Stalling at idle

[1990K2500Fan]

Hi there! I've got a 1990 Silverado K2500 5.7 TBI automatic. Just got this truck last week and have been struggling to fix an issue with it stalling at idle. If you can get it into gear, and down the road, the truck is fine over 25mph. If you're in the range or 25-30 mph and let off the gas it'll stall and completely shut off. Occasionally I can get it to idle for at most 30 seconds during which it surges something horrid before ultimately shutting off.

Previous owner claims this only started after he replaced the throttle, TV, and cruise control cables. I've since adjusted those cables and still it doesn't want to run.

So far over replaced the;

IAC Valve
EGR solenoid (someone tried to do an EGR delete and just put a screw into the vacuum line heading into the EGR and looped the remaining line to run through the vent side of the solenoid, presumably to hold vacuum.)
PCV Valve
A handful of vacuum lines (namely the lines connecting the EGR to the EGR solenoid and the solenoid to the Throttle body)

I'm at a complete loss at what the next step is. Any ideas?

 

[Drunkcanuk]

Fuel pressure readings at idle and while it's under load?

 

[1990K2500Fan]

Fuel pressure readings at idle and while it's under load?

I can't even get the truck to run long enough to get a fuel pressure reading at idle. It starts and then immediately dies

 

[movietvet]

Welcome to the forum from Oregon.

My girl has the same truck and same year. Supply some pics of this mess please.

Previous owner replaced cables and problem started? Then you adjusted and no help? What adjustments did you make?

 

[PlayingWithTBI]

EGR solenoid (someone tried to do an EGR delete and just put a screw into the vacuum line heading into the EGR and looped the remaining line to run through the vent side of the solenoid, presumably to hold vacuum.)

That's not really the proper way to do it. Is the EGR valve still on the engine? If so, hook it back up the way it should be. If not, check your block-off plate for any leaks. If it's bypassing, you'll get too much exhaust going to the intake making it hard to burn, kinda like a stuck EGR valve (if it were still there).

Edit: Do you have any MALF codes? That may point you in the right direction.

 

[1990K2500Fan]

That's not really the proper way to do it. Is the EGR valve still on the engine? If so, hook it back up the way it should be. If not, check your block-off plate for any leaks. If it's bypassing, you'll get too much exhaust going to the intake making it hard to burn, kinda like a stuck EGR valve (if it were still there).

Edit: Do you have any MALF codes? That may point you in the right direction.

I bought a new one to put on, since I tried hooking it back up the right way and it's still not working right.

As for the MALF codes the check engine light isn't on at all, and nothing seems to be wrong with it as far as the truck says. It just seems like it's idling too low and the truck can't keep up. One thing I did notice that I'm not sure if I mentioned or not is on the times that it runs for those 30 seconds, it'll bog down then surge real hard to try and keep itself running. After about two or three times of doing that it just shuts off. I tried sending a video but the forum said the file wast too large to process

 

[1990K2500Fan]

Welcome to the forum from Oregon.

My girl has the same truck and same year. Supply some pics of this mess please.

Previous owner replaced cables and problem started? Then you adjusted and no help? What adjustments did you make?

You must be registered for see images attach

You must be registered for see images attach

All I did was adjust the TV cable by using a screwdriver to press on the button and letting it set against the throttle, then putting the throttle wide open and letting the button go. Other than that I’ve made no adjustments to the cables

 

[PlayingWithTBI]

As for the MALF codes the check engine light isn't on at all, and nothing seems to be wrong with it as far as the truck says

That doesn't matter, on these OBDI systems, they can store a code without the SES Light staying on. It's always a good idea to check them.

All I did was adjust the TV cable by using a screwdriver to press on the button and letting it set against the throttle, then putting the throttle wide open and letting the button go. Other than that I’ve made no adjustments to the cables

If you didn't mess with the min idle screw on the TB, you need to look elsewhere. Got a scanner?

 

[1990K2500Fan]

That doesn't matter, on these OBDI systems, they can store a code without the SES Light staying on. It's always a good idea to check them.


If you didn't mess with the min idle screw on the TB, you need to look elsewhere. Got a scanner?

I did follow a YouTube tutorial and turned the idle screw up a half turn or two. Nothing wild, but I put it back to as close to the factory setting as I could. Problem is I don’t have an OBD1 scanner, but as soon as I can find one for sale somewhere I’m going to buy it.

 

[preinternet]

Hi there! I've got a 1990 Silverado K2500 5.7 TBI automatic. Just got this truck last week and have been struggling to fix an issue with it stalling at idle. If you can get it into gear, and down the road, the truck is fine over 25mph. If you're in the range or 25-30 mph and let off the gas it'll stall and completely shut off. Occasionally I can get it to idle for at most 30 seconds during which it surges something horrid before ultimately shutting off.

Previous owner claims this only started after he replaced the throttle, TV, and cruise control cables. I've since adjusted those cables and still it doesn't want to run.

So far over replaced the;

IAC Valve
EGR solenoid (someone tried to do an EGR delete and just put a screw into the vacuum line heading into the EGR and looped the remaining line to run through the vent side of the solenoid, presumably to hold vacuum.)
PCV Valve
A handful of vacuum lines (namely the lines connecting the EGR to the EGR solenoid and the solenoid to the Throttle body)

I'm at a complete loss at what the next step is. Any ideas?

did you relearn the iac valve or reprogram theb ecm for it