1992 k1500 cooling system and missfire issues

[hunter4ever12]

So here is what I'm working with: 92 k1500 with the 5.0L in it with 233k miles on it. The first problem is it is missing/ stuttering, and sputtering under heavy acceleration. It only does this before its "warmed up" and only if you smash the pedal to the floor. It wasn't doing this though until I installed a new coil. A while back I did a tune up on it and it.showed little to no improvement and was running rich. So I rebuilt the throttle body and "custom tuned" the fuel pressure regulator to make it most efficient for my engine. It helped but still not alot so i decided to replace the coil and wow what a difference that made it accelerates much better and takes less throttle to achieve higher speeds than it used to. But I still have a problem until it gets warmed up then its less prevalent but still noticeable in the high rpm range. So do you think this is due to the engine running.to lean now with the new coil or is my problem something else?

My second problem is this: I have been having cooling system issues for a while. A while back I had to replace the thermostat because it was failing. So I replaced that and the coolant temp sensor right up on top of the manifold as well. When I replaced the thermostat I put on a little higher temp One than stock (205 degrees) because I live in Colorado and my pickup was sometimes taking upwards of 30-40 min of idle time to reach normal opperating temp. So after I replaced them I noticed it did help warm it up faster but not much. I also noticed after replacing that my gauge started reading funny it would read 210 degrees for a while then go up to the next "Mark" which I believe is 240 and then drop back down again it was "bouncing" so not only was that a problem but the fact that it was reading hotter than the thermostat i installed should allow it to I new something was up. Anyway I next replaced the coolant temp sensor in the side of the block. This is where another problem arose. Now my temp gauge climbs all the way up into the "red" 260 degrees, and then falls back down to 240 the check gauges light never comes on tho and I have stopped before while it was in the red got out popped the hood and it doesn't smell hot or feel any hotter than normal temp. So with this one I have no idea what's wrong.My only thought is the gauge itself is bad other than that I have no idea.

Thanks for the help in advance,
Wesley

[777stickman]

I would suggest going back to the stock 195 t-stat. All you're doing is increasing the engine coolant temp, which to me is not good. The oscillating temp gauge is an indication of air in the cooling system. The sensor in the head is for the gauge. Could be you got either a bad one or the wrong one? I'd put the original back in.

I doubt that a new coil will make the motor run leaner.

[j cAT]

the temp sensors may be different. using the wrong one for the guage will mess up the reading.

when operating at high elevations you must have the proper working radiator cap. with no coolant pressure at high elevations the coolant will boiL at less than 212 deg f.

you may have air or worse exhaust in the coolant. this will cause erratic temps.

sometimes using a slightly low thermostat is required like 180 deg f instead of the 195 degf. going higher is mountain country is asking for trouble.

[j cAT]

the other problem may be the cat converters / exhaust restricted.

remove upstream o2 sensors , holes open and test drive.

[hunter4ever12]

How can I tell if the sensor is different. They looked the same to me. And your saying I need to put a new lower temp thermostat in it as well as probably replace the radiator cap? As far as cooling system issues those gave me some things to try but the misfire issue still hasn't been addressed. It doesn't have a cat on it (was a farm pickup when I bought it and they removed it completely and put glass packs on it. It is cut off right behind the cab with 2 90 degrees elbows pointing it straight down. So i don't think exhaust is a problem.

[j cAT]

Originally Posted by hunter4ever12

How can I tell if the sensor is different. They looked the same to me. And your saying I need to put a new lower temp thermostat in it as well as probably replace the radiator cap? As far as cooling system issues those gave me some things to try but the misfire issue still hasn't been addressed. It doesn't have a cat on it (was a farm pickup when I bought it and they removed it completely and put glass packs on it. It is cut off right behind the cab with 2 90 degrees elbows pointing it straight down. So i don't think exhaust is a problem.

you have to check to be sure that these sensors are correct. I found in an 1994 s10 pu. the 4.3L engine used two sensors. these were different.

when installing I found one is called a temp switch for the dash, the other was the ECT/computer temp sensor. they do look different .but will screw into the holes.

on the thermostat I was saying that some may have to install a 180 deg f thermostat. this would be if in a hot climate and or heavy tow hauling hills etc...

normal use you should stay with the spec thermostat which should be 195 deg f. pressure of 15 psi is good.

the exhaust could be plugged as mufflers do sometimes come apart.

miss fire could also be a bad distributor bearing. rotor wobbles or the lower distributor gear worn.

[hunter4ever12]

Originally Posted by j cAT

you have to check to be sure that these sensors are correct. I found in an 1994 s10 pu. the 4.3L engine used two sensors. these were different.

when installing I found one is called a temp switch for the dash, the other was the ECT/computer temp sensor. they do look different .but will screw into the holes.

on the thermostat I was saying that some may have to install a 180 deg f thermostat. this would be if in a hot climate and or heavy tow hauling hills etc...

normal use you should stay with the spec thermostat which should be 195 deg f. pressure of 15 psi is good.

the exhaust could be plugged as mufflers do sometimes come apart.

miss fire could also be a bad distributor bearing. rotor wobbles or the lower distributor gear worn.

I replaced both temp sensors the one thats for the ECM (its up top right by the water inlet/thermostat housing) and the one thats for the gauge in the dash it on the drivers side in the block. So both have new sensors and the problem still exists. I did find that the wires were exposed right where they go into the connector plug for the one in the block so i put some silocone on them but i doubt that would be causing my problem because where the exposed wires are there is no way for them to contact anything but plastic. I will try to put a stock temp thermostat back in as well as replace the radiator cap and see what happens. Do you suggest going with an ac delco thermostat or after market. It has a Stant in it now and I know Stant is a good brand and has been around for years. So does it really matter?

As for the missfire i purchased a new distributor gear and i suspected that could be what the cause was just havent gotten around to it yet. How can I check if the bearings are worn and or if the rotor wobbles?

Also You dont think the fuel pressure regulator has anything to do with it missfiring? Like i said i turned the pressure down on it previously (i have an adjustable aftermarket one) because it was running really rich and it seemed to help a little. But now with the new coil the engine is probably getting the proper intensity of spark and with less fuel coming in than whats stock (because i turned it down to match my engines needs at the time) i would think that the higher intensity spark could be making the engine run more lean and in turn make it ping and missfire like what I am seeing? Is that a probable thought?

[j cAT]

the use of a more powerful coil/spark will attempt to hide issues of improper fuel delivery.

being an old 5L engine when cold and your flooring it I would expect it to studder/bog down.

check that the TBI is spraying properly. both injectors. If the ICM is original I would replace it.

the distributor replacement is a very good idea with miss fires.

too much fuel does cool down the heads. running lean increases heat.. an over active EGR will reduce combustion temps and can cause miss fires.

using a vacuum guage check for 17-20 inches of vacuum at the intake manifold.

make sure the air intake has a heat riser pipe connected and working to supply the intake warmed air when its cold out. if this is gone you will have very poor cold weather engine performance. running rich and bogging down.

a vehicle like this where the OEM components have been removed it could be lots of cause issues.