First start bit wont idle...Need your input

[austinsnake]

First start a couple weeks ago but won't idle with no throttle.

Donor block stroked to 331, mild cam (or so I'm told), ported donor lower intake, donor intake plenum and throttle body, EGR removed/blocked off and smog stuff removed, donor black plastic air hose to Pro-M MAF calibrated to 30lb injectors, kit supplied air filter (MAF calibrated with this filter).

'87 donor harness, dieted and converted from SD to MAF. Remanufactured A9L EEC.

Timed to about 14 deg BTDC (a few ticks toward 1 o'clock if TDC is at 12 o'clock).

Several KOEO codes cleared for TAB, TAD, etc...still have 31 (EGR sensor voltage too
low...don't have the resistor ladder installed), and 95 (no fuel pump relay output fed back to the EEC...apparently something added after '87). Could either of these codes be causing the A9L EEC to have trouble at idle?

Can't keep it running long enough to pull KOER codes.

TPS adjusted at about .95V with KOEO.

Idle air bypass solenoid does NOT click/deflect with 12V applied at the pins. Perhaps this needs replaced but would this cause a non idle situation? EDIT: Fixed, now working!

Throttle adjustment screw should be where it was when I tore down the donor but can't be sure. The throttle plate is just barely closed with no throttle. How much feeler gauge should I be able to slip in there with the throttle fully closed?

Haven't tested vac pressure yet. Vac lines connected as follow under the intake plenum:

Front driver side back to PCV valve
Front pass side plugged
Rear driver side splits into three:
One to donor brake booster
Two to kit heater vac solenoid
Three to fuel pressure regulator
Rear pass side plugged

Fuel pressure comes up to about 40psi with the key on and stays above 35 or so when the engine starts and runs for a few seconds so this seems to be ok.

So...I'm thinking about the following:
1. Clear 31 and 95 KOEO codes.
2. Check vac pressure (do I just remove, say, the brake booster vac line at the booster and measure the pressure there?)
3. Replace the Idle air bypass solenoid. Edit - solenoid fixed.
4. What else?

Thanks for your inputs!

Brian

[michael everson]

Sounds like you might have a large vacuum leak. so you can get it to idle with the throttle? If so adjust the throttel stop until it idles on its own. The idle air is to make up for things like the air conditioner being turned on.

[Jeff Kleiner]

It does sound like a vaccum leak. You said "timed to about 14 BTDC". Did you verify this with a light and with the SPOUT removed? Easiest place to put a vaccum guage might be one of the plugged ports or the hose to the heater solenoid.

Good luck,
Jeff

[cozmacozmy]

"Idle air bypass solenoid does NOT click/deflect with 12V applied at the pins. Perhaps this needs replaced but would this cause a non idle situation? "

Bingo! It should deflect with 12v applied.

[austinsnake]

I cleaned up the Idle air bypass valve and solenoid and it now seems to open correctly with 12V applied.

Re-installed but with same result.

Jeff, I did have the SPOUT out and my daughter timed it with a reliable light while I ran it for a few seconds at a time (she learned a lot about engines in those 10 minutes :-)).

I'm going to find a vacuum gauge tomorrow and see what the pressure looks like.

[cozmacozmy]

Can you get the engine to run as low of a RPM as possible and then unplug the Idle air bypass valve (IAC) connector, the RPM's should drop even more if the IAC and ECM are working like they are suppose to.
Also you should be able to unplug the MAF, remove air filter, etc. to gain access to the throttle body and start the engine. In front of the throttle plate is one hole and behind the plate is the other hole. Can you feel vacuum on the front hole when running?

[austinsnake]

When I turn the key it fires right up, and I have to give it some throttle to get it to run at maybe 2000-2500 rpm. If I hold the throttle steady there it will run for 5-8 seconds and then die. This is very repeatable. If I blip the throttle while it's running it can go a few seconds longer before dying.

Where could air be leaking in?

Air filter is tight to the MAF.
Air hose is tight on the MAF and throttle body.
Hose from throttle body to oil filler tube is connected at both ends by stock looking foam like connectors. Perhaps old and too porous?
New gaskets between throttle body and plenum

EGR port blocked off with an aluminum plate and gasket sealer
Plenum to lower intake seems flush
Hoses under plenum connected as described above

Where else could leakage be coming from?

I will try unplugging the MAF, perhaps it's not properly calibrated?

Cozma, are you referring to the idle air bypass hole or a hole in the throttle plate itself?

It's a newly built engine from a reputable performance engine builder. Had several Vipers and the like being ported, rebuilt, etc in the shop. So I assume there wouldn't be anything bad going on inside.

[cozmacozmy]

The idle air bypass hole.

You didn't mention that it wont run even at 2,000 rpm for longer then 5-8 sec. that is a totally different problem then the no idle problem you started with.
What is "actual" fuel pressure AND volume? (You need volume as well as pressure)
What is the ignition doing while the engine dies out? Do yo have a "bright" blue spark that can jump a 1/2 inch or more during cranking?

