CamH Posted December 27, 2009 Share Posted December 27, 2009 Hey guys, I'm having more MegaSquirt troubles. On Christmas, I was driving along - car was running really great, and all of the sudden, the wideband started reporting very lean while driving (like 16-17), and the car developed a misfire. I've checked all electrical connections, and they look alright, all of the fuses look good. I checked the spark plugs and they were white so I am thinking the wideband is probably accurate. Fuel pressure at idle is just above 30PSI and it goes up with manifold pressure (1:1) just like it should. Another thing I've noticed: the AFRs will vary from when the engine is started (they seem normal) until the engine is revved (they go higher) - so if I change my VE table to get a decent idle prior to revving, it will be too lean after revving, and vice versa. This makes absolutely no sense to me! Anyways, I don't think I should need to change anything in the tune because the car was running so good prior to this. But now I am bashing my head up against a wall. I'll try pretty much anything. Umm, here are two datalogs and the MSQ I am running off of. I'm not sure how helpful they will be though wtf.zip Quote Link to comment Share on other sites More sharing options...
dan5138 Posted December 27, 2009 Share Posted December 27, 2009 Check the basics first. A bad CTS or MAP sensor could cause a lean run. Also don't rule out having a bad fuel pressure regulator. My FPR failed on Christmas and completely flooded the engine. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted December 27, 2009 Share Posted December 27, 2009 I went through a similar problem. I still haven't completely figured it out. My first hunch when it happened to me was dirty injectors. Quote Link to comment Share on other sites More sharing options...
CamH Posted December 27, 2009 Author Share Posted December 27, 2009 Check the basics first. A bad CTS or MAP sensor could cause a lean run. Also don't rule out having a bad fuel pressure regulator. My FPR failed on Christmas and completely flooded the engine. I don't think it's CLT (you meant CLT and not CTS right?) because I am basically ignoring CLT in my tune. (All values about 80F are 100% warmup enrichment.) However, what's the best way to test the MAP sensor? Should I consider buying another MegaSquirt unit? I went through a similar problem. I still haven't completely figured it out. My first hunch when it happened to me was dirty injectors. My tune is actually based on yours! But yeah, I thought about dirty injectors as well. After posting this thread, I went and ran a bottle of injector cleaner through the main fuel pump (which feeds the fuel rail directly), I swapped out for brand new spark plugs (NGK BPR6ES), and I changed the oil (Royal Purple 5-30W and K&N filter). None of these things made any noticeable difference. Quote Link to comment Share on other sites More sharing options...
CamH Posted December 27, 2009 Author Share Posted December 27, 2009 Okay, guys, here is another datalog of the car with an MSQ file. I richened it up a little and it hasn't seemed to have done anything. The thing that really sucks is that this car is my DD junk.zip Quote Link to comment Share on other sites More sharing options...
niner11 Posted December 27, 2009 Share Posted December 27, 2009 I had a MSII problem at one time that was very similar. Turn the key on and check what your manifold pressure is in megatune or tuner studio. Now start the car and see what it is while your at idle. I had a small hole in my vac line from the motor to MS and it took forever to figure out what was wrong. I see your elevation is under 1000ft so maybe a engine off pressure of 100 and idling in the ballpark of 30 or so. Chuck I'm on my mac or I would look at the datalog, sorry Quote Link to comment Share on other sites More sharing options...
CamH Posted December 27, 2009 Author Share Posted December 27, 2009 I had a MSII problem at one time that was very similar. Turn the key on and check what your manifold pressure is in megatune or tuner studio. Now start the car and see what it is while your at idle. I had a small hole in my vac line from the motor to MS and it took forever to figure out what was wrong. I see your elevation is under 1000ft so maybe a engine off pressure of 100 and idling in the ballpark of 30 or so. Chuck I'm on my mac or I would look at the datalog, sorry Cool. Thanks for the advice. I will look in to that ASAP. Also, I just reflashed the firmware on the MegaSquirt. No difference. Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 I had a MSII problem at one time that was very similar. Turn the key on and check what your manifold pressure is in megatune or tuner studio. Now start the car and see what it is while your at idle. I had a small hole in my vac line from the motor to MS and it took forever to figure out what was wrong. I see your elevation is under 1000ft so maybe a engine off pressure of 100 and idling in the ballpark of 30 or so. Chuck I'm on my mac or I would look at the datalog, sorry Well, I just redid the vacuum lines and it didn't help at all. Great advice though! Keep it coming! Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 OK, I just disassembled my fuel filter to check things out. It looked perfect so I don't think I'm having issues with that. Quote Link to comment Share on other sites More sharing options...
