W.E.G.

I was having issues with some of the gauges in my V6 car, so I came across a V8 (from year-unknown IROC or Z28) cluster for a fair price. Figured I'd give it a try.

Specifically, the issues I was having with my V6 cluster were:

• Vehicle Speed Sensor reporting speeds to TunerPro as high as 254 mph (in second gear no less)
• Speedometer needle bounced markedly at slow speeds
• Tachometer permanenty "pegged"
• Temperature gauge only worked occasionally, and then reported temperatures not consistent with conditions (always low, or non-existent)

I'm going to declare the swap a success.

When I bought the gauge cluster, I assumed the tachometer was already kaput, because the needle was way up in the red while the cluster was dismounted. To my great surprise and delight, the tachometer came to life when I installed it in my dash. I know the V8 tachometer and V6 tachometer are supposed to be calibrated so that one won't read correctly if installed in the other. I don't know whether this tachometer is calibrated correctly for my car or not. I'm so excited just to see movement, I'm not sure if I care about accuracy per se. I'm looking forward to tomorrow, when I'll plug in the Moates and TunerPro rig and see how the numbers match up. If the numbers are off, they are not off by a tremendous amount. Not enough that I can easily tell by ear.

The temperature gauge is still reading nothing. The old gauge also read nothing (most of the time). This helps me diagnose that the issue so I can work toward the temp gauge actually working someday.

I took a short spin around the neighborhood. The speedometer appeared to read correctly, and there was no bouncing of the needle. Also looking forward to see whether the Vehicle Speed Sensor reports non-spastic/insane numbers to the Moates/TunerPro tomorrow.

Oil pressure gauge reads at the upper end of its range, beause the V8 gauge only goes to 60, whereas the V6 gauge goes to 80. Frankly, so long as the needle stays in that upper range, I'm OK with that.

Fuel gauge reads correctly.

Didn't check to see whether the light bulbs are shining in full force.

Anyhow, I'm mighty happy with the way its working out so far. Doubt I'll ever peg that 145 speedo with this motor.

Two minute video:


This is the dash it came out of:

OrangeBird

iTrader: (1)

Your right on track , the fuel and temp gauges will read correctly , but the oil will read too high due to the scaling difference and the tach won't be accurate either (I think it should read lower than the actual RPM due to not seeing 8 pulses per distributor rotation and instead 6) I know the 6 has a higher indicated redline and beyond that I've often wondered what would happen if a good 6 tach driver board was installed in an 8 tach (and used in a 6 car) . Of course these gauges were never intended to be precision measuring instruments anyway , more like an "eye candy" dress up better in form than function .

There will be no differences in any other aspects (lighting etc) provided the year of the donor is close enough to the recipient .

W.E.G.

I'm still not 100% sure where on the motor to find the temperature sensor for the temp gauge on the dash.

Four years ago, I posted to a thread that talks about this, but I did not follow-up promptly with my investigation or repair. (better late than never!)
https://www.thirdgen.org/forums/v6/4...ensors-v6.html

Am I correct that a single green wire going into a sensor on the front of the motor (the head?) feeds the temp gauge on the dash?

Tuned Performance

iTrader: (92)

Your correct on the green wire that feeds the gauge. Grounding thevwire the gauge should peg.

W.E.G.

The other possibility for my temp gauge not moving with the new cluster is that the needle is simply hung-up on the cluster housing somehow.

Take a look at how far-buried the needle is on my gauge.
For those of you with V8 gauges, does this position look normal for a cold motor?
It looks to me like it is too-far in the down/cold position.



Apparently, it has happened at least once that the needle was just mechanically hung up somehow on the face of the gauge. This guy discovered that to be the case with his car. As I understand it, he removed the lens from the gauge and flicked the needle, which brought the gauge to life.

W.E.G.

Peg high, or peg low?

Tuned Performance

iTrader: (92)

High

W.E.G.

May have answered my own question.

Guy does the ground-sensor-wire test on his Ford truck. The gauge pegs high when wire is grounded if the dash-gauge is good. I assume the same principles at play on our thirdg-gen gauge.

Drew

iTrader: (58)

Yeah that style cluster has problems with the temp gauge needle hanging up on the edge of the gauge face. It's easy enough to fix, either buy a new gauge, or add a couple needle stop pins.

I cut a couple pieces of about 1/16" stainless wire, approx 5/16" long, and carefully glued them to the gauge face rivets. A touch of flat black paint with a brush to make them blend in, and it's good to go. Once the cluster is back together you can't see the stop pins. If you only add one pin, you'll find that the "bulb test" throws the needle around so violently it'll often hit the stop and bounce back and get stuck at the other end of the scale. LOL

W.E.G.

I could tell it was going to keep me up at night.

Plus its supposed to be double-hot-as-***** heat index tomorrow.

So, why not work on the car in the dark?

