87 Supra N/A : valve issue

[ebolabar]

Ok, I took my car all over Tallahassee to see why my engine was jumping up and down. I dont have a BHG or rodknock. A mechanic checked each of my SP wires with the engine running and my number three valve was the problem. He said I should change my wires, BUT I dont think its my wires because my engine only acts up when its warm. the wires do fine when the engine starts cold. Does temp. affect SP wires? If i cant find an affordable fix, i think im going to hafta sell my car btw if anyone's interested.

[CRE]

Yes heat can effect the ignition wires. If you're not sure they're the issue test them yourself when they're warm. It's covered in the TSRM.

[ebolabar]

But this is why its weird. If I start cold, I can drive all day long if I wanted to without a problem. However, if I turn off the car and let it sit, for a few minutes, then turn it back on, thats when the problem starts. its almost like something seeps only when its hot in and kills the #3 valve. sooo frikkin weird.

btw, sorry for the super late reply.

[Jeeves]

SP wires with the engine running and my number three valve was the problem

How do spark plug wires affect valves? Do you mean the cylinder itself? I don't think you've got a solid understanding of what's going on.

Heat can affect plug wires, very simply. In fact, when I bought my car, someone had repaired the number 2 plug wire, and once it got hot, it would start arcing and I would develop a miss when in boost.

[ebolabar]

That's true I really don't have a solid understanding but I'm getting there. Here's what I think I know. The mechanic guy pulled each wire from the distributor one by one, looking to see which one did not affect the engine when removed. The third wire was the one. It was sparking, but the valve wasn't i guess responding.

I get what you said about your car developing a misfire during boost. But that means that the misfire would develop in the the midst of driving. Mine never starts misfiring while im driving. it only misfires if I startup with a hot engine.

Small note. If i turn it off while hot, and turn it back on within a few minutes, it wont mess up. If i let it sit for about 10 minutes or more, its starts misfiring.

[Jeeves]

Originally Posted by ebolabar

That's true I really don't have a solid understanding but I'm getting there. Here's what I think I know. The mechanic guy pulled each wire from the distributor one by one, looking to see which one did not affect the engine when removed. The third wire was the one. It was sparking, but the valve wasn't i guess responding.

I get what you said about your car developing a misfire during boost. But that means that the misfire would develop in the the midst of driving. Mine never starts misfiring while im driving. it only misfires if I startup with a hot engine.

Small note. If i turn it off while hot, and turn it back on within a few minutes, it wont mess up. If i let it sit for about 10 minutes or more, its starts misfiring.

Ok, just to clarify some things first.

Valves are mechanically controlled objects. The camshaft spins, presses down on the shim/bucket, which presses on the valve stem, etc, which opens and closes the valve.

[img]http://xd.**********s.com/uploads/7f0732dda5.gif[/img]
http://auto.howstuffworks.com/engine4.htm

So, with that said, they can't "Not respond". Now, what your mechanic was testing, was to see if that cylinder was getting spark, fuel, or ignition (overall condition). If one of those failed to occur, that cylinder would in effect do nothing.

So, Really you've got the issue eliminated to one of the following, sorted by probability:

- Spark
-- Not getting spark.
---- Check Plug Wires
---- Check Spark Plug
---- Check Distributor

- Ignition
-- Air/Fuel Mixture not igniting..
---- Spark gap too small/large
---- No Compression
---- Too much fuel or too much air (being that all the other cyl's are working, this is highly unlikely)

- Fuel
-- Not getting fuel
---- Check Fuel Injector

I suspect it's somewhere in the spark side.

[ebolabar]

wow. the image i had in my mind was waaay off. really useful stuff. thanks a ton man. I really hope its spark related

[Jeeves]

Here are a few of my personal old 7M photos:

[img]http://**********s.com/supra/images/DSC05231.JPG[/img]
[img]http://**********s.com/supra/images/DSC05235.JPG[/img]