John Speake

The erratic tach is a sign of a bad signal to pin 1 of the LH, that will screw up the LH operation. So OP needs to find the cause of the bad signal from the EZK.

CJs 928

Thank you for all the replies and suggestions. I may be mixing up terminology-sorry if that is the case.

Basically, in park/drive/reverse the tachometer needle bounces and the car will not maintain a stable idle. When in drive, I have to apply pressure to the gas pedal just to keep it from stalling out. In reverse, oh boy, it bucks like a bronco. The needle (on the tach) bouncing is the result of the car acting like a POS.

I went to JDSPorsche, Elektronic Repair and looked at 928intl's relay tree. I am at an impasse, where the heck is the EZK relay (or what is it's alias). Is it the one that is also a fuse tester? Assuming I don't have one laying around, can I jump 87 and 30 like on the FP relay socket to verify?

CJs 928

OK, think I CSI'd the right relay, XVI 928.615.203.00. I saw this at one place for over $100. If this is it, I hope there is a Walmart price for this somewhere. Will most likely jumper tomorrow after to work and see what happens.

John Speake

You are correct, on your car the fuse tester relay is the EZK relay. You can swap it for an ordinary, good "53" realy for testing.

Tampa 928s

John knows a lot about the control systems, replace the relay use the one for your horn. I still think its a vacuum leak so after that swap if it still stalls go back to basic troubleshooting. Your symptoms are classic for a large vacuum leak when unmetered air enters after the maf. Take your time at each point with the carb cleaner, maf, main hoses, injectors, intake to head, iac, T,B connection hoses.

CJs 928

Just a quick update: replaced the EZK relay with a 53-n/h. Took a small Coleman propane bottle with the metal extension and went all over the engine with it-no surges. I am going to do the MAF checks from Electronik Repair, Inc tomorrow. Next thoughts?

CJs 928

Ok, used the JDSPorsche diagnostics.
MAF connector shows 13.6 VDC between pins 2 and 4. Good
MAF sensor resistor bertween pins 3 and 5 shows 4.2 ohms. Good
MAF idle mixture between pins 3 and 6 shows 411 ohms. Good
XXV relay jumpered (30 and 87), 12.4 volts on MAF connector between pins 2 and 4. Good
LH pin 7 and chassis ground-1.7 VDC, rose to 4.09 VDC when I blew on the MAF hot wire. Good

What should I do next?
Is checking vacuum with the engine running as easy as connecting a mitivac to a vacuum line (next to the booster). Do you squeeze the handle or leave it be?

Thank you

CJs 928

Just need to know where to hook the mityvac while the engine is running.
87 Auto. Not really sure where it should connect.

CJs 928

Doin it the way that makes sense to me:
Spray 1/4 bottle of B12 carb/inject cleaner all over valve covers and intake and around injectors-no surge in idle, but now my paint is shot-crap.
Hooked mityvac up to the vacuum line going to the firewall and yup, gotta HVAC leak. Took it out of the equation.
Hooked to the 4-way next to the brake booster with the engine running, I get 21-constant. Gunned the throttle-goes to about 5 and then up to 22 and 23 and settles back to 21. This looks good to me.
Sprayed another quarter can of B12 down the ISV's throat (did this already with WD40) and several minutes later-it is idling between the 1 and the last segment-idle seems stable (even in reverse and drive). Put some more B12 down the hose again-gunned it and shut it down. We'll see what happens tomorrow. I am leaning toward the ISV now.
What else would you check?

Tampa 928s

Seems your on the right track, your isv my be stuck open cleaning may do it. You can bypass it for testing once warmed up car should run ok. The wsm tells how to check the operation. As I said in the beginning go get it smoke tested to put vacuum leak part to rest. Is it an auto, any smell of gas near the passenger fender?

CJs 928

It is an auto-just for the sake of understanding; you can bypass the ISV when warmed up? How-just unplug the electrical connector or just a relay/fuse (the latter preferred of course), not sure how to unplug the ISV without moving the intake out of the way though. What do I do then?-what testing do you perform when it is warmed up?

As for the smoke testing, until about 2 hours ago, driving it anywhere would be very dangerous (still not confident). The engine will not remain stable unless the gas pedal is engaged at all times-the smoke machine would have to come to me or I would need to tow it there.

Tampa 928s

If your hoses are new you can clamp one shut, I did not say it would be easy!
I have been there done that on 4-928's all with vacuum leaks using my smoker, trying other methods never found all of the leaks. Good news it sounds like a good size leak, go back to your homemade intake pressure tester get it to connect correctly, using soap and water in a bottle look for bubbles.
I thought you said it ran better after the cleaning!

CJs 928

It is running better after throwing B12 down its cake hole. I stated that it was running better and then you posted to still have it smoke tested. I have only ran it for about 10 mins and am unsure of it on the road for any distance. This issue started when I was driving and it was a nightmare getting home-should have towed it then. My comments were not meant to get a rise out of you, but it seems that they have based on the exclamation marks in your post. You and John are the only ones who have responded with help; I'm not biting the hands that feed me-please don't take my wording as an attack; just spouting facts. Since it is running better, what leads you to believe there is still a vacuum leak. If it is because I stated that the car runs like crap (is lacking power)-then smoke test it is.

ISV the hoses are brand new (well about a year old).

I did some searching and found a link on how to build your own smoker (for anyone who is interested-not mine and no affiliation):
http://www.chevytalk.org/fusionbb/sh...hp?tid/223962/
I might give this a shot, If it does not work, I will try to find the closest smoke test facility.