It runs!! sort of. diagnosis help plz

[BlackBaer5.0]

Ive finished assembling and installing the engine. After setting everything correctly, so I thought. The engine idles around 850-900 @ 32psi with 10deg of timing, vacum at idle 15in. When idling it sounds great, steady, with a little lope, no ticking, no hesitation, throttle response it great.

I pull it out of the driveway and it starts to act up. It lurches real bad, pedal very touchy, and backfires/pops through the intake if I touch the throttle, and idles high. When I try to get on it to see if it will clear up its like there is no reaction, it just pops more, if I coast it back to the garage the engine sounds like it is about to stall but keeps above 700ish,

I believe this is caused by a faulty sensor or bad setting , that takes affect in closed loop, but I do not think it has enough time to go closed loop by the time it starts to act up. ( from startup to trouble, no more than 5 mins)

Troubleshooting so far,
-redid valves again, due to severe ticking and low vacum 5-10in, now at 15in steady. ticking is gone,
-replaced old and sticky IAC
-replaced grommet around vac port on brake booster,
-replaced grommet for PVC tube in back of intake.
-reset base idle, ( unplugged iac, backed out set screw and adjusted in untill the engine would run, set it to 850rpm ,, as suggested for this cam. cleared ECU to reset base idle
-TPS sensor is new, and voltage at full open and Closed are w/in spec,
-new o2's , unable to test since I cant get it to run long enough,
-all vac lines are new
- checked for other vac leaks, ( thats how I found the booster and PVC grommet problem.
-double checked ground from batt to chassis, ecu to chassis, and block to chassis,

My next steps
Pull codes again, there were none after I reset the ECU the first time.
Swap out MAF with know good one, for testing
Swap out distributor with know good one for testing
test ECT sensor voltage/resistance
test ACT sensor voltage/resistance
test or just remove EGR system
How does one go about testing the Vehicle speed sensor, or does the ecu do that for me ?

any ideas, or common things to check

thanks
Geoff

 

[90FoxBdy]

Is it getting hot real quick? Check plug wires, make sure your on TDC. Mine did as described when I was 180 out even though I swore I wasn't. Check, then check again, then one more time.

 

[ShortThrow50]

definately sounds like timing or ignition. Recheck that you put the plug wires on the right cylinder and also check at the cap. Sounds like you have one plug wire in the WRONG location. I did this by accident a month ago with my engine and i SWORE i didnt. If that isnt it, restab the distributor again and go through that process

 

[keiser blade]

i agree recheck wires, i did it on my dads 351w truck and had one wire wouldnt even pull outta it place, changed it around good to go

 

[BlackBaer5.0]

The wires are on the correct firing order. but i will check again .
I dont think it would idle or rev smoothly during initial start up if they were not,

Im finding TDC on the compression stroke by pulling the #1 plug and turning the engine until the goes pphhsssttttt out the plug hole, around 0 deg..setting to 10 degs TDC stab the distributor near #1 terminal,

I did not get alot for troubleshooting time today, but one thing I am thinking of is the deg pointer on the block may be off, Im going to play around with the distributor, try a couple more positions.

Do you believe 850 to 900 rpm is to high for base idle? should I set it lower 750 maybe? I was under the impression this cam liked to hunt(rpm) if the base idle was set too low. ?

 

[HISSIN50]

FWIW, it takes 30-120 seconds to achieve closed loop (the HEGO's heat quickly due to the heater element).

I agree with what's been said, and I like your last though. I would start with checking timing again. Kinda sounds like retarded timing.

 

[BlackBaer5.0]

After pulling the codes, The code for "ECT out of range" showed up.

After confirming the sensor was good at the correct ohm/temp.

I found resistance from the ECT plug to pin 4(ect pin) As I began to tear down the intake to look at the wire loom. I took the plug off the TPS pig tail and surprisingly the resistance between the ECT plug ( grn wire) and pin 4 ( white 10-pin) went away. I plugged the TPS back in and the resistance came back.

As a back probed the ECT signal wire to pin 4 , I found voltage on pin 5( TPS)

Also!!, I can change the resistance between the ECT plug and pin 4 on the 10-pin connector, by moving the throttle plate.. Thats some crazy *****

What is causing the short between the ECT and TPS circuits? Why does it go away when the TPS is unplugged. Maybe by plugging in the TPS it completed the short to ground.. ??

Btw the Sig return on both the TPS and ECT are fine,

With this short circuit between the TPS and ECT, it is no surprise the car was acting up so bad in closed-loop!