Yes, the VSS signal from the transmission goes to the ECU.
The ECU generates a 4K signal that can be made compatible with the Fiero speedometer.
I will send you a wiring diagram tomorrow.

Thanks, Joe. I'll pass it on. More good input from the Fiero Community.

quote Originally posted by fierofool: OK, how do you guys avoid the VSS trouble code? Do you have something that converts the signal to the ECM?

The reason for the code is that the ECM is looking for a later (magnetic?) VSS at ~24000 pulses per mile. The Fiero Getrag supplies a couple thousand pulses per mile, but the signal, if it can be seen at all, is NOT what the Caddy ECM wants to see. The type of VSS, the waveform, and the number of pulses (peaks?) per mile are way off.
I was hoping that there was something there that the ECM could see/use, but it would appear that that's not the case.
(I think that if the ECM sees anything at all, it will be enough to stop the VSS code from setting.)
I can turn off the VSS code in the chip, but that doesn't mean that it will run exactly like it's supposed to. (Actually, I thought I *did* turn it off. But I'm not sure, now.)
The biggest issue will be stalling when coming to a stop, as soon as the clutch is pushed in. I can explain why, but I'll spare you, unless you want to hear.

Dakota digital makes an adapter that allows later trannies to work with earlier ECM, but I'm not sure if there is a "reverse" solution.
When Ed did these swaps, he removed the bulb from the Check Engine light. "Out of sight, out of mind." |

I think this is the device that other people have been using.
https://www.dakotadigital.c...ode=prod/prd1192.htm
No guarantees, however.

Edit - I might be inclined to set the minimum idle speed, using the torx adjustment on the throttle body.
That, and disabling decel fuel cutoff might fix the stalling problem. (It'll also likely make it pop and burble while coasting. )

[This message has been edited by Raydar (edited 10-06-2021).]

It was a stretch but the vss plugged in. Raydar, your chip was put back in. No CES light on a drive up the street and back. No stalling. No miss. Getting closer.

The Getrag VSS puts out 4000 ppm, the 4t60e VSS from the caddy would put out 64000 2400 ppm.

I don't know if the 2240 ECU will accept the 4000 ppm input (can this be accessed via tuning software?), but it does put out a 4000 ppm signal.

Edit to correct.

[This message has been edited by olejoedad (edited 10-07-2021).]

Initially, it appears that the buffer is installed for the speedometer. The previous owner had been driving it for a number of years. The speedometer works, now. It has only been driven a short distance, so accuracy probably hasn't been checked against a GPS. There are still some issues with the car that need to be resolved.

quote Originally posted by olejoedad: The Getrag VSS puts out 4000 ppm, the 4t60e VSS from the caddy would put out 64000 2400 ppm. I don't know if the 2240 ECU will accept the 4000 ppm input (can this be accessed via tuning software?), but it does put out a 4000 ppm signal. Edit to correct.

Tunercat allows you to access the PPM setting. But the setting in my ECM was for ~64000 (I think I typed 24000 earlier. My mistake.) but NOT 2400.
When I installed my ('93?) T550 trans, I just made minor tweaks to the "64000" PPM setting to account for tire size.
But I will recheck, just to make sure.

In reviewing MM's excellent 4.9 wiring thread, it appears the 2240 will accept the 4000ppm signal from the Getrag VSS.

Hope you get all of the issues resolved Charlie!

quote Originally posted by olejoedad: In reviewing MM's excellent 4.9 wiring thread, it appears the 2240 will accept the 4000ppm signal from the Getrag VSS.

Didn't know that.
Is it a separate input? Or just a different value entered in the PCM.
Scott's is wired just like the Caddy manual specifies, for the 4T60E. I'll have to go back to MM's thread and look.

[This message has been edited by Raydar (edited 10-07-2021).]

quote Originally posted by olejoedad: In reviewing MM's excellent 4.9 wiring thread, it appears the 2240 will accept the 4000ppm signal from the Getrag VSS. Hope you get all of the issues resolved Charlie!

I think they are getting close, Joe. Maybe another week or two. Haven't heard anything today, but weather down here could be a factor if the car isn't inside. We're having record rainfalls. Maybe tomorrow when it's supposed to clear up. I just leave them alone unless you guys provide some input that could help.

[This message has been edited by fierofool (edited 10-07-2021).]

quote Originally posted by Raydar: Didn't know that. Is it a separate input? Or just a different value entered in the PCM. Scott's is wired just like the Caddy manual specifies, for the 4T60E. I'll have to go back to MM's thread and look.

As I recall you just connect the VSS signal straight to the ECM. The PCM code (PPM) was changed only if you were using the output from the PCM to drive the speedo.

But this is easy to verify by checking the code I uploaded. The code I was using (daily driver) had no check engine light errors. I do not recall if I had my speedo hook to the PCM output or it was wired in parallel to the PCM input. I do know the PPM code was changed as I was using the PCM to drive the cruise module. IIRC the PPM code only changes the correction factor so that the 4000 PPM output is correct. The PCM doesn't care if the signal coming in is 4000ppm or 26000ppm.

