eddieleee

Hey guys,

Long time lurker first time poster, sorry for not contributing yet but everyone has been a great help from the information I have learned about my car.


2000 RX300 150k~ AWD, when starting up its a really really rough idle, after a while it will either die or stabilize. However at some stops it will die after idling to low.

There IS a hole near the O2 sensor on the exhaust, I patched that (its been there and loud for a while) after I patched it with goop (mind you only temporary till I realize all the work that needs to be done) I noticed a loud exhaust-hole type sound coming further up the exhaust that is new and started maybe around the time the bad idle did.

I assume the manifold is cracked, and I plan to put it on stands and check it out myself and take it off if given the chance to closer inspect.

My main question is, will a cracked manifold cause that bad of idling issues? I ask this because I originally thought it was a fuel pump at first until I realized the exhaust had gotten much louder.

salimshah

Do you hold idle with foot on the gas pedal? If so it can be IACV (please search).

You can have the exhaust holes repaired by welding.

Salim

eddieleee

I don't believe I can hold idle (I will retest when the woman gets home), but I can rev it higher (2k+) pretty easily and it sounds great (well normal), I want to say when I try to idle it was still choking a bit but I was more trying to keep it alive so I will retest this.

The IACV is a good point, didn't think of it, but I didn't equate the issue with the car trying to hold an idle, and more towards "choking" but thank you for the perspective that could be the cause.

Yeah I know I can get them welded, which is the plan I was just trying to determine if it was the issue so I knew where to invest my money on, tight budget for the next week, but I can throw at least one repair at it until pay day.

eddieleee

Update: This is an issue persisting under acceleration, doesn't seem to be consistent, both in town and highway speeds.

salimshah

keep the throttle pedal 1/4 ~ 1/3 pressed down when you try to start and back off a bit (to prevent high rpm) as the vehicle tries to idle. [All in Park].

You are trying to compensate for a blocked IACV by giving extra gas by holding the throttle down,

Please read IACV cleanup DIY to get a better understanding.

Salim

Baetke

To answer your first question, yes a cracked manifold (or an exhaust leak) can play havock with the way your engine runs. Any air leak between the mass airflow sensor and the air-fuel sensor will cause erroneous data to be sent to the ECU and it will set the fuel trim incorrectly as a result. Do you have a scan tool? If so, you should be able to tell if your fuel trim numbers are way off.