Sensor Resets?

[philtodisco96]

Hey all, just picked up an 87 Blazer last week and it's running pretty good. It had a surging idle (only cold starts), but I cleaned up the IAC and I 'think' it solved the issue. Also found a new o2 sensor in the truck so I changed that out too. Also replaced the fuel filter as the one in there was pretty crusty. Fuel pump is pretty recent too I believe. Anyways, I'm now getting an issue where the truck wants to stall and sometimes does when I'm giving it only a little bit of gas, it's almost like a revving sort of thing. Soon as I back off the idle kicks in and it's usually fine. Just curious if the sensors need to calibrate and reset? I did have the battery unplugged when I did all that work. I've driven it probably 10 miles so far. If not, what do you think I should try next? At higher RPM's the truck feels GREAT, it's just those low, barely pushing the gas pedal RPM's that are bogging out.

 

[gmbellew]

I had an issue like that once after replacing the EGR valve with the wrong type of EGR valve (parts house has it mislabeled). I replaced it with the proper AC Delco EGR valve and it went away. you can test this by unhooking and plugging the vac line between the EGR valve and the EGR solenoid. if the issue immediately goes away, then the EGR is either bad or the wrong part is installed.

 

[philtodisco96]

I had an issue like that once after replacing the EGR valve with the wrong type of EGR valve (parts house has it mislabeled). I replaced it with the proper AC Delco EGR valve and it went away. you can test this by unhooking and plugging the vac line between the EGR valve and the EGR solenoid. if the issue immediately goes away, then the EGR is either bad or the wrong part is installed.

Ahh I’ll try it! So just block/plug the vac line on the solenoid end of the line?

 

[gmbellew]

Ahh I’ll try it! So just block/plug the vac line on the solenoid end of the line?

yep!

 

[philtodisco96]

yep!

Instantly worked. The EGR is definitely crusty looking too, gonna try that AC Delco EGR

 

[Blue85]

I've seen this kind of problem with a bad or wet MAP sensor. Best case is borrow one from a good runner just to try. Parts stores ones aren't always good and I don't recommend the parts cannon. If it was a TPS issue, you might be able to find a scratchy spot off-idle with an ohmmeter.

There is a sort of adjustment when replacing the IAC: https://itstillruns.com/replace-mitsubishi-eclipse-speed-sensor-7695841.html

 

[imiceman44]

I've seen this kind of problem with a bad or wet MAP sensor. Best case is borrow one from a good runner just to try. Parts stores ones aren't always good and I don't recommend the parts cannon. If it was a TPS issue, you might be able to find a scratchy spot off-idle with an ohmmeter.

There is a sort of adjustment when replacing the IAC: https://itstillruns.com/replace-mitsubishi-eclipse-speed-sensor-7695841.html

I was going to mention the IAC, he cleaned it but didn't mention performing the relearn