hesitation, high cold idle and poor gas mileage

rnoswal · 01-31-2007, 11:59 PM

There is also a cold temp sensor that helps with the cold start injector timing and richens the fuel when cold. If it always reads cold then it will always see the need to run rich. Try checking that sensor.

Russ

sd88supra · 02-01-2007, 03:24 AM

where would this sensor be located? the high idle only occurs when cold. But it warms up fine, and when it does it idles normally. I'm also starting to suspect that my cat is plugged up.

mrnickleye · 02-01-2007, 05:34 AM

Quote:

Originally Posted by rnoswal

There is also a cold temp sensor that helps with the cold start injector timing and richens the fuel when cold. If it always reads cold then it will always see the need to run rich. Try checking that sensor.

Russ

Not correct.

This sensor is called the Cold Start Injector Time Switch, pg FI-112 in TSRM. It only operates during cranking and engine that is below 56*. Never after the engine is running.

When active (only while cranking the motor), it supplies 12v to the Cold Start Injector, which will open and squirt a bunch of fuel into the intake manifold.

To prevent flooding, this switch will stop working automatically (heater element inside it)if you crank the engine over for more than 12 seconds, and it hasn't started.

Quoting myself: The EGR passages on the 7m usually will plug up with miles, and then you don't get any EGR gasses thru. This problem is usually not detected (nor cause troubles)until you have to go in for an emissions test. It causes high NOx readings.
So......
You won't have idling or running troubles with plugged EGR passages, or inop valve.

sd88supra · 02-01-2007, 07:15 PM

Quote:

Originally Posted by mrnickleye

You won't have idling or running troubles with plugged EGR passages, or inop valve.

So, what is causing my poor fuel economy, high cold idle (better yet it runs harsh when cold) and hesitation? I've driven almost 9k miles since my last full tune up (plugs, wires, brakes, compression teset, LSD change, etc). I've also noticed loss in power. I think I'll start by redoing a compression test.

sd88supra · 02-03-2007, 10:32 PM

i looked at the spark plugs and found oil on them. im gonna put new ones in, but can i clean the housing with carb cleaner, or should i use something else?

mrnickleye · 02-04-2007, 12:55 AM

Carb spray down the holes will work. Or brake cleaner spray is less strong, safer.

The oil down on the spark plugs/boots can cause a misfire. You need to fix the leak. Usually the V/C gaskets, #1 & #2. Not the center one. Not a difficult job at all.

sd88supra · 02-06-2007, 01:10 AM

Quote:

Originally Posted by mrnickleye

Carb spray down the holes will work. Or brake cleaner spray is less strong, safer.

The oil down on the spark plugs/boots can cause a misfire. You need to fix the leak. Usually the V/C gaskets, #1 & #2. Not the center one. Not a difficult job at all.

before I teared into the head, I looked for the V/C gaskets in the TSRM and Haynes manual. However, the gaskets are just labeled "gasket" and I'm not sure which ones you are referring to as #1, #2 and center. What do I need to remove to get to the gaskets youre referring to?

Also, could the oil down the spark plugs be a cause of worn piston rings? if so, would I need a valve job or a rebuild?

mrnickleye · 02-06-2007, 04:17 AM

OK...need to know before we go further...did you have oil on the sparkplug electrodes (the part that fires), or on the outside, and the rubber plugwire boots???

Also......
Worn piston rings will usually cause some oil burning and blue smoke out the tail pipe. It will eventually cause sparkplugs to foul (stop firing).

02-04-2007, 12:55 AM	#6
mrnickleye 1000whp postwhore Join Date: Jun 2005 Location: Mojave Desert, Calif. Posts: 1,705	Carb spray down the holes will work. Or brake cleaner spray is less strong, safer. The oil down on the spark plugs/boots can cause a misfire. You need to fix the leak. Usually the V/C gaskets, #1 & #2. Not the center one. Not a difficult job at all. __________________ Had a Red 1989 N/A. Automatic. Sports Pkg. w/wing. TEMS, and some nice MODS. Sold to a friend 10/08/08.

02-06-2007, 04:17 AM	#8
mrnickleye 1000whp postwhore Join Date: Jun 2005 Location: Mojave Desert, Calif. Posts: 1,705	OK...need to know before we go further...did you have oil on the sparkplug electrodes (the part that fires), or on the outside, and the rubber plugwire boots??? Also...... Worn piston rings will usually cause some oil burning and blue smoke out the tail pipe. It will eventually cause sparkplugs to foul (stop firing). __________________ Had a Red 1989 N/A. Automatic. Sports Pkg. w/wing. TEMS, and some nice MODS. Sold to a friend 10/08/08.

01-31-2007, 11:59 PM	#1
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	There is also a cold temp sensor that helps with the cold start injector timing and richens the fuel when cold. If it always reads cold then it will always see the need to run rich. Try checking that sensor. Russ

02-01-2007, 03:24 AM	#2
sd88supra 3" Exhaust Join Date: Oct 2005 Location: San Diego, Ca Posts: 190	where would this sensor be located? the high idle only occurs when cold. But it warms up fine, and when it does it idles normally. I'm also starting to suspect that my cat is plugged up.

02-03-2007, 10:32 PM	#5
sd88supra 3" Exhaust Join Date: Oct 2005 Location: San Diego, Ca Posts: 190	i looked at the spark plugs and found oil on them. im gonna put new ones in, but can i clean the housing with carb cleaner, or should i use something else?