my86z

For some reason my car is experiencing an odd hesitation right at 3000rpms, when I'm hard into the throttle. Would this be a slight indication of a worn optical pickup inside the distributor? Or, if anyone else has experienced the same issue, what else would cause it?

New plugs, wires, distributor cap and wires; with less than 1000 miles on them.


By the way, the car with this issue is my turbo.


Wink
86 NA auto
86 turbo 5 speed (JWT ecu, 3" turbo back, MBC set to 12 psi)

Z Car Barbie

The usual cause of this is a bad O2 sensor.

my86z

I'll give that a look. I'm not pulling any codes from the ECU. But that doesn't mean that the o2 sensor isn't bad, yet still within the ecu's self-check ranges.

Another z owner says that the fuel injection crossover is at 2800rpms. And that may be what I'm experiencing.

Z Car Barbie

Oh, so you did check the codes. I wouldn't suspect the 02 sensor is the problem then. I assume you received Code 44, right?

How long have you had the JWT ECU? The problem didn't occur immediately afterward, did it? If not, then, yeah, the problem could be within the dizzy. Have you checked the timing?

my86z

Well, I purchsed the car with all the goodies already installed. So I have no idea if it had the same problem before the ecu install.

Yes, 44 was the only code given by the ecu when I pulled the codes today.

Igntion timing is around 20*. It sorta oscilates plus or minus 2 aruond 20*.

Z Car Barbie

It sounds like you might have a vacuum leak. Sometimes vacuum lines don't leak until pressure builds-up on increased load, and can be difficult to check for leakage at normal idle. This would make sense in your case, since you're not getting any error codes and appear to have problems only on WOT.

my86z

Sounds fair. I'll get out my trusty old propane bottle and have a look see if anything's leaking.

It's just odd that it's always at 3000rpms tho.

my86z

Well, I think I've fixed the hesitation issue. I checked my ignition timing, and the previous owner had it set to 20*BTDC. So, I adjusted it to 15*, as per factory service manual. And I dialed back a couple psi of boost. So far, it hasn't hesitated at WOT yet. (Crossing Fingers)


Thanks for the help!!!!

Z Car Barbie

That's awesome! I'm so glad she's running right. Thanks for posting again to let us know what you did to correct the problem. Not many people do that, and it really helps others who may have the same or similar issues with their Z.

my86z

No problem. Isn't this why we have forums such as these in the first place?

I did notice something of important value. I placed a multimeter on my O2 output wire and went for a test drive before I made any changes. It seems that on my last boost setting, I was dangerously close to leaning out. I was reading .90volts at wot/boost. And now, with the reduced timing and boost pressure, I'm reading between .92-.95 volts.

I think my next purchase will be a host of gauges. Something more reliable than the stock oil pressure/temp. And defiantely a wideband O2 setup. I'm kicking myself in the **** for not having these installed on the car yet, especially in a modified motor such as mine.

Z Car Barbie

Yeah, that's what caught me off-guard on the timing issue - I've never chipped, so that wasn't something that alarmed me with your problem to begin with. Please post your future modifications when you have time. We can always use good "How To's", "Installations", etc., and pix are definitely a bonus!