biggiefl

I just bought this 1990 last month and it had a dead battery. I charged it and it worked ok but I did not trust it. Motor ran great and pulled like a train. Bought new Interstate battery with ZR1 specs and since it drives like it's in valet mode or little better. Runs out of juice at 4800 or so. Read many threads and will start with vac line under the computer as vac pump now started to run. I replaced air filter as it was not installed properly thinking it was sucking in air. Cleaned everything and still the same. If I unplug 4 prong connector under computer it bucks at 2500 or so and light comes on(was told Map connector?) I have not checked fuses but 2nd rail is not coming on. I make sure temps are up as well. WIll check everything I have read but I doubt fuel pump(s). Any other ideas?

ZR-71

What other changes occured while changing the battery? Or maybe shortly before the battery was changed. Gotta be something different since the last time it ran properly

Goldcylon

Have you scanned for codes? Does the Service Engine Soon light come on in the Drivers information Center or DIC. If it was the MAP hose you would notice a high rpm as soon as you start the car. If you have no high idle I am suspecting either a problem with the secondary injectors or the secondary fuel pump. I am guessing here but since you left out a high idle in general symptoms this is a fairly experienced and educated guess that the car is not getting enough fuel. I could say replace the fuel filter as well but it's never just the fuel filter. GC

biggiefl

Yes I am idling very high....1600?


Did not want to put too much info in initial post as some do not like to read long posts...sorry. Before I changed the battery it would idle a tad high but settle down quick which I heard is pretty normal. Now it idles so high I don't have to give it gas to get her moving, just let out the clutch Due to my schedule I probably won't be able to mess with it until Thursday.


Before change:
1) idled slightly high but would settle down to around 800 at a light.
2) Had all 375hp
3) Idle would hunt up & down if it idled for a few minutes.
4) no lights on dash


Now:
1) idles at about 2k and settles down to 1600 or so.
2) Decent power(not 375) but falls on its face at 4800.
3)Idle does not hunt
4)Vacuum pump is cycling, never noticed it before change.
5) Car does not just fire up but starts, runs a tad rough for 2 seconds then perks up.
6)No lights on dash Does not run any different before or after 176 degrees


Most likely a Vac leak, just need to hunt it down.

mhobtr

There is a vacuum line connection above the battery that is easy to knock off during a battery change. If disconnected, the secondaries will not activate.

I had this problem, along with several others created by mechanics who didn't know what they were doing, on my '91 barn find.

biggiefl

That is what I figure. If anyone has any other things that they have encountered(common problems) let me know. There have been a few unexperienced ZR1 people under the hood on this as it was on consignment for a while. The cover for the TPS is missing, air filter not in correctly and clamps not tight, etc. Nothing major but I will get it all corrected. Just need to hunt down small parts on e-bay. Once secondaries are corrected, new oil change and new filter. Mine drains down.


Thanks in advance.


PS...I have owned my 1980 Vette since 1990 so familiar with them. Not so familiar with electronics(bought a Chilton's) but this is pretty old school so should not be a huge problem. My 80' has a 383 stroker running 400+ to a 700R4 with a 2400 stall going to 3:73's. ZR1 is fast but not as fast or as dangerous as my old girl so all should be fine there

Goldcylon

1600 is NOT normal an unmodified ZR-1 normal idle is about 550 to 600 rpms. I agree now with with this information you could have a have vacuum leak under the plenum. The MAP sensor hose Is easy to check as it is on the back side of the plenum. GC

biggiefl

Found Vac leak. EGR? next to TPS sensor on plenum was off. Idle is around 650-700. Still don't have full power. Going to mess with the keyswitch once I fix my power steering leak.

Goldcylon

Does the Full Power light illuminate in the DIC when you turn the key?

biggiefl

Yes it turns on


I am going to check if SES bulb is there.


I am going to play with the key while driving as well.