Cold Start Issue (1 Viewer)

[LXMUTT]

Hello all,
This last winter I was having issues with cold starting. When the temp drops over night and I start up in the morning the vehicle acts like its not getting enough air or fuel and sputters at low idle until I tap the gas peddle and then it starts running like it should. I had a throttle body code over the winter during these cold starts and recently replaced the entire throttle body so that makes me think its not air related. Does anyone know where or what I should look for to start diagnosing the problem? All coils and spark plugs look good. Air filter is new. No engine codes show up. Its on a 2002 LX470.
Thanks in advance

 

[Eicca]

I’ll suggest MAF since I’m on that kick. Try cleaning it with some CRC and reset the computer.

I got a used one for $25 off eBay and wow it made a difference, even though my car wasn’t running “badly” before.

Also, you might take a whiff of the exhaust on cold start and see if it smells abnormally rich or lean.

 

[LXMUTT]

I’ll suggest MAF since I’m on that kick. Try cleaning it with some CRC and reset the computer.

I got a used one for $25 off eBay and wow it made a difference, even though my car wasn’t running “badly” before.

Also, you might take a whiff of the exhaust on cold start and see if it smells abnormally rich or lean.

I recently cleaned the MAF over the fall. It had a ton of built up crud on it. It started rough again this morning and the exhaust smelled different, not sure how to distinguish between rich or lean though.

 

[Eicca]

I recently cleaned the MAF over the fall. It had a ton of built up crud on it. It started rough again this morning and the exhaust smelled different, not sure how to distinguish between rich or lean though.

Did you reset the computer after cleaning it? It could also still be bad.

Rich would be like a cold start on a winter day, lean would be like after it’s fully warmed up and idling.

 

[2001LC]

Make sure to disconnect battery for 30 minutes when cleaning MAF. Clean and grease battery post while off. You can do now.

A ton of crud on it is unusual. Indicates no air filter or bad one for some time. Old Throttle body must have looked bad too. Not good for valves.

May have water in gas and crud.

Add a can on fuel cleaner to gas tank like 44K. Consider new gas filter.

Use good gas.

 

[LXMUTT]

Did you reset the computer after cleaning it? It could also still be bad.

Rich would be like a cold start on a winter day, lean would be like after it’s fully warmed up and idling.

Yep I reset the computer after then let it idle for 5 min. can a vacuum line leak cause a rich running engine?

 

[LXMUTT]

Make sure to disconnect battery for 30 minutes when cleaning MAF. Clean and grease battery post while off. You can do now.

A ton of crud on it is unusual. Indicates no air filter or bad one for some time. Old Throttle body must have looked bad too. Not good for valves.

May have water in gas and crud.

Add a can on fuel cleaner to gas tank like 44K. Consider new gas filter.

Use good gas.

Battery was disconnected for over 30 min when I was replacing the throttle body. battery posts are clean with some dielectric grease added. It was like a thick layer of dust on the MAF and required a lot of CRC to clean up to see metal. It was never cleaned by the previous owner.
how would I check for water in gas?
looks like fuel filter was replaced 70k miles ago.

 

[2001LC]

Yep I reset the computer after then let it idle for 5 min. can a vacuum line leak cause a rich running engine?

FSM sates to disconnect battery then MAF. As long as disconnected after it's okay!

Yes, should have no vacuum leaks. All hoses need replacing if cracked. May also have leaks at injectors or intake.

Don't buy cheap gas or gas coming from old filling station tanks, they leak.

In aircraft they have a drain at bottom of fuel tank. A clear tube is used to drain off some to check for water. Water is at bottom fuel on top. We don't have a good way to check.

Your T-body may also be sticking. Was it new or used.

Sensors may have bad wires adding to resistance and thus what ECM see.

Clean spark plugs and check gap (don't change gap of used) and good color on coils plastic (not brown) with new boot kit may help also. I just installed all new Dense plugs and coils. I don't mix. Denso is OEM.

Other things need checking. Fuel dampening device, fuel pressure regulator, fuel injector. 44K will help clean injectors.
A long crank to start after sitting may indicate fuel injector leaking down. Pulling injector and sending to have tested and rebuilt is sweet.
Look in first link in my signture, under engine, Coils and fuel stuff. May find some help.

