PlatSilvSc

iTrader: (2)

This thread refers to the problems people are having with their sc400's hesitating and "hiccupping". My friend’s 1996 sc400 had the same problem.

I checked only one of his plugs, and it seemed fine. A week later, after him complaining, we decided to change all the plugs and vacuum hoses.

So while removing all his plugs, on the passenger side of the engine, the last plug closest to the firewall had rust, and flakes of rust around the plug and around the hole.

I thought of one explanation for this, above that last spark plug, the heater control valve is located, and previous owner probably had a leak, and it leaked directly onto that specific plug.

So, in conclusion, cleaned the hell out of the chamber and replaced all plugs, ran new vacuum hoses, and car has absolutely no hesitation.

This may not be the problem for everyone, but if you have checked only one plug, check all of them!

Attempts to fix hesitation before this:
Cleaning throttle body
Cleaning MAF with electrical cleaner
Seafoam in gas tank and intake system
Oil change
ECU reset
Tranny Flush

DriftNsc3

Good advice is always welcomed!

khouseal

Been stuttering for a few weeks so getting ready to start attacking it. Just read your post, and checked the heater control valve, it was leaking! You may be on to something. Thanks for posting!

sliva001

what type of plugs did you guys use? oem ones? i'm debating if I should get ngk/denso iridiums.

PlatSilvSc

iTrader: (2)

I picked up Denso's from AutoZone, $1.96 each, seems to do the job. Guy at AutoZone said that denso is used by all Toyota. I really do not see the point of paying $5 each spark plug; it will come to $40+ tax for spark plugs, as apposed to $16+ tax.