I am curious to know if a bad o2 sensor would give me these symptoms. Now the ecu is not throwing a o2 code. It is throwing a maf and iat code which were both replaced and the problem still persist.

Problems:
Once started (cold) it idles high like it should for a second then after about 3 mins, idle comes down and the car bogs. It will stay on but it just bogs bad. If you give it throttle it will rev but it does it in stages almost. Like its misfiring. Its hard to explain but the revs arent smooth at all. It shakes alot also.

Putting it into any gear (other than neutral) will bring the rpms down to about 600 and the whole car shakes(like it has a bad motor mount). This problem has stumped me and I cant figure it out. All of this happened out of no where. Drove it fine, parked it, came back two days later and bam runs like dog *****.

Things Ive tried:
New maf and iat
Hardwiring the fuel pump ecu plug
Tapping on FPR
Checking cap and rotor
Swapped out ecu


Dont know if this helps but I pulled number 1 plug and it is running lean.

Any help would be great, thanx guys

 

Check your spark plugs... I would also check your coolant temp sensor..

 

I did a tune up on the car a couple of weeks before the problem came. I did plugs, air filter, fuel filter and fuel injection cleaning.

 

Check the gap on the plugs...

 

Same thing happend to me, i did a full tune up without new wires going to my plugs. Once i put on new wires it fixed the problem. However this was because i washed the engine so idk if it will be the same problem, but worth a try cant hurt it

 

Oh forgot I did put no plugs wires on it.

What is the gap supposed to be?

You dont think a o2 would do this kinda thing? I mean usually if it were to be a gap or wrong plug it would do it right off the bat but this was like a month after the tune up was done...

 

Make sure you got spark everywhere bro. Check coil. etc,

 

I'm guessing a small blown head gasket. My car does the same thing, vibrates at idle like a bad motor mount. Occasionally missfires, and I've done a full tune up and I still have the same issue. Come to find out I have a small blown headgasket.

 

I guess I will have to pull the intake back off and check all the plugs. I hope its not a head gasket I dont have the patience for that.

 

Well for one thing, every headgasket for me which is about 3-4 on various cars. They always ate coolant. Had to add weekly, That is one sign. The other sign is if you take the coolant fill cap off the radiator, they will either bubble or steam up. LIke shoot steam literally out.

 

Neither of that happens to me, no missing coolant, no smoking, no coolant leaks or in oil.

 

when you get the plugs out make sure they arent cracked ive bought new ones before and found a nice crack on the side. i would deff try to get a readding off the ect

 

I put a new ect in just a min ago and drained the battery a little to erase the codes and it still does it. Its so weird that it isnt throwing any codes now. Im thinking its going to be the o2 sensor/s

 

I'm not experiencing quite that much of a problem bit my sc400 does have the weird shift/hesitation problem at 1100 rpm. Could all of us be dealing with a throttle position sensor? Or idle air control valve?

 

I swapped out the iacv as well, still nothing. Anyone know where I can find a fsm on a sc300. If i had that I could test everything and go from there before I start dumping money into this thing. Lucky for me I have a parts car to snag parts from.