[GTOreturns]

Why isn't this thread a sticky anymore?

[jrichker]

Originally Posted by GTOReturns

Why isn't this thread a sticky anymore?

It is.

See Daggar's sticky of all sticky's " Useful Technical Thead Index" at the top of the 5.0 Tech form. Inside are all sorts of great tech notes and upgrade information. I think this method of collecting all the good tech notes in one place s a great idea.

[zlyles]

I'm gonna go out on a limb here, and sound stupid for a minute. is the IAC and IAB the exact same part? All through these posts I've heard people referring to cleaning the IAC in one post and cleaning the IAB in another post, one person saying the IAC is the thing on the front of throttle body with wires, and the picture labeling that same part as IAB. So, yeah I'm a little confused.

Zak

[jrichker]

Originally Posted by zlyles

I'm gonna go out on a limb here, and sound stupid for a minute. is the IAC and IAB the exact same part? All through these posts I've heard people referring to cleaning the IAC in one post and cleaning the IAB in another post, one person saying the IAC is the thing on the front of throttle body with wires, and the picture labeling that same part as IAB. So, yeah I'm a little confused.

Zak

The IAB and IAC are the exact same part.

Ford changed what they called it sometime in the early 90's. It did not change the part or its function, just the name to conform to the emerging SAE standard for all motor vehicles.

[jrichker]

Originally Posted by jrichker

The IAB and IAC are the exact same part.

Ford changed what they called it sometime in the early 90's. It did not change the part or its function, just the name to conform to the emerging SAE standard for all motor vehicles.

Be sure you read the very first two posts in this tech note. That's where all the tests and fixes are posted.

[zlyles]

From my original post at:
http://forums.stangnet.com/showthread.php?t=736443

Originally Posted by zlyles

I have an 89 5.0. Up till recently it ran and idled great. It still idles great. My problem is, once it warms up, sometimes it will stall every time you take your foot off the gas. I can crank it right back up no problem as long as my foot is on the gas while cranking, and it will stall out again, OR I will rev it as it tries to stall, and it will idle at about 1500 RPM's for about 10 seconds and then stall all over again. If i start driving it's just fine, and the very next light i stop at, it will idle perfectly. Sometimes while driving my check engine light will flick on for a second and turn off, however, when it was hooked up to a scanner, it showed no error codes, I even ran it long enough for the light to flicker and it still gave no codes.

Any ideas?

Thanks,

Zak

After being directed here by jrichker, I went through about 7 of the steps, at which point i got bored and went to something else... my hideous cooling fan wiring harness. This consisted of a generic fan wiring harness from advance auto, and an additional 5 prong relay. Being as I have a 2 speed fan from the late model 4.6L, it was running low speed based on the thermometer lodged in the radiator fins, and flipping on high speed with the A/C. Wires were all over the place, and ugly colors too, so I did some cleanup work and also wanted my low speed to run constantly when engine is on. I ripped out the harness and wired my own setup with two 5 prong relays. I was able to unscrew the ground screw for my high speed relay by hand with a socket. After the rewire, my car has not stalled once while running with or without the A/C on. Apparently the sloppy ground for my A/C relay was the cause.

I still have a problem I've had pretty much since I bought the car. Very frequently after the car warms up, I can turn it off, and when I crank it back up it has idle problems and will stall. After I re-crank, and give it gas for a bit(10-15 seconds) the idle will smooth out and run on it's own. Any ideas? I've already cleaned my TB, IAC, MAF, Air Filter, replaced fuel filter, and I'm about to go pick up a brand new IAC from the dealership.

Thanks,

Zak

[mustangfan1990]

Mine surges bad too, Mine is a S/C car. Since I installed the S/C it doesnt want to idle It will idle like at 500 RPMS till either I rev it up and it will hang up there for a few seconds and then fall and die OR it will idle at 500 then die either way DIES any suggestions, I read the list and the only thing I havent tried is the elbow that goes to the S/C but I have a power pipe that replaces that elbow

[jrichker]

Try clocking the MAF (rotating the MAF housing). Sometimes that helps place the MAF sensor inlet in smoother flowing air so that it gets better airflow and makes more accurate readings.

[mustangfan1990]

Originally Posted by jrichker

Try clocking the MAF (rotating the MAF housing). Sometimes that helps place the MAF sensor inlet in smoother flowing air so that it gets better airflow and makes more accurate readings.

ok I will try that...also the car just started poping at idle every few seconds , sounds like in the exhaust, could this be the culprit of the idle or is it running lean at idle

[mustangfan1990]

bump

[jrichker]

What did you get when you dumped the codes?

[98BLKGT]

I have a surging idle for the first two minutes when the engine is cold. (No surge in temps above 80) Had that since buying the car.
From your list, the only steps that list cold idle problems are the IAC and base timing. Are there any other things I am missing in regards to a cold idle only? I have an F cam and I'm starting to think it may be a rich/lean condition that may need a tune for open loop.
(BTW new IAC, air/water temp sensors, and 12* timing, some backfiring into the intake under load only if engine very cold)

[87coupe50]

If your having crazy issues with your throttle sticking or idle staying higher than what it's set at, try loosening the 2 TPS screws a little.
EDIT: maybe that wasn't my entire fix! also check your throttle plate screws to make sure they haven't loosened and when you tighten them MAKE SURE your throttle blade is not binding with the throttle bore!

