and put in an aftermarket temperature gauge and see if it's possibly overheating and my t-stat or waterpump are stuck. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 Or not...because it seems to need some kind of special wrech/socked to get the damn sensor out. I really don't think that's my problem, anyway. I need to find something else that can cause this. Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted January 29, 2016 Member Contributer Share Posted January 29, 2016 I would think that it is temperature related but make sure all the grounds for the ecm are in place . I know that this is in a buggy but still look at the wiring diagram as the only change you have made is to a ground circuit which can provide a ground route for the ecm if there is not another ground route . The diagram for the wiring is available here in the download section and should help Just make sure that there is a good ground circuit for the ecm and then if needed you can unhook sensors that might help isolate the problem . There is a good chance it is the throttle position sensor that has gone but my bet is still the ground circuit . I hope this helps . Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 I'm trying to sort out now what all wires from the ECU should be straight to ground. As an update....the FI light that was present from a clogged fuel line months ago was cleared. The ECU reads no other codes and that one has not come back. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 I ran new grounds from the battery to the frame, radiator, engine, carriage, engine cradle, and I ran one from the only wire I could find from the ECU that I could see was a straight ground. No change. Link to comment Share on other sites More sharing options...
Forum CEO HispanicSlammer Posted January 29, 2016 Forum CEO Share Posted January 29, 2016 temp is in the vee of the engine block under the throttle body. If I can remember correctly. Im thinking a vacuum leak myself, probably into the fuel pressure regulator, or map sensor. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 29, 2016 Author Share Posted January 29, 2016 I'll check the lines to both...but if it were leaking at the fpr would it cause this sputtering and dying? It seems that it would cause RPM to rise. But it does act like fuel starvation...I think the ECU is just not spitting fuel in after the engine is warm. Link to comment Share on other sites More sharing options...
makenzie71 Posted January 30, 2016 Author Share Posted January 30, 2016 Checked vacuum on a few peoples' advice...it pulses so it's hard to be really sure but it's pulling the needle past 20lbs at idle. Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted January 30, 2016 Member Contributer Share Posted January 30, 2016 Maybe disconnect as many sensors that are easy to get at plug them in one at a time to see if there is any change .Process of elimination . Link to comment Share on other sites More sharing options...
makenzie71 Posted January 30, 2016 Author Share Posted January 30, 2016 What all do I look for? I know there's a map sensor and a engine temp sensor. If I unplug the engine temp sensor it's harder to start and runs rough for a minute (when cold), but then no change beyond that. I don't think there's that many sensors to pull from and I'm pretty sure that if one were just flat out faulty it would send a message to the ECM, and thus the FI light...correct? Not trying to be argumentative with suggestions...I long for someone to tell me my assumption is wrong and I should "do that thing" and it fixes everything... Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted January 30, 2016 Member Contributer Share Posted January 30, 2016 I dont think it is a bad sensor ,but instead a poor connection either at the ecm connections or at one of the sensors . I would suspect the main problem to be the throttle position sensor but it could also be the map sensor circuit that gives load information to the ecm . I would also start with some basics like are the plugs really fuel fouled or oil fouled ,check the fuel pressure regulator by unplugging vacuum and check to see if it changes anything . Spray a little carb cleaner around the throttle body boots and see if anything changes better or worse . Sometimes it is something very simple that we try to over analyse problems . Link to comment Share on other sites More sharing options...
makenzie71 Posted January 30, 2016 Author Share Posted January 30, 2016 I will check the TPS and map sensor circuit in the morning, though I have to admit I find it hard to believe either would just suddenly fail without sending a fault to the ECM...I'd also love to be wrong and be able to isolate a solid problem. I will check the plugs as well. They're easy to replace...I may just throw some new ones in. I tried carb cleaner around the throttles and I did actually find a vacuum line open. It's apparently been open since I did the swap, but I plugged it all the same. No change, of course, other than dropping the idle speed down. Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted January 30, 2016 Member Contributer Share Posted January 30, 2016 This sounds weird but just thinking can the tps and map sensor plugs be changed as that will also give very errattic readings to the ecm . I think they are the same plugs but different colours Link to comment Share on other sites More sharing options...
makenzie71 Posted January 30, 2016 Author Share Posted January 30, 2016 Like is it possible they were switched? I can say for certain they were not switched. Or do mean to replace them? I'll definitely inspect them in the morning. Can the map sensor cause my problem? Seems if it was acting up it would act up at all times. Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted January 30, 2016 Member Contributer Share Posted January 30, 2016 I would look closely at the plugs and maybe pull off the vacuum line going to the fuel regulator as these sometimes will leak giving a very rich mixture . Any fuel coming out of this could be your problem . It seems strange that there are not any codes set but that usually indicates that it is outside the parameters of the fuel system . Yes the map sensor can cause this to happen ,follow check steps in service manual Link to comment Share on other sites More sharing options...
makenzie71 Posted January 30, 2016 Author Share Posted January 30, 2016 I tried to test the map sensor but the manual requires me to use a test harness. Can I just test the wires for the map sensor at the ECU or does this test harness do something more significant than just give me test points? There was no fuel coming from the regulator vac line. I pulled the plugs and, while they don't look great, they don't look like "hey this is obviously your problem". They're cheap, I'll be replacing them anyway. Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted January 30, 2016 Member Contributer Share Posted January 30, 2016 Not sure if you are able to check colour of the spark while you have the plugs out but a weak orange one is not good , white or bright blue is best . Link to comment Share on other sites More sharing options...
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