Edit: the wiring is different between the 4T60E and manual - but the VSS signal is fed to the same pins on the PCM. With a manual car, you have to trick the PCM to think that it is in drive.

[This message has been edited by Mickey_Moose (edited 10-07-2021).]

quote Originally posted by Mickey_Moose: As I recall you just connect the VSS signal straight to the ECM. The PCM code (PPM) was changed only if you were using the output from the PCM to drive the speedo. But this is easy to verify by checking the code I uploaded. The code I was using (daily driver) had no check engine light errors. I do not recall if I had my speedo hook to the PCM output or it was wired in parallel to the PCM input. I do know the PPM code was changed as I was using the PCM to drive the cruise module. IIRC the PPM code only changes the correction factor so that the 4000 PPM output is correct. The PCM doesn't care if the signal coming in is 4000ppm or 26000ppm. Edit: the wiring is different between the 4T60E and manual - but the VSS signal is fed to the same pins on the PCM. With a manual car, you have to trick the PCM to think that it is in drive.

Interesting. Thanks once again.
In this particular car, the VSS is wired to the ECM. (We had it unplugged, to ohm out the wires.)
It doesn't make sense that the speedometer would work, but that the VSS code would still set. At least I understood that the speedo worked.

[This message has been edited by Raydar (edited 10-07-2021).]

It was setting the vss code because it was unplugged. Once cleared and plugged in, the code didnt return.

Well... that might have a little bit to do with it.
Kidding aside, when Scott and I ohmed out the wiring, we obviously didn't plug it back in. But Scott mentioned that it was setting that code, before that. It's why we were checking, in the first place.

quote Originally posted by Raydar: Interesting. Thanks once again. In this particular car, the VSS is wired to the ECM. (We had it unplugged, to ohm out the wires.) It doesn't make sense that the speedometer would work, but that the VSS code would still set. At least I understood that the speedo worked.

Both the speedo and ECM can be wired directly to the VSS - this would explain why the speedo would work, but a code was thrown if the ECM does not see the pulses. The speedo can also be wired to the ECM 4000ppm output - in this case the correction factor needs to be inputted correctly into the code or the speedo will be off.

Re: check engine light - if the bulb is removed because it is on, there is something wrong with the wiring (or programming). This works as it should on my car.

As for the timing thing, I cannot really offer anything more as it looks like it all has been covered. I only things I would have suggested is checking TDC and distrubutor and to also verify the that the timing gears are setup up correctly (the chain didn't jump a tooth). It sounds strange.

edit - maybe there is just a bad connection at the ECM, maybe a bad pin in the connector that is not making proper contact?

[This message has been edited by Mickey_Moose (edited 10-08-2021).]

Numerous people have verified that TDC on the balancer and the piston are in sync. All spark plug wiring is in its correct position. They have set the distributor on #1 at that point and the car didn't run or ran very poorly, only with the jumper. The distributor has been repositioned with the engine set at TDC and has allowed the car to be driven under its own power, up and down the street, but it is still not running correctly.

I had a chance to drive the car today. The idle changes from rough to smooth, depending upon what the oil pressure gauge is doing. When it pegs, it runs very roughly. When it drops down to a proper oil pressure, it runs smoothly. This is an intermittent thing of about every 10 seconds. I don't know which is the one creating the effect. The temp gauge will quickly move to the red, but it doesn't seem to be overheating.

Under acceleration, it seems as if the timing is off. Initially, it will lurch with good power, then it begins what I think sounds like a misfire. Whether that's caused by too much or too little advance will have to be determined by Troubleshooter. My damaged hearing range doesn't easily detect spark knock.

So, they are going to look at the old distributor to see if there's any alignment indicators and also look into the Field Service Manual engine rebuild section for information on resetting the distributor after a teardown.

[This message has been edited by fierofool (edited 10-08-2021).]

quote Originally posted by fierofool: ... I had a chance to drive the car today. The idle changes from rough to smooth, depending upon what the oil pressure gauge is doing. When it pegs, it runs very roughly. When it drops down to a proper oil pressure, it runs smoothly. This is an intermittent thing of about every 10 seconds. I don't know which is the one creating the effect. The temp gauge will quickly move to the red, but it doesn't seem to be overheating.

I posted this on the club board, too. But the "offscale" gauges sounds like a ground problem. The fact that the car runs poorly, concurrently, is not surprising to me.

I know that you have been working very hard to solve the drivability problem and there are so many good suggestions on this post. I'll go with Steve on the possibility of a ground problem but whatever the case do not throw in the towel. You could always scrap the entire 4.9L powertain management and bolt on a Summit self tuning fuel injection system. You will need the earlier 4.1L manifold and it is an $899 investment but its basically a plug and play install. Had I been doing a stick swap that would be my approach.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Thank you. Steve provided a distributor position pic today at the meeting. Ours is still about 60-90 ° counterclockwise. I'm sending them the pic so they can try it in the other position.

Update October 17.

