2.8 TBI V6 - Won't run with MAP conn. after TBI rebuild

[armyBob]

Background:
89 Trooper v6
New fuel filter
New PCV valve
New plugs (AC Delco R43TS)
New wires
New cap
New coolant temp sensor
Rebuilt TBI, including new FPR
Injector spray pattern looks good (one has a little dribble)
Timing at 10*BTDC
Idle set at 800 rpm (or it was until i toyed with the idle stop)
Compression at 150 all around.
Fuel pressure 11-12 psi
TPS set at .46 volts

After rebuilding TBI, it wouldn't start. I finally got it started and it blew white smoke, I thought it was the solvents burning off. Turns out I fouled the plugs, so I replaced them and it started, but was still smoking. Pulled the fuel pressure fuse and it starts, and runs ok until it uses the fuel up. Now if I disconnect the MAP sensor it will run and is even drivable, but barely so, and is VERY hard to start afterwards (like it's flooded). Tried a new IAC, new MAP, to no avail. If I try to run with the MAP plugged in it will burp, smoke, stall unless I give it lots of throttle (which would then foul the plugs again). What is wrong with this thing? No trouble codes (well, did get Rich Exhaust), ECM gives 12 code and outputs serial data. HELP!!!

--------------------
89 Trooper
v6, 5 speed
4x4
177,000 mi

[Doubt_Incarnate]

white smoke is normally coolant burning out. but it doesnt make sense in your case. do you have an o2 sensor? that mght be work replacing, other than that it seems like to much gas, but. again the white smoke indicates coolant, black is for excesive fuel, but if its getting coolant in their somhow, not all of the gas will burn and it will smell rich.

[sharkey]

try bumping your tps up to .55 volts. .46 is a little low and can cause issues with it being that low. normal range for closed throttle is .50-.65

[armyBob]

I don't see how it could be coolant, it was fine before the TBI rebuild and just sat there, compression is great, and it runs ok w/o the MAP sensor.

Yes i have 1-wire o2 sensor.

I tried to get the TPS at .5, it kept getting off when i tightened the screws.

Could it be a bad TPS? Maybe i got some carb cleaner on it?

Today I will hook it up to my laptop w/WinALDL and take a look. ALso I know my battery is weak from cranking it so much, will swap.

[armyBob]

OK, it's not the battery.

Readjusted TPS, got it at .53v.

The spark at the plugs is orange, jumps a good 1" gap.

I forgot to reconnect #2 cylinder's wire after I tested the spark. The truck ran on 5 cylinders (still, WITHOUT the MAP sensor connected)!

MAP voltage is really high, even with the new sensor (like 4.8v at 600 rpm). It is an aftermarket unit, maybe I need to call Chevy for a Delco?

[geoffinbc]

Aftermarket units are sketchy at best. Have you run it with the ECT sensor disconnected?

[Guest]

Wait, the Map voltage is almost 5 volts, at idle? Check your ground to the map. At that voltage the ECM thinks that the engine is under heavy load and will fatten the mixture.
Ground may be diconnected or broken somewhere in the harness.

[armyBob]

It is related to the MAP sensor, but is not the sensor itself or the wiring. The MAP voltage is staying high (4.8v) at startup, it should be about 1.2 v. If I manually suck (no jokes) the port on the map sensor, I see the voltage drop. The sensor is connected to the port between the fuel lines, which is not clogged nor does it leak. Clogged cat maybe? I had it running this morning, map voltage was normal, i thought it was a loose connection to the computer. Nope, the gods have frowned upon me. rats!


I checked the voltage with a scan tool and manually at the ECM leads. Still high! No vacuum leaks that I can tell, at least none large enough to cause the map to not respond. I mean, it doesn't move at all. Maybe I'll try a different port...

[bszopi]

Maybe I'll try a different port...

That is what I was going to recommend. If you can create a vacuum by sucking and the voltage corresponds correctly, then the best bet would be to try a different source for the MAP vacuum. Just because there aren't any leaks at that hose doesn't mean that its drawing enough of a vacuum to trigger the MAP correctly.

[armyBob]

Tried the EGR vacuum port (which is manifold also I think). Nope. Now I can't get it to run at all, even with MAP out of the loop, but it's probably flooded. Any other ideas? Could I have clogged the cat (I doubt it since it was running briefly earlier today, and the map values were normal)? Thanks again.

[armyBob]

When the truck was running earlier today it WAS making vacuum, so i tried running some seafoam thru it. I don't think it's started since! I'm going to remove the o2 sensor and see if i get vacuum. I really hope I didn't clog the cat.

[geoffinbc]

You need to reall confirm your timing. If this thing has not been running enough to se timing it could be the source of all your problems. Especially no vacuum.

[armyBob]

The timing was fine at 10*BTDC before this mess.

What about the spark? What color should it be? It is orange, and will jump 1 inch or more at the plugs.

[geoffinbc]

If you are using a spark tester then the spark should be a nice briliant blue colour. Distance doesn't count. That just means the voltage is high. Colour should be blue that means it hot. Go buy a spark tester.

[armyBob]

I used an old spark plug with the ground electrode removed. I'll get a spark tester.