surging idle on startup then dies?

dieselmandustin · Jul 3, 2016

Just helped a buddy put a motor in his truck. He did the Windows mod on his old motor got this motor from a wrecked truck. Everything on the motor checks out fine compression wise. It starts right up no problem and idles smooth for a few seconds then the idle starts to oscillate up and down till just quits. Starts right back up and same issue. Any ideas what could cause this? All sensors are off the original motor and it didn't have this issue. Kinda stumped.

gnxtc2 · Jul 3, 2016

What year is his truck and what year did the donor motor come from?

Billy T.
[email protected]

Mikey1 · Jul 3, 2016

its my truck. The model of the truck is a 2000 the motor was a late 99. It has new ipr new honey badger hpop. New valve springs pushrods. Etc. Tried changing the cps no change. If i keep it at a high rpm it runs completly fine smooth no missing. Buz test came out fine. No excessive blowby. When i was at its worse. It would idle but i could put the pedal in the floor and nothing would happen. I changed the ipr and it came back but it still acts like it trying to find idle. It jumps from 600rpm to 1000rpm

gnxtc2 · Jul 3, 2016

MAP sensor hooked up?

Billy T.
[email protected]

dieselmandustin · Jul 3, 2016

I finally got logged back in bud. Thanks for answering his question.

Mikey1 · Jul 3, 2016

Yes i thought the same with the map sensor i actually changed it out and still no change. Took out the chip still no change just really touchy throttle from the single shots. Glad you finally got logged on buddy!

Magnum PD · Jul 3, 2016

Air in HPO system?

Mikey1 · Jul 3, 2016

It doesn't seam to be air. When its in a higher rpm it runs great. If i hold it at any rpm lets say 2000 no load. It will atudder but it studders up in rpm not down. Then when i let off its constanly searches for idle.