JasBass

Project for the morning my friend. The kick pads are out of the car so it's no big deal to get to the ECM. Its the original 89 ECM and considering the garbage work i've had to fix on this car, it wouldn't surprise me if someone tried to check that circuit the wrong way and messed it up

TheBlaster9001

You'll get her better than her former glory one day. At least you're closing in on a fix to this issue. Re-manned ECMs usually don't run too much, at least.

JasBass

So, wasn't expecting this result. Pulled the pin and reconnected the ECM. I got EXACTLY the same volt readings as I did with it connected. Confirmed it 3 times. I threw the old TPS on there and actually got 0.5V higher at WOT. I re ohm'd the ECM reference wire and got 0.00 on everything except for 200 setting (pic below). Seems odd that two TPS' would fail at the same reference pin, but it sorta seems like that is what we have here. This was a brand new BWD unit

TheBlaster9001

That would seem that the TPS is at fault - one other check you could do - when the TPS is at WOT, is the 5v power reference still at 5 volts? If so, the new TPS seems shot.

JasBass

Yessir, checked that and it held 5v the entire time. Taking this one back and we'll see what we get with a new unit. On the bright side, learned a lot in this process. I appreciate the help I'll touch base when when it comes in and installed

TheBlaster9001

You're very welcome! I like brainstorming for diagnosing, keeps me in practice for when something breaks next. Hopefully this will fix it, I've had bad sensors out of the box before too. I'll look forward to the update!

JasBass

Dude...got the replacement, hooked it up and it actually read lower than the other one

I took some 10g wire and jumped the bottom 5v and top ground to the TPS removed from the car. Then measured directly from the TPS middle pin to see what the TPS was putting out. It put out bad data. The car wiring is just fine, the issue seems to be with BWD's build quality and QC. At this point I said screw it, returning the BWD and have a new Delco unit coming. I don't care it was a little more money, I just want a NEW sensor to work lol

TheBlaster9001

Jesus.. the chances of that have got to be incredibly slim. That's very frustrating.

JasBass

It'll be closer to the end of the week before the Delco gets here. But the frustrating part of all of this is that I have to get the car inspected tomorrow lol. I'm having to try and get the old original TPS back on there and get a somewhat consistent idle and I straight up cant. I go through the entire process and have it idle really nice at 700, closed loop, IAC isn't hissing, life is good. Then I let it sit for like 30 minutes and come back and fire her up, and it wants to idle at 1800 and I can hear the IAC hissing and backing out the set screw all the way only brings it to 1,100. How crucial is the learning drive after you go through the IAC process? And how crucial is it that the EST wire be disconnected. I see instruction both ways about the EST being connected or not.

confab

I won't use BWD anything. I tried some of their speed sensors once. They have a lifetime warranty. This is fortunate, because that is how long you will be replacing them.

Customers would come back in 30 days.. 60 days.. Etc.. With the same condition and, lo and behold, the sensor was crapped out.

It happened over and over to the point it can't just be random chance. It can't be a "bad batch"

They just suck out loud..

Good luck with your idle problem.

JasBass

Always learning the hard way here lol, Cheers man

aklim

Hissing that you can hear isn't an on-off thing. You can hear it ONLY WHEN it opens enough. Are you sure you have 700 rpm as seen by the ECM? The EST is for the timing not IAC

JasBass

aklim

Which may or may not be accurate. And you may be trying to adjust in spite of an air leak.

When the car is idling well, what is more accurate to say is it HAPPENS to fall within the range of adjustment.

When there is a hissing, it is because the IAC is opened up wide enough FOR YOU TO HEAR. It doesn't mean anything. Mine hisses when the AC is on and it has to open it up more. I think a scanner will resolve the issue as to what the RPM is and whether there is an air leak or not.

The FSM method is very sterile when it ASSUMEs that there is only 1 issue. That being the setting for idle is out. If the Tach is not accurate, you are adjusting for something incorrect. If there is an air leak, see above. IF the timing is wrong, once again, see above. IF you have made mods, well..... FMS assumes everything is 100% perfect except the idle adjustment which we don't know if it is or not. People like the FSM method because it is cheap and easy and doesn't require a scanner or anything else. It is also not as tolerant of any issues.

TheBlaster9001

I've never disconnected the EST for idle setting, only for timing. A hot start leading to a high idle is a weird condition. It should not do that. I would assume that is the result of the TPS acting goofy?

Did the TPS still hold ~.5 volts when the car was hot and idling high? It seems as though we do have one issue that is with the TPS sensor, but if it's output didn't change, yet the idle was high when hot, that may indicate another issue. However, for what it's worth, If the sensor for some reason 'spiked' signal voltage when the key was turned to 'on', the ECM could have tried to read something higher than .5 volts as 0% throttle, which could cause a high idle once the ECM realizes the TPS voltage isn't correct.

I'd get this new Delco sensor on and make sure it can reach 4.5 volts at WOT, then do the idle reset process again. With any luck, that will solve the high idle issue, but if it doesn't the issue may be with the IAC or the Tach input, in which case you'd need a way to datalog to easily troubleshoot.

JasBass

First:
So, let me plead some ignorance for a sec then. What scanning setup are you using? I was under the assumption in order to set anything on the car I needed to get the whole ALDL connect, run it to tuning software, and be able to burn it into the chip. Have I missed a basic step here in being able to have a scanner and set things on an 89? Ideally i'd like to be able to get in there and set IAC steps accordingly.

Second:
During the IAC reset process, once I get it settled right where it runs nice, I see instructions for either turning the car off and plugging the IAC back in or just plugging the IAC back in while it's running. 6-1/2 dozen situation?? The high idle only seems to show its head after i've plugged back in, ran the car again and then let it sit for an hour or so. When I come back, it'll idle high.

Let me do the idiot check here too to make sure the issue isn't me. When resetting, after I jump AB for 60 secs, key off, remove jump, crank, the car absolutely will not start until I adjust the set screw decently far forward. At that point it'll idle, unhappily, at 500. I might give it a half turn to get it to 600. Key off and reconnect IAC. Restart and all seems happy. Come back in an hour and restart, 15-1800 idle.

JasBass

Man, this thing is testing my patience. I want to learn, but damn, it's testing my patience. Yet I still love it On the bright side, passed inspection

TheBlaster9001

Well that's good news, at least. I edited my above post to contain my .02 as for what to do next.

JasBass

I agree with it. I had to patch this together last night to get the car inspected today. When driving today, it idled high until I put it in reverse and actually put a small load on it. Then it dropped to 6. When driving for a while, it went to 8. After inspection it was at 11. It's the Wheel of Fortune of idles right now. We'll see how the delco unit does, if it ever ships and moves. Stores had to order it here

TheBlaster9001

Third time (or TPS) lucky, I hope.