I have blazer 2006. the RPM gage is below 0.5 that makes the head lights weak and cooling goes hot(i dont mean heating ) when i stop while the engine is running but whenever i accelerate the cooling become cool.please i hope u can help

Your torque convertor will stop the engine stalling.

no engine told at all.
308 really means, this.
#8 combustion pressure (HP) power is weak, or weak combustion.
caused by many things not just spark 3 things ASE otto cycle gas engines.! (basics)
1: bad engine, bad valves and compression test on #8 fails
2: spark bad #8 spark plug, wire set HV or COP bad. to 8 or cop boots bad on #8 (boots HV carbon tracked or useless)
3: injector bad. leaking or 1/2 clogged or even dead.

in that order, other odd cause but real.
intake runner gasket to #8 is sucking air, aka bad intake gaske.

some cars injector 8 has a bad seal ring sucking air.
bad head gasket but near #8 is worse .
warped head #8 worse here. and makes gasket fail overheated engine top cause.
keep in mind all we know is #8 is weak not why, only tests using real tools finds it.
I do a compression test on #8 and below 150psi is no good WOT.
swap injectors 7 <:>8
do RAD leak down test find coolant leaks not discovered yet.
check scan tool PID LTFT on both banks. SAME,
check 02 , S1B1 and S1B2, FOR CLOSED LOOP STATUS HOT IDLE
MAKE SURE HOT ENGINE PID ECT IS 180F SCANNED.
engine unnamed.

• 2004-2009 - 3.7 L (226 cu in) Magnum V6, 210 hp (157 kW) at 5200 rpm and 235 lb?ft (319 N?m) at 4000 rpm.
• 2004-2007 - 4.7 L (287 cu in) Magnum V8, 235 hp (175 kW) at 4500 rpm and 300 lb?ft (407 N?m) at 3600 rpm
• 2004-2008 - 5.7 L (345 cu in) Hemi V8, 335 hp (250 kW) at 5200 rpm and 370 lb?ft (502 N?m) at 4200 rpm (MDS equipped for 2006+ 5.7 L engines for improved fuel mileage)

;

Didn't find 97 ranchero in US automotive database. Is this a US vehicle? I looked for wiring diagram? I'd have to check starter motor wiring circuits and make sure engine isn't trying to seize when it gets hot or starter motor.

so what works and what not.
so far we have cluster issues
does car drive, ok day and night.
and all accessories?
did engine stall driving?
did Head lights dim? on, driving?
my guess is the engine stalled or idled below 300rpm
and the ECU went to Key on self test mode, (they all do that)
watch the RPM guage? see that needle, ?
if it goes below 300 rpm that is engine stall.
or worse
This cars cluster is really just a digital display
so if the PCM cant talk to the cluster, the cluster will go nuts.
for freeze.
We use a scan tool to see whats up.
or use the cluster self test covered in the shop manual.
the cluster has 2 fuses that can be cracked/loss or corroded.
the cars battery can go weak.
if the charge/battery light glows, engine RPM good
then the alternator systems is failing
if the volt meter (if opted) in cluster drops below 14v, and engine is still running, the same, alternator system failure
or even a loose belt at the alternator.
if the battery voltage drops too low , all electrics go nuts.
and engine stalls.
what dies first with low battery , is luck of the draw....
so what was battery voltage
and engine RPM at the point of failure.??????????

Year, make, model, and enigine please.

use a scanner to reset the CPU as the program is corrupted from the flat battery

are you saying , it stalls (RPM on dash goes to 0)
or RPMs are below 800(hot and is wrong) ?
or that all the above is ok, but I have lost engine power?
if A/T transmission slip, (RPM goes way to high and MPG dont track RPM correctly)
is car an A/T
when asking for help , stated engine size and transmission options.
we dont know. and Civic sub model name is good to... we are blind here.

thet moment stop your engine and grab top radiator hose, feel the heat then grab lower radiator hose they have to be hot same heat. Top hose very hot is radiator blockage, Or lower hose very hot thermostat damage ,for test thermostat tide whith a string or wire have one glass cold water and juck boiling water deep thermostat in and you have to see the opening if is not then you have to replace it. Don ever youse radiator flush with the thermostat on. Blown head gasket means continual air bubble when you remove radiator cap special white froth,check for loose or damage hose and heter leaks when cooling system is under pressure.check low and high rpm exhaust fumes.

If you have a coolant temperature gage in the instrument cluster and it is running cool replace the thermostat. If you have an "idiot light" for temperature make sure the engine is hot and check the top radiator hose to be sure its hot.

Check The ECM (engine control modual) And The TCM Relay, Is your traction control light, service engine light, and check gages light on. If so most likly the TCM Relay Or Component Has Failed, My 06 4.2L Ascender Did the same thing on and off for a while, system lacks power and begins to run hot and chug. The Relay is next to the Starter Relay Under the hood on the drivers side Fuse pannel, its the same relay as the starter one, i just swamped mine out tilll i could get it replaced, just remember, it might make it hard to start after u swap it till you replace teh starter one then. Also check ur spark plugs after the issue is fixed, it fouled a couple of my plugs! Hope this helps.