 

[LXMUTT]

FSM sates to disconnect battery then MAF. As long as disconnected after it's okay!

Yes, should have no vacuum leaks. All hoses need replacing if cracked. May also have leaks at injectors or intake.

Don't buy cheap gas or gas coming from old filling station tanks, they leak.

In aircraft they have a drain at bottom of fuel tank. A clear tube is used to drain off some to check for water. Water is at bottom fuel on top. We don't have a good way to check.

Your T-body may also be sticking. Was it new or used.

Sensors may have bad wires adding to resistance and thus what ECM see.

Clean spark plugs and check gap (don't change gap of used) and good color on coils plastic (not brown) with new boot kit may help also. I just installed all new Dense plugs and coils. I don't mix. Denso is OEM.

Other things need checking. Fuel dampening device, fuel pressure regulator, fuel injector. 44K will help clean injectors.
A long crank to start after sitting may indicate fuel injector leaking down. Pulling injector and sending to have tested and rebuilt is sweet.
Look in first link in my signture, under engine, Coils and fuel stuff. May find some help.

I'm thinking it could be vacuum leak from the PCV and hoses, but the only issue with that is that this only happens when temps drop at night, like a storm front moves in. rest of the day its fine, which doesn't make sense for a vacuum leak

I only put 91 in it and there only two gas stations to choose from in the town I'm currently located.

T-Body was new OEM from camelbacktoyota. Do new ones stick?

I cleaned sparkplugs and replaced 2 cracked coils with denso (loose plugs) last summer. didn't check gap.

What sensors should I check for bad wires?

Ill throw a can of 44k in and see how it works.

 

[2001LC]

All vacuum leak is something I correct on tune up always, first thing. PCV hose are always first to go. Lines coming up from PS vane pump bad often and leaking. Airbox if not on right leaks. Stop them all.

Hard to say on wires. I find blueing in wires depending on age and were the rig lived. As these age, this become more and more of issues. Big 3 is part of solution.

New T-body should be fine.

I found a lot of benefit replacing all spark plugs and coils with Denso ( no junk) NGK plugs are good. Denso coils kits are nice cheap way to go also, if not just all new coils. Not just a few plugs and coils depending on mileage and history. Torque wrench is your friend on with spark plugs. But can use sung and 1/4+ turn with new where washer never crushed. Loose plugs heat and tighten until they walk out to much.

Many system on a 100 series. Get back to factory spec and with OEM parts is what I do always.

 

[LXMUTT]

All vacuum leak is something I correct on tune up always, first thing. PCV hose are always first to go. Lines coming up from PS vane pump bad often and leaking. Airbox if not on right leaks. Stop them all.

Hard to say on wires. I find blueing in wires depending on age and were the rig lived. As these age, this become more and more of issues. Big 3 is part of solution.

New T-body should be fine.

I found a lot of benefit replacing all spark plugs and coils with Denso ( no junk) NGK plugs are good. Denso coils kits are nice cheap way to go also, if not just all new coils. Not just a few plugs and coils depending on mileage and history. Torque wrench is your friend on with spark plugs. But can use sung and 1/4+ turn with new where washer never crushed. Loose plugs heat and tighten until they walk out to much.

Many system on a 100 series. Get back to factory spec and with OEM parts is what I do always.

PCV lines have some cracked ends so I'm currently ordering OEM hoses, clips, and PCV.

I was planning on doing the Big 3 this summer but looked at all the grounds and didn't see any corrosion or bluing.

spark plugs are also on the to do list for this summer, around 70k on them I think. 14ft/lb torque right?
Denso coils are too expensive to replace all at once so I just look for signs of aging(discoloration, boot cracks, coil cracks) and replace as needed.

can all of this be effected by the cold? because that's the only time this ever happens.

 

[LXMUTT]

Also I checked the live data with a code reader and its showing the engine is running rich on start up at idle (Negative fuel trim levels). I'm getting 15-17mpg average highway driving.

