smallblock12 Posted August 27, 2014 Report Share Posted August 27, 2014 so my 86 has a new motor with around 1500 miles. been redoing tons of things and it was running great with the exception of leaks. i finally got the leaks all takin care of and it starts running choppy and dies in the middle of the road. finally got it bump started and made it home. its an all stock 86car does throw a mas code, but i was told its because my tps isc reset isnt correct and its not pulling enough air at all time to read over 10hz. it will idle smooth but if you let it idle all the way down for like 20 seconds it starts to get choppy till you tap the gas againnew/ repaired:injectors, new clips soldered, checked all connectors, have tried and tried and gotten the tps isc as close as possible, new cap and rotor, coolant temp sensor and stedibani adjustable fpr.so i oredered a new set of ngk wires and brass cap and rotor along with a walbro 255 hoping that its just my stock fuel pump gettng hot and failing. any other suggestions if this does not fix the problem Link to comment Share on other sites More sharing options...
speedyquest Posted August 27, 2014 Report Share Posted August 27, 2014 Have tested both your tps and isc to ensure they are within spec as per the manual? That could cause your issues. Especially if your tps doesn't pass the sweep test. Link to comment Share on other sites More sharing options...
smallblock12 Posted August 27, 2014 Author Report Share Posted August 27, 2014 so the tps could cause it to run choppy and tall out randomly once its hot? itll run fine sometimes and other timess not Link to comment Share on other sites More sharing options...
speedyquest Posted August 27, 2014 Report Share Posted August 27, 2014 Well even if you have the TPS at the famous .5 volts after its warmed up it can still not pass a sweep test. A sweep test like the service manual describes will show whether it has a smooth transition from the "closed" position to the full "open" position of the throttle plate. What can happen is that the tps sends choppy signal to the ecu which obviously would see it as the throttle plate moving. It can cause bad idle, so can a bad isc motor. Link to comment Share on other sites More sharing options...
smallblock12 Posted August 27, 2014 Author Report Share Posted August 27, 2014 the bad idle isnt what im worried about. its the bogging stalling out randomly when its at full operating temp. like its starving for fuel or no spark. Link to comment Share on other sites More sharing options...
mbruneaux Posted August 28, 2014 Report Share Posted August 28, 2014 the bad idle isnt what im worried about. its the bogging stalling out randomly when its at full operating temp. like its starving for fuel or no spark. Could be related.. Link to comment Share on other sites More sharing options...
Shelby Posted August 29, 2014 Report Share Posted August 29, 2014 off over looked is the wiring and connectors , make sure ALL connectors and wiring to them are in perfect shape Link to comment Share on other sites More sharing options...
pure_insanity Posted August 29, 2014 Report Share Posted August 29, 2014 Makes me think about the cts. Coolant temp sensor. That thing will do some funky stuff. The wiring plug to the cts on most cars ive seen looks pretty poor. Link to comment Share on other sites More sharing options...
smallblock12 Posted August 30, 2014 Author Report Share Posted August 30, 2014 (edited) its a new cts and the wiring looks good. i swapped tps's and tries doing the reset again. no matter what the car wants do do a small idle surge after you rev it unless you keep the idle around 1200. you can get it to idle around 1000 but afte 10 seconds or so it drops to 750 and gets choppy. still has a hard hiccup under wot acceleration at 3k but is smooth under light acceleration. still trying to make time to put the walbro 255 in. Edited August 30, 2014 by smallblock12 Link to comment Share on other sites More sharing options...
Shelby Posted August 30, 2014 Report Share Posted August 30, 2014 whats the air/fuel meter doing at idle ,, if you don't have one they are a very useful tool in trouble shooting vacuum leaks and fuel , sensors problems one thing looks good means nothing ,,the terminals them selves MUST BE CLEAN and making a good connection I've seen the connectors look like new but once unplugged the terminals looked like trash , making little or NO connection , so unplug and clean each and every connector on the engine , and fuse box's , basically clean every connector you see Link to comment Share on other sites More sharing options...
smallblock12 Posted August 30, 2014 Author Report Share Posted August 30, 2014 ill go over it tomorrow and i need to wire up a narrowband to see if its a lean condition or rich. ran out of places to check for vacuum leaks. i deleted most of them and replaced old with new. i just rebuilt the throttle body and hooked up the vacuum canister so my heater controls and everything work correctly under boost. out of the 6 others i've owned this is the only one that has led me into a dark corner. what stumps me is the mas code being the only code its throwing Link to comment Share on other sites More sharing options...
Shelby Posted August 31, 2014 Report Share Posted August 31, 2014 a torn or ripped air boot can cause all sorts of weird symptoms and codes to be set Link to comment Share on other sites More sharing options...
smallblock12 Posted September 3, 2014 Author Report Share Posted September 3, 2014 Well after going g through everything again, I finally found another issue. Driving In the rain, wipers on, headlights on and defrost the ampere gauge dropped hard and it had a consistent choppy idle. It tested at 12.2 volts idling So I ordered an alternator from autozone. But I was wondering, I have a 90 amp galant one my buddy built for my talon. Plug is the same as the 88 89. Could I splice the plugs and run it. I had no idea the 86 was even different Link to comment Share on other sites More sharing options...
Recommended Posts