95 Chevy g20 5.7 K-series - bogs down after running for a while in hot

[ratbag]

I have a 1995 Chevy G20 Van, 5.7 liter TBI motor(k-series), for a while now, it runs fine in traffic
for about 1 hour, and for about 2-3 hrs on hwy. Then it stalls, bogs down. On hwy, usually
stalls when slowing down upon entering a town, sometimes while driving down open hwy.

Doesn't happen in cool or cold weather so far. 1st started when I moved out of Oklahoma,
never happened there. I ran non-ethanol gas in Oklahoma, since then all seems to be ethanol
gas. I started adding a fuel conditioner for ethanol, but no change. Had radiator flushed
really well and replaced thermostat and fuel filter, No luck so far. Acts like it's
overheating, but temp gauge stays from 1/4 to 1/2, THX

[Jsdirt]

Usually when something like that happens only when hot, or in hot weather, it is an ignition component failure. When they're intermittent like that they can be a real pain in the ass to troubleshoot.

 

Another possibility is the fuel pump could be getting weak. Or, there could just be a loose connection somewhere (battery terminals, etc.). Fuel pressure test will let you know how the pump is doing. Wouldn't hurt to go over all the wiring starting at the battery and going out from there, too.

 

If it starts and runs perfect until the engine heats up, then you can rule out fuel & connections - it's more than likely something failing in the ignition system. Even bad wires can do that if they're old and crappy enough.

[ratbag]

Heya thanks for the input. Yes - the Ignition Control Module seems to be a usual suspect. It does start up fine, no smoke or leaks, so I'm thinking something electrical too.I put a good quality new fuel pump in when I got it, new fuel filter also.

This wkd I am pulling the turtle shell and replacing:

Airf filter,distributor cap & rotor, plugs, plug wires, Ignition Control Module, coolant temperature sensor, radiator cap, PCV valve.

I was looking into MAP sensor and Oil Pressure Sender as well, but from what I read on those it would likely be smoking and not start well, and throw engine codes.

I had to replace muffler about a year ago, so I am thinking mebbe I should replace the catalytic converter. Lordy but the shops tend to charge extravagently for that. I can buy a good quality catConverter for like a hundred bucks, but shops be quoting in excess of 300.00 to get it done..

 

If it is still misbehaving after my wkd work, I'll take it to a shop with a live-data diagnostic tool. It is not throwing any engine code lights.

I'll post my results, this seems to be a pattern in these tanks, maybe I can add to the data on a cure, haven't found any consistent pattern for cure in my online research.

 

Thanks again!

[Jsdirt]

No prob - glad to help.

 

I wouldn't worry about the cat unless you live in an area that does tailpipe testing for inspection. If it's clogged I usually punch a pipe through it, or remove it altogether, just to let the vehicle breathe. I remember my old '85 Monte Carlo gaining 3x the power, and going from 12 mpg to over 22 on the highway after hollowing the cat out. Thing was plugged solid. Got to the point where I couldn't accelerate at all.

 

Codes on a '95 are even more vague than on the newer OBD-II systems. Borderline useless. On those vehicles you can normally get by with just basic, old school troubleshooting. I think after you replace all that stuff you'll be in good shape anyway. Doesn't take a whole lot of money to keep these old systems happy, unlike with OBD-II.