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91 k5 running rich...only gets 160 on temp????

i dont think he has said they read the same, at the same time yet, but he did say he put 3 t-stats in, and unless he is pulling them out of junk trucks, i cant possibly see 3 in a row being bad, but there are alot of unknowns and its always hard to diagnose something on limited info

dyeager asked him the correct questions
 
ok i want to apologize anyone whos been working on cars 30 yrs(longer than ive been alive) is experienced in my book........ok all thermostats were brand new. when the engine was hit with the laser it will read 186-192 even though the gauge says 160 when the gauge decides to read 200 it is accurate according to the laser and obd its also accurate when warming up to the point of 160.its like something just happens that makes the gauge say 160 and the computer thinks its cold.replaced both sensors(head and intake)brand new shot them with the laser with engine running ir read they were 188-190 at the points where they screw in.no codes come up when diagnosed either. i wonder if something is shorting out or a glitch? if it was bad wiring i would think there would be times where it would not read at all on the gauge instead of just falling to 160,and if there was bad wiring going to the computer i would think i would be seeing bigger problems than just running sluggish. and yes i have watched the gauge drop 30 degrees in about 5 sec right to 160 ,its never any lower than that..drive for another couple minutes, next red light look down and its right back to 200 another couple of red lights back to 160...shoot the block and ir read 192? there is a notable difference in performance when this happens and i know my gas mileage is suffering. thanks for the help and sorry,im now aware im talking to people who know what they are doing
 
im just throwing this up here, doesnt totally make sense but nothing seems to on this one. hows ur fan clutch, can u turn it by hand with the engine off?
 
havent considered that ..................wouldnt i see over heating if it was bad?
 
im thinking that its stuck and spinning at full speed, instead of the clutch making it spin faster when it gets hotter under the hood
 
Apologies accepted on my end. :thumb: Now, have you checked all your grounds yet? With TBI there should be a ground that is grounded on the t-stat housing stud, is that there and in good condition? I had to replace my ground wire connection there as it broke over times of being removed and reinstalled. Also, do you have a ground strap from the engine to the firewall and another from the engine to the frame?
 
may have had a brain fart there, im sorry to backtrack, but when the gauge reads 160 is the engine actually at 160? and does the computer and the gauge always agree on the temp?
 
chevyuser74 said:
may have had a brain fart there, im sorry to backtrack, but when the gauge reads 160 is the engine actually at 160?
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when the engine was hit with the laser it will read 186-192 even though the gauge says 160
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No, he just posted that info a few minutes ago. I'm thinking now he may have a ground issue.
 
sorry, but just to be clear both the dash gauge and the computer both read 160, when the ir gun reads 188?
 
i will check my grounds tomorrow thats something i need to look at closer.it might make sense as to the immediate change,thanks i will have to do that tomorrow though i have to work in 5 hrs. ill let you know as soon as i do.once again thanks for taking the time and not trying to charge me 90 dollars an hour!
 
No problem, grounds are everything in vehicles but even more so in GM vehicles since GM uses grounds to activate everything. We should charge you 25.00 though and apply it to you becoming a paid member on the best GM site you'll find. :D
 
no the engine is at proper temp 187-192 gauge will say 160 when i hooked the computer up my truck was cold,ran it until the needle was climbing up from 100 computer folled it and looked to be accurate i didnt follow it all the way to 160 though
 
j everett said:
no the engine is at proper temp 187-192 gauge will say 160 when i hooked the computer up my truck was cold,ran it until the needle was climbing up from 100 computer folled it and looked to be accurate i didnt follow it all the way to 160 though
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so the computer is reading accurate, just the dash gauge is inaccurate?
 
you could say that when the gauge says 160 and the block is 192 but not all the time. ithink its right its just being sent wrong info because sometimes it reads 200 and the block is 200 when this is the case you also notice a difference in pep which i guess would mean the computer is also reading its hot and leans out the fuel mixture what i cant get is if the computer and gauge run off different sensors whats happening to affect BOTH of them????
 
I am unsure of specifics, but would not be surprised if it was,like 4x4High said, a ground strap issue. Concevievably, ground strap makes intermittent conact, skewing gauge and sensor. Computer feeds more fuel to raise temp, but is unable to 'cause of electrical problems. Just a thought
 
for what its worth i had the same issue with my truck i culdnt figure it out. so i finally changed out the temp sensor, thermostat, and gauge problem solved. have you tried cleaning out the prongs and connection on your dash? i did all of this and it fixed my issue good luck.
 
Sender for the computer (CTS) is indeed different, should have let it continue to operating temp to see what's happening. If it's an intermittent issue, I'd want to drive around while watching the CTS, and see what happens. If gauge and CTS both go wacky at the same time, then it's definitely something along the lines of a ground issue.
 
well, woke up thursday morning and it warmed up to 200 and ran fine,but i checked my grounds and all seem to be ok checked dash connections and every thing was tight.so now i guess ill have to wait untill it starts acting up to start troubleshooting again?this is so confusing.this truck is lucky i love it
 
Really just need to break this down. We've verified (assuming the IR gun was right) that the dash temp gauge is not reading correctly.

What I don't think I've seen clearly, is whether the CTS accurately reports information to the ECM (you watched it to 160*, but thats where you say the problem starts, so it doesn't really say much). That is the ONLY thing that is going to affect how the engine runs in regards to temperature that is tied into a temp sender. You really need to make sure this is happening all the way up to operating temp, and you need to make sure that you replicate the conditions that seem to make the truck run worse, while you have the CTS monitored.
 
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