History: I have been hunting down my intermitent sticky throttle/high idle problem for about a month now, since I bought the car. The car seemed alright but ran very rich. Thanks to this forum I figured out how to dump the codes and found out that I needed a to adjust the TPS because it was out of range. It first measured .002. I did some adjustments but could only get it to .68 even after widening the holes with the dremel. That's when it started: intermitent sticky throttle/high idle (what I mean by this is RPM's would stay at the RPM it was when I pushed in the clutch or drop very slowly, put it in gear and the car would increase speed with out me touching the gas, idle wouldn't return to to base while stopped at a light - sometimes 1200/ most of the time 1800, seemed like the idle was possesed and did what ever it wanted to). I would try different things: clean TB, IAC, MAF, Filter, new TPS and kept checking range after I did different things, base idle adjustments, even found 2 vacuum leaks - one on a broken vacuum cap and another on the bypass tube for the supercharger (boost is great now!) All these things seemed to help a little but the problem would keep coming back, sometimes better sometimes worse. Codes were always: 15 - SCT chip causes this, 85 - CANP not connected/ smog removed, 95 = Fuel pump briefly lost power or something like that.

I was reseting the base idle at 900 and after I did I readjusted the TPS, disconnected the battery and reconnected the IAC. When I started the car back up I let it idle for about 2 minutes to start relearning and the idle wouldn't drop below 1200. Maybe it just needed more time to learn -so I went out for a little ride. It was a little better but still wasn't right. When I got home I grabbed the throttle linkage with my hand and could slightly move it back - idle would drop right back to 900. Flipped the throttle and again it stuck around 1200 and would not drop on its own. Something had to be sticking! WTF!! I've already rerouted the throttle cable, checked the throttle plate when I was cleaning it, everything! I loosened the 2 TPS screws a quarter turn thinking maybe they are binding the throttle plate and the idle went right back to base idle. Flicked the throttle and right back to base idle. Took it out for a ride - perfect! Maybe the aftermarket TPS's are a little bigger than factory?

[Dan02gt]

My dad picked up a well used '91 GT a year or so ago. The car had 169K miles on it and had idle issues. Mainly high idle, we did a 10 minute tune up and set the timing. This fixed a few issues but not the high idle so I turned my attention to the IAC. It had a ton of carbon and gunk in it so we tried to clean it with the normal spray methods to no avail. The valve just would not seal due to all the buildup.

I said what the hell let's take it apart and clean the plunger and seat. We found out that the metal end cap does nothing but keep you from taking it apart. We cut 2 small slits in the cap 180* apart to allow it to easily be removed like a bottle cap. Underneath metal cap it a plastic cap that screws in, unscrew it with a pair of needle nose pliers. You can then remove the plunger and cleanup everything good as new. If you don't mess up the metal cap too bad you can put it back on so it looks like its never be messed with.

[Ryno8705]

I have something to add to #16 but I have to give a brief background of my surging. My car is a 1994 5.0 GT with simple bolt ons and a full MAC 2 1/2" exhaust with shorty headers. I had a bad surging idle problem until I replaced my IAC (or IAB) sensor. After the IAC replacement I had an intermittent surge that I could correct simply by revving it once (tap the gas and it would calm right down). Then while fixing something else I realized timing was at 8*... I bumped it up to 12*(running 89 octane) and I have not had any sort of surging since.

I think 8* isn't enough and 10* should be the minimum. My car ran much better and sounded smoother after only changing the timing from 8* to 12*. I'm sure 10* would have done almost the same thing because that's what they were set with from the factory, but I went straight to 12*.

[keithnra]

just gettin in on the great info.

[dragin92gt]

good stuff

[sidewayzgt23]

This is a great thread! My only problem is that it has grown so big that I am getting mixed up on what to try next. Can somebody please direct me in the correct direction on what to try? I have a 94 GT with a 306ci, AFR 185's and a stage 3 cam (kinda big). When the car is idling correctly it is at 900 RPM. Lately on cold starts it surges between 900 and 1100 RPM for about 15 seconds and then idles correctly. I give the car about 1 minute to warm up and then take off. When I put the car into gear and take off it wants to stall by idling low. By the time I get down the block it is fine. The car will idle fine for 5 minutes of stop and go and then start to act up when it is warm. Then the idle will surge at 900 then 1100 then 700 and lower and lower until it stalls on me (It never surges over 1100 RPM). I did recently replace the IAC. Was I supposed to reset anything when doing that? Any suggestions?

[jrichker]

The first two posts contain all the fixes, so you don't need to read the whole thing to fix your problem fix.

