Help me create the "Surging Idle Checklist"

Signs of vacuum leak?

I noticed on my car the other day that the seam between the throttlebody and the EGR spacers has what looks like a fine layer of carbon like it's seeping out from the inside. Wierd. I don't recall it ever having that before and I have never had the throttle body off the car. Last week it idled at like 650 or 700rpm (sounded mean BTW) and then the next morning it ran like garbage at start up and then once warm it surged slightly.

I have a slight, ocassional surge and I've checked/cleaned everything. Gotta look at the grounding and check for vacum leaks though. Neither of thoe occured to me before.

My car has a B303 cam. If I turn on the A/C it surges worse and more often. AT cold start up it idles ok for maybe 30 seconds then it stumbles and coughes and then the idle jumps to like 800rpm and then it starts to settle and idles past 650-700 and stumbles and coughes again. It repeats this cycle till it either stalls or gets warm enough to run correctly with the occassional slight surge.

Any one have any suggestions?

I tried everything on the list but guess what worked??

I had an idle of 1500rpm. And an occasional surge. Stayed that way until I disconnected the throttle cable! Idled right down!!

I pulled the cable backwards out throught he maze of vacuum lines and rerouted it in a nice sweeping way...

Perfect idle. No surge. No 1500rpm. Bliss!

I tried everything on the list but guess what worked??

Just had full exhaust installed and a clutch. Boy. Like a new car! REALLY wants to go now! I keep running out of road!

With my 89 conv i had a horrable surgeing idel after i did some mods to the motor!i put a e-303 cam 1.7 rockers,trick flow intake dynomax headers and some more stuff it was 5 years ago so i dont remember but i had a horrabile problem!! I thought about it and put a 2600 stall converter in my AOD and that fixed it! and after a few years i got sick of blowin out AOD`s.I put a crap t5 in it and at low speeds i do get a surging problem! but now i just let out my clutch!

hey guys this is zeus for those who have forgot me i am finally back after an extremely harsh winter up until now.
anyways i am looking at completely going through the stang checking everything to see if it works etc. i bought the car with and s-trim an a lot of other mods i am not a mechanic and dont know a whole lot about how to fix cars but i know that my car hasnt been healthy for a while, example i get 7 1/2 miles to the gallon and i am fairly conservative with the gas. my idle has always been a problem along with the motor dying after hard stops at lights or anything, i dont know where the MAF is please someone help me out. also what should i do to make sure that my car is healthy what should i check and how etc. with hissin and Jrichker i figured that i was asking the guru's. please someone help i want my stang running strong but i need some help from you to help suggest what to do to check and fix it

thanks
(im glad im finally back)

1st, a suggestion: dirty fuel pump sock (filter). I replaced mine when upgrading my pump (it was BLACK), and instant "smooth-as-glass" idle...

Second, a question: to clean the 10 pin connectors, what should I use?
Electrical contact spray and di-electic grease? WD-40?
Thanks as always for good info!

ok i think i found my pcv i would take a pic to show yall but my camera wont fit lol. Is it right in the middle of the intake manifold? Its pretty much inline with the intake runners?
If that is the case then friggn' autozone gave me the wrong pcv valve.
Which one should i buy? Oh and I took my IAC and wow my TB has a horrible path for the air to go in and out the IAC. Im in the process of opening up my IAC ports.

yes, that's the right one. Go back to autozone and tell them to get you the right one, or go to ford (prob. more $$)

Surging Idle

This worked for me. 1. disconnect battery for 30 minutes. 2. Disconnect plug to idle air control on front of throttle body. 3. connect battery. 4. Start car and set idle with adjustment screw to the RPM you want. 5. Shut down car and wait two minutes. 6. Reconnect idle air control. Shut off all accessories, radio, A/C EVERYTHING. Start car and let it idle for two minutes then shut it down. 7 Wait two minutes, then put ALL accessories ON and start up the car and run for two minutes. Shut car off. Wait two minutes, start car up and see how it does. Hope this helps someone.

Great sticky but because of the name I didn't realise hi idle was included here. The motor is still fairly new. I set the idle per the instructions on a website I was refered to by Hissin50. It worked great and the idle was fine at 900.

