Question about 1990 Chevrolet Corvette

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1990 corvette tach reads to high

The computer sees 900 rpm but the mech tach is reading 2500 rpm when 2000 real rpm is reached the mech tach is passed 8000 rpm

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6ya6ya
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Posted on Jan 02, 2017

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keemo68
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SOURCE: Dim light in instument panel at night on my 1989 corvette.

there could be a bad connection between your dimmer switch and the lights themselves. often times through vibration and wear and tear the connectors degrade. check this first. also the dimmer switch itself could be the cause.check all the connections associated with the panel lights, look for loose wires and/or bad connections if there are none replace the dimmer switch

Posted on Apr 17, 2009

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  • 82 Answers

SOURCE: I have a 1991 z28 the tach goes to full deflection when I turn the car on. When car is off it read o RPM. How do I fix it?

try changing the tach filter. Mine was located on the fire wall behind the distributor on a 1984 z28

Posted on May 05, 2009

  • 1 Answer

SOURCE: Only the speedo lights up, the tach, fuel gauge

HATE to be the bearer of potential bad news BUT , the C4 Vettes are notorious for having dash / instrument cluster woes .
Most likely , yours is a bad one .

Posted on Jun 13, 2009

  • 22 Answers

SOURCE: My Tach on the 2005 Monte Carlo either reads low

Well the only real fix for that is to replace IPC. The new one should come programmed and ready to go

Posted on Feb 05, 2010

ryanlutton
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SOURCE: 2004 trailblazer - tach read

Time to replace the stepper motor behind the tach.

Posted on Dec 21, 2010

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Buick Lesaber, Lower then 1800rpm most time runs fine, Once in while surges high rpm's like driving fast 1900 & above rpm bucks /2100 smooth's out.


Need to take to a shop with a GM tech 2 or higher scan tool. These tools can actually display various sensor readings and voltages in real time and can be used while driving the car to recreate the issue. These are super expensive scan tools so most shops don't have them. Call around or bite the bullet and have a dealer do it. The money you spend on a correct diagnosis will be saved by not throwing random parts at it based on guess work.

Nov 01, 2016 | 1995 Buick LeSabre

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Hi and thanks again for your help with my past projects. I took my 2008 jeep commander to advance auto to have diagnostic done, because check engine light comes on and off sporadically. The instrument...


The transmission would have to be dropped to correct this problem. However, if the car is driving and the transmission isn't slipping, you could have a bad sensor in the transmission but noting wrong with the mechanical part of the transmission. If money is tight and it isn't slipping, I would drive it until it has a further failure.

Mar 22, 2015 | 2008 Jeep Commander

1 Answer

2008 Jeep Commander running fine then slows. Then its won't shift or move over 30 mph. Engine light comes on. Code says chip in transmission needs replaced. Need a good & honest Transmission Shop


there is no chip in the trans. sorry.
check fuses.
then this time scan it and write down the DTCs errors numbers.
and post those, we cant guess these critical facts.

find any ASE shop, and get it checked.
they dont need to cheat you,there work load is near infinite.
no reasons at all.


no over 30mph, did the transmission up shift.?
is it stuck in 1gear. surely you can count the gears shifted?
if not , get a real mech.
if the transmission file the FSM stall test. then this it.
1: tranny RPM goes too high RPM (engine RPM) this is transmission slip.
2: RPM in drive, 1,2, or R, is too low below 1500rpm. STALLED.
this is weak engine. not trans.
see?

google stall test transmission. and read.
or read the FSM
or read same on alldata.com

Sep 16, 2014 | 2008 Jeep Commander

1 Answer

Had new battery installed on a 2002 PT Cruiser. Later the same day the car was cutting off/stalling at red lights. A diagnostic came back with a computer failure. Had a new computer installed/programmed....


let your mech do his job.?
and if the battery drops below about 10v, the ecu will fail (lie), and guess what, that is NOT a bad ECU./pcm/bcm,tcm, etc.)_
if you do\'t like your mech. get a real ASE mech. and win.


real ASE mechs never throw parts, ever. (cept a tune up)

learn to monitor cars 12vdc system, get a harbor fright , charge testing tool, cheap, has LEDS. or learn to use a voltmeter
my car has a dash gauge, called volts.

if the volts shows at 14v running then the charge system is working
and the ECU is now working good, with full voltage.
engine off, the voltage is 12.6v (room temp) and means battery (rested) is fully charged. STATE OF CHARGE, method.

over heating must be fixed first.
it can wreck and engine fast. stop dont pass go, do not collect $200 , halt./
why not put a new fan belt on it for $10.
get a GATES or GY, Gatorback

now lets delve in to why you mech is (asleep in class?)
belt new, and tensioned to spec. some belts slip and do so with out a sound!, gee, get a new one? why risk $3000 motor for $10 belt. ?????

park a hot car, look at every inch of engine bay and pavement, for green AF leaks, (fix that first) got low water level in rad, every morning cold?
fix that first, and is #1 DIY check anyone can do.
Look in the rad neck cold, not the overfill tank, that be weak.
now what they do:
1: compression test. (do that first any time and engine overheats
takes 30min or less if sparks are easy to reach. some are not.

