92 sc400. Car starts then boggs down and shuts off

[tony.anytime]

I drove a full day of work then went to go home and the car started, then shut right off. started it again and if i feather the throttle it will stay running but real rough; doing this i managed to get it on the highway and drove it home 30 miles. it bogged down three times during that time but i kept the rpms high, like 4k, and it picked back up. it still starts now but as soon as the idle tries to settle it shuts off. has a new fuel pump. haven't changed the filter yet but is was old when i bought the car this past march. suspect a sensor but which one if so?

 

[tony.anytime]

sc400 bog down

Found the problem. the plastic cover on the bottom of the intake tubing prior to the throttle body fell off leaving a hole open for extra air to be sucked into in the engine. which is bad for the air flow readings. sealed it off and on the move.

 

[cribbj]

Good catch!

Air coming in "after" the MAF causes all kinds of weird "starving" type behavior because it's trying to run so lean. First thing people think is that it's a fuel problem, next is ignition. Finally, after changing most of the "tuneup" type parts, get a new fuel filter & fuel pump, and their injectors cleaned, they find an air leak as you did.

Hopefully it didn't cost you too much?

 

[tony.anytime]

It was about to cost me. I already purchased a hig flow fuel pump and was procrastinating on putting it in. This gave me a reason to install it, and started checking the spark. once that those tests were done onto to testing sensors. I finally threw my hands up and took it to a shop with the intent to leave it overnight and the mech found it within 10 minutes compared to a days worth on my part. I was so relieved! only ran me $30 and a full day home with the kids.

 

[Nick M]

First thing people think is that it's a fuel problem

For good reason, as you listed.