Help me create the "Surging Idle Checklist"

Go back to the first 2 entries in this post on page #1 and read them through. Dump the codes, fix whatever codes come up, then work your way through the checklist. Since I can't be there to see and hear exactly what you problem is, the checklist contains a lot of steps to eliminate the most common problems.

This is my first post, but I have been reading the forums for the past couple of months. I recently purchased an 89 5.0 Texas HP. The car has all of the upgrades to pass California smog regulations (just passed last week). The car had BBK heads, BBK intake, BBK throttle body, BBK headers, and an upgraded cam when I purchased it, and I think that is it.

The car drives great and it starts up with no problems. The issue is when I come to a stop and downshift, the car will stall or start to surge and then stall. If I come to a stop and not downshift, the car will idle around 1100 RPMs for a couple of seconds and then settle at 900.

I have run the codes and everything is good for both KOEO or KOER. Here is a list of the items I have taken care of so far:

1. Replaced the IAC
2. Replaced the TPS and set to 1.03
3. Looked numerous times for vacuum leaks and replaced/repaired anything suspicious. ( although, I feel like this is the culprit)
4. Replaced both O2 sensors.
5. Voltage above 13.8 at 1000 RPMs
6. 10 pin wiring connectors look OK
7. The MAF looks clean. The Sensor area is clean as well as the sensor.
8. Air filter is in the wheel well area.
9. Replaced the fuel filter.
10. Checked the grounding wires and they all seem good.
11. Didn’t get any codes for these
12. Have not checked yet
13. these two are the same
14. VSS sensor defective or wiring damaged. – Replaced the sensor.
15. Replaced the EGR valve
16. Need to check, but had it checked when I first bought the car and had it Dyno tuned, which didn’t help the stalling issue.
17. No black smoke.

I’ve tried to set the base idle, which is difficult with the cam, but I followed the instructions best I could. I have reset the computer after each item was replaced. I removed the IAC adjustment plate, only because many in the forum said it is not needed. My throttle body is clean.

Not sure what else to do.

HD

Update: I do not need to be driving and gets worse when warm.
HD

Is this car an auto or 5 speed trans? Check the door sticker code and see, since most HP came with an auto trans. Code TR points to the transmission type. AT indicates an auto trans, 2 indicates a 5 speed. See http://www.mustanggt.org/forms/89decode.htm#door for more help.

TR says "2". And it is a 5 speed.

Remove the passenger side kick panel, and remove the 2 screws that hold the nylon strap that mounts the computer. Check the part numbers on the end of the computer. The proper number for a 5 speed computer is A9L. The A9P computer is for auto trans cars, and has diffferent programming for the slow to a stop situation. The A9L causes a noticeable increase in RPM as the car slows to a stop. This "dashpot" effect keeps the car from stalling when you slow to a stop.

Just took my salt and pepper 10 pin extensions out. Had to break all clips then they slide apart.didnt run well without the extensions. Put extensions back in and runs great. If factory recalled and added these this must be the reason.

I'm pretty sure my computer is giving no code.My bolt ons include 75mmBBK tb and C.A.I. also bbk 76mm mass air calibrated 19lbs.bbk headers off road h-pipe and flowmaster exhaust. march underpulley ,all emissions removed including smog pump,egr delete,
I also encountered the surge idle dragons. changed tps and solved the problem. also rpms didnt drop immediatley when shifting and seemed to stick around 2,,200rpm changed iac and throttle cable fixed problem. Now with all my bolt ons and emissions removal this 90 lx vert is running incredible........i just lined up next to a souped up monte carlo in my little home town blew his doors off...i seem to be getting decent milage. Finally with a computer giving no code not even an 11. How is it my stang running so well with out the ecm functioning.

