Rough start when Hot

[quatin]

I have a 2000 4runner 4 cyl and recently it's been very rough to start when the engine is already hot. It's not a hard start, but a rough start. The last crank makes the engine jump/jolt hard.

I haven't noticed any other symptoms, there's no error codes. I've replaced the spark plugs/wires with no effect. I have a OBDII scanner that bluetooths to my phone and the coolant temperature reads correctly as it warms up. The only problem I have is a cheap cat converter that's causing fluctuating readings with my O2 sensors and vacuum pressures when accelerating, but I'm not sure how that could cause ignition problems.

Any thoughts?

 

[jrs101srj]

Any updates on this issue?

i'm having what seems to be a similar issue on my 2000 t4r 2wd limited. have you found any resolution? thanks.

 

[Lug1]

Did you replace with Denso plugs or NGK ?

Cleaning your IAC might help and is not a bad thing to do in any case.
There are some internet threads suggesting hot rough starts can be cause by a dirty IAC (Idle Air Control) valve.

 

[bwarren]

Have you checked your exhaust manifold? The 3RZ FE is notorious for cracked/leaky manifolds. Before I replaced mine with a header it would have trouble starting when hot.

 

[jrs101srj]

i haven't replaced the plugs. i replaced the starter in january, but that is the only maintenance that i have done "pre-issue", the problem started late feb/early march. since the issue started, i cleaned the maf sensor (then dropped it on the ground, then cleaned it some more, then after reinstall got a check engine light, then replaced the maf, then engine light was off again).

the engine jumps/jolts when cranking and seems to coincide with each revolution of the engine. then when it finally fires, it makes the starter grinding noise because i am not fast enough with the key release.

 

[jrs101srj]

new symptoms to add - now rough start/engine jolt occurs at cold start also, had a temporary misfire yesterday but cleaned up within a few miles.

 

[jrs101srj]

RESOLVED - For me anyway.

ok. it's fixed. a good friend of mine told me once "when you hear a stampede, look for horses before zebras" and i thought that is what i was doing. it turns out however that i was in fact looking for zebras. :frusty:
it was the new starter that i put on going bad. another new starter in place, problem resolved.