Then I reset the timing. As I adjusted the timing the idle increased. I tried to reset the idle following the same process, buty ran out of travel in the idle set screw. I had the screw completely removed and the idle was still at 1000rpm.

After driving a little the idle does not drop below 1100-1200rpm. Jricker made a comment earlier that leads me to believe that the tps would cause this. I would think this to be true even at the retarded timing level I was running when I made my first idle adjustment?

The current timing setting is great. The motor pulls very well until I chicken out, which is about 3500 with the fresh motor. It may be happier with more advance but that would bump my idle even higher.

Do the idle adjusting plates help restrict airflow through the IAC? I saw one here, but it doesn't say much about it.

Oh yeah I am getting codes 33, 44, and 94. Most likely cause that stuff is no longer on the car.
Any help would be much appreciated.

vristang said:

Great sticky but because of the name I didn't realise hi idle was included here. The motor is still fairly new. I set the idle per the instructions on a website I was refered to by Hissin50. It worked great and the idle was fine at 900.

Click to expand...

Well I saw opened up my IAC hole a lil bit. Till I could fit my thumb in both thru both ways. god it was gunky in there I spent 15 minutes cleaning everything. When i got the car started it idled around 1100 which is of course is to high. I havent tried to reset the idle yet but I pray it works. Here are some pics of the gunk and how small the IAC hole is.

Does anyone have a part number on the PCV? Could the car idle high because of a vaccum leak?

How about this.

When my timing is retarded to the point that I noticeably loose power, I can adjust the idle to where ever I want. Lower than the 900 that seems to be best, if I wanted to be dumb.

When I advance the timing and make no other change, I runout of travel on the idle set screw before I can get the idle below 1000rpm.

All of the hoses are in good shape as they have all been replaced.

If I had a vac leak wouldn't it still have the same effect with retarded timing?

I checked for leaks yesterday, but will try agin this afternoon just to make sure.

Thanks
jason

I reset my idle and it still idles like boo boo with the AC on it doesnt surge as much but taking it out of gear and coming to a stop it falls on his face dies or "surges." I reset the idle to around 900 (thats as low as my TB would allow). so I give up with the AC on my car idles better without the IAC. I hate removing stuff like that, but if it does more harm than good...

jrichker said:

Advancing the timing (within reason) makes the engine speed and vacuum increase on any healthly engine. If you had a small vacuum leak, advancing the timing would still increase the idle speed.

Click to expand...

You were dead on jrichker. My problem was a vac leak. But it was a little tough to find it since it was coming from the lower intake manifold, on the lifter valley side. I was actually pulling full engine vac on the crankcase! Check out the pics, you can actually see the bottom surface of the head through the intake port of the gasket.

Opening up the IAC

Ranchero,
I've set the dead stop screw on bottom of the TB, adjusted the TPS to 0.984, opened the bridge in the IAC and unplugged it and for the first time I have a steady 1000 rpm idle.Now for the questions,
1. Do you leave the IAC unplugged?(if I plug mine back up the idle goes to 1200 rpm's)
2.If you don't plug it back up is there anything bad going to happen to the motor?
3.If I wanted an idle of say 800 rpm's how do I adjust to that?

I can live with 1000 rpm's but would like to get to around 750 to 850 my cam is as follows if it helps 544-560,232-242 at .500 with a 112 lobe sep.

Thanks Scott

p.s. great thread!!!!

Henpecked said:

Ranchero,
I've set the dead stop screw on bottom of the TB, adjusted the TPS to 0.984, opened the bridge in the IAC and unplugged it and for the first time I have a steady 1000 rpm idle.Now for the questions,
1. Do you leave the IAC unplugged?(if I plug mine back up the idle goes to 1200 rpm's)
2.If you don't plug it back up is there anything bad going to happen to the motor?
3.If I wanted an idle of say 800 rpm's how do I adjust to that?

I can live with 1000 rpm's but would like to get to around 750 to 850 my cam is as follows if it helps 544-560,232-242 at .500 with a 112 lobe sep.

Thanks Scott

p.s. great thread!!!!

Click to expand...

With the 112 lsa you should have a pretty good idle, even with all that duration. (I assume a typo, and it s/b 232-242 at .050)???
Basically you unplug the IAC, set the idle where you want it with the set screw, then plug the iac back in. here is a site that details it better though.

Good luck