Indeed, the temp needle was hung up on the metal bezel-face of the gauge cluster.
It just didn't look right to me before. Needle looked almost like it was spring backwards somehow.

I pulled the clear plastic bezel (six 5.5mm screws), and gently pried the needle free of the metal bezel with my ignition key. Once clear of the metal bezel, the needle immediately jumped to the midpoint position. When I turned the key on the needle responded to circuit voltage, and settled at about 90-100 degrees - which corresponds to what the coolant temperature probably is after cooling just a bit since the afternoon's test-drive.

Didn't want to ****-off the neighbors with me revving the motor in the driveway at midnight. So, full test will have to wait until the morning.

W.E.G.

Thanks for the suggestion on the stop-pins Drew.

I'm wondering if another option might be also to just use a carbide cutter-tip on the Dremel to relieve the spot on the metal bezel-face where the needle seems to be physically catching?

The needle seemed to be hung on the metal bezel when I freed it. Is there something else behind there that it could still be hanging on besides the metal bezel?

I tried to make the needle repeat the hanging for the video, and I couldn't seem to get it to hang on the metal. So, that makes me think there could be something unseen causing it to hang.

Drew

iTrader: (58)

You could relieve the bezel, but then the bulb test might make the needle spin like a propeller. LOL

W.E.G.

Didn't have time for a road-test / data-log session today, so tested the temperature gauge this afternoon in the driveway, just to see if the gauge moved normally. I think it did.

Longish video is uploading to YouTube. Should show live once its done uploading.


For the TLDW crowd, I hold the RPMS around 2700 to get the needle moving quickly. As the needle approaches the red zone, I let off the throttle and allow the motor to idle (in its usual rough-idle manner) at idle speed.

The fan kicks on as the needle creeps into the red (about 6:30 in the vid), and the needle drops to around 220, which is where it seems to be happy as a "steady" temp.

The idle lumps and jerks for a couple minutes, and the temp goes back up to to almost the red (about 12:00in the vid). Fan kicks on, and the idle-speed comes up just a bit, and the idle smoothes briefly as the needle descends back to about 220.

I let it lump-along until the motor cuts off on its own.

Motor restarts easily. Let it run for a minute, then cut it off.

Observe gauge needle hovering around 220, but descending very slowly.

One more re-start for good measure, let run for a minute, and cut it off.

I'm pleased. I seem to how have a working temperature gauge!

John in RI

iTrader: (167)

The Printed Circuit on the back of the cluster is specific to 82-85 cars, then was changed for the 86-88, & then 89 cars. The BRAKE warning tell-tale light was moved from far right of the cluster & bezel to the far left, so if the "wrong" printed circuit is used there will be a conflict between a back lighting bulb & the / BRAKE warning light.

Your tach will be about 33% off ( or maybe it's 25%?? ) when using the wrong version (V6 vs. V8). The V8 distributor sends 4 pulses per revolution & the V6 sends 3.

If you install a V6 tachometer board on a V8 tach,... I'm pretty sure you get a V6 tach.


Edit: If that dash housing you pulled the cluster from is all original,... the dash badge shows it came from a "HO car". All the gauges are the 85-89 style,.... so the cluster housing/printed circuit might be from an 85. If it's from an 85 than it will cause a conflict with the BRAKE warning light in your 88. (previous owner could have swapped all the gauges into his 85 original cluster or installed a complete 86+ cluster,... who knows ! )

W.E.G.

Thanks John!

I hope to gather some TunerPro data tomorrow to get an idea what matches-up with what.

I'm gonna try to set up the camera so I can narrate while TunerPro records and reports. I find it a little difficult with TunerPro, when just watching a log play, to try to remember what road conditions were present, and what the dash gauges were reporting. Hopefully, an iPhone vid with my voice blabbering in the background will allow some of the experience to match-up a bit better.

W.E.G.

Test of the ’88 V6 with new dash and running TunerPro RT today.

There is a video of today’s effort at the bottom of this post.
• I attempt to narrate, while simultaneously recording laptop screen
• The laptop screen shows the TunerPro screen with six gauges.
• The video has a hiccup at 2:30 because I had to re-start the recording due to my iPhone shutting down due to excess heat.

The six gauges are:
• Vehicle speed
• Engine speed
• Engine temperature
• Oxygen Sensor
• Idle Air Control Position
• Injector Pulse

I am very pleased that the replacement dash also has a working tachometer, and working temperature gauge. The tach and the temp gauges were both non-functional in the original V6 dash.

The old (original dash) logged a VSS ( vehicle speed sensor ) error report.
• The replacement dash included a replacement VSS.
• The VSS on the old dash, reported to TunerPro, ridiculous vehicle speed numbers. Frequently reporting 254mph when travelling at low speeds. Lots of other way-high numbers when driving through the neighborhood.
• The replacement dash reported no crazy vehicle speed numbers.
• TunerPro consistently reported vehicle speed about 5 mph higher than the dash speedometer.
• I was using my iPhone to record the laptop screen, so I couldn’t compare any of the speedometer numbers to something like Waze. I will do that comparison soon.

