That is what I was saying earlier regarding loss of fuel pressure up top. Now that you’re running Brian’s tune I am confident that it is a mechanical issue, and not in the tune. Rent a fuel pressure tester, connect to a valve on fuel rail securely. Idle in neutral. Apply the throttle. Watch to see if the gauge suddenly drops at higher RPM. More difficult to do in gear with a manual of course, but would underline it...

- Rob

 

Hmmmm ok, I'll check. If it drops off at higher RPMs or while driving, most likely pump? From what I can remember, I'm pretty sure I replaced the fuel pump when I did the TPI swap, as I pulled the TPI tank and sender/etc. out from the GTA and replaced pump before I put it in this car as they are a PITA to replace otherwise. And it has a new fuel filter as of a few weeks ago. BUT, pump could still go bad, stuff happens.

 

Steady 42psi, no drop even under WOT while driving, drops to 36psi for a second or two while letting off throttle but pops back to 42psi fine. No pressure bleed, stays at 42psi with car off for 4-5minutes.

 

Kevin, I just got home from work, and I cannot see the log. Was talking with Brian (Tuned Performance) and he mentioned your Code 13 and O2mv issue being locked. You might need a new O2 sensor. Check the wiring to see if the wire is okay. If good. Replace the O2 sensor with a Denso.

- Rob

 

 

 

Ran another log tonight, replaced O2 sensor for the heck of it as I don't remember if I replaced it during engine swap and it was only $20. Old sensor had a orange/rust tint to the part inside the manifold, don't know if that's normal or not. I didn't have long enough leads for a ohm meter, so I'll fab something up tomorrow after work and see if I can go from O2 pigtail coupling on left side of block to purple D7 on the ECM and make sure pin is good to ECM. But still, I should get a 0mV on the O2 ECM value if there is a break in the wire, right, and not a "ghost" value of fluctuating milivolts in the 430-450 range like I'm getting? That being said, I didn't run the diagnostic testing, as I was running out of time (vehicle is not at my house, and didn't have the correct tools to get to the stupid O2 sensor easily, took a little longer than planned), but will try and go through the flowchart and check all connections tomorrow.

Here's a new log from a short drive tonight. A little better than last night, but still not back to life yet. I still have Code 13 (O2 Sensor) error and now a new Code 36 (MAF Burnoff) error. These photos are from my 1988 service manual. I will also pull off MAF relays and check all connectors and pins, as well as on the MAF itself. Both of these have one potentially easy fix in common - bad connections at the ECM, so I'll start there tomorrow, then move to testing O2 sensor ohm reading to make sure no break there as harness will be unplugged.

 

The ecm is at least getting a 02 reading but its just barely moving. the o2 ground wire d6 to the back of your cylinder head could be the issue. im not sure you would see the .450 if there was a open in the purple wire.
or faulty ecm. if you cant solve the code 36 it can be tuned out. I would focus on the code 13 I don't think the burn off causes any change to the ecm to effect running .
see the code 13 description the o2 will swing when warm 100-999mv

 

No, I am almost positive that it will still read the 450mv bias. It's great that you swapped in a new O2 sensor, but you really need to check the wiring at this point; check for corrosion on the O2 sensor connector, check for a defective ground circuit; and bad connection at the ECM. The MAF Burn Off error code might just be intermittent due to the poorly running engine.

Disconnect the battery for a few to reset...

- Rob

 

I know you guys talked about maybe the MAF sensor. Why don't you unplug it and drive the car as you would and see what happens ?

 

I checked wiring and voltage coming out of D7 purple at ecm and at o2 sensor is 0.18v to D6 tan and body ground, not 0.45 with key on, or engine running. Wiring otherwise looks ok and I moved grounds and checked connections. Battery is new and has voltage of 13v.

 

High BLM in the log from what I was told... giving the appearance you are running lean, but I bet you smell a little gas in the exhaust. Skewed voltage reading. This notoriously points towards a bad ground. Try cutting D6 and run an entirely new ground to the chassis...

- Rob

 

change your vom to mv or .18v is 180mv still not enough.
you may have to ohm out the purple wire.
No need to unplug the maf the signal looks fine bad advice look at the datalog gps correspond to rpm and speed . looks ok to me. Burn off 36 is a clean off of the hot wire element has zero to do with a maf gps reading.

 

Alrighty, will run a new ground and report back.

