Weird Tach behaviour...

[zigg]

My tach seemed to read low at idle(about 250-300rpm) even though I am convinced the engine is idling normally around 600. On the hwy, it seemed that sometimes when I'm at 60mph, it shows 2000rpm, and others, it shows around 1600. I know it shifted(E4OD) through the gears properly and the torque converter is definately locked(hitting the brake makes it jump up about 300rpm).

So, I harvested the tach sensor from my '86 which has always worked consistenly, and put it in, and now it shows no rpm at idle, but jumps up to 600 as soon as I touch the throttle but when I'm driving, and decelerating, it drops to 0, and the trans OD light starts to blink. Stops as soon as I touch the throttle.

This can't be right or good.

Any thoughts?

I've actually got a third Tach sensor in my shop, but the plug is cut off, I'd have to wire it in...I might pop that in tomorrow night...

I've always been afraid of this Tranny...

The speedo jumps when it gets up over about 60mph too, so I'll have to look into that...

Zigg

 

[Petri317]

If you can, try the third Tach sensor. I have an 89 that will read 0RPM at idle when I first start it, but normal (I think) at higher RPMs and perfectly normal at all RPMs when the engine warms up (after ~10 minutes of driving.) The little wires are pulled partially out of the sensor, and I have a spare used one that I will swap in when I have some time. If I'm not mistaken, the Tach sensor contributes data to your transmission "computer" thingy(not positive, but this is what I've heard.)

My Speedo is jumpy too, but in my truck it is mechanical, and I believe it is electrical in your 93 (once again, not positive.)

This thread may help: http://www.oilburners.net/forums/showthread.php?t=17720

BTW: Nice truck . Glad to see all of the bubbling coolant issues are gone!

 

[towcat]

zig-
get a new sensor. If the sensor has got time on it and the insulation on the wires are swelled and/or gummy, the end is near for the sensor. The "known good" one can easily be damaged once the wires get moved around on R&R. Also, a clean tach signal is critical for the longevity of your E4DOA. I do have one cluster left for the 92-94 body IDI's, so if you want to try that, you're welcome to but be warned, there's very little to go wrong on the diesel tachs.

 

[Agnem]

Zigg, I know the Moosestang does something like this. I have a new sensor to put on it, but I've been holding out on changing it since it works fine at anything above 1000RPM. I've noticed that these tachs seem to be voltage sensitive. For instance, at night in the winter, with the lights and blower motor on, and volt meter near 11, the tach hardly will move at idle. If I shut the accessories off, and the volt meter shows 14, it will come right up and read correctly (in the cold). In the summer, or the heat, it must get a high internal resistance and it acts like low voltage again, but higher RPM's generate enough of a signal to get through. You might make sure your cluster and sensor wire have a good ground, and good B+ .

 

[zigg]

OK, thanks guys, I'll check these things out.

Other than that, I really love the thing. It runs beautiful, and so far so good, no bubbling. I'm waiting for a downpipe for my stock ATS turbo, and I'm gonna slap that on, and a pyro, and then I can get out there and drive it, now that the break-in-new-engine paranoia is starting to fade...

 

[94johnh]

Zigg

I agree with Calvin get a new one, I had all of the effects you mention, tryed cleaning and such , but when I put the new one on no problems. hat was at the meet at Mossyrock, Wa.

john

 

[wwwabbit]

Zigg, the ford dealers had them for a hundered and some odd when I got mine last year. You are welcome to come out and try mine in your truck to see if that is it, mine is good, and under a year old.

 

[zigg]

Zigg, the ford dealers had them for a hundered and some odd when I got mine last year. You are welcome to come out and try mine in your truck to see if that is it, mine is good, and under a year old.

Thanks for the offer..."a hundered and some odd"....holy cow, I didn't want to hand over my first born(well, now, come to think of it, she has been a real pain in the a.. lately,,,hmmm,,,,

Well, anyway, I pulled the odd one out of the inj.pump cover in the pile 'o parts in the back of my shop. Had to solder a fitting onto the end, but put it in and lo' and behold, it works perfect.

Tranny's shifting nice, no blinking OD light. Thanks for the help...as usual guys, you were right on the money...

Now to have a look at the speedo sensor...(Calvin, I might take you up on that offer for the cluster if'n I can't find anything at the rear pumpkin.

WWWabbit I was just out your way last weekend to go to the marina and have a look and see if there were any boats for sale. I've been there a million times to go fishing, but I drove right by. Seems progress has bulldozed it's way out there too, as there are now condo's where the marina used to be...

Sheesh!! Where will it end...?

Get your umbrella out, looks like a storm a commin....

Zigg

 

[towcat]

Now to have a look at the speedo sensor...(Calvin, I might take you up on that offer for the cluster if'n I can't find anything at the rear pumpkin.

zig-
refresh my memory. what's the issue there? If it is a bad sensor, is your ABS light on or has it been disconected?

 

[wwwabbit]

Good you go it working! I know, I was glad I had the lube when I went in for mine....

Yep, there was more then one nose out of joint with the councel when they let that happen.

 

[zigg]

zig-
refresh my memory. what's the issue there? If it is a bad sensor, is your ABS light on or has it been disconected?

Calvin

The speedo seems to work fine till I get to about 55, then it starts to jump about 5-10mph. The faster I go, the worse it gets.

I thought the speedo was electric(no cable) and I also was under the impression the signal comes from the fitting on the top of the pumpkin on the rear axle.

Truck is a 93 1/2, and has ABS supposedly, but I've never tried to figure if it works or not. There is a light on the dash that comes on, and goes out when it starts, but overall the brakes work awesome, so, knowing how many of our units have crappy brakes, I just elected to leave well enough alone.

I could just put up with the speedo too, 'cause I mostly don't pay much attention to it anyway since I have an amazing bear detector,I pretty much drive to suit condtions.

I had it up to about 75mph last evening for about 10 mi. I think I'm going to drop the timing back a tiny smidge, 'cause there's still a bit too much rattle, but, Man that truck runs smooth with the balanced engine. It was like a big ole' Cadillac...

Zigg

 

[Al_E]

try cleaning and lubeing the cable, and if that dont help try cleaning the movement inside the speedo head carefully. A little dust and fuzz does weird stuff.

 

[towcat]

try cleaning and lubeing the cable, and if that dont help try cleaning the movement inside the speedo head carefully. A little dust and fuzz does weird stuff.

'92 and up uses the electric speedo. Signals are drawn off the ABS sensor in the rearend.
zig-
It's a strong possibility that its in your speedo as long as the ABS light isn't lit when the needle is dancing. Key thing is the danged ABS light