Hey guys,

I swapped my engine out in my 2001 max (1:1 swap, no upgrade) and it's started up fine for the past few days, including today, however it's been having a high idle (~1300rpm). I assume because the engine came with throttle body, IM, and everything and you need to idle relearn when swapping those. I went to fix it today and was going to do the idle relearn procedure and I wanted to make sure I wouldn't have a problem unplugging the TPS. I unplugged it and then I was interrupted and had to go do something else. When I came back it slipped my mind that I didn't reconnect the TPS. I tried to start the car and it cranks, sounds like it's caught and then dies when it goes to idle. I plugged the TPS back in and it hasn't started since. Same thing every time.

I searched around the forums and found someone saying when you start the car without the TPS plugged in it sets the car in some kind of fixed throttle/fixed timing mode? Is this why it's not starting?

Any ideas how I could reset it? Or any other ideas what could be causing this problem? I've disconnected the battery and left it for a bit, I've checked the voltage to the TPS connector ( a bit above 5v ), the throttle cables are connected according to FSM procedure, I took off the airbox and looked at the valve and it opens and closes fine and isn't dirty.

I mean it could just be a giant coincidence but it seems odd it started fine every time until I started it with the TPS disconnected.

EDIT: Ran a ground from the bolt above the crankshaft sensor by the tranny to the neg. battery terminal and it starts again.

 

did you unplug the tps while the vehical was running or did you shut it off first

 

It was off, battery disconnected. I unplugged tps, went and did something, came back and connected battery. Turn key, crank, almost starts then gives up and goes back to cranking.

 

So I tried the following:

• Checked battery.
• Added ground from tranny case to neg. battery cable.
• Checked TPS and positioned it to spec.
• Replaced TPS with another one from my other engine.
• Checked all fluids and added more gas ( was below 1/4, now above )
• Checked butterfly valve; opening and closing fine.
• Accelerator wire, etc all connected properly with a little slack.
• Checked all grounds

As much as I hate to call it a coincidence I'm coming up dry on the problem being related to me trying to start with no TPS plugged in.

I took a video last night of the attempted starts hoping someone will hear it and say "check this." because I'm at a bit of a loss right now, so anyone's educated guess would be much appreciated.


It cranks between 400-500 RPM and during those little jumps you can hear where it almost sounds like it's taking I see it jump up to about 700 RPM and then give up and go back down to cranking at 400-500rpm.

The only other thing I've thought of but haven't tried yet is replacing the gas all together. The gas that's in the tank is from almost 6 months ago and has been sitting there this whole time. It could even be regular octane I'm not sure what the original owner used. It just seems odd it would run fine until that one start with the TPS unplugged.

 

The ground I added to the tranny case was replacing the original tranny -> body ground. After checking all relevant sensors and still unable to get spark I decided to go crazy on the grounds. I cleaned every ground on the engine, replaced the original tranny -> body ground with a freshly soldered one and ran a ground from the bolt above the crankshaft sensor on the tranny to the neg. terminal and she's back up and running.

Guess it was a giant coincidence that the ground stopped working after trying to run the car with the TPS disconnected.

I guess it wasn't a complete waste of time as I did get to confirm all my sensors are working correctly.

 

nice! Grounds are crucial!