SidWell Posted December 28, 2009 Share Posted December 28, 2009 Do you have old log files from last summer? Check you vacuum readings at idle from an old log and look at the vacuum at idle now. That will tell you right away if it is a vacuum leak. Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 OK, I just compared the log files from today, with a log file from the 24th (the day before it started running poorly) Apparently, now it idles at 36KPA, and on the 24th, it idled at about 30KPA - however, I'm not sure that this indicates anything out of the ordinary because I now have it idling slightly higher and I had to go up in my VE tables to get it idling at a decent AFR. What do you think? Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted December 28, 2009 Share Posted December 28, 2009 I am wondering if your MAP sensor is going bad, but in looking closer to your datalogs, I see a lot of weird data. I also see a lot of accel/decel enrichments taking place. Strange voltages, strange RPM readings.... Here is what I would do. Recalibrate the TPS, re-enter the data for the temperature sensors, raise your accel/decel thresholds and see what that does. It also looks like your voltages are low. Check your alternator and your battery. Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 I am wondering if your MAP sensor is going bad. Any good way to test for this, or should I just consider ordering another MegaSquirt unit? Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted December 28, 2009 Share Posted December 28, 2009 Read my above post again...I edited it as I found some strange things in the logs. I have no idea what is making the weird data. Electrical noise? Bad battery? Shorted wiring? Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 Voltage looks low, huh? Do you think just the voltage being low could affect everything else to that extent? I'm gonna go toss a charger on the battery right now and let it sit for a while and give it a shot. edit: not ignoring the rest of your post. It sounds like you're noticing some nose in the TPS signal - I've had this the entire time. I think it has to do with its proximity to the coil. It hasn't caused any issues for me in the past though... Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 Okay, so, I left the battery on the charger until it the charger said it was done. Hoping this would work, I took it out on a drive, and to get gas. So, anyways, it ran like crap the whole way there. While I was waiting for the gas to pump, I richened up the VE table. By 40. Across the board except for the bottom left part of the table (idle was doing fine) Anyways, that made it run pretty much fine, but it doesn't really solve my issue. There's no way my VE tables should be this high with a 6.4 req fuel and 550CC injectors! Anyways, here's another datalog and MSQ if anyone cares to look at it. datalog200912272146.zip Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted December 28, 2009 Share Posted December 28, 2009 I dont have a minute to look at your new datalogs but in the last one, the voltage was around 12.3 volts with the car running. Plus there were several drop outs in the data. You should have around 14 volts in a running car. Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 Hmm, I wonder if that means my alternator is on the way out again. These remanufactured alternators are garbage. I did put the battery on a charger before that run so it seems like that should have at least temporarily solved the issue. I doubt that the voltage is only dropping for the MegaSquirt because it gets its power right from the + battery cable where it connects to the starter... Quote Link to comment Share on other sites More sharing options...
niner11 Posted December 28, 2009 Share Posted December 28, 2009 Sorry that this has not been an easy fix so far. I see variations in my idle kph just due to changes in atmospheric pressure I suppose it's not a big difference from 30 to 36kpa at idle. I run two different boards and everytime something is wrong and I swear its the MS unit itself......I swap it and the identical symptoms appear on the other one. It always seems to be something external. (though the 3.57 board is much cleaner regarding noise) For the money, if you can't chase this down I would by a stim if you do not have one. If the MS board is responsive on the stim with different inputs and reads normal atmospheric kpa then I would trust it. Just curious, is your car still running poorly at mid rpms? or is this just at idle right now? Quote Link to comment Share on other sites More sharing options...
CamH Posted December 28, 2009 Author Share Posted December 28, 2009 Sorry that this has not been an easy fix so far. I see variations in my idle kph just due to changes in atmospheric pressure I suppose it's not a big difference from 30 to 36kpa at idle. I run two different boards and everytime something is wrong and I swear its the MS unit itself......I swap it and the identical symptoms appear on the other one. It always seems to be something external. (though the 3.57 board is much cleaner regarding noise) For the money, if you can't chase this down I would by a stim if you do not have one. If the MS board is responsive on the stim with different inputs and reads normal atmospheric kpa then I would trust it. Just curious, is your car still running poorly at mid rpms? or is this just at idle right now? I may consider ordering the stim this afternoon. I think I am also going to try replacing the alternator, and a user on another forum suggested that I measure the resistance through the injector wires from the DB37 connector to the actual injector connectors. Seems like a solid enough idea. Also, the car was running great across the entire powerband. The issue from the other thread was actually due to a stuck injector and I corrected that issue by swapping out to a set of RC Engineering 550CC injectors. Now, though, I am having issues throughout the entire powerband. Quote Link to comment Share on other sites More sharing options...
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