 

ok sorry not experienced with the computer read outs. Just was thinking of trial and error

 

So I grounded tan d6 to good ground, still 0.18v... driving it to the house today I felt it enter closed loop (I think) and suddenly it lost a lot of power, and I barely made it home, exhaust smelling like gas. Let it sit an hour and finished driving it up the driveway with good power again, so I think it’s definitely a bad o2 reading. But if I now have a good o2 ground, do I have a bad ecm if voltage reading still isn’t good?

 

Can you attach a test wire to the o2 to test voltage . The purple wire might have to much resistance.

 

Ok give me 30

 

Made jumper and checked purple wire, no problems, 0.4ohm total resistance (meter set at 0-200ohm/lowest detection) from o2 connection to d7 at computer, so that’s not the problem.

 

Unfortunately... at this point, part of the process of elimination would be to get your hands on a donor ECM and see if it fixes the issue.

- Rob

 

The only thing I can think of is aiming a infrared gun at the o2 while engine is warm to see if it gets to 5-600f. If not try a 3 wire afs74 o2.

 

It gets plenty warm I’m sure the way I’ve driven it hard. Got a yard ecm on the way. Will try that. Im sure the ecm has a circuit issue somewhere hence the low voltage.

 

I have a problem with my T.P.I that I haven't gotten around to fixing but it sounds similar. My car drives 100% fine up until about 2800-3000 RPM. Then it backfires into the intake like crazy and gives me nothing. Surprisingly I can still cruise at 90 at like 2800 rpm on a good downhill. Anyways through my research its the fuel pressure regulator being stuck open. Like $38 bucks. Everything will look good and and test fine because its stuck open. Under full acceleration it can't build up the amount of pressure needed so the engine thinks its starving so forces more air into the motor so it doesn't die. Hope this helps.

 

Thanks, but you don’t have quite the same issues as I do. As stated my fuel pressure is fine at idle and while driving, and engine runs smooth. Computer is next.

 

I was unclear on the answer. Was the o2 mv moving engine warm with just testing at the o2 ?

 

Come again Batman...

I stopped at the signal from the ecm. It’s not 450mV like manual says it should be across d6 and d7, it’s 180mV across whether cold or at operating temp, engine off or on. I’ve posted the logs up here and o2 values are pretty much holding around 450mV

 

Taking the ecm out of the picture. Engine warm o2 disconnected.
does the mv change ? Toggle up and down

 

Didn’t try just measuring o2 disconnected. You’re saying stick an ohm meter on the block and to single wire out of o2 and see if I have a defective new sensor?

I edited my post above while you were posting and it says what I checked on ecm.

 

Correct , you need your vom on mv . A ungrounded or unheated or silicon poised o2 wil stay at .450. .
althoight it shouldn’t need a 3 wire o2 that might be the fix.

 

SOB. I think I have a bad new o2 sensor. I took one lead of the voltmeter and hooked up to the connector that went to o2 sensor near the front of the block, then put the other lead onto the block. Ran the engine up the hill and got it hot prior; 0mv. Ran to negative and positive terminals of battery as well, all 0mV. Bugger to change with stock manifolds.

Ohm reading of 1 to block from connector as well.

Also got a new ecm no change at 0.17v across d6/d7.

 

What did you run to the battery terminals . Sorry didn’t follow the last bit of what your did.
You shouldn’t need one but a acdelco afs74 isn’t much. Just 3 wire hookup. Power from the esc module pink/bulk stripe or fuel pump relay wire to the pump.


https://www.ebay.com/itm/TPI-TBI-3-W...8AAOSwLVZVt9ay

 

I kept one lead on the o2 sensor, then checked other lead to manifold, then tried negative batt and positive batt just to see if manifold ground was faulty. Make sense?

3-wire o2 is next I guess. One wire to ecm, one to power and third to a good ground?

 

Gotcha, correct. Power, ground and signal. Not sure what else you should try.

 

Ok I’ll see if I can find one locally tomorrow and wire it up using the old o2 harness.

 

That is the adapter I run due to the long tube headers, w/heated O2 sensor. Run one of the two white wires directly to the fuse box, and tap into one of the two extra ports that GM provided. Don't splice into an existing wire for feed. With the replacement ECM being tried with the exact same result, this now rules that out and points right back to the O2 sensor narrowing it down, and that of course was a pun for those paying attention. Although a bad batch of parts is unfortunately common in today's auto parts outlets, it's still bothering me that,.. meh, if the heated O2 fixes the issue, and I hope that it does, then go for it. The LT1 always did well for me, still running one today;

https://www.autozone.com/engine-mana..._399771_0_1382

- Rob

 

Got the Bosch 13077, two white wires; one goes to power and one to the ecm right (shouldn’t matter)? Black is ground? I wired up one to battery and checked the other end and it was battery voltage (12.x V); just want to make sure this is correct before I plug the connector into the ecm and fry something.