No code 11 (two flashes when the computer dumps the codes)? The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.

surge and idle issues were solved by a tps.also idle didnt drop when shifting and wanted to cruise at 2,000 rpm that was i.a.c....also replaced accelerator cable . havent had idle issues,or the crusing sticking or any of those problems. when i changed acc cable it helped but then i homed in on the i.a.c. the one i got whistles but seems to work well. i'm a backyard mechanic but plugs,wires,and vacuum leak could cause idle and surge issues. this post really helped me thanks guys. getting my 89 hatchback out of body shop in a few days.

it just had a solid tone was a actron i believe i borrowed it so i dont have it now. stang runs great no check engine light. if i unplug maf or iac run noticeably worse. so can i assume my ecu works. i get it checked again . i will try your bypass method with test light since i dont think my check engine light fucntions.thanks

sorry it took me so long to get back.my 90 doesnt have the red /white wire to run test. i found another that looks like it but its by the starter relay like a foot away. that looks like test port but has two blck/white wires going in its live. I'm getting my 89 lx out of shop tomorrow . i will run check on that.

i did have a question?? if my emissions are removed and unplugged ,will i be able to get codes or is that a factor?
and on the 90 i will need to make a test cable .just have to find that wire.wierd that test wire down by the relay do you know what it for?

Missing emissions equpment will not prevent the code dump from working. The missing or non functional equipment will set a bunch of different codes.

Removing the pollution control equipment from a 5.0 Mustang is a bad idea. All you have accomplished is to make the computer mad and spit codes. The pollution control equipment all shuts off at wide open throttle, so the HP losses from it on the car are 2-5 HP. The catalytic converters may soak a few more HP than that. None of the pollution control equipment reduces the HP enough to cost you a race in anything but professional drag strip competition. I seriously doubt that you will be in the final runoff on “Pinks”, so leave the smog equipment in place and make sure it is working correctly.

Know what does what before removing it. Remove or disable the wrong thing and the computer sets the check engine light and runs in "limp mode". Limp mode means reduced power and fuel economy.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by James Probst :ISBN 0-8376-0301-3.

It's about $20-$45 from Borders.com see http://www.amazon.com/ . Select boo...le to check cars, but it is still Federal law.

Hey whats up back with codes on my 89lx 5.0 hatchback. koeoff 11... keeon got 94,44,33....cats and smog pump removed but cannister and sensor as well as egr sensor and water lines hooked up. should i dump the codes ?or will it matter?
wasnt able to find test wire on my 90. not sure where wire is will try to find it when i get time. the 90 has all emision sensors removed and unplugged,

Any advice for my configuraton. both cars had off road h-pipe when i bought them.i removed the pumps,but i figured they werent functioning.

check engine light isnt on in either car .

There may be codes present in the computer and the check engine light isn't on. The only way you can ever know is to dump the codes. If you don't get an 11 (Key On, Engine Off) and another 11 (Key On, Engine Running), you have problems.

okay got a 11 with koeoff and got a 94,44,33 for koeon.emission sensors are still plugged in and vacuum lines in tact but smog pump and cats were deleted. should i dump these codes or will it matter. this is on my 89lx auto. i still havent found wire on the 90lx vert 5spd im assuming it will throw more codes since the egr sensor and cannister sensors were deleted,vacuum lines capped.throttle body has egr delete plate. i'm sorry i don't mean to waste your time off topic. the 90 has no test wire .any tips on a jumper or a place to splice in. note both cars run great. a/c in 89. hey jrichker thanks in advance for any help. I feel like i'm cheating but short on time. i will try to research the books you suggested . learning efi slowly. I try to do all my own repairs and maintainence. Its nice to get some tips ,thanks.

Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

Revised 28-Oct-2009 to correct code definitions and operation.

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them

Code 44 RH side air not functioning.
Code 94 LH side air not functioning.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them


Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal flickers. Remember that the computer does not source any power, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1.5 ohm.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif


EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.

connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connnect the test jig or to directly to manifold vacuum.

Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).

apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

if engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
Use your finger to cap the open port on the vacuum tee.
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 2-5 in vacuum?
if not the EVR has failed

EGR test jig


The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.