Are my issues related? (1 Viewer)

[ElPolloBlanco]

I’m not talking about my mental health. My truck has been acting strange. Last summer while on a trip to the Sierra NF my coolant temps were all over the place. I have an ultra gauge hooked up. My dash gauge was pegged in the middle maybe a little higher this section of uphill climb gets my ride a little hot and bothered sometimes. I watched my temps drop on the ultra to like 85 degrees. Then back up. This happened off and on for that whole trip.

Everything was fine on that end until the last few days. P0116 codes and weird temps. I’m thinking the temp sensor is no bueno. A 2k start up idle comes along with the weird temps. Even without the code.

I’ve also had other problems I think are fuel related. I occasionally get a rough start. I can’t say when I first noticed it, but my rig seems sluggish first thing in the morning. Sometimes I get a rough start that either shuts the truck down or needs throttle to get the RPMs up. No codes associate with this. I recently had the interior out for a project and checked the sending unit at the tank and the sock in the tank and all was right per the FSM. I pulled the plug in the relay and the truck starts smooth, then dies. Pull the relay and no start at all. I’m thinking the contacts inside the relay aren’t connecting the right way, but I’m not sure.

Because of the two separate issues, it’s hard to isolate the problem, combine the fact they are both intermittent, and it’s near impossible. I don’t want to waste time throwng parts at it. I’m thinking a replacement of the temp sensor and the relay should solve my issues though. What do y’all think?

 

[gummycarbs]

I had a crazy high idle cold start idle due to leaking vacuum hoses. The biggest improvement came from the PCV valve and both hoses, brake booster hose, and (I think) the hose that connects to the underside of the EGR modulator. I also cleaned ton of gunk from the IAC valve.

Dunno what's going on with your temperatures. Sounds like a bad sensor or ground.

 

[ElPolloBlanco]

I had a crazy high idle cold start idle due to leaking vacuum hoses. The biggest improvement came from the PCV valve and both hoses, brake booster hose, and (I think) the hose that connects to the underside of the EGR modulator. I also cleaned ton of gunk from the IAC valve.

Dunno what's going on with your temperatures. Sounds like a bad sensor or ground.

The idle is intermittent and tied to the low temps. When the temp is where it is supposed to be, it’s fine. A better way to explain it is if the truck is started after it’s already warmed up. If the engine is warm, but the temperature is wrong, the idle is high. My vacuum lines look good.

Another thing with what I think is the fuel issue, every once in a while the truck does that weird throttle thing where it throttles itself up and down. I think it’s the EFI remap or whatever.

 

[scottryana]

Change your temp sensor first. All the issues could be explained by the temp sensor. The odd throttle thing could be the cold enrichment. I would do just the temp sensor and re-evaluate.

 

[RayRay27]

Change your temp sensor first. All the issues could be explained by the temp sensor. The odd throttle thing could be the cold enrichment. I would do just the temp sensor and re-evaluate.

Which temp sensor are you referring to? I have been dealing with a similar issue. The truck starts fine And idles near 1450 rpms until warm and drops down to normal 650ish range. Then when I drive it and stop at a red light the rpms drop to about 400. But while I'm sitting at the light it creeps back up to 650 and is fine after that.

 

[ElPolloBlanco]

Which temp sensor are you referring to? I have been dealing with a similar issue. The truck starts fine And idles near 1450 rpms until warm and drops down to normal 650ish range. Then when I drive it and stop at a red light the rpms drop to about 400. But while I'm sitting at the light it creeps back up to 650 and is fine after that.

He’s talking about the one that feeds the ECU. Not the one that feeds the dash.

Thanks Scott, I’ll start there.

 

[LS1FJ40]

Which temp sensor are you referring to? I have been dealing with a similar issue. The truck starts fine And idles near 1450 rpms until warm and drops down to normal 650ish range. Then when I drive it and stop at a red light the rpms drop to about 400. But while I'm sitting at the light it creeps back up to 650 and is fine after that.

I’m having this same issue with my 93. Hoping to have time tomorrow to dig in to it. Been crazy busy with work...

 

[thatcabledude]

I’ll start there.

I had very similar issues with my 94 probably 2 years ago. When occurring the ECU would dump enough fuel to flood the truck and kill it if you didn't keep revs up at a stop. VERY intermittent and very aggravating. Hard to diagnose with OBD1 as it didn't trigger a CEL.

Swapped the sensor with new OEM, never happened again. I have since done an engine swap, but still have the like new sensor. PM me your address and it's yours.

 

[gnarlytoes]

My 92 with 3fe started idling high and rough a few days ago. I found one of my temp sensors broken. Hopefully replacing it will solve the problem.

Hard to see in the pic, but the plastic plug is broken where it meets the brass nut.

 

[ajax1]

Temp sensor will cause all this, where I would start.