 

Black is signal to the ecm. It doesn’t matter which white wire is hot Or grounded.

 

Shoot. So both white wires are for heater. The black goes to ecm. Good thing I checked.

 

 

Pretty sure both whites are for heater.

 

Yep. Taking a drive now. Currently o2 in tunerpro is at 0.00​​​​​​. Now warming up and numbers in the 50-70 range and number value is yellow instead of black so that must be good.

 

Now I’m getting o2 lean error and no more readings from o2, at yellow color 0.00

 

Yes, black to the ECM, one white ground, one white switched...

If the heated O2 sensor is displaying 0, and the engine is still holding back, then it kinds goes back to what I was originally pushing towards, a fueling issue. I know you checked pressure during idle, and raising the throttle, but were you ever able to check fuel pressure under a load while driving? Before we get back into that side of it, just do me a favor and check the wiring at your TPS...

- Rob

 

Yes, I checked during driving, hooked it up and poked out the hood and took it for a drive, I think I posted it a few posts up what I found... so fuel should be GTG. Just got back, here are four logs; every time I start the car the O2 reading starts at 0.00 and slowly (slooooowly) climbs, most I saw during driving was around 50 I think on the 1st log (log marked 5th or 6th in this attachment), then 30 or so on next to last one (7th), and it was a downhill coast for a few miles and then a slow drive home (8th) as I was at E on the gas tank - didn't realize I'd burn through a full tank this fast during all this testing. I did notice that it disconnected while logging a few times, so I don't know why. I switched out to my original computer on the 8th log, but as I was out of gas I couldn't make another hillclimb.

But yes, on all logs I eventually noticed a "Lean o2" condition and the car wasn't as peppy. Still couldn't roast the tires, but much better than old school O2 sensor.

Check wiring to TPS as in what? It's hooked up. I'll get the manual when I get home and see what to check.

 

Meaning check with a multimeter, test voltage while opening the throttle, or using Tuner Pro. I cannot see any of your logs so I have to go by what Brian is telling me...

- Rob

 

You can’t see logs? Why not? TPS is good I discussed range in this thread; goes to 4.5 or so at WOT.

 

Only use this laptop for WUD datalogging, set up for dat files only at this point. As for the TPS I must have missed that part of the discussion, but good to know that it was checked off. Again, if I am repeating any of the discussion just bear with me. You checked fuel pressure with no load, as well as having a load, which is great. Did you pull the fuel pressure regulator vacuum line and check to see if it is leaking during key on, or when applying throttle? If the heated O2 sensor is telling you you're lean up top, then you're lean up top. I mean unless your timing is that far off, you are simply losing fuel pressure (or fuel) like I mentioned earlier in the thread.

- Rob

 

could very well be a tps issue, looking at log 8. first half of the log. watch the tps vs engine rpm. no tps movement but rpm was continuing to rise.
going down a hill maybe ?
The ecm never sees any cross counts the o2 moves alittle but seems like the reading are false very glitchy and on the lean side.
@RBob got any suggestions ?

 

Exactly Brian! That is why I mentioned to check the wiring, something just seems off with the TPS...

- Rob

 

Yes on log 8, I was going downhill, a steep hill (one of the hillclimbs I do up to a mountain lake that the other three logs picked up), so half the log was spent mainly coasting, hitting the brakes and shifting in and out of gear around sharp corners. Log 5 was driving there and then starting up the hill before it lost connection, then log 6 and 7 are starting at the point and going uphill (both lost connection I believe). Log 8 was coming down from the top. But no, TP shows TPS as good. But maybe it's not as good as it should be? I'll play the log and drop it here as a video for you @RBob .

Edit: That's not going to work - no way to show data and monitors all at once, at least not on my screen. You need to just install TP on your laptop, would make life easier, no?

I also noticed at low O2 levels the level would jump around initially (0, 4.5, 0, 5, 0, etc.) until it "warmed up" or something and levels would stay steady around 8, 9, 10, 13, etc.

Also, why would the reading be at 0 for a few minutes if this is a heated O2? And if I turn engine off and do another log and fire it up after 10 seconds, why is the reading off the O2 still at 0 for awhile if temperature hasn't really changed in manifolds and ECT? That doesn't make sense to me.