HI all, I have an 87 with a zz4 motor, BBK 58MM TB and 24LB Accell Injectors. I can't seem to get a good stable Idle. The only way I can stableize it is to remove the PVC valve from the valve cover. I have checked for vacume leaks and could find none(all new hoses). Also if I disconnect the MAF the idle flattens out, but I think this is because the computer is in limp mode. Could the ZZ4 be having problems with the PVC or do you think I am having other problems?

 

I'm having the same problem, but it's not a ZZ4, but it's still not stock. Do a search for minimum air, and let me know if you're able to get it set because mine is demonically posessed

 

It just dawned on me, the guy at the shop told me he set the timing at 10deg btc, it should be 6, think this could be the isue? I will reset it tomarrow.

 

I have a similar setup, had similar idle problems.
Advance changes made no difference.

Have you got headers?
Most of my idle problems went away when I fitted a heated O2 sensor as the headers run too cold at idle dropping the sensor out.
Also note , the BBK bleeds air directly into the plenum not through the holes in the base of the plenum direct to the ports like the stock setup does.
Has been mentioned as a issue by others sorting idle problems

 

I didn't use headers, just the stock center drops(might change later$$$). I also tried reinstalling the stock TB with no success. Any idea what the O2 cross counts should look like at Idle? This problem persists from cold to hot, open and closed loop. Well, I am going to go play with the timing anyway, couldn't hurt to have it right. Thanks

 

I think these idle surge issues all begin with open loop mixture problems, most likely a MAF calibration that has drifted or changed due to other mods. A Dirty or oily MAF wire, descreened MAF, Cold air kits, various intake mods, exhaust reversion, vacuum leaks, etc.

Once the rpm starts to cycle, the calulated load value also begins to oscillate. With load increasing as rpm is dropping, this causes both extra enrichment and reduced spark advance which further complicates things. Now both fuel, rpm and spark are oscillating with no end in sight unless conditions change, until either the motor stalls or the throttle is opened to break the cycle.

I have solved most of my idle issues with MAF calibration work in the chip and recently also preventing open loop enrichment vs load for load values 112 and below.

This has permitted more stable fueling at idle which has helped to smooth the surging.

I still have some issues with my startup fueling for warm starts (start up coolant 100F-140F or so). But its only a question of getting the correct mixture as a function of temperature and start up temperature for all conditions.

Consider things that can affect the mixute. Fuel pressure, vacuum leaks, MAF calibration, O2 sensor condition, intake mods. In many cases, I think tuning the MAF calibration is the only real answer.

 

how do you fix the issie w/ the BBK?

 

As suspected, the timing correction cured nothing. OK, so I am at my end, I think I need a custom chip. Any Idia's I live in Nevada and don't know anywhere to have this done.

 

 

Do they have a web site or number? Also, why can I not read this post when I am logged in?