Engine missing when it is hot

[91Supra313]

I have a built 7MGTE ( check signature for mods ). It is currently running 18psi. I have two problems.

1. Very hard to start when cold. After it warms up it starts easily.
Battery is good ( as per Autozone )

2. When car is cold it runs perfect. After it warms up there seems to be a miss, and hesitation.
Plugs are +1 heat range from stock
AFR reads 13-15.5 at idle
same for light throttle
10-11 on WOT
the miss bumps all readings up to either off the charts or very close to it. Then they drop back down.

I am picking up a COP mod from a member on here once he checks his PMs. So that will be added. I figured it has something to do with my ignition so I am checking on that first mainly because I want that mod done anyway. Any ideas would be GREAT!

 

[mecevans]

If its bumping the afrs like that its a ignition missfire. My supra only misses in closed loop .

 

[91Supra313]

That is what I thought it was. Which is why I am picking up a COP mod from another member on here. I might go ahead and pick up a ignitor while I'm at it.

 

[91Supra313]

Purchased the ignitor from another member a few hours ago, and waiting to hear back from another one about the COP mod he has for sale. I can only pray to the car gods this fixes the problem. There are no vacuum leaks, no boost leaks, so I am running out of ideas. The timing is correct to. Read that off of cylinder 1 plug lead.

 

[D.J.T.]

The reason it doesn't want to start up when cold could be the Cold start injector.

 

[91Supra313]

Well what it does is just click. I have to do it a few times really fast in order to have it try and turn over. Once I get this miss problem even close to being solved then I will work on the starting issues.

 

[honeydew]

Starter.

And where is the miss? Part throttle cruising, Full Throttle? When in the powerband? When, during what boost? AFR?

 

[D.J.T.]

Ok heres a list of things i can think that will probably help

Change spark plugs
change spark plug wires
check that the coil packs are grounded
change coil packs
check compression
if compression is good check the injectors, one might be dirty & isn't spraying well or might be electrically damaged
if compression is bad pull the cylinder head & check that all the valves are closing. If valves aren't closing FIX.
If valves are closing, time to pull the engine & get new piston rings.

This was happening to my MK2, it would be working fine but then started missing & work fine again & star missing until finally it stayed missing. We pulled the spark plug wires one by one until we got to the cylinders that were bad. How did we know? pulling the spark plug wire of the cylinders that were bad it didn't affect how the engine was performing. pulling the spark plug wires on the working cylinders would make the car run worse. Did compression test, it was good. Changed the injectors. problem solved.

 

[honeydew]

10:1 on 18Lbs is crazy rich. SAFC? I think some widebands/Air fuel gauges only measure to 10:1 you may be dipping lower than that. There's your misfire. Lean it out to 12:1, you'll get better power, lose your misfire and keep your plugs running clean.

Just to compare: I ran 21Lbs at 11.5:1 Full race drag strip styles. I could have leaned it out a bit more but was chicken. New build.

Edited to add: Oh AND you are running hotter plugs? Ya lean that out.

 

[digihonk82]

My 7mgte with 440's missed once it reached operating and was closed loop idleing. I did the lexus/injector upgrade and of course, in went some newer nippon-denso top feed 560cc low-imp. injectors and fired it up to my delight she idled like a brand new car!!! But I just realized you did this mod as well....still wondering about those injectors....you get them used??

 

[91Supra313]

All of the mods were on this car when I got it. There is no Lex mod on this. There is no AFM. HKS VPC got rid of that plus the help of the f-con. This car is on ebay and for sale locally. To be honest I'm tired of spending money on a car that will never be finished. This is my 5th one and not one has run long enough for me to do anything with it. So, when and if this sells, I'm getting something different. Which means any of my Supra stuff will be sold dirt cheap. It is listed on ebay and locally for 10k. If most of the people that have car in way worse shape can fetch 3-5k for theirs then 10k is no problem for this one.

 

[digihonk82]

Oh yeah cool, the VPC is similar to MAF or MAP? Why are you getting rid of it. I know when they aren't running the way they are supposed to they can be a nightmare but the oppisite of that is exactly why I own mine!!! It idles smooth with no misses... by no means a perfect car....but no misses!!

 

[91Supra313]

I have been dealing with these cars and their problems for almost 4 years now. I'm over it. Unless I find a Supra that really blows me away or a rolling shell that is in just about mint condition that I can build from, then I'm out of the game. I just want to relax and cruise. Which I why I have it listed locally for a trade. I wouldn't trust any Supra to be driven long distance because of fear of blowing a head gasket or something else on these cars breaking. I know all cars have their faults but when you can't drive to see family in the car you love for fear of breaking it, then it really isn't worth it.

 

[digihonk82]

I just think...and hear me out...that you are complicating the idea of owning a vehicle like this. Sure they can be temperamental after 100 thousand miles, and if my R154 wears out to where I cant drive it I would be very nervous, but right now I feel like I've , thru process of elimination, eliminated all of the glaring problems and got down to fixing some cosmetic issues and minor oil leaks!

 

[Nick M]

10:1 on 18Lbs is crazy rich. SAFC? I think some widebands/Air fuel gauges only measure to 10:1 you may be dipping lower than that. There's your misfire. Lean it out to 12:1, you'll get better power, lose your misfire and keep your plugs running clean.

Rich is easier to fire than lean. Notice how he said in closed loop is when it starts missing? The ECT sensor has leaned out his mixture. He should look at his ignition.

 

[91Supra313]

I just think...and hear me out...that you are complicating the idea of owning a vehicle like this.

I'm not complicating anything about owning a vehicle like this. I am selling the car and if it doesn't sell then I will troubleshoot it. Right now I'm tired of owning a money hungry car. It is always fix this and fix that. If you can't take long cruises in a car that you love, what is the point of owning it. To sit in a parking lot and look cool because you own a Supra? I have done that and wore the tshirt from 4 different countries with these cars.

Mods please either delete or lock this thread that way it doesn't get out of hand or off topic.

---------- Post added at 06:50 PM ---------- Previous post was at 06:49 PM ----------

Also dig, I'm glad that you have figured your cars problems out. Right now I don't have the time, money, or patience to even bother with it. I have more important things to worry about that a 23 year old car. Hence the reason I am now trying to sell it.