Work has ceased on finding the problem with Scott's 4.9. A little condensed review.

When he bought the car, it was randomly missing on 4 cylinders. No particular thing could be identified as the cause. No bumps in the road, no acceleration or deceleration, no turns. It would just do it, then it would begin running on all 8 again. For a while. Sometimes a short while, sometimes a long while.

Scott, Roger, Raydar, TopNotch, and maybe some others I'm not aware of delved into the car. Every sensor on the engine was replaced to no avail. The distributor was replaced to no avail. One day while still troubleshooting, just by sheer accident, it was found that a fuse block that held among others, two fuses for the fuel injectors had a faulty set of contacts on one of the injector fuses. Move it one way and it would run on all 8. Move it the other way and it would only run on 4.

That problem was resolved by replacing and repinning a new fuse block. But with that problem being solved, another had reared its ugly head. It ran horribly. With lots of input from club members and Pennocks members, just about every theory was explored. ECM. PROM. Grounds. Timing. Timing. Timing again.

The engine would run smoothly with the ALDL jumper in place but would either die or run very roughly as soon as it was removed. So, diagnostics was frequently interrupted to remove the battery, go underneath and replace the serpentine belt when the engine would buck. It was finally determined that the cause of the belt jumping was due to a poorly made idler/tensioner bracket. Several configurations were looked at and considered until finally one was fabricated and that issue was solved.

It was scanned and rescanned. It was analyzed with oscilloscopes. Nothing showed up. Again, timing was looked at. Troubleshooter noted something that he felt was a little odd about the distributor and the cam sensor inside the distributor because when the trigger tab on the bottom of the rotor button plate passed through the sensor, the rotor button wasn't pointing at the #1 wire terminal. He wanted to dissect the old distributor to see just how it worked on this particular engine, but that distributor had been discarded long ago when the new one was installed.

Assuming the spark was breaking down, the ignition coil was replaced with a new one. No change. The cam sensor was replaced with a used one that was in the trunk of the car. No change. Both the coil and cam sensor that was removed were put back into the new distributor.

Yesterday, after attending a local car show, I went to Pull A Part and yanked a distributor from a 93 Deville and delivered it to Troubleshooter so he could analyze it. So, instead of tearing it apart, he swapped it out, pulling the new distributor and putting in the one from the parts yard. Set it according to the factory service manual and fired it up. It ran smoothly with the jumper. It ran smoothly without the jumper.

It could possibly pull a wheelie on the road if the clutch didn't slip. But we kept to the speed limit as we delivered it back to Scott this afternoon. Having replaced the coil and the cam sensor without result, the only thing in the distributor left is the pickup coil and the ICM. One of those was defective right out of the box.

Final diagnosis: Defective Distributor Components.

Thanks to all who contributed to the effort to prevent Scott from utilizing his 45 and propane torch. The tensioner bracket was fabricated by Headhunter1ID, Gabe Anderson.

I would also like to introduce and give a HUGE THANKS to Troubleshooter, better known to all of us as Georgia Fiero's TopNotch, aka Pat Swayne.

Good news. Glad you finally found the problem. Yes the 4.9L distributor as pointed out contains both the reluctor/pickup coil to trigger the spark signal and a cam sensor to feed its position to the ECM. My guess is that the cam sensor was bad but in any event the owner should now be happy as the efforts paid off..

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

It wasn't the cam sensor that was bad. That was swapped out in the new distributor and it had no effect. The ignition coil was also swapped out in the new distributor and it too had no effect. The distributor I picked up at the yard was horrible on the outside. The engine was covered in leaves and pine straw. When TopNotch opened it up to see how the inside worked, he said it was very fresh inside and looked like it had good quality components, so he cleaned the outside, replaced the O-ring seal, and installed it. He set the timing by the factory service manual, just as he had done with the new distributor that was in the engine. The car started right up and ran with and without the jumper in place. Problem solved. Thus the belief that either the ICM or pickup coil in the new distributor is the culprit.

And to think, had he went ahead and dissected the junkyard distributor, the problem still would not be found, today.

All of you who pitched in to help gave lots of valuable information and guidance. It is very much appreciated.

Im at a loss for words........ I was pulling my hair out and about to crush the car when Charlie stole it, said it was going to be fixed.......... I dont know how to thank everyone that was involved, almost the entire club helped with it, and a lot of folks on PFF. No Charlie, you cant have the torch or the 1911, but I promise I wont use them on this car.

Now that it runs correctly the next project will be the clutch. I may not have the availability until next year, we will see how it goes.

Again, thank you to everyone who has been helping with this car.

Some of the most frustrating issues to resolve are those where a bad new part is thrown in the mix and assumed good just because it was new.

quote Originally posted by fieroguru: Some of the most frustrating issues to resolve are those where a bad new part is thrown in the mix and assumed good just because it was new.

We see that all the time at work (occasionally after driving 3 hours, both ways, to grab something from the warehouse.)

"Bad from stock? Noooo... that never happens."

[This message has been edited by Raydar (edited 10-21-2021).]