Looking For Help On Surging Idle. Went Through Check List, But Still Surging.

exhaust reversion, If you run open headers, exhaust will back-track (at low rpm - low exhaust velocity) and cause 02 sensors lean at idle. in my case, I had two 1/4 inch openings at the bottom of the header flange because the entire midpipe got bent upwards.

What I think is happening is you get a column of hot air moving down the tube, the exhaust valve snaps shut and the column of air continues to move. at the tail end of the column it gets spread out like a rubber band creating a temporary vacuum. It didnt make sense to me either, but there are a lot of examples on youtube of exhaust leaks creating 02 lean conditions.
 
  • Sponsors (?)


As a master certified technician I can say it is possible. While diagnosing emission related problems I have come across it a few times. If the leak is close enough to the o2 sensor it can screw up readings.
 
I listened to the injectors and they are all clicking away nicely. BTW, they were cleaned and tested about 6 months ago, and are the 4-hole Explorer type. I already set the idle according to directions from (I think) TMoss thusly; I pulled the IAC connector, set the mechanical idle to around 6-700 adjusting the TPS to indicate .93 volts. Reconnected the IAC and the idle came up to about 800. I had previously cleaned the IAC, which wasn't very dirty to begin with. When the engine is cold, I can disconnect the IAC and the engine still runs at a lower rpm, but then disconnecting the spout makes it die. The vacuum is better since sealing the lower intake gaskets. I'm getting about 10" at the TAB now, but that still seems low for an E303 cam.

I'm no longer getting 94 and 44 codes and don't have any exhaust leaks. Hmm, where to next? Maybe I should set the idle again since I was still getting codes 94 and 44 when I set it last. Also, I may not have had the spout connector out when I did it.

What does turning on the headlights with the battery disconnected do? I did disconnect the battery for 10 minutes or more but didn't turn on the lights.
 
I listened to the injectors and they are all clicking away nicely. BTW, they were cleaned and tested about 6 months ago, and are the 4-hole Explorer type. I already set the idle according to directions from (I think) TMoss thusly; I pulled the IAC connector, set the mechanical idle to around 6-700 adjusting the TPS to indicate .93 volts. Reconnected the IAC and the idle came up to about 800. I had previously cleaned the IAC, which wasn't very dirty to begin with. When the engine is cold, I can disconnect the IAC and the engine still runs at a lower rpm, but then disconnecting the spout makes it die. The vacuum is better since sealing the lower intake gaskets. I'm getting about 10" at the TAB now, but that still seems low for an E303 cam.

I'm no longer getting 94 and 44 codes and don't have any exhaust leaks. Hmm, where to next? Maybe I should set the idle again since I was still getting codes 94 and 44 when I set it last. Also, I may not have had the spout connector out when I did it.

What does turning on the headlights with the battery disconnected do? I did disconnect the battery for 10 minutes or more but didn't turn on the lights.

You vacuum is still low, I would expect 12"-14" of vacuum at 650-750 RPM even with an E303 cam. Connect the vacuum gauge to the spare port on the vacuum tree to do vacuum testing; I don't recommend using any other vacuum source.

Use a timing light to set the timing. The engine should not die when the SPOUT is removed; that suggests that the timing is not set correctly.
Setting the timing:
Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the drivers side marks.

Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see that the marks machined into the harmonic balancer hub.

Make sure that you set he timing when the engine is up to operating temperature.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug.

Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

attachment.php




Redo the base idle set procedure as I posted it. Failure to idle with the SPOUT removed and IAC disconnected suggests that there are still basic problems with the engine that are not related to the computer or sensors.

Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks. Check for a clogged air crossover tube, where one or both sides of the tube clog with carbon.

attachment.php


Revised 21 Sep 2012 to correct the description of the process that sets the code and include Thermactor Air System diagram.

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 TAD solenoid/TAD diverter valve directs smog pump output to either the crossover tube attached to the cylinder heads or to the catalytic converters.

The O2 sensors are placed before the catalytic converters, so they do not see the extra O2 when the smog pump's output is directed to the converters or the input just before the converter.

The 44/94 code uses the O2 sensors to detect a shift in the O2 level in the exhaust. The smog pump provides extra air to the exhaust which raises the O2 level in the exhaust when the smog pump output is directed through the crossover tube.

When there is an absence of increase in the O2 levels when the TAD solenoid/TAD diverter valve directs air through the crossover tube, it detects the lower O2 level and sets the code.

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:
Note that the engine must be running to do the tests unless stated otherwise. For safety’s sake, do test preparation like loosening clamps, disconnecting hoses and connecting things to a vacuum source with the engine off.


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 following computer tests are done with the engine not running.
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. Turning the ignition to Run 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.

The following computer tests are done with the engine running.
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 with the engine running. 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

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



The computer does not use non-volatile ram to store the codes and data gathered from the adaptive learning algorithm. It uses plan old volatile ram; take away the keep alive voltage (pin #1 on the computer) and the ram is cleared. Turning on the headlights insures that any stray voltage stored in capacitors in any of the electronic equipment in the car doesn't find its way back to the computer and keep the ram powered up.
 
