Viprklr

iTrader: (5)

After 5 months of building this Viper Killer I finally started it up last night. Unfortunately I have to hold the gas in about 50% to keep it running. I set the TPS, which btw goes no higher than .6v throttle closed, even pulled the IAC and cleaned it again. Still the same problem. I can't set the IAC according to the tech article without the car running.
Now, the car does run on it's own with the IAC completely removed. Is it bad or do I have some other problem?
I did a basic valve set on the stand but I prefer the engine running method. Idiot proof.

Viprklr

iTrader: (5)

Did I stump everyone? Suggestions?

1bad91Z

iTrader: (1)

What is your fuel pressure reading with vac. line off at idle?

What did you set your base mechanical timing to?

BA92GTA

Just trying to get up to speed on the problem. I had some of the same symptoms and found that a few of the fuel injectors were leaking.

It does sound like the IAC is bad and should be replaced.

Make sure the O2 sensor didn’t get damaged or wet during the rebuild. This closes the loop in the fuel to air mix. Mine was bad after sitting exposed to the elements during my rebuild. Elements, what I mean to say is pressure washer.

joejoe

iTrader: (1)

The TPS sounds like its bad (should be .54v closed). Have you done a computer tune for your mods to the motor? that could be some of the problem.

good luck

Viprklr

iTrader: (5)

Static fuel pressure is 44
running it's 40

Can't exactly set the timing until I can get it to keep running reliably. Right now it's set to where I can get it to run. More and it doesn't. Less and it doesn't.

The O2 sensor is not in the loop in open loop so it shouldn't be an issue. Besides, I still need to weld in a bung so I can hook the O2 up. The injectors aren't leaking. My fuel system holds pressure for at least an hour before dropping 8 psi.

I've ordered an IAC. Hopefully that fixes it but if there are other ideas i'd be interested.
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.54v. Depends on where you look. I can get my TPS down to .49 and as high as .60/.61v.
I haven't done any type of computer tune yet besides put back in my stock programming and add a little SA (DIY Prom suggestion). My laptop OS needs to be re-installed before I can get any scans.

BA92GTA

Okay, I see where you are going with this.

When the engine is cold we are running in an open loop. Once the heats from the exhaust gasses heat the O2 sensor the ECM begins to adjust air to fuel we are said to be in a closed loop.

If the O2 sensor never heats up we are perpetually stuck in an open loop while the ECM is constantly running in a cold engine start mode.

You are likely compensating for the extra fuel being dumped with more airflow. Have you pulled a plug to see if it is wet with gas? Are you getting a lot of gas fumes from the exhaust? If the pulg is wet and the fumes are heavy, then I’m certain your problems is due to the absence of an O2 sensor.

I would go ahead and get the O2 mounted it is important at start up of the car. I agree the TPS should be changed also.

Oh and congrates on getting the rebuild done, I finished mine last year and had hell getting it tuned. Although I haved to say it was well worth the effort and I learned alot on the way about sensors and how the ECM uses them.

Viprklr

iTrader: (5)

Thanks for the congrats. Unfortunately it appears my shift cable is broken as well. This car build has just been plagued with problems.

I understand what you're saying about the O2 but the O2 is not needed at startup. My car starts fine without the IAC installed but does not start with it installed. I picked up a new one today and it had a broken electrical connector. (PLAGUED!) So now I have to wait until tomorrow to replace that.
I've pulled 3 plugs and none of them are wet. The exhaust does not smell rich. It just smells like an um-emissioned car. I'll replace the TPS if the IAC doesn't fix the problem but I don't believe it to be an issue.

Viprklr

iTrader: (5)

Just a little update.

Put in the new IAC, mechanically re-timed the whole thing, and she still didn't really want to start. Sounded multitudes better though.
Still had to hold the throttle open ~20% to keep her running. Running out of ideas I swapped my prom in the ECM to a backup with slightly different tuning on it and now she runs on her own with only a little help with the throttle at startup. After she starts I can let go of the throttle and she keeps purring.

I hooked up a Snap-On scanner to it before changing the prom and noticed that I was not getting any more than 11 degrees of spark advance. Yes my wire is connected. I have yet to check the SA with the other prom.

1bad91Z

iTrader: (1)

Lower fuel pressure by a couple PSI and turn the idle adjustment screw up on the throttle body to idle it up a hair. Then reset the TPS to .54 volts with throttle blades closed. If you can get it to run in closed loop, re-tune the VE table and idle RPM vs. coolant temp table. It should run a bit better then.

What do your plugs look like?

Viprklr

iTrader: (5)

I'll give that a shot.
Closed loop will be an issue for a bit. Still need exhaust fabricated hence no 02.
My plugs were dry, black, and sooty. Of course I had a timing issue just before I pulled them out. It ran rich. Now that the timing's straightened out i'll have to re-check a plug.

Viprklr

iTrader: (5)

Little update - still has issues.
IAC is new and doing it's job
TPS is set at .54v and doing it's job smoothly through 100% throttle.
There are no vacuum leaks.
Timing is set at 8 BTDC.
I broke down and set the valve lash CompCams way.

It'll idle at 1000rpm but not below. That translates into a lot of adjustment with the idle screw. Something has to be wrong mechanically but i'm out of ideas. Maybe I am looking at strictly a prom issue now.

Hopefully my exhaust piping gets here this week so I can get it installed and start running my wbo2. That'll be when the real fun in tuning comes into play.