We have an 86 TA with TPI. The car has 32K miles on it and is used as a weekend cruiser. I bought a add on chip that cancels out the 9th injector due to starting issues. That corrected that problem. I selected the off road version so that most of the emissions are locked out.

One problem we have been fighting for many years is that the engine acts like it gets vapor-locked when driving long distance in the mountains pulling a grade. I know, several of you are going to say that's not possible. After pulling a long grade, the engine will die when one lets off the gas. It won't idle. It starts right back up, however one has to keep the RPM around 1000 to keep it from shutting off again.

Once one has turned around and is headed down the mountain, the issue stops and it runs normally.

I have a large alluminum radiator with twin Spall fans. They are set to engage at 195 F. I am running a 195 t state. The engine runs at 195 regardless. The max altitude we are at is 6400 feet. I know that it's supposed to be impossible for a TPI to vapor lock, however the symptoms are so similiar.

Any ideas on what might correct this problem?

 

With the emissions deleted how did you handle the actual physical components of the emissions systems?

 

I've read accounts of members around here having issues when fuel tank is low and they turn a sharp corner, engine will sputter for a bit because gas is sloshing around in the tank and injectors get temporarily starved. is your tank more than half full when this occurs?

 

Connect a scan tool, look at the data stream. Verify EVERY sensor and computer output. Examine the fuel trims, especially when the engine is running bad.

 

The emissions are still intact. This problem predates the modified chip. We have been chasing this problem for 18 years. I plan to install headers on the car and dual exhaust. The emissions will be dealt with at that time.

 

Fuel tank is always full except one time. This is a national park with no places to buy fuel, so we fill the car with ethanol free premium before each trip.

We replaced the fuel tank, sending unit, and fuel pump a few years back due to a leak. This problem predates this repair. The repair had zero effects on the issue.

 

no codes.

The car has given a check engine light if we can't find non-ethanol gas. It comes from the O2 sensor. That sensor has been replaced twice with no effects on the problem..

 

"Codes" are the BEGINNING of computer diagnosis. From a certain perspective, "codes" can help...but the REAL DIAGNOSTIC POWER IS IN THE DATA STREAM.

STOP using a "code reader" and start using a REAL SCAN TOOL, ideally one that can provide a graph of the sensor voltages rather than just text--but text is better than nothing. Look at the sensor outputs of EVERY sensor. Look at the computer outputs to the various actuators including EGR, IAC, ignition system, etc. Inspect fuel trims particularly when the vehicle is running badly.

Moreover, if the symptoms are so much like vapor-lock...CONNECT A FUEL PRESSURE GAUGE and test for pressure problems in the mountains.

Lotsa folks complain about ignition modules that fail when hot. That's never been a problem for me, but I can't totally discount the number of folks claiming that replacing the module "fixed" their heat-soak issue.


For the record...consider that the problems may be CAUSED or made worse by the aftermarket "off road" PROM that is obviously not suitable for a street-driven vehicle. Commercially-available aftermarket PROMs are notorious for causing unexpected outcomes when actually plugged-into a street-driven vehicle.

 

A friend of mine used a scanner that's in a laptop computer. I don't know much about them but it's not it's not just a code reader. He checked every sensor.

I hadn't considered that it might be ignition related.

The odd part is as soon as we turn around and decend the mountian the engine levels out runs perfect.

We have been chasing this problem for 18 years, and the aftermarket chip was a last ditch effort to see if locking out non essential functions might correct the issue.

The chip made the car faster and more responsive, however it didn't have any effect on the issue. It only shows up when assending a long grade. Highway 441 enters the GSM National Park at 2000 feet above sea level. The engine gradually runs worse until it won't idle at New Found Gap 5500 feet above sea level. I can push it on up to Glingman's Dome parting area at 6500 feet. It doesn't get any better or any worse. If we shut it down and let it sit for an hour or so it runs normally when restarted.

if it's running badly after decending the mountian for a mile or two, all is well again. That's what made me think that it's a fuel issue as opposed to an ignition issue.

I drove the car 60 miles each way to a doctor's appt and it ran perfect all of the way over and all of the way back. It was a 4 lane highway with a 55 MPH speed limit. The road assends Balsam Gap, from 2000 feet above sea level to 4500 feet. The difference is the speed and constant climbing compared to up and down hills with a gradual assent.

What ever is happening is very specific to driving conditions.

 

Just taking a stab in the dark. Could this maybe be caused by the Fuel Tank Vent Valve?

Hawks Restoration Parts - 82-92 Camaro Firebird V6 & V8 Fuel Tank Vent Valve

 

I considered that the tank isn't venting properly, but early info was that it cleared-up immediately upon turning down-hill.

But now we're hearing that the car doesn't always run great downhill, sometimes it requires some additional time.

So, yeah, next time you run uphill and it doesn't run right, loosen the gas cap and see what happens.

Another possibility is that the computer isn't compensating for the change in air pressure from increasing altitude.

Supposedly the throttle position sensor has been checked, but I wonder if there's a bad spot on the sensor that sends screwy data when the throttle is opened far enough to go uphill. But I don't think those are the only possibilities for this thing running bad.

 

Thats a pretty good thought. If the vent is cracked, then the tank is venting all the time. And these vents do crack.