2: rad leak down test. (cracked block or head) a hand pump tool.

3: exh, fumes in rad neck test. blow head gasket. a tool.
Blue green liquid changes color, oops? you found it.
PYRO:
4: checks temperature of each rad tube, for same temp drop
end to end, if this passes the RAD is good. All pro mechs know this test and use an IR pyro temp gun, ,and saves many a burned hand. and finds bad rads, so easy its like MAGIC !
if all else fails. (passes above)
we then remove the pump, some pumps can be very hard.
FWD cars sux this why, (buy a jeep!)
the impeller gone or rusted to nill.
bearings shot and leaking green. out the front.
seal shot in same , bad bearings always wreck that seal,.
humpty was pushed.
Im sure i missed a step.
but you get the idea.
and if your mechanic do these. find another.

more?
A: he checks cam and spark timing if way off, the chain or cam belt slipped. belts last 60k, period.
B: The ECU many have ERROR to report,
in fact any scan tool an monitor engine heat.
and all these facts are considered

Over heating (macro) can be
engine producing too much heat (retarded timing?)
or bad cooling system.
or both. (straw breaks camels back deal)\'

Keep in mind Entropy wins everytime.
and find a ASE mech. and win big.

btw 2, a pro mech replaces the ECU last, never first.
as you can see, he failed you. here.
i bet you where taken for a ride....

Oct 04, 2013 | Chrysler PT Cruiser Cars & Trucks

1 Answer

1991 geo prism brake and battery came on while driving for few minutes then went off what's it trying to tell me?


the battery is really charge failure.
but happens normally under 2 ways.
1: motor stalls, (car have M/T or A/T)
2: motor RPM drops real low, to like 500rpm or less. near stall.
and generator (alt) drops off line.
all normal, next time , look at RPM of engine when the lamps come on and that tells you what is happening.
buy a tachmeter, if no dash tach opted.
or use a mech. tach and use it while driving.

Feb 11, 2013 | 1991 Geo Prizm

1 Answer

How to adjust a 650


Turn each of the four (two if not a double pumper, on some) screws in just till they stop (not tight). Turn each out about one and a half turns.
Attach a vacuum gauge to any available port that carries full vacuum (in base of carb or on manifold).
Attach a tach to the ignition system (hand held, attaches to negative side of coil or slot marked "tach" on dist cap).
start the engine and turn throttle linkage adjustment to the lowest rpm the engine will run at.
adjust either of the front screws out so therpm and vacuum increases. As soon as it moves, do the same at each of the other screws. Repeat this till you have reached the highest rpm and vacuum reading. If rpm exceeds 800 while doing this, lower it at the throttle linkage. If any screw stops responding, don't adjust it any further. (happens on old carbs sometimes).
Usually after you reach the highest point, it's best to turn all the screws back in around a quarter turn.
Adjust the linkage so the rpm is at the factory setting for the engine you have or, if modified, generally best is between 800 and 900 at idle in gear (if automatic).
If it's on a Chevy engine, timing should be at 32 degrees total advance, base timing at around 12 degrees.
Adjustments cannot be made if there are any vacuum leaks or if fuel bowl floats are not properly set. Highest idle rpm and highest vacuum reading does not always happen at the same time. You are looking for the highest vacuum reading with the idle being smooth.
Holley carbs have many adjustments. Accelerator pump stroke and curve, squirter size and jet size determine how well the carb is "fine tuned" to your usage. On 85 and up automatics, transmission control cable MUST be correctly adjusted or you can quickly kill the transmission.

Sep 11, 2011 | Chevrolet Silverado Cars & Trucks

1 Answer

2003 Ls v8, has no power after, runs but only in low rpm's even with the accelorator to the floor. some mech's say it's the computer. Any other possible causes


Give us any codes you may have ,if you have any
MIL Lamp or Wrench Light on the dash

Not the PCM (computer)

What in detail has been tested?

V8 or V6 ?

Did this drivability symptom come about over
time,I don't see it just happening all at once

What about preventative maintenance Items?
Do you keep a log book?

Does the Tach Flair or stay around 1,800 rpm
when driving

Jun 17, 2011 | 2003 Lincoln LS

1 Answer

My electric system has gone haywire. The tach


SOME GAS CAPS CAN BE VERY HARD TO REMOVE , IF YOU TRY WITH A PAIR OF LONG PLIERS YOU SHOULD BE ABLE TO REMOVE. THE TACH PROBLEM SOUNDS LIKE THE SPEED SENSOR MAY BE BAD

Sep 28, 2009 | 2001 Oldsmobile Aurora

1 Answer

Problems wont pass 4000 rpm's


Depending on the model of accord. It may be a VTEC malfunction in the computer. If it's an EX it is a VTEC

Jun 16, 2009 | 1999 Honda Accord

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