Automotive Forums

I recently took my Sienna to an Auto Repair Shop because my check engine light came on. The tech told me that my car's computer read Random Misfire. He then told me that he did not know exactly what the problem was, that he would basically have to take my car apart under the hood to find the problem, "like a surgeon" would. He tried restarting my computer and the light came off but as soon as I started driving home the light came on again. I took my car back and he told me that the only thing he could find wrong with my car was that there is an exhaust leak. Would an exhaust leak cause my Check Engine Light to come on and if so, what can I do to repair it?  

No, an exhaust leak will not cause the CEL to come on.
Sounds like your "mechanic" {if he really is one} took the easy way out and cleared your code to shut the light off.The light came on again because there is a problem {random misfire} find a mechanic who knows what it means{possible faulty dist cap,coil,plug ect..}and will diagnose
the electrical system further.  

A random misfire code means that one or more of your cylinders are misfiring. A lot of things can cause a misfire- bad spark plugs, spark plug wires, a bad ignition coil, bad distibutor cap or rotor. Those things can be taken care of with a tune up...usually. A bad sensor will do this too. certain sensors can do this if they get disconnected. There are a lot of other things that can do this. Get a second opinion. That guy sounded like a hack. What "restarting" your computer means is that he went in a erased the codes casuing the light to come on. If the problem is not fixed, its just gonna come back on. If it comes on a starts flashing....get it to a garage asap. And no, an exhuast leak won't do that. It kinda sounded like he was talking down to you. Definately have someone else look at it. Ignoring it will cause more costly repairs later...trust me!  

Well, I took the car back and they replaced the spark plugs and the wires leading to the spark plugs. The coils are fine. The code read PSO300, random misfire. I picked up my car today and everything felt fine and then the light came back on. I don't what else to do. They did all this work on my car and didn't charge me. The only thing I paid for were the spark plugs and wires which I myself got from the dealership.  

ALSO, I was told by the mechanic that my car does NOT have a distributor cap.  

Your cars ignition system is distributorless.Take back to mechanic and
have him clear the code via scan tool.  

Do ALL cars have distributor caps?  

No, only cars with distributors have caps.  

well, my mechanic came and picked up my car to take it to the shop. I am still waiting to hear from them. Everytime I get the car back from them it feels great, like new. But when the check engine light comes on them the car feels horrible. They are going to do all this work at no cost to me which I guess is a good thing.  

I'm glad your mechanic is at least trying to take care of ya. Fortunately misfires are confined pretty much to a specific system. And yes a lot of cars(and trucks) are now distributorless. When your car starts running poorly again its because the misfires mess up the balance of the firing order. The engine is designed so that each spark plug fires its cylinder in a specific order. When a cylinder is fired out of order or it does not fire at all, it throws off the balance. Its kind of like an irregular heartbeat. ...i know blah blah blah
Keep me posted...................good luck  

I spoke to the mechanic again and he says that the computer now says that the thermostat is faulty. He checked it and he said that the valve that opens to let the coolant into the engine(I'm going by my memory) when it gets to 185-190 is opening and letting the coolant in before it reaches 150. Could make sense considering that they had to replace the temperature gauge sensor per the computer error code from before. Does anybody have any input on this? Let me know.
THANKS!!!!!!!!!!!!  

At least a thermostat isn't ridiculously expensive. But I don't understand why that would make your car run so poorly. Question: After you picked up the car from having the plugs done and it started running poorly, did it overheat? Did the temp gauge stay at cold?  

Now my mechanic tells me that the computer says REPLACE OXYGEN SENSOR. They don't know what to do at this point because they keep getting different codes. I asked them if they had checked to see if I had a lean mixture and they said that they hadn't thought of that but would check it out. This is getting very frustrating.
The car never overheated.  

My mechanic called and told me that they tracked the VIN number to California. Apparently the car is a California emissions car and the car has the towing package without the hitch. Apparently the car was custom made and I guess the person backed out of the deal and they sent it to the east coast to be sold. He said that the reason why my car is acting crazy is being everything that has ever been replaced in the car was replaced with east coast emissions components. Does this make any sense?  

Yeah.....cailfornia emissions standards are different from federal emissions standards and accordingly, replacement components need to be specific for cali. standards. Its gonna suck though if you have to Re- replace all recent work done if its on your dime.