95 k1500 350 TBI bogging down when air temperature is cold?

[lowkey]

Hey everyone,

I'm about at my wits end trying to figure this out, hopefully y'all can help!

I have a 95 k1500 with the 350 tbi. It's been having a reoccurring issue where it bogs down while I'm driving, and will even stall when I'm slowing down to a stop. However, this EXCLUSIVELY happens whenever the air temperature drops to 0°C or lower (I live in Canada).

What could be causing this issue? I finally figured out the other day (thanks to this forum) what hose is missing that runs from the passenger side manifold to the air cleaner, could this hose be the problem?

Thanks everyone!

 

[Schurkey]

Yes. But it's not the only possible cause.

The air cleaner has a thermostatic element that mixes hot air from the stove on the right exhaust manifold, with cold air from the fender. The idea is to supply relatively consistent air temperature to the throttle body which prevents throttle icing, and improves mixture distribution.

But throttle icing is most common at 40-ish degrees F. which would be about 4--5 degrees C.

Start by replacing the hot-air hose, and assure that the thermostatic element and the flapper door in the air cleaner snorkel is still working.

After that...verify fuel pressure and connect a scan tool. Review the data stream, verify EVERY sensor especially when the vehicle tends to stall. The earlier TBI vehicles did not have an air-intake temp sensor, but maybe '95 does. You should download a service manual for your vehicle, there's links to them on this site.

 

[lowkey]

Yes. But it's not the only possible cause.

The air cleaner has a thermostatic element that mixes hot air from the stove on the right exhaust manifold, with cold air from the fender. The idea is to supply relatively consistent air temperature to the throttle body which prevents throttle icing, and improves mixture distribution.

But throttle icing is most common at 40-ish degrees F. which would be about 4--5 degrees C.

Start by replacing the hot-air hose, and assure that the thermostatic element and the flapper door in the air cleaner snorkel is still working.

After that...verify fuel pressure and connect a scan tool. Review the data stream, verify EVERY sensor especially when the vehicle tends to stall. The earlier TBI vehicles did not have an air-intake temp sensor, but maybe '95 does. You should download a service manual for your vehicle, there's links to them on this site.

Awesome, thank you! I'm currently trying to find a hose. How would I check that the element is working? Just hold a lighter underneath and see if the flapper door moves?

I haven't checked fuel pressure yet, so I'll get that done too. Would a fuel pressure issue cause it to run poorly only in cold weather? It's been perfect in temps above 0°C.

I've been looking for a scan tool for this OBD1 based on the recommendation from this forum, haven't been able to find that Snap-On unit yet. I did, however, download the service manual already for some other repairs I've had to do.

 

[1997]

to test the "flapper" i carefully used a propane torch to warm up the element.

any codes set?
how old is the 02 sensor?

When my 95 was having similar issues, it turned out to be the 02 sensor.
Scanner didn't detect as "bad", it appeared to working as it should.

might wanna have read through here see if it helps ...

Surging idle on cold start

Hello everyone, my first post! '94 5.7 TBI with 145,000. Truck is original and last year developed a miss/bad idle in gear. I replaced the IAC, TPS and EGR, plugs, wires, cap, rotor, still had the problem. Checked the fuel pressure, good, 13 psi. No codes. Next, I noticed that the...

www.gmt400.com

 

[Schurkey]

Awesome, thank you! I'm currently trying to find a hose. How would I check that the element is working? Just hold a lighter underneath and see if the flapper door moves?

Pop the convoluted hose off the snorkel end, with the hot-air hose connected to the underside.

Look inside the air cleaner snorkel. Flapper should be shut, so that all the air is coming from the heated-air hose.

Start engine, allow to warm up. Flapper should move at least part-way open allowing a mix of hot and cold air into the throttle body.

Using a flame to test the thermostatic element would likely work...be REALLY CAREFUL to not overheat the thing and destroy it. The thermostatic device that operates the flapper is calibrated to hold something like 110 degree air temp. Hitting it with a 1000-degree flame is beyond what it was designed for.

I haven't checked fuel pressure yet, so I'll get that done too. Would a fuel pressure issue cause it to run poorly only in cold weather? It's been perfect in temps above 0°C.

Probably not...but worth verifying.

I did, however, download the service manual already for some other repairs I've had to do.

Very good.

 

[lowkey]

to test the "flapper" i carefully used a propane torch to warm up the element.

any codes set?
how old is the 02 sensor?

When my 95 was having similar issues, it turned out to be the 02 sensor.
Scanner didn't detect as "bad", it appeared to working as it should.

might wanna have read through here see if it helps ...

Surging idle on cold start

Hello everyone, my first post! '94 5.7 TBI with 145,000. Truck is original and last year developed a miss/bad idle in gear. I replaced the IAC, TPS and EGR, plugs, wires, cap, rotor, still had the problem. Checked the fuel pressure, good, 13 psi. No codes. Next, I noticed that the...

www.gmt400.com

I actually just changed the o2 sensor about a week ago! Took a month for the god damn engine light to come on and finally tell me what was going on, it used to bog every time I drove it. I ended up changing the TPS, both coolant temp sensors, fuel filter x2, and the IAC in hopes that it would solve it, then the o2 sensor last. Now it just bogs when it's cold and snowing/raining out.

Definitely going to check that thread out when I get a chance, thank you!

 

[lowkey]

Pop the convoluted hose off the snorkel end, with the hot-air hose connected to the underside.

Look inside the air cleaner snorkel. Flapper should be shut, so that all the air is coming from the heated-air hose.

Start engine, allow to warm up. Flapper should move at least part-way open allowing a mix of hot and cold air into the throttle body.

Using a flame to test the thermostatic element would likely work...be REALLY CAREFUL to not overheat the thing and destroy it. The thermostatic device that operates the flapper is calibrated to hold something like 110 degree air temp. Hitting it with a 1000-degree flame is beyond what it was designed for.


Probably not...but worth verifying.


Very good.

Awesome, I'll give this a shot once the new hose arrives. Thank you!

 

[lowkey]

Alright y'all, she's back with a vengeance. Hot air hose has been installed. The truck ran perfectly all week, until the snow hit. Now it's back to bogging down, so I'm thinking the active snow may have something to do with it?

I also had the CEL come back on with Code 13, but the O2 sensor was just replaced. What else would cause a code 13?

I've also noticed it's running colder than it should be according to the gauge in the cluster. I've replaced the temp sensor next to the thermostat, next up is the one on the driver's side of the engine. Does anyone know which one sends the readings to the gauge and which sends it to the ECM?

 

[Jonathanhicks]

Alright y'all, she's back with a vengeance. Hot air hose has been installed. The truck ran perfectly all week, until the snow hit. Now it's back to bogging down, so I'm thinking the active snow may have something to do with it?

I also had the CEL come back on with Code 13, but the O2 sensor was just replaced. What else would cause a code 13?

I've also noticed it's running colder than it should be according to the gauge in the cluster. I've replaced the temp sensor next to the thermostat, next up is the one on the driver's side of the engine. Does anyone know which one sends the readings to the gauge and which sends it to the ECM?

The sensor for the gauge should be on the driver side head

 

[lowkey]

The sensor for the gauge should be on the driver side head

Thank you!