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Anyone dealt with hot weather tuning?

dyeager535

dyeager535

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Had my truck out on Monday, and it has been unseasonably warm here. 90's. Don't drive the truck that uch, so it was unusual for it to be out in this sort of heat.

Long story short, it didn't want to start after I parked it. Truck ran/drove great up until I shut it down and let it sit for 15 minutes or so. Try to start it, and it cranks and cranks, but made little effort to actually start.

Once it DID start, lots of sputtering on acceleration in gear. Out of gear engine sounded fine with lots of throttle. Once I took it out of gear, mashed the throttle, then put it back in gear, no more issues.

Unfortunately with our climate, it's going to be hard for me to repeat the issue to diagnose after this week or so. Not to mention with no AC, not really liking the idea of doing any work on it lol.

Only two things I can think of are heat soak or how enrichment (both injector PW and IAC) works based on startup engine temperature.

Heat soak I wouldn't *expect* to be an issue as other than what I put the engine in, it's no different than GM installed in the Camaro's, and they don't have a systemic problem with this I'm aware of.

As the heads are Vortec though, I wonder if the mixture requirements at higher startup temps are different enough that I need to modify how the setup determines optimum. I really have never had to deal with temperature related issues before, so this is going to be new to me for sure.

Anyone dealt with similar? I know there are plenty of you that play around in 90*+ heat. :)
 
TBI computer should adjust if the engine is within tolerances for the program. Might want to check your O2 sensor and IAC.
 
All good ideas, as little as this thing gets used I'd *hope* the components are still good (all were new on install, but it's been years) so I'll check them out. Only reason I believe the temp compensation COULD be an issue is because the heads/piston/exhaust are different and perhaps at this "extreme" temp situation they are exacerbated.

It seems intuitive that everything else would be in order, as I pulled down 17MPG on the 281 miles I had on the tank before fillup, with logging road driving, pass climbing, etc.

Just datalogged a month ago (last I drove) so up until then the O2 was working fine, and IAC wasn't doing anything weird. IAC was cleaned before I put the setup together. CTS was reading correctly as well, however underhood temps were nowhere near what they are now.

Not that an electrical problem isn't a potential culprit, this issue just screams "you won't believe what the cause is", so I'll check it all. Won't hurt to ensure everything is good.
 
I have experianced simular Long "Restart's" On my 87 GMC Jimmy TBI
in our Heatwave/Drought Here in East Texas,

>>> I am curently using a sheet Metal Screw,,
to hold the Trap Door in the Air Cleaner Housing Tube,
>>>For Cool Air and close the Hot air tube from exhaust Manifold
while waiting on,,
a THERMAC Actuator, (been to lazy to get one)
>>>>...that mounts under neath the filter assembly
with a Door that controls >>warm air from exhaust Manifold thru a Corugated flexy tube,
then at near full warm up it shuts off the heated Air and uses the Cooler Fresh Air coming from Coresuport at Grille ,,

It has Not been working ,,
it still has Spring for return,,
but has a Sealed Wax Pelet in Tube for control,,and has Failed,,
>>>>Even a Hair Dryer Test it would not openthe Fresh Air Duct,,
And Reducing the Air Flow,,
And It Causes other Problems,lol

On a Rare Cool Rainy Day,, in the past
it still starts but our Winters are realy Mild,,
But I beleave it Takes longer to warm up,,before it performs well
Mike
 
Yeah TPI doesn't run THERMAC, so I don't have to worry about that.

I played around with tunerpro RT last night, looking at the settings, and most of the hot engine settings have a "threshold" where things change around 190-200, which I'm guessing I was hitting. It looks like I'm running rich anyways (working on actually doing tuning now) so if I get idle fueling right, I may actually resolve the issue.

Worst case, until I get it resolved, is to park nose downhill on hot days. Love the manual trans. :)
 
Ignition module. Heat usually makes them act up if they are getting weak.
Pick up coil also. Check the 2 leads coming off of it when engine is warm. Should be 500- 1500 ohms. If not, replace the PU coil.
 
The 454 in my K3500 has a hard time on hot starts during the summer but then again it's 100*-110* all summer here. In the mornings it fires right up but after it warms up and it's hot outside it takes a little extra to get it to fire.
 
Don't the TBI BBC trucks have a "hot start" module or somesuch? Never really could understand those things, obviously there was SOME sort of problem, or they wouldn't have used it, but why didn't they just change the programming in the ECM?

In starting my tuning, it LOOKS like it's running rich across the board anyways, so I suspect that is throwing the tune off in the "extreme" conditions here when it's over 90*. :)

I'm going to work on fueling across the board and see what happens.
 
I don't know anything about a "hot start" module, I'll have to do some research and see.
 
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