TxDiesel007

Guys in a nutshell here is the issue

My tach is goin nuts, i take off and the tach just jumps up high then comes back down to normal rpms, in the process, the lights become brighter, then they dim, and the radio either turns off then back on, or it just skips and cuts for a split second... both of which can happen at random

it dont matter if i take off in first low or second gear, trucks been doin this for a couple of days now, it didnt really phase me till now.. Tonite this is what i observed

I didnt turn on the AC, but i switched the fan on, and i was able to kinda see the tach bounce and the radio skip (i have a cd in it that is brand new) and it did it a couple of times,

The cruise control dont work, (vac line was eaten away by battery acid) so im not sure about that one either

Is it the possibility of a bad tach sensor? Any and all help is appreciated, i dont want to fry my stereo system, nor fry anything else on the truck...

Thanks guys!

ON EDIT:

Tuesday, 11/28, i have made the following observations on the the truck. The tach seems to go haywire only when i do a hard launch in first and second gear to take off, it will rebound off 3 or 4K rpms and go back to normal, the radio will skip every so often when it does that, IF i have the AC on, it will skip all the time and the tach will go much screwier than it usually should, Batteries and alternator charge fine, the gauges work well, the speedo works well, its just the leapy tach and skipping radio that concern me

Crimedog

I'm pretty sure your aim should be on the crankshaft sensor. Do a search for it, it seems to be a culprit to a lot of problems. If I remember it usually causes no speedo or tac as well as a number of other things. Or, perhaps it could be a loose ground somewhere.

JKM

I am with Matt , Sounds like the ESS, I would check it , as well as the wiring going to it , there is a place where the wire comes down over the front of the engine that it can rub through the insulation. If it was getting false signals it could very well give those symptoms.

TxDiesel007

Im not gettin this one

what is the ESS? another question, the crank sensor and the RPM sensor, are they the same thing? (IE the one u work with when u repair the KDP) Im gonna check this thing out later on and see what i can find or do about it. Does this thing have a fuse anywhere that could have gone bad?

Worst case scenario, i have to buy a new one, how much are they?

Sorry guys, electronics are not my bag

Rick

haloman

The last I knew you had a pretty good size stereo in there. Are you sure some of your wires didn't get moved around during your twins install? Maybe a power wire is over another signal wire for your tach now?

TxDiesel007

Never had problems with the sensor till now

my theory is that if the stereo had anything to do with the tach sensor or the wires got messed up, it would have happened right then and there when i started the truck up, ive had my twins on almost a month and this issue just started,

IT is a good suggestion tho, and ill have to better take a look at everything later on..

Thanks!

Rick

infidel

In my years of chasing down electrical problems I've found that by far the most common problems are caused by the owner's electrical work. Thoroughly check in any area that you have recently been fooling around with.

gmctd

I agree - when you do something - anything - and something else breaks, recheck the last thing you did, and you'll find the cause, and the culprit

Follow it thru to all the 'last' things you did.

TxDiesel007

Went out during my school lunch hour

checked the truck completly (took me an hour or so) I didnt find any bare wires, checked the stereo connections, all was well, didnt pull the tach sensor (im assuming its the same as the crank sensor) but didnt notice any wires out of the ordinary. I still didnt find a short, or a loose ground, or a bare wire for that matter, im still stuck

The last wires that I messed with were the main power wire to my capacitor for my stereo, but that one either works or it dont, i removed it to clean my battery terminals and posts and put it right back.

Last project on the truck was crossdrilling the exhaust housing and reworking my wastegate. im certain i didnt remove any wires when i did that, just the top turbo and i redid my wastegate with 1/4 inch rubber hose...

Im startin to turn my aim towards the crank sensor more and more, im gonna have a reputable shop check it tomorrow to see what they can find... if anything

Thanks again fellas!

PS any idea how much for a new crank sensor? i dont want no sticker shock, and is it directly related or worked from the PCM? i hope i didnt kill that thing or harm it,

Rick

gmctd

Even a new sensor will give erratic output if the gap is not properly adjusted - iirc the spec is exactly 0.050", but don't quote me on that.

However, it will definitely not shut your radio down, or cause any other electrical conundrums.

Also however, the hi-power radio connections and current draw can cause tach and other electrical conundrums - as will loose\oxidized grounding.

Your crank sensor could be flaky, but check the gap for required clearance - maybe it vibrated loose - then check the connector.

TxDiesel007

u hit the nail on the head with this one

the tach sensor was sort of off, i know u can fold a business card in half and it will snugly go into the gap between it, sure enough my gap was off, so i retightened my tach sensor where it goes, Also my stereo had one bad ground to it as well, which caused it to flicker on and off, While i was at it, i went ahead and redid my connections for my batteries and re sprayed them with the red spray to prevent acid formation..

So far so good, but i still need a sound filter (scoche) for my speakers...

Thanks for the advice guys

Rick

Lil Dog

Glad you got it fixed. I was going to suggest a bad ground to the engine or something like that.. With a hard launch you can torque that engine up a bit in the mounts and pull a weak wire. Good fix no less.

gmctd

Since it's winter-time, you might try some ear-muffs to filter the speaker noise - errrrrrrr......oh - you're probably talkin' emf\rfi filters, right?

Never mind..................