snowboard419 Posted April 7, 2015 Share Posted April 7, 2015 So my truck has been running very poor lately. Running very rich, missing and stumbling from idle to high speed hot and cold. I replaced spark plugs and read the new plugs after about 50 miles and they were quite sooty. Initailly i thought maf, coolant temp, tps. but all have tested perfectly as per fsm. fuel pressure is correct. and i just replaced the maf with a junkyard unit but no change in running at all. I have ohmed out the wiring harness from all sensors to ecu and everything is coming back spot on. I am starting to run out of ideas. Your thoughts? Link to comment Share on other sites More sharing options...
adamzan Posted April 7, 2015 Share Posted April 7, 2015 o2 sensor? Link to comment Share on other sites More sharing options...
snowboard419 Posted April 7, 2015 Author Share Posted April 7, 2015 It is reading ok based on the ecu self diag. I also unpluged it in an attempt to get the engine to run in open loop, but still no change. Link to comment Share on other sites More sharing options...
Kingman Posted April 7, 2015 Share Posted April 7, 2015 Checked timing and/or the belt it's self? 1 Link to comment Share on other sites More sharing options...
Precise1 Posted April 7, 2015 Share Posted April 7, 2015 Are you sure you are getting a good spark at the plugs? Any vacuum leaks? (only considering they might compound the problem) No ECU codes? It doesn't happen often, but sometimes the ECUs fail. Check the connection there, and look for water damage? B Link to comment Share on other sites More sharing options...
snowboard419 Posted April 8, 2015 Author Share Posted April 8, 2015 checked spark at a couple of random plugs, tested fine. I have sprayed the entire manifold looking for vacuum leaks with no avail. ECU shows no codes but it does read rich on the mixture test. No signs of any water near the ecu or connector but i have not actually opened it up yet. I have yet to check timing, i had inspected the belt not very long ago. but those are my next steps before I source an ecu. I have an M30 ecu in my garage waiting to help a vg34 nistune build but i don't want to be changing any wiring until i have this thing running well so i know if i screw anything up during the swap. Link to comment Share on other sites More sharing options...
chrisq Posted April 9, 2015 Share Posted April 9, 2015 Definitely check the timing with and inductive timing light. Seems like you are describing some of the symptoms of off timing. Your FSM will tell you where it should be (probably 15 before top dead center). Easy to reset or adjust. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
snowboard419 Posted April 19, 2015 Author Share Posted April 19, 2015 So I think I have it figured out. I burrowed a vantage pro lab scope from the snap-on guy and started poking around. I did a voltage signature test on the injectors and had some readings that were all over the charts. cyl # 2 looked good but everything else was off. so i then ohmed out all the injectors one by one and got the following. #1 no reading #2 12.75ohms #3 no reading #4 10 ohms #5 75 ohms #6 41 ohms. so I am kind of amazed this thing even runs. Anyone have a set of injectors for sale?? Link to comment Share on other sites More sharing options...
rickpyle13 Posted April 21, 2015 Share Posted April 21, 2015 I've got some on a spare fuel rail Link to comment Share on other sites More sharing options...
toughroad Posted April 21, 2015 Share Posted April 21, 2015 Do a compression test and lets see the result. Link to comment Share on other sites More sharing options...
Precise1 Posted April 21, 2015 Share Posted April 21, 2015 So I think I have it figured out. I burrowed a vantage pro lab scope from the snap-on guy and started poking around. I did a voltage signature test on the injectors and had some readings that were all over the charts. cyl # 2 looked good but everything else was off. so i then ohmed out all the injectors one by one and got the following. #1 no reading #2 12.75ohms #3 no reading #4 10 ohms #5 75 ohms #6 41 ohms. so I am kind of amazed this thing even runs. Anyone have a set of injectors for sale?? I question the no readings and that only 2 injectors were in the proper 10-14 ohm range. Try it again with a different meter. I have a few, not 6. What color code do you have? B Link to comment Share on other sites More sharing options...
snowboard419 Posted May 17, 2015 Author Share Posted May 17, 2015 Hey, sorry i have not made an update in a while but here is where we sit. I had re tested all the injectors at the actual injector and got very similar readings with 2 different meters and earlier i said no reading when i should have said out of limit reading they were in the mega ohm range. so i got some injectors online and swapped them out, new vac lines, valve cover gaskets, upper intake, etc. put it all together and it ran a lot better but still has a dead miss at idle worse when cold. so did a compression test finally( should have been the first or second thing i did ) and the readings are as follows #1-130 #2-130 #3-130 #4-130 #5-130 #6-10 all of the good cylinders were within 1-3 psi of each other. But I tell you what I am a damn pro at getting to that number 6 plug now. Time to find a vg33. Link to comment Share on other sites More sharing options...
fleurys Posted May 18, 2015 Share Posted May 18, 2015 could it be just a valve spring that is broken on your number 6 ? At 10 psi, this is pretty significant loss of pressure and for me it's either a huge hole in the piston or a valve that stays open... Link to comment Share on other sites More sharing options...
Precise1 Posted May 18, 2015 Share Posted May 18, 2015 Agreed, that something is so different on 1 cylinder makes me think of head issues as well. I have heard of cams breaking occasionally... A VG33 is always a nice upgrade, but it might be worth just pulling that valve cover gasket and see if it might be a reasonably cheap/easy fix. You know your situation best. Sorry it wasn't an easier fix! B Link to comment Share on other sites More sharing options...
snowboard419 Posted May 19, 2015 Author Share Posted May 19, 2015 I was able to do a poor mans leakdown test by removing the valve stem on the compression tester and hooking it up to my air compressor and there is a significant amount of air going by the rings, that was my first hope was valve train issues but it is not looking like that is going to be that simple. Link to comment Share on other sites More sharing options...
rickpyle13 Posted May 19, 2015 Share Posted May 19, 2015 Well how do you know air is getting past your rings and not escaping through a valve? Link to comment Share on other sites More sharing options...
snowboard419 Posted May 20, 2015 Author Share Posted May 20, 2015 The air is coming out the oil fill cap not the tail pipe or intake. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now