joecar

Jeff,

This sounds like the wiring to the IAT sensor is fractured (where it loops out of the harness conduit just before it goes into the connector).

sore

Just for the record, I'm just getting the hang of the sensor readings so excuse any of my dumb questions.

My car doesn't have cats. And i don't believe i have O2 extensions. I'll check later today.

My spark advance is all over the place, but i just assumed it was because my idle is jumping around.

I did have an extension on the MAF harness. I took it off but initially still have the same negative temp reading with the new MAF. I'll check again today and see if the negative temp is there and if so, i'll wiggle the harness to see if it changes.

At one time i did have a code that said my o2's were switching slow. And when i brought the car to a shop the mechanic also mentioned that they were switching slow.

My friend will post the HPT data log shortly. But this log was done before i changed the coolant temp sensor, thermostat, throttle body and MAF..I feel like the car is running a little better now that i changed those parts, but maybe that's just wishful thinking.

R_trim 93GT

iTrader: (1)

Here is one of the scans that we did on October 9, 2015.

ECT was 75 deg F and this was an initial start where we just let it sit and idle until it stalled after almost 6 minutes. I never reviewed the log closely because we ended up checking a lot of mechanical and electrical items to see if we could figure out the problem.

There is some weird stuff happening around the 5 minute mark. O2 voltage goes to zero for a little bit and then back to over 900mV. STFTs are +20%. ECT jumps from 162 to 181 and then back to 162 deg F. I think we gave it some throttle to log a different rpm range.

Right at the end, things look decent but the O2's aren't switching and it died.

sore

After we noticed the temperature jumping around, I changed the temperature sensor and that didn't help, then replaced the thermostat and it fixed the problem.

Nicelysedate

iTrader: (3)

Good for you. I wouldn't have thought the thermostat would cause those type of problems.

sore

The thermostat fixed the problem of the coolant temperature jumping around, not the surging idle/hesitation problem.

I really wouldn't have thought the thermostat would have caused the temperature to jump around like it was doing. I thought it would either be stuck open or shut. Makes me wonder if its a fluke, and i think changing the thermostat fixed problem of the temperature jumping around when it may really be a wiring issue since i'm having this idle problem also.

joecar

I think the problem is still there (ECT does not jump around like that, by replacing the TS you've narrowed the operating range of the ECT sensor, but the problem is still there).

sore

When I replaced the TS, I replaced it with the same TS that I took out. Which is a factory one with a temp of about 220 deg. F. As much as I wanted to change it for a lower temperature one, I didn't want to make any changes to the car until it is running right again.

Because the coolant temperature sensor and IAT sensor wiring is routed in the same wiring harness, and since both of these sensors were giving me odd readings it was making me think the problem was in the harness. But, visually it looks good, and wiggling the wires doesn't change any readings.

Nicelysedate

iTrader: (3)

Ok so for the surging watch your spark advance. In the video it looks like it's pulling a lot of timing out. I saw it go down to zero a few times. That could be caused by quite a few things, IAT being one of them (I wouldn't think it would pull it to zero though).

Can you check and see if you are getting knock retard on that scanner?

sore

Hmmmm. I haven't thought about knock retard. From what i can tell, my scanner doesn't show knock retard.
For what its worth, i haven't had a knock sensor code.
Something i've wondered, ...Is there anything with the DOD that can cause the issues i'm having?

sore

sore

LilJayV10

iTrader: (39)

The log showed no knock retard on the log or histogram.

If you force open loop in the scanner or lock the timing does it run any different?

Have you checked the fuel pressure?

Nicelysedate

iTrader: (3)

I would say your best bet would be to find someone with hptuners at this point or something similar.

Forcing open loop and being able to control spark advance would really aid in trouble shooting.

Nicelysedate

iTrader: (3)

After looking an a stock LS3 tune file the spark advance jumping around is caused by overspeed spark tables. Stock allows in to pull out up to 20 degrees of timing.

Honestly I'm stumped. Its possible that your throttle body is the problem, even though its new or maybe the wiring to it.

I wonder if maybe the Active Fuel Management is kicking in when it isn't supposed to.

LilJayV10

iTrader: (39)

Does that engine have a cam phaser? I don't have any experience with AFM/DOD engines.

LilJayV10

iTrader: (39)

I'd also like to see a log file holding the rpms at 1500-3k to see what it does. The 02 activity is strange.

If the 02's are telling the truth, the PCM is pulling out over 25%(total trims)...that's a lot.

LilJayV10

iTrader: (39)

I'd start with the basics first. Battery test, alt test, AC ripple test, voltage drop. Verify fuel pressure and would probably scope the fuel pump. Also since it's a DOD/AFM engine, which I "assume" has a cam phaser I'd also verify oil pressure w/ a mechanical gauge.

joecar

AFM/DOD uses the valley plate with the solenoids to starve the 8 lifters.

VVT uses the cam phaser.

joecar

+1 on test the basics.

Have you replaces the fuel filter...?

Also check the engine grounds for voltage drop.

Which DTC's are you getting...?
If you clear them do they come back...?

Also check the ignition relay, swap it with another like relay.