Plug on coil question

Is changing the coils just to replace them, since I don’t know if they have ever been replaced, a waste of money? 279k miles on the truck. I’m replacing the alternator, starter, spark plugs, battery cables and battery. Just wondering if I should bother with coils too or not.

 

They're easy to get to for a swap at any time. My opinion is wait until you have symptoms that may be coil related

 

Back in January I did have a check engine light come on so I took it to Toyota to have them diagnose and they told me I have low compression in cylinder 3 and they recommended replacing the injectors and that will fix it. Well it fixed the check engine light but they said it was still showing a misfire on their live scan. So I replaced the plugs and wires when I got it back from them and no check engine light until last week. So I took the plugs out and checked the gap. Cylinder 2 was out of gap so I fixed it and put them back in and no check engine light since last week. I even took it to Napa and orielly to read the check engine light and Napa said connection error and orielly said contact customer support I was like well I’ve never had that happen before. Idk what to do now. I just want to put some love in the truck. I love the truck.

 

You can check the resistance of the coils using a multimeter. If they're out of spec then replace them. But at $~80 a piece I wouldn't do so without first testing them.

Also, have you checked the compression in your cylinders? If the dealership said it's low, it's worth checking. If it's low enough, new everything else (coils, plugs, wires, injectors, etc.) won't matter

 

yes I checked compression after they did. I got good compression in 1,2 and 4. Cylinder 3 had 60 psi. Toyota also did a leak down test and said when they put a rubber glove on the exhaust it filled up so they said pressure was escaping through the exhaust valves but the service manager advised me not to check the valves that it would be a waste of money. He said honestly just keep putting oil in it and driving it . OH AND THEY DID THE LEAK DOWN TEST AFTER THEY ALREADY REPLACED THE INJECTORS THAY COST ME $1,400. Shouldn’t they have done the leak down test first? Weird thing is the truck still runs and drives amazing. Idles a tad bit rough but nothing crazy.

 

and the check engine light is back

 

You need valves bud.

 

Sounds like you have a burnt valve or cracked head. You can try adjusting the valve clearance but the damage may already be done if it's been hanging open for a while. If it's just the one valve and the head is okay still then just replace that valve, shim them all to spec and carry on

 

Stop taking it to the dealer and fund an independent shop you trust. Dealers are bad at this kind of diagnosis more often than not.


Also agreed, probably a burnt valve. Head will have to be pulled and valve replaced. It’ll run better and have more power once fixed… mine did.

 

Yea sounds like they bamboozled you into wasting a ton of money on injectors you probably didn't need. Don't give them another penny, and get your head and valves inspected by a reputable shop, or save yourself a large chunk of change and pull the head yourself.

 

As a FWIW… the 2.4 and 2.7’s seem to have cracked heads with over 300k on them, thats just how it is so if/when you do the job don't be surprised about the increased expense. Yes, the dealer should not have put injectors in with a 60 psi compression. It all depends on what you want to do about it. Take your complaint to the service manager and ask him why injectors were installed in a motor that is unfit mechanically. He could argue that we did put in new injectors and you owe us money for the parts. The reply to that is it should have not been done at all, you replaced parts before the diagnosis, not smart. You could try to get the labor costs back and keep the new injectors in her or go to small claims and get it all back, but that is a time consuming process.

 

Any dealer telling you injectors will fix low compression is a fucking SCAM

 

Well if it is a cracked head would I have coolant in the oil or oil in the coolant? Oil and coolant are both normal.

 

Not necessarily. But if a properly conducted leak down had air flowing out the exhaust side, valves would be the first place to look. Either way that head is coming off

 

OP, if it were my truck I'd try checking the valve clearances, especially on cylinder 3 exhaust valves and if possible try to adjust them back into spec.

You could get lucky and fix the issue without pulling the head. Worst case it doesn't work and you waste a couple hours of your time.

 

Agreed. At worst, you’ve done part of the work for a head removal anyway

 

only thing is to adjust them they are pucks so I would have to figure out what size pick I need and wait for them to come in the mail or see if my local dealer has any in stock which I doubt. But I definitely will check the valves.

 

If you have a pick and pull yard anywhere nearby, I'd go and try to scrounge a decent assortment of them. Almost every 90s Toyota model used the same size valve shims.

 

okay sounds good. This is what I got when I plugged in.

 

Cylinder 3 misfire, could be alot of things but given the circumstance of lot compression on 3 it's most likely a mechanical engine fault