wfot

That map sensor looking thing is a pressure differential switch. It monitors the vacuum on the back half of the secondary diaphragms that open the secondaries. If the secondaries do not hold vacuum when open, that differential switch tells the ECM to not let the engine go above about 3k. If it is unplugged, ie not getting a vacuum signal, or broken, I don't care what you do the engine won't go over 3k. Fyi

I am kind of having the same situation, over a week or 2, the performance just died off. I have done the above and everything seems fine. I am thinking the coils. The prior owner changed them out for acels and i put the stock ones back because of high rpm/high load issues and it helped then. So I thjnk the stock coil/s my be arcing or dead...

biggiefl

I get 5k+ before it falls off. Like I stated, if I disconnect that plug by ECM(electrical) it will NOT go over 3k. I did not however look for the vac line going to it. Will look tomorrow but I don't think it is that. I am going to jump pink wire, check vac line under ECM and get the fuel filter changed. After that I'm not sure what else I personally can do but I'll keep trying stuff and narrowing it down. Good thing is engine is 100% along with the rest of the car....we'll get this

biggiefl

Well....found the vac line under the ECM and it was not connected. It was a thin hard line going into a soft 90 degree elbow. I connected it and the pump still runs every 2 seconds. If I remove the vac line going to plenum in middle of the plenum the and put my finger on it, it stops just like in Dynomite's instructions. What next guys? Check valve? Which one? Anything else to check before I take the plenum off again?


I ran it but did not drive it as I doubt my secondaries will work with a vac leak like that. My pump did not run like that before.....damn thing breaks while it sits.

ccmano

Good work. Looks like you still have a leak under the plenum. You won’t know till you get under there and check everything. I would start by replacing both the check valves, cheap insurance. Use a hand vacuum pump to check the circuits.

Go ahead and drive it. I’ll bet you’ll see a difference. It’s a misconception that the vacuum pump operates the secondaries. Manifold vacuum is the primary source of vacuum. The pump simply supplements vacuum once manifold vacuum drops with extended opening of the throttle Plates.
H

biggiefl

We got bush......damn it sounds awesome at 7k.

thank you everybody for your help. Happiest day since it got delivered on my birthday in august....wooi friggin hooo

ccmano

Woohoo.. congrats! I thought that might be the case. You can actually have a fairly good leak in the secondary vacuum system and the car will run ok. Haibeck says the pump only has to pause for one second to have adequate secondary vacuum.
Enjoy!
H

JThomas

Congratulations on fixing the problem. That's what I like about the ZR-1 group, always willing to lend a hand, or offer support.

biggiefl

That's why I came here and ZR1.net. Honestly this place helped the most as I could not access .net at work. Thanks again...until the next time.

jss06c6

Well I'm late reading this, but Hans nailed it. My issue was the check valve. I moved it to the side of the plenum to allow me to replace it without pulling the plenum. $2.50 part caused a plenum pull to repair. My secondary vacuum pump cycled every 4-5 seconds and manifold vacuum at WOT is insufficient to overcome the check valve leak on my '91. I changed the check valve and the secondary pump never cycles at all once it establishes correct pressure. Runs fabulous.

Enjoy!

Dominic Sorresso

Most of the forum members here are also on the Registry.