Ps, a vacuum, leak on a fuel inj. engine will make the idle run high, but unless it's not a leak the size of a power brake booster or actually even larger it will still run.

[cozmacozmy]

Actual fuel pressure while the engine is running, then as it dies... added to clarify above.

[austinsnake]

Pressure stays at 35-40 while it runs for a few seconds.

[michael everson]

I would check and see if the intake gaskets were installed corectly. I have had them slip during reassembly and cause a major vac leak. While its running, spray some water where the intake and heads meet and seeif it gets sucked in. Also make sure there is nothing interfering with the upper to lower intake fit. Some upper intakes have a large vacuum tree on the underside that can interfere with certian valve covers.

[austinsnake]

Some forward progress!

I pulled off the MAF connector and it ran a bit better, and then with two turns on the throttle screw it will now idle by itself...very lumpy (perhaps normal for the cam) but steady.

I'm running red 30lb injectors and a Pro-M MAF that was calibrated for 30 lb-ers...I'll re-check my wiring into the EEC (I added this as part of the SD to MAF conversion).

Michael, thanks for the tip on the intake gaskets and water trick...I'll check this. I'm using the stock intakes and valve covers.

Ever closer!

Thanks for your continued input and support,
Brian

[cozmacozmy]

Keep working at it. My knowledge is stock only and I'm mostly a GM guy. I have never gotten into the aftermarket F.I. side of things, so I'm limited there.
The basic is what matters the most. Suck, squeeze, bang, blow, and in the correct order is what is needed.

One little trick is to use propane introduced into the throttle body while it's dying out to see if the cause is a lack of fuel.
As for checking for vacuum leaks, I use carb cleaner to spray over suspected area... just need to be careful as it is flammable and will ignite if you have spark leaking from bad plug wires,etc... If you have a leak, the carb cleaner will make the idle will increase.

Another check is to put a volt meter on the signal line of the O2 sensor(s), and make sure you have good switching from .10mv to .90mv (checked when O2's are warm)
A rich condition will have the voltage stuck high around .8-.9mv and a lean condition will have the voltage stuck low around .1-.2 mv
This is where I'm not sure what "normal" maybe due to aftermarket cams, and other parts, but it should still switch from high to low.

To see if the O2's are reading correctly if it's stuck high or low, introduce a vacuum leak if the O2 is stuck high to make it go lean, and add propane if the O2 is stuck low to make it go rich. You should get an immediate change in voltage.

[austinsnake]

I just put a vacuum gauge on the brake booster line and the vacuum pressure seems to be the culprit! Starts right up and pressure is about 20, then with no throttle, within a couple seconds it drops rapidly down to 5 or so, barely idling, and then dies. Off to find the source of the leak!

[Greg1209]

After i installed my new engine last year I chased a bad idle situation for longer than I care to admit, tps, iac, fuel pressure, fuel pump, vacuum leaks - all good. It turned out that the wire connection to the mass air meter was not pushed down as firmly as it should have been; looked good and had been off and on several times. One time, more in frustration, I really pushed on it and it went click. Idle problem solved!

Greg

[austinsnake]

Greg...I'll check that out...

[cozmacozmy]

"vacuum pressure" is an oxymoron, you can't have vacuum and pressure at the same time. Just letting you know.

In post #8 above, you never answered the question about the symptom changing, is it that I just read it wrong?

[austinsnake]

Resealed all of the vacuum connections under the plenum with RTV, same for the PCV valve, throttle body and IAC, replaced the PCV hose that had a small crack, checked all the hoses for leaks and then resealed/reinstalled the plenum.

I checked compression on a couple of cylinders and they are about 155-160. Seems right for a brand new motor. Just wanted to make sure there wasn't something going on there. I guess I should check them all to be sure.

With 2 turns on the idle screw and timing about 12-13 BTD (good and steady with the Spout out) the motor will now idle on it's own (that is progress!), but the vacuum still seems low at about 10, vs what I think should be around 20, correct? Only other place I know to check for a leak is the lower intake connection to the heads (and I suppose compression on the other 6 cylinders). Will try spraying some carb cleaner around the seam tomorrow to see if that effects anything.

Now that it runs I was able to pull KOER codes. I get the following:

22 - MAP sensor - converted from BAP, vac connection left open, stock wiring connections. Will check wiring back to the EEC.

41 & 91- left and right EGO below 0.5V - lean condition. Would this be consistent with having a vacuum leak? Will check these connections and ohm out the sensors but I assume they were working when pulled out of the running donor 3-4 years ago.

31 - EGR stuff missing with no resistors in place to fake out the EEC.

Getting closer. Seems that I likely fixed one or more vac leaks but more remain, and I need to check out the KOER codes.


Brian

[cozmacozmy]

It's hard to say what "normal" vacuum is going to be when running do to the unknown size cam you have.