Cold start hesistation for just a moment

[98Gate]

Hey yall, got a technical question

My 98 4runner w/311k miles has been having an issue on cold start. Nothing crazy but on a cold start it will sort of hesitate at about 1kish rpm for about a second then soar up to the usual 2kish rpm and idle down as usual. I just have done a timing belt, wp, all new sensors(crank, cam, TPS), cleaning throttle body, IAC, plugs/wires, coils, cleaned MAF. New o2 sensors. This is an issue that has actually been going on before the big 100k service interval I just performed. Ill put a video down showing what I am talking about. Just wondering on suggestions in terms of what it could be. I am curious if it is fuel related, given that if I pull the EFI fuse and reinstall, it will start perfectly. All parts are OEM or denso. Let me know what yall think

- YouTube

-98Gate

 

[brillo_76]

What is your engine temp reading through the OBD 2 connector. As you done mostly everything you needed to. I am wondering if your temp gauge for the ecu is acting up. May not be. Another possibility is a slight vacuum leak somewhere in the intake as well that sealing and then acts normal. Kind of an odd one you hit us with.

 

[98Gate]

What is your engine temp reading through the OBD 2 connector. As you done mostly everything you needed to. I am wondering if your temp gauge for the ecu is acting up. May not be. Another possibility is a slight vacuum leak somewhere in the intake as well that sealing and then acts normal. Kind of an odd one you hit us with.

Well odd can be a good thing! Because hopefully we can track this down so if someone down the line has this issue, its something that can used for diagnosis. I am going to plug it up here in a sec and give the results for the engine temp reading. I sprayed brake clean on all of the vac lines after the job was done and didnt have a lick of rpm change BUT I didnt really spray near the manifold gasket. My rig has been doing well accelerating at low speeds but seems to struggle a bit more climbing steep hills or getting up to highways speeds, almost like I am getting high rpms but not quite the best power transfer. I would think that would have more to do with age but it seems a bit more sluggish that I remember. Maybe just a very slight hesitation at accelerating at a full stop. It still has the factory injectors, fuel pump and fuel pressure regulator and my next project was to replace all of those. On top of that, the fuel economy seems a bit worse than usual. Maybe 210 miles per full tank rather than the usual 240~ish I remember. I do drive it mostly in the city though. I just started it up after getting off work and it fired up perfectly. Ive had this car for 15 years so I definitely baby it over little things
Thank you for your feedback and it there are other things I can test, ive got a good code reader with good live data available and also a good multimeter so let me know. I cannot tell you how much I appreciate the help.

-98Gate

 

[brillo_76]

Well odd can be a good thing! Because hopefully we can track this down so if someone down the line has this issue, its something that can used for diagnosis. I am going to plug it up here in a sec and give the results for the engine temp reading. I sprayed brake clean on all of the vac lines after the job was done and didnt have a lick of rpm change BUT I didnt really spray near the manifold gasket. My rig has been doing well accelerating at low speeds but seems to struggle a bit more climbing steep hills or getting up to highways speeds, almost like I am getting high rpms but not quite the best power transfer. I would think that would have more to do with age but it seems a bit more sluggish that I remember. Maybe just a very slight hesitation at accelerating at a full stop. It still has the factory injectors, fuel pump and fuel pressure regulator and my next project was to replace all of those. On top of that, the fuel economy seems a bit worse than usual. Maybe 210 miles per full tank rather than the usual 240~ish I remember. I do drive it mostly in the city though. I just started it up after getting off work and it fired up perfectly. Ive had this car for 15 years so I definitely baby it over little things
Thank you for your feedback and it there are other things I can test, ive got a good code reader with good live data available and also a good multimeter so let me know. I cannot tell you how much I appreciate the help.

-98Gate

Your Valves would probably need adjusted as well. Your over the 250K to 300K as that is when some will go out of spec. Would cause slight performance issues. However, I doubt it would effect idle much. That's probably a different issue.

That's a slight project and best to do when you do the valve cover gaskets because you have the valve covers off..

 

[98Gate]

Your Valves would probably need adjusted as well. Your over the 250K to 300K as that is when some will go out of spec. Would cause slight performance issues. However, I doubt it would effect idle much. That's probably a different issue.

That's a slight project and best to do when you do the valve cover gaskets because you have the valve covers off..

Im pretty sure the valve adjustment is with the little shims? Is there a reliable kit to get for doing that? Im gonna have the manifold off for the fuel system revamp so it will be a good time. The covers arent leaking but I will go ahead and do it while im in there. Ill get the engine temp reading as soon as I can get to my dang code reader. Thank you again!

 

[brillo_76]

Im pretty sure the valve adjustment is with the little shims? Is there a reliable kit to get for doing that? Im gonna have the manifold off for the fuel system revamp so it will be a good time. The covers arent leaking but I will go ahead and do it while im in there. Ill get the engine temp reading as soon as I can get to my dang code reader. Thank you again!

Nope.. Thats part of the problem. You have to buy the shims from Toyota and change each one.

They do make a tool to remove the shims. Its a process but try to aim for the middle of spec but as long as they are in the spec range you cut them adjusted.

Just watch the temp reading to see if its seems accurate. As it maybe fine but if the ecu is getting the wrong temp readings would explain your funky idle.