A word about the checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work your way down. Jumping around will possibly cause you to miss just what you need to see to find and fix the problem. Don’t skip any steps because the next step depends on the last step working correctly. [/b]

[keithnra]

printer not working so subn

[93 teal terror]

Just wanted to add, I purchased the scanner from the link in the first post and they sent me part # 3149 which is the extension cable and is the same price. Called them and told them what happened, they have a new package in transit. Couldn't ask for better customer service

"Or for a nicer scanner see EQUUS DIGITAL FORD CODE READER (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30."

[Red9250]

Just thought I would add:

When troubleshooting the O2 sensor ground you may need to run a ground strap from your h-pipe to the body to get a good ground. The O2 sensors ground through the h-pipe then through the headers to the engine.

My stock headers and h-pipe wouldn't give my O2 sensors a good ground path resulting in codes 41 and 91. I tried almost everything I could think of to fix the codes. As a last resort, I installed the ground strap from a bolt on the h-pipe to the body and the codes went away. Its been about 2 years and I haven't seen a CE light.

[Black1987Stang]

Originally Posted by Red9250

Just thought I would add:

When troubleshooting the O2 sensor ground you may need to run a ground strap from your h-pipe to the body to get a good ground. The O2 sensors ground through the h-pipe then through the headers to the engine.

My stock headers and h-pipe wouldn't give my O2 sensors a good ground path resulting in codes 41 and 91. I tried almost everything I could think of to fix the codes. As a last resort, I installed the ground strap from a bolt on the h-pipe to the body and the codes went away. Its been about 2 years and I haven't seen a CE light.

Good idea, most people wouldn't think of it

[jrichker]

Originally Posted by Red9250

Just thought I would add:

When troubleshooting the O2 sensor ground you may need to run a ground strap from your h-pipe to the body to get a good ground. The O2 sensors ground through the h-pipe then through the headers to the engine.

My stock headers and h-pipe wouldn't give my O2 sensors a good ground path resulting in codes 41 and 91. I tried almost everything I could think of to fix the codes. As a last resort, I installed the ground strap from a bolt on the h-pipe to the body and the codes went away. Its been about 2 years and I haven't seen a CE light.

The standard O2 sensor ground is an orange wire that comes out of the engine mounted fuel injector wiring harness. Ground it to either the back of the cylinder head or one of the intake manifold bolts. The 4 cylinder O2 sensors are 4 wire and will fit in a 5.0, but they do not use the same grounding method. The 4 cylinder O2 sensor harness is also different from the 5.0 harness.

An extra ground is OK, but the stock one should work just fine. Make sure the secondary power ground from the intake manifold to the body isn't loose, damaged or missing. it provides the ground for the alternator, gauges and A/C compressor clutch.

[jcm-3]

Great thread. I'm new over here, and don't remember if I saw a link from another Mustang forum or not, but great thread.

I have been fighting with some idle and throttle issues for some time now. (as alot of us have) Recently, it started when I went to a new tuner and he reset my tune. At that time, I had also made some fuel system changes, but the idle issues didn't really happen until the tune was reset.

We were trying to fix a long-time fuel lean condition above 5500 rpm, and ended up fixing it by making a few fuel system changes: replaced the GSS307/T-Rex combo with a GSS340 (ditched the T-Rex), swapped out the 42's with 60's, and added a Kenne Bell Boost-a-Pump.

I had an old Autologic chip, which doesn't have alot of tuning parameters. So, I upgraded to a newer chip, and my tuner spent alot of time trying to get the issues resolved. It had a high idle, was hanging way up during shifts, surged a bit, and was very slow to come down. But, if I put the clutch in, then it would come down. Very frustrating especially considering that we had finally figured out my top end lean condition.

Here's what I did:
Fixed my grounds - I had relocated my battery to the trunk, and the gound was connected back there to the chassis. I had also hid my wires, had the computer ground connected to a spot under the fender liner, and the screw was loose. ^%$#@!~ I ran a new ground wire from the battery to the tranny, and also extended the computer ground to that same spot on the tranny so it is in contact with a ground wire coming directly from the battery.

Did the base idle reset - I have always experienced that when I did the base idle reset (Ford Mustang Base Idle Reset), as soon as I reconnected the IAC, the idle would go up a few hundred rpm. And, since my idle was high lately, even after doing it, I decided to set it very low with the IAC disconnected. I set it to about 500, and then used the idle bypass plate to raise it a little bit so that it would keep an idle. When I reconnected the IAC, it went up, and is now around 850-900 or so. The custom cam doesn't seem to like stock idle rpm, so that is about as low as I can go.

Reset the tps - which is, of course, required after resetting the idle. I was only able to get it to about .93 volts without elongating the holes, but after tens of hours of research on this in the past should be fine.

Cleaned the 10-pin connectors - Ford Fuel Injection 10-pin Connector Fix Nothing to add here

Used the idle bypass plate - I know that alot of people think this is a band aid, and it probably is. But, I spent ALOT of time tweaking the allen screw with this after the above things, and have it idleing very nicely now! It is actually a pleasure to drive, doesn't die, the idle comes down nicely when driving, and it idles great at a stoplight. I think this is what really helped, as it still had alot of surging and would die even after the other things listed above.


The car is a joy to drive again. I haven't been driving it much because it was annoying to drive with the hanging idle.

Sorry for the book.