WHAT COULD THIS MEAN????

[pipedream73]

Ok so I'm coming out of my local CVS store and i get in my 93 f250 7.3 idi and start her up,,, everything was fine except that i noticed that my rpm gauge was bouncing up and down from like 600 to 1000 to 0.... then it would just stay on 0 until i hit the pedal however the engine did not sound like it was acting up or anything and this is definitely new.... just wanted to make sure that you guys don't think its to serious and i would like to hear that I'm just being paranoid but please let me know what you think

 

[cpdenton]

Probably bad connections on the sending unit.

Not really a big problem, unless you have an automatic transmission. It needs the tach signal to shift properly.

 

[Wvdirtroad]

Mines doing the same thing. Consensus seems to be a bad connection on the sensor in the timing housing cover.

 

[Runningaford]

Mine's doing the same thing as well ........Perhaps we're being punished for frequenting CVS.....


It seriously amazes me the planned obsolescence on so many things; the same parts on these trucks, or any given thing are always to blame, and even designed into said product....grrr.

 

[The Warden]

Probably bad connections on the sending unit.

Not really a big problem, unless you have an automatic transmission. It needs the tach signal to shift properly.

FYI that only applies to the E4OD...if you have a C6, the tach signal is not critically important.

However, if you have an E4OD, this needs to be fixed ASAP, or else the lack of a tach signal can make the transmission misbehave, with the possibility of causing internal damage. As others have said, it's probably either a bad sending unit or a corroded or frayed wire.

 

[Spun4Fun]

Tach sensor might be on it's way out which latter on will throw your shifting pattern and you might notice O/D light flash if it's an AUTO tranny

 

[pipedream73]

Ok so this might sound stupid but how do I fix this and where is this sensor located and maybe someone had a diagram or am I over thinking this. Also how do I know what tranny I have. Sorry for the stupid questions.

 

[mblaney]

Sensor is located on the IP gear cover - partially covered by the vacuum pump. Easy job to swap it out, you don't have to remove the vacuum pump to change it.

If you have an automatic it will be the E4OD

Sensor pic here http://www.oilburners.net/forums/showthread.php?57249-LAZY-TACH

 

[Waystro]

Ahh That's Why I Love my C6.

 

[Spun4Fun]

Maybe one Day i can convert the Green Machine to C6 ... I think cpdenton had done that conversion

 

[snicklas]

...If you have an automatic it will be the E4OD

Not necessarily. The 83-87 have the C-6 Automatic. The E4OD did not come along until 87ish..... The quickest way to tell if it is an E4OD is if the truck has an "O/D Off" button either on the dash (87-91 Bricknose) or on the end of the shifter (92-94 OBS)

If its a C-6, the tach not working is an annoyance, but an E4OD it is a MAJOR ISSUE.

 

[sjwelds]

Maybe one Day i can convert the Green Machine to C6 ... I think cpdenton had done that conversion

Talk about going bass-ackwards!

 

[Spun4Fun]

i mean manual .. had a gray moment for a second

 

[pipedream73]

Will that actually cause a problem with the tranny. I ask cause first I started realizing that the tranny changes gears at weird rpm. I'm hoping my tranny isn't messed up. How much does this tach sensor go for and is it ok to drive the truck until I can get it

 

[snicklas]

Will that actually cause a problem with the tranny. I ask cause first I started realizing that the tranny changes gears at weird rpm. I'm hoping my tranny isn't messed up. How much does this tach sensor go for and is it ok to drive the truck until I can get it

Sounds like you have an E4OD then. What year is your truck? I think others have found the tach sensor in the ~$85+ dollar range. I strongly recommend against driving the truck. If it is shifting funny, the TECA has put the transmission into "limp mode" which is designed to allow you to get to a safe stopping place (like the next exit if you are on the interstate) and have the truck towed to a shop. Limp mode puts the transmission into an extremely high pressure mode, which can make the shifts slam, and it might not use all the gears..... If you need to goto the Emergency Room, and the truck was the only option, drive it. You just need a fresh coffee.... drive something else till its fixed. Don't kill a $2,000+ transmission over a hundred dollar sensor........