Having trouble with running lean on Silvertop / ECU advice

[The Bloody Panda]

Here's what I'm experiencing:

If I unplug my TPS my AFR is high 12's to low 13's in the powerband at WOT, which is precisely where I prefer it to be.

When TPS is connected the engine runs lean when I open the throttle anywhere from a little bit to all the way. It will eventually richen up a bit to the 14's on the AFR but I have to wait several seconds of the engine running lean as piss and performing very poorly.

Timing and TPS are set to exact factory specs. My 20V has velocity stacks, a TRD copy header with an HKS Hi power exhaust, and it's running with the Blacktop ECU. All engine internals are stock. My 86 drove perfectly fine this way for years but now I suddenly have this issue. I replaced the TPS right off the bat but that changed nothing. I swapped in a spare Blacktop ECU that I had lying around but that changed nothing.

A friend of mine suggested fuel injectors or fuel pressure regulator as the culprit for the leanness. Perhaps he is correct since he knows much but I don't know if that makes sense since I have plenty of fuel when the TPS is disconnected. My fuel pump and fuel filter shouldn't be a problem since both have been replaced in recent times. However, I've never touched those fuel injectors or the fuel pressure regulator so I feel like my friend might be right even though I don't understand how I could have plenty of fuel when the TPS is disconnected.

I'd like some thoughts on either what else this could be or a confirmation on the reasoning behind suspecting the fuel injectors or fuel pressure regulator despite the adequate fuel when TPS is disconnected.

As I sit and think about it some more perhaps the ECU is trying to give my engine the correct amount of fuel but doesn't realize that it's not since the fuel injectors or the fuel pressure regulator are boned. But maybe when the TPS is disconnected the ECU just dumps all the fuel it can in there rather than what would be the correct amount if the injectors or regulator were working properly.

Thank you very much for all the help.

[NikNes]

Sounds strange. Usually when something goes wrong the engine runs richer than normal. Maybe the wideband is reading a false lean condition? This can happen if you have an exhaust leak or a cylinder doesn't fire due to spark/etc since the wideband only picks up the unburnt oxygen. Hope that helps, but its just a stab in the dark. Let us know if you get it fixed - it could very well be the fpr.

[yoshimitsuspeed]

NikNes makes a very good point about making sure there aren't any leaks before the WB.
What does it idle and cruise at?
Does the behavior change if you reset the ECU?
Are you sure your MAP sensor is the right one, hooked up and working properly?
I would do all the on car tests on the TPS, AFM, MAP and O2 sensor. This tests the voltage at the ECU and will confirm that the component is working properly and that the wiring is good and the signal is getting to the ECU.

[The Bloody Panda]

The wideband is good. I replaced it recently and my exhaust is completely welded together all the way to the wideband and there is a new exhaust gasket between the header and the engine. Also the wideband does read a very nice reading when TPS is disconnected, at which point my car runs very strong. When the wideband reads lean my car runs very weak and sounds like garbage.

When the TPS is connected the AFR is in the 14's at idle and cruise.

The behavior does not change at all after many ECU resets and it doesn't change when I run my spare Blacktop ECU either.

I have tried 3 different MAP sensors and they all produce the same condition. My car was working fine on these various MAP sensors before my problem suddenly appeared. If the MAP sensor is disconnected my car will hardly run at all.

It just baffles me how great my AFR is when TPS is disconnected when I'm at WOT, my car runs as strong as ever with it disconnected.

[onnaj]

I really think you have a vacuum leak somewhere. Those hose go weak during time. They can give strange effect on the engine.

[The Bloody Panda]

Hmm, I don't know. I'll check the hoses per your advice since I haven't recently. However, I replaced every hose not long ago with a brand new kit but since my issue happened so suddenly maybe you're right. None of my vacuum leak experiences caused my engine to run so lean before though so I am a bit skeptical but I am hoping you're right.

[yoshimitsuspeed]

It's always good to rule out vacuum leaks but generally they would have a much greater impact at idle than at WOT so I doubt that is the problem.
I would definitely start with the on car tests. Maybe you have short in your harness or something funny.

[The Bloody Panda]

Now that you mention it, perhaps the wiring is the most likely cause. When my problem suddenly started I had no change what so ever in the way my car idles. The TPS sensor has been tested good and so has the ECU. Dr. Tweak did my wiring so I was thinking it couldn't be that but maybe so.

[NikNes]

Any luck?

[The Bloody Panda]

The weather has been terrible here all week and I'm wanting to do a diagnostic after I drive my car around on my reset ECU just to see if any new codes come up. I doubt any new codes will but I'm wanting to do that before I move forward with anything else on this issue. Oh, and I can't drive my car in the rain because it doesn't have door windows or the rear window to save weight.

[MisterJerk]

It just baffles me how great my AFR is when TPS is disconnected when I'm at WOT, my car runs as strong as ever with it disconnected.

Have you checked the TPS with a multimeter per FSM? Might need some adjustment?

[The Bloody Panda]

It is set to FSM specs. All my readings on the multimeter were within the ranges of the FSM, including WOT.