Dieing after startup

[jonathon]

This is a weird problem that's been happening for a little while now on my Suburban.

First startup of the day(or after it's been sitting for a while) it seems it will start, run for a few a seconds and then just die. This happens in park and in gear. The occurrence is random, sometimes it will, some times it won't. After it's warmed up no issues at all, and it only happens right after startup.

I pulled the codes, and got nothing(other than 12 of course). I'm thinking it may be an ignition issue, but beyond that I'm not even sure where to start.

 

[Mike D]

If it is carbureted either the choke is not resetting or the choke pull off ( vacuum operated ) is not working. Also remove the distrubitor cap ( leave wires attached ) and spray WD-40 into the cap. Wipe out excess and reinstall cap. Carbon residue and moisture could be bleeding off high voltage, until it heats up and dries out. Some Q-jets had an electric heating coil in the choke. It could be burned out ( open circuit ).

 

[jonathon]

It's TBI... I'll take a look at it tomorrow. I'm planning to do a tune up sometime this month anyways.

Today it wouldn't do it at startup, but once in gear it would die, start it up again and it would be fine.

 

[Mike D]

The IAC may be sticking on initial start up. Remove IAC cean plunger(?) and passage with a good Carb & Throttle Body Cleaner. You might want to check the Throttle Possition Sensor (TPS) with a digital volt meter. At idle it should read 0.45 - 0.55 volts. There may be a proceedure to correctly check the TPS. Have you changed the fuel filter? The extra resistance the fuel pump is fighting ( the filter ) on initial startup is dropping the fuel pressure and causing the engine to quit.
Here is a cheap fix that was used during the late 70s when fuel injection was new.
Phase the fuel pump - Only in the mornings upon first use of the vehicle.
Turn key "on" for 5 seconds , then off. Repeat 3 times, on the third time go all the way to start. If it starts and stays running your problem is solved. It also means you have a weak fuel pump. I would replace the fuel filter just to minimize any restrictions. Also start saving your pennies for a new fuel pump.

 

[jonathon]

Thanks for the info! I'll be chasing all this down. Fuel filter was just changed(Napa Gold) about 6000-7000 miles ago(4 months if I remember right, yes I drive a lot ).

I've got a brand new AC Delco pump to put in when I do my shackle flip next month.. I figure while the tank is out might as well since the pump is original.

 

[jonathon]

I'll admit I haven't checked the dist. cap yet, going to do that this week..

Now it's behaving a little worse.. idle is a little rough and under wide open throttle with a load it stumbles(like I'm hearing afterburn coming down the pipes and it bogs down bad), however if I keep it moderate it does just fine. My fuel economy doesn't seem to be effected.. still getting 13-14 average.

 

[Mike D]

Check your spark plug wires. A bad wire will misfire under load. If you have 60,000 miles on them they may have gone bad. All it takes is one wire to cause hesitation and stumble under load.
What I do ( you may or may not want to try this ) is carefully grab each wire while my other hand is holding a good ground ( unpainted body nut ). If I get zapped by any wire I replace the whole set. Buy a good set ( not an el cheapo brand from China or Mexico ).
The only other way to check the secondary wires would be to remove the hood, find a deserted road with no street lights, and accelerate from a dead stop at night ( several times ). If you see random flashes of light from the engine compartment, the wires are shorting out to ground ( causing that cylinder to misfire ). Replace the wires.

 

[jonathon]

Well the set may or may not have a lot of miles on them but they are at least 10 years old since this truck was barely driven 6000 miles a year.

AC Delco wires okay? I'm doing a new cap, rotor, plugs, and wires as soon as my stimulus check comes...

 

[jonathon]

Okay.. odd question, but would a malfunctioning EGR valve cause these sort of issues? Pulled the cap and the contacts looked pretty clean(no build up anyways) and I tested the wires. I'm not getting any codes though.

The reason I ask is my mom's S-10 is doing similar things.. and it's throwing a code 32(EGR Valve). Rough idle, dies when put into gear unless you give it gas, and under WOT conditions it bogs down. Got the EGR valve for her Blazer, so we'll see..