jwthemechanic Posted June 9, 2013 Report Share Posted June 9, 2013 (edited) I just got my maft hooked up and there is a major misfire when any boost is present. Had the same problem before the maf-t. My first guess would be the distributor vacuum adv/retard is not working but it seems to work when I apply vac or pressure (just swapped and same prob). Can anyone think of any other reason this would happen? This is a newly installed engine swap from a 88 starion into a 87 montero.I checked the wiring from ecm to the maf-t because it was missing the plug just like the maf-t I bought. I am going to reset TPS again and see if that helps.(reset and still same prob). Is there a chance the schematics are wrong for the green/red wires? Are there any sensors that would be affected by boost? MAP or something that senses boost? I know some starions have a boost sensor but I thought that was just for the electronic gauge to work. Edited June 9, 2013 by jwthemechanic Quote Link to comment Share on other sites More sharing options...
jwthemechanic Posted June 9, 2013 Author Report Share Posted June 9, 2013 (edited) Just found a broken wire in harness!! Hope this is the prob. (edit. Not the problem) Please help Edited June 9, 2013 by jwthemechanic Quote Link to comment Share on other sites More sharing options...
spoolinturbo Posted June 9, 2013 Report Share Posted June 9, 2013 well you said you had the problem before the maf-t. I would have fixed that before you installed the maf-t. But I would still buy a new vac advance, they are cheap and u can have a known good part in your problem tree for fixing the issue. check plugs thoroughly they will be a good indicator as to what is going on. If you haven't changed them recently, or gapped them. wires condition ect. Back to the basics is what I say. Quote Link to comment Share on other sites More sharing options...
jwthemechanic Posted June 9, 2013 Author Report Share Posted June 9, 2013 (edited) The engine is rebuilt. It was throwing the maf code when I first hooked everything up with the stock maf. That is why I got the maf-t. Everything else checks out. It runs great till any boost is present. The maf is set up as a blow thru Edited June 9, 2013 by jwthemechanic Quote Link to comment Share on other sites More sharing options...
spoolinturbo Posted June 9, 2013 Report Share Posted June 9, 2013 and you are not getting any codes with the maf-t? if your misfiring under boost, I would still check your plugs, wires, coil, FPR, fuel filter. under load these items will cause a misfire. especially if your running fine and not under load. what kind of plugs are you running? Quote Link to comment Share on other sites More sharing options...
jwthemechanic Posted June 9, 2013 Author Report Share Posted June 9, 2013 (edited) No codes with maf-t or ecm, swapped FPR, swapped dist., unplugged knock sensor (no timing change when disconnected but sensor was pretty rough looking). I am going to check plugs and the coil resistance. The wires are newer with no visible damage. Is there any way a bad maf could cause this? It is being blown thru and it was used. It runs very well till I hit a little boost. Edited June 9, 2013 by jwthemechanic Quote Link to comment Share on other sites More sharing options...
Amonje123 Posted June 10, 2013 Report Share Posted June 10, 2013 What are your afr readings? Quote Link to comment Share on other sites More sharing options...
jwthemechanic Posted June 10, 2013 Author Report Share Posted June 10, 2013 (edited) Don't have afr yet. Wideband is waiting for exhaust system to be installed. dumping out down pipe for now. I really think it is ignition related, the spark plugs are the ones recommended on this forum (# update coming) and look to be burning clean. The coil might be breaking down under load but is testing good. Is there anyway to check the ignition control box? Edited June 10, 2013 by jwthemechanic Quote Link to comment Share on other sites More sharing options...
Squrlsquash Posted June 10, 2013 Report Share Posted June 10, 2013 besides these issues, have you checked the spark plug gap?ignition issue could be fine at idle and misfire under boost Quote Link to comment Share on other sites More sharing options...
StarquestRescue Posted June 10, 2013 Report Share Posted June 10, 2013 You need to tune the maft. A wide band gauge is required for that. You also should do a boost leak test by pressurising the intake track after the turbo or through it. However it is easier to plumb up. If air leaks after the airflow meter the engine will run richer than it should. In blow through there are less places for this to happen. In blow thur, your mas should be after the innercoler. The vacuum advance can be tested with air pressure and a mighty vac if you have access to them. Quote Link to comment Share on other sites More sharing options...
JAinsworth Posted June 11, 2013 Report Share Posted June 11, 2013 I take a new piece of vacuum line, put it on the dizzy, and suck on it. You should have immediate resistance and not be able to draw any air in. Then place your tongue over the end of the line and see if it holds pressure. If it does, you VA is good. Jimmy Quote Link to comment Share on other sites More sharing options...
Technology Posted June 11, 2013 Report Share Posted June 11, 2013 Also, fix problems before modding the car. I had a crazy misfire once that turned out to be a missing jet-valve. It had just disintegrated and was leaking air, causing problems. I replaced a lot of stuff and spend money on a bunch of stuff that I didn't need. Quote Link to comment Share on other sites More sharing options...
jwthemechanic Posted June 11, 2013 Author Report Share Posted June 11, 2013 No jet valves, Engine swapped into a carbed montero, never even sat in a starion, the parts were pieced together from this forum. The coil turned out to be bad even though it tested ok on the bench (knew not to trust that). Now it is searching idle even after 2 tps resets. I'm going to rebuild the TB (if I can find the seals i bought) and swap the isc. Too bad I have to wait till next tues to have the exhaust fabbed. I really should have just dropped a chevy 4.3 in, but this has definitely been a refresher course of the 80's cutting edge tech. Quote Link to comment Share on other sites More sharing options...
mike.horist Posted June 20, 2013 Report Share Posted June 20, 2013 (edited) The distribuiter on the pickup truck has a vac advance. the dist.on the turbo motor has a boost retard. swap the pickup dist out and use the conquest dist...toss the timeing mark out the window, mark your harmonic balancer , by taping it over find the center and use a protractor from your kids pencil case at 30* b.t.d.c.... Edited June 20, 2013 by mike.horist Quote Link to comment Share on other sites More sharing options...
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