Okay we've already established in my previous post that I can't install a distributor right. Now I have a new problem, the car will not start unless I open the throttle a bit then the idle is wandering a bit. I tried to set it at 800 r.p.m. hoping to help the start problem. It also dies as soon as I put it in gear, if I feather the throttle it will stay running in gear but about 200-300 below what it idles at in neutral. I put in a new IAC so I tried putting the old one back in but no difference. I have set and reset both IAC's a couple times. The only mod I have made that might cause this is 1.6 roller rockers. When it is running it is crisp and very responsive. Before I tore it down to do the upgrades it started almost as soon as I touched the key. Same cam, same throttle body as before mods. Before I did the mods the idle was a bit erratic but nothing like it is now. I've already tried the search but found nothing so I hope you guys can save my butt again. BTW, timing is set at 6* advance.

 

YOU don't set the idle. The idle speed is programmed into your prom. All YOU set is the minimum air adjustment. Obviously, that has not been done. Have you cleaned the IAC air passages in the TB? Are there any vacuum leaks? What does the EGR look like? First and foremost, have you checked to see if any codes have set?

RACE ON!!!

 

This is a tricky thing that lots of people stuggle with.

Here is the best way to think about it. Your motor at idle get air two ways. (1) through the TB, and (2) through the IAC.

Ideally you want ~90% of the air required at idle to be coming through the TB and 10% through the IAC. The less going through the IAC, the better, so 95% TB and 5% IAC is also good.

Most of the time when people have problems they have WAY too muich of the air coming through the IAC. This leads to the IAC trying to fight itself. It will cause the motor to gallope and eventually can even cause stalling. Most of the time the tell-tale symptom of this is you need to keep your foot on the gas at idle or it will stall.

OK, how to fix this. Here again is a simple way to think about it. Unplug the IAC, you can follow the procedure in your manual, advisable. However what your doing in understandable terms is your eliminating the air that flows through the IAC, and only using the TB air. So you need to determine what idle you want to have. Lets assume 900rpm for a cammed up motor. This is another thing people do not udnerstand. If your car is modded, your going to loose the 650-700rpm idle. Yeah you can get it to idle down there, but if the car is shaking and stumbling, your TOO low in your idle. You want it to somewhat smooth out, and 800-900 with most cams you should be fine. This also keeps the oil pressure up nice and not down around 20psi. Moving on.

Once you determine your min idle, what i do is open the TB blades via the screw on the TB till I am around 75-100 rpm away on the low side from my desired idle. You have now just achieved your 90-95% air through the TB. When you plug back in the IAC, assuming your chip is adjusted for 900RPM, the IAC will pick up the rest of the air required to achieve the 900rpm programmed RPM.

This % through each will adjust with changes to items like putting your car in drive. When the extra load from the trans is put on the motor the RPMs will decrease, and the IAC will open some extra to get to again the pre-programmed idle.

Its a very simple system, but very few understand what its truely doing. Remember the 90/10 rule and you should be good to go. If your car is modified up, you really should have the chip idle setting adjusted. If you need more idle, you can open the TB blade and the idle will naturally raise, but your IAC will be completely closed, since its trying to cut the air back to the RPM your already higher than. In this case it would be 100% of the idle air going through the TB.

Hope this explination helps!

 

I have set the minimum air adjustment a couple times with both IAC's. I completely cleaned the IAC passages while the tb was off. No vacuum leaks, EGR has been eliminated, and no codes have been set

 

Since you have had the distributor out and had some difficulties reinstalling it, I would start by thinking you may not have set your timing as accurately as you indicate. A low idle can be caused from retarded timing. Did you disconnect the brown wire by the brake reservoir prior to setting the timing? Also, are you sure that you are looking at the timing marks correctly on the tab?

I know you are probably tired of fighting this problem but think back on all you have done. Retrace your steps to narrow down the possibilities. Ensure your wires are placed in the right order on the distributor cap and each wire goes to the correct plug. Then put a timing light on it and forget the marks. Turn the distributor to obtain the correct idle speed and see where your timing mark is. I think you will find the mark will be close to being off the scale. If you find this to be the situation, it will tell you to look again at your plug wire placement.

This may not be the final stop but it is an easy starting place. Good luck. Let us know what it turns out to be.

90Indy

 

Thanks 90 Indy, the timing is right on as is the location of the plug wires, it runs too smooth and strong in neutral for any of this to be off. I used paint marks on my balancer and timing tab so they would be easier to see. Timing was set while the engine was idling at 600 r.p.m. and the tan wire was disconnected.

 

TPS is set at

 

.625, to eliminate off line stumble. This is the same setting I used before the mods.