strange cutting out/backfiring problem

[nissan ka]

i have a 95 ka-t with a blow through mafs that has been running amazingly since last june up until recently. this is what happened

yesterday on a trip from tallahassee to daytona, florida which is a ~250 mile, 4 hour trip, i started having and overheating problem. the characteristics were a blown headgasket. it started heating up after 100 miles of travel, i stopped, let it cool down, and kept driving where it did it 40 mile later, then 20 miles again after that then just bobbed kind of for the rest of the trip. so the next day i did a compression test and it came out fine. all cylinders were 180 or over. so i changed the thermostat and the old one had seemed somewhat stuck closed. i also changed my oil and washed the engine bay.

the washing of the engine bay is what my dad and i think the problem is. we left the house and made a 15 or so mile trip where the temps stayed normal but a new problem arrived. whenever you would start to head toward boost, the entire engine would buck, stutter/hesitate, and backfire. we thought water had gotten into the spark plugs so when we got home we dried out every spark plug and harness clip in the engine bay, and i checked for any boost leaks. well its been an entire day and we have been trying it out at intervals all day and its still doing it. it seems to be getting better, but its stil pretty bad. if anyone can halep that would be awsome.

thanks, dimitri

[nissan ka]

so its still bucking, but not while the wastgate arm is disconnected so there must be some boost leak im missing or maybe a bad injector o-ring or something.
but no, its not the old thermo, its a new one. the system is completely burped. i did a comression test and it was slowly losing compression. i am closing off certain things like my heater core and turbo coolant lines individually to mark off possible leak spots. i think it might be the radiator, mainly because over winter break i had to seal it up with wet-weld. im going to try another radiator after i check the other stuff to see if thats it.

[DJ_Sunrise]

Washing the engine bay shouldn't cause any problems.. We wash dozens here at toyota with no problems.. Spraying shit left and right no issues. The only things I can imagine are boost leaks bro. Measure the outside diameter of the intake for your turbo. Go to home depot or lowes and buy a pvc elbow of similar size.. if its too big.. you wont be able to slip it into the existing coupler.. so try to get a similar diameter.. worst case scenario, you can tape around one end of the elbow to make it slip well into the coupling for the turbo intake.. Oh.. so anyway.. buy a pvc elbow, and cap it on one end. drill a hole where ever conveniant, and shove a tire valve stem through it. Glue it. If you wan't, ill send you pictures of the one I use. Take off intake, mount the beotch.. Pump air by means of compressor through it.. Have someone watch your boost gauge.. Don't go too high.. 2-3 PSI higher than you plan on runnind. Oh.. do all of this on a COLD engine. You will hear a shitload of leaks all over the place, believe me. Fix =) If you need help, email me. [email protected]

-Bart