Running rich and dies when put into gear when cold

[MXR597]

I'm really confused and I need your help guys

So to give you guys a timeline to start with here is a list of what I've done to the truck already:
- Changed the EGR valve (OE replacement), solenoid, and replaced the vacuum line a year ago (EGR works fine, I have a vacuum gauge on it)
- At the same time changed the MAP sensor (SMP replacement) and its vacuum line\
- Two weeks ago I replaced the TPS (SMP) sensor
- Thursday I got the O2 sensor tested and it is working like it is supposed to but always reads lean at idle

Starting Friday night and happening again this morning when I start the truck it goes to 1500 rpm and slowly idles down to about 950 rpm, I didn't figure that was a big deal because it has been a little cold out but it has never done that before. But when I shift into reverse it stumbles and dies. Start it back up put it in reverse again and I can drive off and it runs and shifts great after that. So what could be the problem? I really don't know... Is the TPS bad already? New spark plugs are hopefully going in next week and the spark plug wires are brand new (Taylor wires). Any help would be greatly appreciated cause it has to last me at least 3 more years and I have to drive 200 miles on Friday. Thanks!

 

[someotherguy]

ALWAYS helps to give YEAR, MODEL, ENGINE, sometimes helps to give miles, you did well to mention what you've recently done to it though because mentioning the vacuum line to the EGR tells me it's most likely a TBI V8...

Check/replace coolant temperature sensor (CTS/ECT) next to the thermostat. Even if it's not the problem, they go bad over time, and you won't usually notice until it's giving you problems. If it's old, replace it.

Check the harness grounds at and next to the thermostat housing.

Check MAP sensor vacuum line from rear of TBI to the sensor, especially the rubber boot where it connects to the TBI.

Richard

 

[MXR597]

ALWAYS helps to give YEAR, MODEL, ENGINE, sometimes helps to give miles, you did well to mention what you've recently done to it though because mentioning the vacuum line to the EGR tells me it's most likely a TBI V8...

Check/replace coolant temperature sensor (CTS/ECT) next to the thermostat. Even if it's not the problem, they go bad over time, and you won't usually notice until it's giving you problems. If it's old, replace it.

Check the harness grounds at and next to the thermostat housing.

Check MAP sensor vacuum line from rear of TBI to the sensor, especially the rubber boot where it connects to the TBI.

Richard

Oh wow I totally forgot to list that stuff
1993 GMC K1500
5.0L TBI and the 4L60E
214K miles

Sorry It has been a long day

Also may be worth noting that the vacuum lines are just tubing from tractor supply with clamps on the ends. Anywhere I can get OE replacement lines?

 

[slippy3002]

My truck did the same thing. It was the IAC in my truck

 

[Yamaben]

200k miles is a lot of miles on a distributor. There is a reasonable chance the bushings could be shot. At least change the cap and rotor if you haven't in a while.

 

[MXR597]

Update: So yesterday I pulled every vacuum line and cleaned and checked for leaks, didn't see any so I put them all back on the truck and started it, it ran fine... RPM's were low it did not run super rich (Still a little though).

I'm not sure what happened, new coolant temp sensor is going in next week along with a new thermostat and valve cover gaskets.

Holding off on an IAC valve for a little bit but will buy one this summer no matter what.
As for the distributor, it is newer, not sure how new but it has less than 100,000 miles on it and has no play in it.

 

[michael hurd]

Base gasket under the TBI? I would pull the 3 bolts and check what it looks like.

Edit: re-read the post, it's idling slow rather than fast like a vacuum leak... IAC pintle stuck? Check the grounds at the thermostat housing... most of the time they will come off in your hand when touched, at least in the salt belt.

 

[someotherguy]

If it's running rich enough for you to notice, and you choose to ignore my advice about the CTS, well, good luck to ya.

Richard

 

[MXR597]

If it's running rich enough for you to notice, and you choose to ignore my advice about the CTS, well, good luck to ya.

Richard

I put in the update that i'm putting a new CTS in next week once it gets here... I checked the wires but didn't notice anything out of the ordinary

 

[MXR597]

Update: Drove 200 miles yesterday, transmission ran pretty hot and got to 220. It finally threw a code 22, which is low voltage on TPS. Guessing that the TPS I bought was bad. Heading to the store to buy a new one.