Hesitation, stalling, hard to start

I have viewed a couple dozen of your threads here and this board has really helped me diagnose some problems with my own S-10. I remedied a problem I was having and would like to pass the experience along to you who may be having the same thing happen with you.

I had trouble slowly (over a couple of months) appear which caused my truck to run rich (could smell gas), smoke when cranked and shifting (black puffs), stumbled when I pressed the accelerator (acted like it wanted to go dead), it wanted to die on me until it warmed up and then it was really hard to get cranked when I turned it off once it was warm, and finally it would try to die out when I let off the gas with the RPMs up.

I first replaced the fuel filter thinking it was a low fuel pressure related problem but that didn't effect it at all. Then I replaced the throttle position sensor (TPS) and that helped some but not enough. I took off the exhaust gas recirculation valve (EGR) and it didn't have any chunks or bits of carbon sticking it open but I could hear them rattling around inside it but couldn't get any to fall out. But the engine ran much better without the EGR attached. I had cranked the engine with the valve off hoping to blow out some of the carbon but didn't see anything come out.

So I put the EGR valve back on and went to Advance Auto to pickup a new one. They didn't have one and couldn't orrder one since the warehouses were empty. So while there I pickup a new temperature sensor since my gauge had been reading low. And it turns out that was the cause of all my problems.

After screwing in the new temp sensor, it started perfectly, wouldn't hesitate when I pressed the gas, wouldn't try and die out coming off a high RPM, and would restart with ease after warming up. So check your temperature sensor before investing in the more expensive sensors, this one was only $22 at our Advance. Money very well spent.

Thanks for all the tips and advice!

Phillip

That also solved one of the two problems I had also with my 91 S10 2.8 TBI. The low temp sensor output was keeping yours and mine computer open looped or in a limp mode and as a result, it would be rough running depending upon the condition of a lot of things. This is probably the key sensor to determine which mode the computer can go into.

I had to fix this problem first than tackle the other one which was intermittent operation when hot. I found it today. One of my TBI injectors was intermittent because of a bad connection in the computer connector. I cleaned it up and squeezed the socket for a better connection. So far, it seems to be working and the truck runs as good as a new one now.