Last edited:
Today I checked the base timing and found it was around 10 deg. ATDC!?!? Either I was reading the marks the wrong way or it slipped because the hold down wasn't tight enough and moved when I was replacing the cap and rotor. So I put it to 10 deg. BTDC and it runs much stronger, especially at the lower rpms. I also reset the base idle with the SPOUT and IAC removed to 650 rpm (as low as it wanted to idle comfortably) and reset the TPS to .99 volts. I then disconnected the battery for 10 minutes with the lights on, turned them off and reconnected it. I ran the engine at idle for a few minutes, shut it off for a few minutes and ran it again for a few minutes with the lights, blower and brake lights on.

I am only getting 8" vacuum at the tree, so I know there's still a vacuum problem. Pulling the plug off the tree to test it didn't make a difference in the engine idling, but I could easily feel the vacuum. I pulled the connection to the check valve for the interior and it had vacuum. Plugging it made no difference in idle. When driving, if I step on the brakes a few times they get progressively weaker and harder to push.
 
Well, since I couldn't find any external vacuum leaks, I disconnected the hoses from the intake and blocked the ports, hooked up the vacuum gauge to the PCV hose, blocked the little air hole in the throttle butterfly, plugged the PCV valve hole in the block, and turned the engine over with a remote starter button. Result? ZERO vacuum. It would appear I still have an internal vacuum leak, which would explain the performance (lack thereof) and the fact that I can't hear or find any leaks. Did I do this test right? Miss anything that would cause lack of vacuum? Maybe the starter isn't turning fast enough? I'll pull the upper intake off, removing as few other parts as possible, stick a hose down the lower intake ports and listen for air leaking with the crankcase pressurized again. Any other suggestions?
 
After much thought and research I think I've found the problem. Reading an article in Mustang 360 I found this: "Expect a 112 or possibly wider figure on cams for computer-controlled 5.0 engines. Any less and there isn't enough vacuum at idle to accurately signal the computer, and the idle control goes haywire." That's what I was afraid of. The E303 has only 110 degrees lobe separation. I'm buying a new cam. Anyone want a barely used E303?

Read more: The Right Camshaft For Your Ford Mustang - 5.0 Mustang & Super Fords Magazine
Follow us: @ModMustangs on Twitter | ModMustangsandFords on Facebook
 
Plenty of guys running E303 camshafts in EFI cars with success.
Lucky for them. Maybe not degreeing the cam was a factor. I could see how some might be spot-on and others not idle well due to timing. I still want to go with something with more LSA for low end torque and fuel economy. My understanding is the E303 works better for 5 speeds, not my AOD.
 
I talked with someone briefly at Comp and he recommended the XE260,
He must have meant the XE264 as there is no XE260 for SBF. That number is for a Harley. So I just ordered my XE264HR, P/N 35-349-8. The wider LSA will give me the performance, smooth idle, vacuum and fuel economy I'm looking for. I did a lot of reading and research before pulling the trigger - something I should have done before.
 
[QUOTE="cobranger, post: 8916626, member: 203094" I just ordered my XE264HR, P/N 35-349-8.]
Installed with engine in car. I lifted the lifters out of the way with magnets. Total time about 10 hours. Gasket scraping was probably the hardest part.
 
Last edited:
So many times you read these threads and the OP fixes his issue and never shows up again. Well I fixed it and want to share my experience for anyone else who may run into this problem. The E303 cam is for racing. It is not a good street cam, at least not in my case. I just got the Comp cam in and it runs great. Pulls hard at all rpm and just passed California smog. If any weekend racers want a gently used E303 cam just PM me.
 
So many times you read these threads and the OP fixes his issue and never shows up again. Well I fixed it and want to share my experience for anyone else who may run into this problem. The E303 cam is for racing. It is not a good street cam, at least not in my case. I just got the Comp cam in and it runs great. Pulls hard at all rpm and just passed California smog. If any weekend racers want a gently used E303 cam just PM me.
Thank you for your reply, it helps all of us when we encounter odd problem. I have heard that the Ford letter cams were outdated and that there are many better aftermarket alternatives. Yours is one more voice to add to that group.
 
I don't run a E303 cam ...i run a stage 1 cam but i know a lot of people that do run ford letter cams without any problems. I had the same problems as you years ago with surge and bucking...and that's with a trick flow cam. So i think the cam is not the problem i think that the computer is getting bad signals from weak or bad sensors. My problem turn out to be the bap sensor and ect sensor and i didn't get one code from the computer besides code 11.
 
I don't run a E303 cam ...i run a stage 1 cam but i know a lot of people that do run ford letter cams without any problems. I had the same problems as you years ago with surge and bucking...and that's with a trick flow cam. So i think the cam is not the problem i think that the computer is getting bad signals from weak or bad sensors. My problem turn out to be the bap sensor and ect sensor and i didn't get one code from the computer besides code 11.
After all the smoke testing, sensor checking and adjusting for best performance, the ONLY thing I did was change the cam from one with 110 degrees LSA to one with 114 degrees LSA. I could have run the E303 with a rough idle and bad gas mileage and I'm sure people do, but I improved my performance significantly with this one change. My computer is working fine. Passing CA smog test is proof that the system works well together. The overlap on the E303 reduces the intake vacuum to the point where the power brakes fade out. It runs great at high rpm, which it was designed for...racing. With the 114 LSA, I have plenty of vacuum and the profile gives me more power at all rpms.