 

[LXMUTT]

I looked further into the live data after the vehicle was warmed up and at idle. long term fuel trim stayed at -12.5. It looks as though a few sensors are messed up though. the short term fuel trim Bank 2 sensor 2 is reading 99.2% which looks out of place. also the short term fuel trim for B1 S2 is reading N/A. the volts on my O2 sensor for Bank 2 S2 is much higher than the others, so could this mean it would then send too much fuel in and cause a rich or lean running engine? I'm a novice when it comes to engine issues

 

[trdcorolla]

Color screen code reader! Gotta get me one of those one day!

 

[white_lx]

O2B1S2 and O2B2S2 (secondary) sensors are only used to determine cat efficiency (emission requirement).

B1 and B2 (L&R) both have around -12% total fuel trim (ST+LT). Since both banks have similar trims, the problem is affecting both banks equally. That indicates a MAF issue or high fuel pressure (stuck regulator?).

Positive fuel trim can also be caused by a leaky injector but you would need an equal amount of leak on both banks to have identical fuel trim numbers. That is very unlikely.

I would start with the MAF. Do the total trim numbers get worse at higher RPM?

 

[Eicca]

My car had negative fuel trims of almost identical numbers before I changed my MAF. Get a used one for cheap and see what happens

 

[2001LC]

PCV lines have some cracked ends so I'm currently ordering OEM hoses, clips, and PCV.

I was planning on doing the Big 3 this summer but looked at all the grounds and didn't see any corrosion or bluing.

spark plugs are also on the to do list for this summer, around 70k on them I think. 14ft/lb torque right?
Denso coils are too expensive to replace all at once so I just look for signs of aging(discoloration, boot cracks, coil cracks) and replace as needed.

can all of this be effected by the cold? because that's the only time this ever happens.

Toyota has it at 13ft-lbf if FSM We've been going up with spark plug torque to slow walking out. Spark plugs Alert Alert Alert!

Guys are right the LT FT is to -12.5 is to much. Working through all systems tuning is key. Then consider MAF.

Denso cheaper than Toyota Denso. Watch for deals. But if looking good boot kits, many really like!

Don't pay to much attention to these 2UZ until warmed up. Also check coolant level and temp, your temp a bit low. Running rich does this, so does weak thermostat.

 

[LXMUTT]

O2B1S2 and O2B2S2 (secondary) sensors are only used to determine cat efficiency (emission requirement).

B1 and B2 (L&R) both have around -12% total fuel trim (ST+LT). Since both banks have similar trims, the problem is affecting both banks equally. That indicates a MAF issue or high fuel pressure (stuck regulator?).

Positive fuel trim can also be caused by a leaky injector but you would need an equal amount of leak on both banks to have identical fuel trim numbers. That is very unlikely.

I would start with the MAF. Do the total trim numbers get worse at higher RPM?

So after work I disconnected my batterie for 30min then drove 60 miles. here are the numbers after and during the drive. What do you think?
Car at idle

Car cruise control set at 65mph

parked and reved to 2100rpm

My car had negative fuel trims of almost identical numbers before I changed my MAF. Get a used one for cheap and see what happens

did you reset the computer(disconnect battery) before your replaced MAF?

Toyota has it at 13ft-lbf if FSM We've been going up with spark plug torque to slow walking out. Spark plugs Alert Alert Alert!

Guys are right the LT FT is to -12.5 is to much. Working through all systems tuning is key. Then consider MAF.

Denso cheaper than Toyota Denso. Watch for deals. But if looking good boot kits, many really like!

Don't pay to much attention to these 2UZ until warmed up. Also check coolant level and temp, your temp a bit low. Running rich does this, so does weak thermostat.

when I saw you post that spark plug thread I went straight to my cruiser to check! which led me to find those two loose plugs and two cracked coils that I replaces

Do those numbers above look better?

coolant levels good. must not have been completely warm. these last numbers are with coolant temps at 186F. new oem thermostat last summer with TB job.

 

[Eicca]

Still a little steep at idle, looks fine at RPM.

Again, exactly what my car was doing with the bad MAF.

But, definitely go through all the other tune items first. Vacuum leaks plus a bad or sort-of-dying MAF will cause issues.

 

[LXMUTT]

Still a little steep at idle, looks fine at RPM.

Again, exactly what my car was doing with the bad MAF.

But, definitely go through all the other tune items first. Vacuum leaks plus a bad or sort-of-dying MAF will cause issues.

I've got parts on the way! thanks for your help.