This car has been a persistent pest with the “bucking bronco” behavior.
• In an hour’s combined driving time today, there was not one instance of the bucking bronco.
• I’m not prepared to say the new VSS solved the “bucking bronco” issue, but at least today’s performance is encouraging.
• The only drivability complaint today I would mention is the usual rough idle.
• I sometimes have to bump the throttle a bit to be sure it doesn’t die at traffic lights.

Short summary of my impressions today is this:
• I believe the coolant temperature reported by TunerPro was too low (probably around 30-45 degrees low at full temperature).
• I believe the coolant temperature reported by the dash gauge was too high (probably around 20-40 degrees high at full temperature).
• TunerPro tachometer reports a higher RPM number than the dash tachometer.
• I don’t know which tachometer is correct – or if either tachometer is correct. I need to connect an external tachometer to compare. Logically, the TunerPro RPM number should be the correct one, because its reading the pulse-count at the ECM. The ECM is correct for this car. Whereas, the dash tachometer is not correct for this car.

W.E.G.

A few temperatures recorded with the Harbor Freight infra-red thermometer in the driveway right after I cut off the engine.
• 203 – upper radiator hose
• 145 – lower radiator hose
• 159 – intake manifold
• 172 – temperature sensor on motor (feeds gauge on dash)
• 258 – exhaust manifold (driver side)
• 183 – valve cover (driver side)
• 203 – valve cover (passenger side)
• 163 – harmonic balancer center bolt
• 185 – top side of water pump
• 244 – EGR valve
• 203 – top of radiator
• 202 – cooling fins on radiator (near top)
• 121 – coolant overflow reservoir (below fluid level)
• 102 – roof of car
• 111 – battery
• 154 – distributor
• 189 – oil pump housing

QwkTrip

iTrader: (22)

Sometimes my memory is worthless, but I have a faint memory that V6 and V8 tachometer are same except the numbers are printed on a different scale. Maybe you can just swap the screen for the V6 screen.

Other option is to change the calibration resistor. That's how I managed to keep my V6 tach with the V8 swap, but you need a wave generator to calibrate. Or wire in a variable resistor that you can adjust by hand until it reads right. But honestly, I don't think it's worthwhile to do all that work to a V8 tach because the redline is ridiculously low. V6 tach is much more worthwhile to save.

W.E.G.

Yeah, ultimately the two things I really want to fix the most about the driveability is the "bucking bronco" and the lumpy/stall idle at stop lights.

I'll admit, I haven't done a knock-down-drag-out check for vacuum leaks in the years I've owned the car. I fixed obvious leaks, and replaced perished hoses. I'm thinking about getting a decent smoke machine (or making a jack-leg homemade rig) to try to find leaks I may have missed. Wouldn't surprise me if I don't still have a leak (leaks) that is the biggest cause of the lumpy idle.

I don't know if the supposed undiagnosed vacuum leak could be the source of the bucking bronco. I'd be tickled if swapping the replacement VSS cures the bucking bronco. The bronco is far worse the annoyance than the lumpy idle.

Precise accuracy of the dash-gauges is really only a small interest. Although, it really is nice to have a working temp gauge, even if it does read about 30 degrees higher than actual. As for the tach, whether it is right or not, I drive by ear, and hardly ever look at the tach. I'm not sure the rev-limiter will even let me "red-line" on the V8 gauge! I pretty much ran it all the way up today in second gear a bunch of times. Even TunerPro wasn't reporting anything over about 4800.

W.E.G.

Ran an instrument comparison test today of the V8 dash in the V6 car.

Moral of the story: Dash always reads low - both tachometer and speed.

Comparing tachometer: Dash vs. Timing-Light vs. TunerPro
Comparing speedometer: Dash vs. Waze vs. TunerPro

On the tachometer test, I believe the timing-light and TunerPro were telling the truth.
The dash gauge was lying. The dash gauge gave consistently low readings. There is some inconsistency in the report below, because its almost impossible to get the motor to lock in to an exact RPM condition. The various reported gauge readings are close, but not precise.
At moderate driving, add about 300 RPMS. At full beans, add about 600 rpms.

On the speedometer test, I believe Waze and TunerPro were telling the truth.
The dash gauge was lying. The dash gauge gave consistently low readings. Waze and TunerPro gave identical speed readings. Even though the speedometer dial is inaccurate, this is good information, as I am confident that the VEHICLE SPEED SENSOR in the instrument cluster is feeding accurate information to the ECU, even though the speedometer dial is showing an incorrect reading.
Around town, add about 6 MPH. On the highway, add about 8 MPH.

W.E.G.

As a minor issue, it looks like I will need to install a couple stop pins on the temp gauge as was suggested earlier.

At key-on today, the temp needle pegged north of 260, and hung up on the housing.