I have recently installed a J-Spec in my 87TII. The first J-Spec ran fine, idled fine, just smoked really bad. So we sent it back and got a different one. While the motor was gone, I installed a couple of mods.... TID & cone filter. My mechanic thought since there was going to be much more air, more fuel would be needed, so new 720's were installed. I know it would run rich since the ECU still thinks there is 550's in there, but I didn't think it would affect the idle. Any ideas???

We are planning to take the 720's out until my S-AFC arrives, just to get the motor running properly. What else should I do?

 

No, they don't kick in until 35-3800 RPM IIRC.

PaulC

 

It'd probably help if you told us what was up with the idle...

 

very low, 600-700, very rich, exhaust pops, adjusting the BAC and A/F is not helping.

 

TPS is adjusted using two light method.

 

did you use 4 720's or keep the 550 primaries? if you kept the primaries then the secondaries shouldn't affect idle. unless, you have a leaky injector. idle low, and i'm guessing you tried the idle adjust screw the variable resistor and the idle stop. if not try all of those also if your running 720's all around then swap the 550's back in to the primaries and you should be fine until you get the s-afc.

 

TPS

 

Also, chk for exhaust leaks.

 

stock primaries are still in there. I don't think I have a leaky injector, but anything is possible. The car ran great with the other engine, same primary injectors. I swapped throttle bodies with one I had lying around, no change. Put the J-Spec BAC on, no change. WTH??? I do have 2 extra 550's from my secondaries, maybe I'll throw those in my primaries and see what happens.

 

What is the real idle when the car is warm and the initial set coupler is in?? When the initial set coupler is installed, it kills the feedback to the bac, so the engine has to idle on its own. Should idle at 750. If not, make it.

When you removed the *rats nest* and emissions, what did you do with the vac lines that were on the back of the throttle body? Two of those lines supply fresh air to the idle system. The large hose that goes to the oil injector spider is supplying fresh, filtered air directly to the rotor, thru the oil injectors. The other line that was located directly below that line, supplies fresh, filtered air to the fuel injector bleeds. If you cut off that supply of air (the two hose), you are cutting off some of the idle air.

Your tid is suspect number one.

Where is your vac line for the fuel pressure regulator now attached?
Check the compression. One rotor stronger than another will cause irratic,odd idling.

Secondary injectors won't effect idle unless they are leaking, OR the grommets that seal them to the housing are leaking air. Same with primary injectors.

The rich/lean screw (variable resistor) set wrong will cause an erratic idle.

 

You'll have to help me out on the initial set coupler, I don't know what that is. The 3 vac lines on the back of the throttle body: Top two are hooked up and the bottom one is capped. He did the rats nest removal for me while the car was down, but I know there is one solenoid left...it has something to do with the fuel. Have not checked compression, yet, but will. The variable resistor has been adjusted back and forth, with no real gain.

*edit*
I found out what the initial set coupler is. I will try that.

 

There are no exhaust leaks, all new gaskets.

 

this is a different J-spec engine? How are the compression numbers? Stuck side seal?

 

The comp numbers were the usual J-Spec numbers ~120. But I don't trust those.

 

OK, with the initial set coupler in, the idle did not change at all. Nor was I able to change it with the screw in the BAC.

Moved the rich/lean screw to obtain best possible idle. It is still low, 600RPM, but the motor doesn't shake as bad as it did.

The secondary injectors are balanced and blueprinted with brand new grommets and pintle caps.

 

The secondaries will not effect idle...Big vacuum leak? Stuck fuel pressure regulator?

 

I finally was able to pull the plug on the BAC with all accessories running and the result was no change in idle. Upon further inspection of the plug, I came across one of the connectors on the plug has backed it's way out of the connector. How can I get this wire connector back up into the plug?

 

I'm hoping it's a poorly seated injector....... checking it out tonight. The BAC will be fixed with another plug, hopefully that'll help adjust the idle.

Hailers,
Above you mentioned that my TID is suspect #1. Care to elaborate, please?