Some idle craziness

[1988WHTGT]

Ok, I have posted some before about this, but I have more info for everyone to help me with, ha. I'm just going to copy and paste everything that I have typed out. Just letting you know in case it sounds funny.

First what all my car has:

Stock shortblock, Edelbrock Performer RPM heads, Performer RPM cam (same specs as e-cam), Professional Products Typhoon intake, 65mm FMS TB, BBK CAI, 24lb injectors, C&L 73mm MAF (for 24lb injectors), no smog, no A/C, converted to Mass Air, Walbro 255 pump, PowerFlo fuel pressure regulator, stock fuel rails etc, BBK longtubes, stock alt, Proform e-fan, Optima red top, MSD coil, stock distributor, Tremec TKO 500, aluminum driveshaft, stock rear end with 3.55's and trickflow girdle, Tokico Illumina Adj. struts and shocks, aftermarket rear upper and lower control arms (can't remember the brand right now). Hell I dunno, there might be more.

The idle surges ALL the time. Have to hold the gas to the floor on hot starts for it to start. Anytime its running it shuts off if I don't give it gas. I've reset the idle, checked tps, IAC, timing etc all seems fine. I'm still starting to wonder if the alternator just isn't putting out enough juice to run everything.

OK, got it to idle. I pulled the vacuum hose off of the vacuum tree and plugged the hose. With no cap (just open) on the vacuum tree it idles. But if I cap the vacuum tree and the hose it surges like normal. Would that mean I have a bad vacuum tree?

OK, tried another vacuum tree...I think it may be a bad booster

I took the upper off, cleaned and resealed everything and it still does the same ####. I've sprayed all around the damn thing and haven't found anything.


I talked to my buddy that helped me build the motor this morning. He was saying with it idling right with the huge vacuum leak (hose to brake booster plugged, but brake booster spot on vacuum tree open) that it sounds like its running way too rich. Does that sound right? My fuel pressure is right around 38-40 psi. Could a ####ty O2 sensor cause a crap idle?

I've always just used Autolite 3924's (with the Edelbrock heads) and have never had a problem. What's the best gap to run them at? I'm not gonna let this car keep pissing me off. I pulled the codes last night. I only pulled them KOEO (at normal operating temp) b/c the baby was asleep. Also remember that I have no EGR or smog/emission stuff, so I know I could get some codes just for that Here's what I got:

31: EVP or PFE circuit below minimum voltage

81: Air diverter solenoid fault, intake air control circuit failure/air injection diverter

82: Air diverter solenoid circuit fault or air supercharger bypass circuit fault; integrated relay control module

85: canister purge solenoid circuit failure or adaptive fuel limit reached: lean

84: EVP/EGR/EGRV, EGR vacuum regulator circuit failure

95: Fuel pump secondary circuit fault

Code 95 is the one that stood out to me since code 85 said lean. Now wtf is the fuel pump secondary circuit? Is that the relay under the drivers seat?

Sorry it's so long, but I just wanted to get all the info out there! Any help is GREATLY appreciated!

 

[Noobz347]

I've not read your other posts but it does sound as if you're pulling unmetered air from somewhere (causing your lean code and adaptive limit code).

It also appears you have multiple problems. You're running 24lb injectors... What computer are you running? Even if your meter is supposedly "tuned" to run with computer X and 24 lb injectors, that doesn't always account for the injector slope, and/or minimum injector pulse (can cause hard starting).

I'd continue to look into the unmetered air problem first. Maybe your brake booster or whatever else is pulling vac is allowing that air into the system. Keep blocking off possible sources until you've found the culprit. You'll then need to get the thing on a Dyno or do some data logging with a wideband meter to see what's going on at startup. A tune will then be in order to make it all happy together.

 

[1988WHTGT]

I know I need to get it tuned, I just don't have the money with a baby at home and my wife not working . I have an A9P and an A9L computer. It has run fine on both of them before. It actually seems to run better on the A9P. This thing is driving me crazy!

 

[Noobz347]

Plug lines one by one and leave them plugged until you stumble onto the one that screams BINGO!

Once there, start unplugging them one by one till they're all unplugged or you find another noticable difference.

 

[larrym1961]

On your code 95, Mass air converted cars will show a 95 until you run a wire tapped into the Fuel pump relay under drivers seat. A wire spliced into the PK/BK wire (relay hot wire) to pin #19 on your ECU.
Although it does not cause a problem and will not affect the way your Mustang performs, is what I have been told by Ford Racing Tech. I just did the wiring just to eliminate the code 95, there was no differance in performance!

