Well, a year later, and I’m still having problems with this 1992 S10 Blazer with the TBI motor, vin number Z. Still runs like garbage at startup, runs okay when you give it gas, but idles very badly and runs bad on low RPMs. I replaced the IAC valve and the TPS. Took it to a shop and they put a USED EGR solenoid on, ran fine and boom as soon as it gets cold, I’m back at it. The valve has not been replaced so today I took it off cause I bought a new valve and it’s completely different from the new one. The new vacuum housing is enclosed while the old one isn’t, the vacuum port is at a whole different position and it’s the only valve that I can find online (I got it from napa). Doesn’t seem like the valve isn’t working cause I can push the tab and see the little plunger in the old valve move and suck vacuum in and out. Does any one have any ideas?? Should I just put this new valve on and see what happens? So tired of this...

 

check for vacuum leaks first, and move on to using a blockoff plate to rule out the EGR system as an issue if that doesnt give any indicators.

 

I have an 89 S15 Jimmy 4.3 VIN Z TBI. The problem could be the ECU Temp Sensor. There are 2 Temp sensors. One on the side of the head and one by the water inlet. The one by the water inlet controls the fuel mixture. You need a scan tool to see what the ECU thinks the temp is. It is also cheap enough that you could just replace it. The EGR should be closed at idle and when the engine is cold. When the engine is cold it should be in open loop operation. The main input is the temp sensor. Once the engine is warmed up it will go into closed loop where the O2 Sensor plays a big role in fuel mixture.
The sensor in the head if for the dash light or gauge. The water inlet sensor is a 2 wire sensor and the head sensor is a one wire sensor. Hope this helps. The EGR could be leaking by also. If you have a vacuum pump you could apply vacuum directly to the EGR and open the EGR. Idle should change for the worse.

 

last week I put a new EGR valve on it, but it’s completely different from the one that came off of it. At first it didn’t work, but once I took off the hose to the new EGR valve to the EGR solenoid, it worked, and when I put the hose back on the solenoid, it idled fine. No check engine light. But even with this new, weird looking EGR valve that every parts store said is the correct fit for the TBI motor, I still had to give it gas on start up. Now it has sat for a week and it’s cold so it’s only cranking now. I swear, it seems like the new EGR valve isn’t the correct part but is the ONLY MODEL that parts stores sell. The only one that I can find that looks like the part that came off the engine is on rock auto for 70 bucks. May have to go to a junk yard...or put a backing plate on it like the first guy said. It’s so annoying!!

 

I also replaced the temp sensor that sits on top of the intake next to the thermostat housing, but even with the new sensor it’s reading is on and off on the digital dash

 

The dash reading is from the sensor on the side of the head, The only way to see the temp from that the ECU sensor is seeing is with a OBD 1 Scanner..