alexdimen

iTrader: (13)

So, i'm having some idle issues. Namely, low idle with lights, fans, accessories on. The idle holds steady no matter the RPM, but can go down too low with high load and the engine stalls.

I'm suspecting my TB screws need adjustment and so does my TPS. Here's my problem:

In the manual under "throttle body", all it has is the TPS adjustment, fast idle cam adjustment (aka thermowax), and the ISC solenoid test.

Where can I find the specs on setting:

-The screws on the front of the TB for the primary/secondary plates. (I fiddled with them and want to get it back to normal)

-The air bleed screw.

Also, what does each of these do? Which should I be messing with to set my idle and in what order?

Eggie

Chuck Westbrook's PFC notes package has a very informative section on throttle-body setup. Or you could just open the bleed screw 1-2 turns.

alexdimen

iTrader: (13)

Are those notes purchase only? I don't think I could justify buying them since I don't have a PFC...

Am I right that the 3rd gen FSM doesn't have a section about setting up the throttle plates, etc? The 2nd gen manual tells you exactly how to clearance the double throttle valves/plates and everything...

wstrohm

FWIW, my experience has been that the secondary throttle stop screw should be adjusted so that it is closed almost fully, but not enough that there is an initial stickyness when manually opening it. That will let a little air by, but it can be compensated by closing the primary throttle butterfly using its stop screw. I would set the air bypass screw out about one-two turns, then set the other two adjustments as above for a 720 rpm idle. Fine adjust per the air bypass screw. Adjustment is correct when you cannot hear a change in idle speed between having the TEN-GND jumper in and having it out. Not until after that is done would I adjust the TPS, since it is definitely affected by the throttle stop screw adjustment.

alexdimen

iTrader: (13)

I'll give that a shot. Thanks alot.

alexdimen

iTrader: (13)

Well, the TPS narrow range reads WOT (5 volts) all the time. Probably why the car suddenly started idling/starting like ****... replacement on the way.

alexdimen

iTrader: (13)

I put in a good TPS and set it up properly.

Then I found out my leading coil was flaky and just replaced the leading coil along with a new ignition harness and new leading plug wires. Spark is now solid.

BUT....

The engine is still hard to start. Sometimes it barely gets going and other times it's so bad that I need to use my fuel cut switch.

It's also impossible to set an idle on it. It seems like whenever I get it set it changes after driving it.

Then, whenever the fans come on it drops and stalls out.

At one point tonight I had it set at 1k rpm, the fans came on and it stayed at 1k. Then, I cut out the parking lights (which I had on at the time) and the RPM's drop and the engine stalls.

wstrohm

Normally the ECU (sorry, PCME) controls the Idle Air Control Valve with a series of pulses, whose width is modulated according to the feedback from the Tach signal. If you have set the idle with a jumper between "TEN" and "GND" in the Diagnostic Connector, with all electrical accessories (like A/C, lights, etc.) OFF, and engine fully warm, as I wrote above, then the PCME should act to hold the idle speed constant when you add alternator load. (The idle speed should rise some when the A/C compressor cycles on.) I'm guessing here, but if the engine stalls when you turn OFF the parking lights, most likely there is a ground return problem somewhere that is affecting operation of the ECU.

alexdimen

iTrader: (13)

When you say ground return problem somewhere, do you mean in the engine harness?

I'm not familiar with the term "ground return" either. Is that like saying there is a damaged negative wire on a component?

wstrohm

Could be a bad ground wire in the harness, but more likely a corroded or loose connection at a chassis ground point. By "ground return" I was referring to the whole path from the PCME's's connector(s), through one or more of its wires going to chassis ground, to the chassis itself.

In looking through my '94's factory manual, on page Z-30 I came across a unit called an "Electrical Load Control Unit." It apparently reads the position of the combination switch on the steering column (parking/headlights), the HVAC rotary switch (A/C, heater fan, etc), and the condition of "CPU #1" (a pot full of various electrical loads). It also has two interfaces with the PCME: terminal 1F and terminal 3B. I presume one of these is telling the PCME how to adjust its idle speed based on electrical load. The "ELCU" box is located under the cover panel for the PCME against the right side of the passenger cabin, and its connector is black ("B1-20"). The box's ground return wire is a black wire in that connector terminal "M," and goes to chassis at ground point #7. Ground point 7 is up high behind the dash, sorta behind the instrument cluster. (See pix of pages Z-30 and Z-31 of the 1994 FWM attached.)

alexdimen

iTrader: (13)

Wow, I didn't even know there was such a thing as an ELCU. I'll have to look into that.

That said, I really feel that my idle problem is related to the hard start problem, since they occured simultaneously and without provocation. I hadn't worked on the car recently when it started to happen. It was just hard to start one day and idled way low when stopped.

I doubt the harness or ground points are faulty. The engine harness was stripped, inspected and re-wrapped (after a few minor repairs, such as the oil level wire, etc). The engine bay part of the engine harness was also removed and re-wrapped.

I fiddled with the idle today and have it hanging around 1000 rpm no matter what. It's still nowhere near perfect.

The prolbem I have with idle now is right after I start it up. It's still hard to start and has a very low idle once it gets going. I have to bring it up with the accel pedal and then it stays up.

When starting, I have to turn it over with the my fuel cut off, then turn the fuel pump on once it catches.

FWIW, I've got my cut switch in-line with one of the coil wires on the circuit opening relay.

The injectors were cleaned and tested during the rebuild ~1500 miles ago, but I'm going to do a leak-down pressure check on the fuel system anyways. I'll also do a compression test... I'm almost afraid to, but the car runs and pulls hard.

wstrohm

Are the two cold-running idle speed adjust screws (on the firewall side of the throttle body) set up per the manual, i.e. the screw that sets the throttle opening by its position on the marked "cam," and the one next to it that sets at what coolant temperature the first screw drops off the cam?

alexdimen

iTrader: (13)

Actually, I didn't even mess with those... but I know what you're talking about. I've actually read through that section in the manual several times.

The only screws that I changed were:

air bleed
secondary plates adjust
primary plate adjust

...and I think I can still figure out where the plate adjustments were originally from the original paint marks.

I will spec out and adjust those rear screws if the compression and fuel pressure tests go well.


Edit:
Oh, and I almost forgot to mention I've been hearing this intermittent sound at idle and sometimes right after startup. It almost sounds like rattling or air bubbling from behind the dash, but I realized it may be on the other side of the firewall. Could it be the ISC solenoid/valve rattling? What happens when I unplug that solenoid connector?

alexdimen

iTrader: (13)

Fuel pressure test:

~38 psi and held above 20 psi for 5 minutes with pump off

...but while the pump was jumpered, I could hear fuel rushing/spraying from the injector area. It sounded as though an injector was spraying or fuel was flowing. Is that normal? Sounds like it may be the FPR also...

Compression test:

rear rotor: 110 psi with valve closed, even sweeps with valve open

front rotor: 75 psi with valve closed, even sweeps with valve open

I tried the front rotor a second time after squirting some 2-stroke oil in the plug hole and it got to just about 110 psi. Even sweeps again.

alexdimen

iTrader: (13)

Ok, I just got it running and put the vacuum gauge on it.

Not good... the ****** didn't even pull 10 inches of mercury. It pulled 19 inches right after I built it.

The beer drinking starts riiiiight... NOW.