 

[1988WHTGT]

OK, did KOER test and got these:

13: RPM at idle out of range-low

42: HEGO (Ho2S) sensor voltage high/system rich or HEGO (Ho2S) sensor signal out of range/always rich or No O2S switching detected

92: HEGO (Ho2S) sensor voltage high/system rich

 

[Noobz347]

Those are codes that I would expect to get if there was a vac leak and the EEC was doing all it could to richen up the fuel.

 

[1988WHTGT]

Grrrr....so where is this stupid vacuum leak?! ha

 

[jrichker]

Code 42 & 92 (engine running) System rich - Fuel control or (memory) System was rich for 15 seconds or more (no HO2S switching) - Fuel control. Look for leaking injectors, fuel pressure too high, cylinder(s) not firing due to bad ignition.
Code 42 is the RH side sensor,
Code 92 is the LH side sensor.

Testing the O2 sensors
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.

There is a fuse link for the O2 sensor heater power. According to Ranchero50, it is in the wiring near the passenger side hood hinge. Measuring the voltages will give a clue if it has shorted to the O2 sensor signal lead. The O2 sensor voltage should switch between .2-.9 volt at idle.

Code 13 - Key on Engine off - ISC did not respond properly (extends to touch throttle then retracts for KOEO) – ISC

Key on Engine running - Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too high)

If your idle is above 725 RPM, the computer will set this code. Normal idle speed is 650-725 RPM. Higher than that means that someone has mechanically set the idle speed by use of the idle speed screw, and has effectively disabled to computer’s ability to control idle speed.



Do a cylinder balance test to spot misfiring plugs or stuck injectors...But first you'll need to fix the code 13. If the engine will not hold a steady 1400-1600 RPM under computer control the cylinder balance test will randomly point to different cylinders.

Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a
jumper wire or paper clip to put the computer into test mode. Start
the engine and let it go through the normal diagnostic tests, then
quickly press the throttle to the floor. The engine RPM should exceed
2500 RPM's for a brief second. The engine RPM's will increase to about
1450-1600 RPM and hold steady. The engine will shut off power to each
injector, one at a time. When it has sequenced through all 8 injectors,
it will flash 9 for everything OK, or the number of the failing cylinder
such as 2 for cylinder #2. Quickly pressing the throttle again up to
2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is
weak and isn’t putting out power like it should. See the Chilton’s Shop
manual for the complete test procedure

Here's the link to dump the computer codes with only a jumper wire
or paper clip and the check engine light, or test light or voltmeter.
I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

Do a compression test on all the cylinders.
Take special note of any cylinder that shows up as weak in the cylinder
balance test. Low compression on one of these cylinders rules out the
injectors as being the most likely cause of the problem. Look at cylinders
that fail the cylinder balance test but have good compression. These
cylinders either have a bad injector, bad spark plug or spark plug wire.
Move the wire and then the spark plug to another cylinder and run the
cylinder balance test again. If it follows the moved wire or spark plug,
you have found the problem. If the same cylinder fails the test again,
the injector is bad. If different cylinders fail the cylinder balance test,
you have ignition problems or wiring problems in the 10 pin black &
white electrical connectors located by the EGR.

How to do a compression test:
Only use a compression tester with a screw in adapter for the spark
plug hole. The other type leaks too much to get an accurate reading.
Your local auto parts store may have a compression tester to rent.
If you do mechanic work on your own car on a regular basis, it would
be a good tool to add to your collection.

With the engine warmed up, remove all spark plugs and prop the
throttle wide open, crank the engine until it the gage reading stops
increasing. On a cold engine, it will be hard to tell what's good &
what's not. Some of the recent posts have numbers ranging from
140-170 psi. If the compression is low, squirt some oil in the cylinder
and do it again – if it comes up, the rings are worn. There should be
no more than 10% difference between cylinders. Use a blow down
leak test (puts compressed air inside cylinders) on cylinders that
have more than 10% difference.

See the link to my site for details on how to build your own blow
down type compression tester.


See the "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes] for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

 

[1988WHTGT]

New update: Car idles perfectly with MAF unhooked. I drove it back to work, ha. But as I kinda figured it would do, it falls on its face at WOT.

 

[Noobz347]

So either a faulty meter or a transfer function / injector sizing is out of whack.

Disconnecting the meter will put the EEC into limp mode, but you're really not cutout many possible causes by discovering that it will idle well in that mode.

The problem can still lie with many or several other sensors considering that they're almost all ignored by the EEC in limp mode.

 

[1988WHTGT]

Yea, that's what I figured. I was just happy to hear it sit there and idle, ha.