 

[phattyduck]

Nope.. Thats part of the problem. You have to buy the shims from Toyota and change each one.

They do make a tool to remove the shims. Its a process but try to aim for the middle of spec but as long as they are in the spec range you cut them adjusted.

Just watch the temp reading to see if its seems accurate. As it maybe fine but if the ecu is getting the wrong temp readings would explain your funky idle.

Just finished doing this. It is a huge pain.

It definitely is totally worth at least CHECKING the valve clearance while the valve covers are off. At that point you can decide what to do (if there are none that are tight, maybe just send it for a while until you want to do the project, etc.).

I bet something else is going on here though.

-Charlie

 

[brillo_76]

Just finished doing this. It is a huge pain.

It definitely is totally worth at least CHECKING the valve clearance while the valve covers are off. At that point you can decide what to do (if there are none that are tight, maybe just send it for a while until you want to do the project, etc.).

I bet something else is going on here though.

-Charlie

Yup.. That's what i figured should be done if at the every 250-300K. As like you stated you already there and a great piece of information to know the status of your valve clearances...

In this instance, its not valve related. It may help his engine be more efficient though. I also wonder if this leads the cracked head scenario. Where the head will crack between the cylinders. As its mostly always around the valves too. May not but just a theory.

 

[98Gate]

Update:

Engine temp sensor is reading normal from what I can tell BUT. I noticed coolant in the valley. I am not exactly sure if that is what the issue with cold start is but I need to get the intake manifold off to get the coolant under control. Heres a video of what she is sounding like. It almost completely died during cold start. It seems like it gets worse the more days I leave it without starting. I am STUMPED. Seems a little more “diesely” sounding as of late. Cant tell if its valves or noisy injectors. I thought id let the pros listen and chime in

- YouTube

-98gate

 

[98Gate]

What is your engine temp reading through the OBD 2 connector. As you done mostly everything you needed to. I am wondering if your temp gauge for the ecu is acting up. May not be. Another possibility is a slight vacuum leak somewhere in the intake as well that sealing and then acts normal. Kind of an odd one you hit us with.

She stalled out on me during a hot start now! I had the AC on and it couldnt keep up. this thing is making me pull my hair out

 

[phattyduck]

The lower intake manifold has a water passage through it that can leak if the coolant hasn't been maintained. There is also a heater pipe under there. Either could be leaking into the valley. The intake manifold parts could leak into the intake ports. Hopefully the head and lower manifold aren't damaged and it can be fixed with a couple gaskets...

Help - coolant in the valley - why?

-Charlie

 

[brillo_76]

So you basically its an intermediate stull out. When you kick the ac on does the idle go up to 700 rpm? You should notice a idle jump when the AC is on.
Any white fog smoke on startup when its cold?

 

[98Gate]

The lower intake manifold has a water passage through it that can leak if the coolant hasn't been maintained. There is also a heater pipe under there. Either could be leaking into the valley. The intake manifold parts could leak into the intake ports. Hopefully the head and lower manifold aren't damaged and it can be fixed with a couple gaskets...

Help - coolant in the valley - why?

-Charlie

Ive got the gaskets ordered another with a new knock sensor harness.

 

[98Gate]

So you basically its an intermediate stull out. When you kick the ac on does the idle go up to 700 rpm? You should notice a idle jump when the AC is on.
Any white fog smoke on startup when its cold?

Ac idles up a little bit as per usual. Almost like it hits maybe 800-1k rpm at start, immediately drops to 500 for a second or two then will correct itself and climb back up. No white smoke. Is IAC ever a culprit on startup?

 

[brillo_76]

Ac idles up a little bit as per usual. Almost like it hits maybe 800-1k rpm at start, immediately drops to 500 for a second or two then will correct itself and climb back up. No white smoke. Is IAC ever a culprit on startup?

Can be if it really gummed up. As that controls your idle. Have you ever cleaned the IAC? As there are many write ups and videos on how do that project.

 

[98Gate]

Can be if it really gummed up. As that controls your idle. Have you ever cleaned the IAC? As there are many write ups and videos on how do that project.

IAC is clean as a clock, just cleaned when I did the timing belt. I am, for some reason, thinking it might be fuel related. If I prime the pump many times when turning the key, it seems to like that and will fire up strong…. I have the manifold off so I am about to put a brand new set of injectors, fuel pressure regulator, gaskets and the dreaded FUEL PUMP AHH. Should I go ahead and cut an access hatch in my passenger body panel? Jk

 

[phattyduck]

If I prime the pump many times when turning the key, it seems to like that and will fire up strong….

There is no fuel pump prime function. The fuel pump only runs with the key in the START position or while the engine is running, controlled by the ECU.

I'm in the middle of a fuel pump (upgrade) right now. Watch the Timmy the Toolman video on the fuel level sender - its the same process. The tank itself isn't too heavy if it is close to empty.

-Charlie

 

[og80gt]

I had the hot start problem and changing the Fuel Pump Regulator fixed that.

My car would also die on me when coming to a stop once in a while cause of low idle and changing the IAC valve fixed that.

 

[brillo_76]

So you had a bad fuel regulator and a defective IAC valve. So now you all patched up?

 

[og80gt]

Yup, fixed both my problems…