Exactly as the subject line states. My car starts doing a sort of chugging/hiccuping thing exactly at 40-45mph. Other than that the car runs great and smoothly. I have absolutely no idea why it does this! Anyone else have a similar issue? And advice would be helpful! Thank you so much!

 

I think there's at least a few of us with this. Idk what to do about it so I just drive 50. lol is that bad? It only happens when I'm going a constant 40-45. Same with you?

 

99% sure it's your TPS (throttle position sensor on the throttle body) and/or throttle stop screw settings. I've been trying to get mine dialed in for several months and have it just about right with my latest adjustment. One way to be positive is to disconnect the TPS plug. If the problem goes away, you know it's your TPS. Just don't drive that way for long or you'll get a bunch of CEL codes popping up.

My TPS adjustments are extremely finicky. I had to buy a new multimeter because the tiny fractions of a milimeter either direction required a sensitivity beyond that of my cheap, old one. Other people haven't reported it being that fine of a line to get right, so your luck may vary.

Also, I found it very easy to replicate the problem on mine on uphills, so that provided an easy way to test if adjustments had fixed it.

 

Yeah they are, it jumps from like .2 to 17 within a fraction of a mm it seemed (lol what are the odds you said the same thing... I only read your first sentence...). I used a connector from the junkyard that was actually off of the tps and it worked I guess. not sure if changed or not taking it off and stuff, but you can't really check that.

 

Make sure you read the thread about sc400 hesitation fixes

 

Funny you mention that, my hesitation returned last night and was somewhat more annoying today. After working on stereo stuff I remembered to pop the hood and take a look at hoses, and sure enough, one of the vacuum lines had popped off. (Annoyingly, the barbs aren't all quite the same size and the hoses fit loose on some of them.)

In my experience, vacuum lines are the first (and easiest) thing to check for general hesitation issues ... and the one least often mentioned. But, for that ~40 mph issue, I'd be shocked if it isn't TPS related.

 

Check vacuum hoses after that check ignitions like coils, wires, plugs etc. Also make sure your getting fuel.