msmoore

It idles at around 800 but it seems to take 5-10 sec to drop from around 1200-1500 to 800.

mike100

That's pretty normal. There are some measures you can take to alter the idle hang with custom tuning, but it sounds like you are most likely battling bad injectors or ignition problems. Even if it turns out to be ignition related, change the injectors anyhow- they all go bad (92 and below cars).

If your idle misses from time to time just sitting there as you listen, the injectors are also most likely bad. Mine cleared up and ran sooo much smother after I did mine.

It's just something that has to be done on these cars and isn't hard to do- it's just a $$ thing to buy the parts. All the other early regular C4 vettes also get this problem, but they only have to buy 8 injectors- and if rebuilt- pretty cheap cost.

Z51JEFF

When I did the injectors on my 91 at 8000 miles I also replaced the plug wires and coils at the same time,both with OEM parts.At maybe 7000 miles on the new G.M. coils one of them died so in went a new set of MSDs and I put the LT5 wires back on the car.At such low miles on the OPs car I wouldn't replace the wires-coils.Ive had my plenum of maybe 5 times,it to the point now I dont have to dig out the pictures to get it back together.

WydGlydJim

As mentioned, idle hang on a '90 is common, can be as long as 30 seconds, which seems like an eternity. It was an area of customer contention, and was addressed in later cars, and can be tuned out. There are a few things to check while under the plenum. All my vac lines were ok, when I changed injectors a couple of years ago, so I did not change any, but that's just a chance to take. There are a couple of "two vacuum line line couplers", that most guys put seperate lines on, because they are a common source of vacuum leaks. I put new couplers on, and they have always leaked, I need to change them to seperate lines. Aslo need to tighten, and put locktight on the bolts holding the cylinder case ventilation cover (#15 on pic) in place, as it is a source of oil leaks.....other than that, and a good cleaning, have fun! I generally think igniton parts should be good for 100K mileage from my experience in the indsutry back in the day, but here again that's just a chance. I really don't think the plenum pull is that bad at all, so I didn't care if I had to go back in later. I'll try to find a pic of the vacuum couplers. The vacuum block or couplers, is in the second pic just next to the electrical connector, and the A/C lines coming out of the compressor. You can see I replaced with new, but they still leak. I would replace them with two hoses. I'll add a couple more befoer and after photos...it should be as clean as the after photo when you get done!

HammerZR1

Call Jon at FIC, he'll tell you. I think they come with orings on the secondaries, but not the primaries, or visa versa.

I have had the FIC rebuilt injectors in my car for over 2 years now and no problems. Flywheel was rattling before install and great afterwards. Drove the car to the 2010 Gathering from Idaho over 2000 miles. 27 MPG average and it runs great. Hope this helps.

DMark

Yup, Jim Van Dorn knows LT5s.

Here is an example of his work on my Beast.



Just be careful if you go and see JVD. I also started out just needing some new injectors (went with the FICs - outstanding) and before I knew it JVD had me talked into another 50-60hp that I didn't know I needed at the time.

Hey, what color is your car? While I no longer have my ZR-1, I'm in the Nashville area and might know its background if you got it local.

msmoore

I now seem to have a vacuum leak that did not exist prior to removing the plenum. When I ground the pink wire to test the secondaries, as long as the secondaries are engaged, the vacuum does not leak down. When I remove the test lead to release the actuators, the sec. pump kicks on every 8-10 sec.

mike100

My sec pump will sometimes turn on once every 30 seconds or so (lately it has been sealed totally tight). There seems to be the smallest leak at the pump itself where the hose goes in, not so much the lines going to the solenoid...but check those. If you route the hose across the cooling hose wrong, that could also cause a bit of a leak at the coupler too.

A $30 vac pump tool can test all of the hoses.

msmoore

Should I be concerned about a very slow leak? It seams to be at the solenoid. I tested both ways from that connector and it was tight.

Z51JEFF

This does sound like the solenoid.There is info on a replacement on the ZR-1 site.

Paul Workman

I'd be curious as to what changed to result in the leak (albeit not at all severe). But, other than the annoyance it might cause me, technically, it isn't bad enough to cause a problem with the secondary operation. A vacuum problem big enough to affect secondary operation will be flagged by a code triggered by the secondary MAP sensor upon attempting to open the secondaries.

Secondary port throttles...Who needs 'em anyway??

FWIW, Many of the ZR-1 pilots, including me, have deleted the entire SPT system all together. That is another topic discussed at length here and on the Net Registry as well, so I'll just say that once the new calibration is installed and the system is removed, it never is a bother again.

I'm just sayin...

P.

msmoore

I think it's the connector itself. I backed it out just a bit so that the little rings/nubs on the fittings on the switch hit new rubber on the connector. Seems to have solved the problem.

msmoore

I'm making good progress and have the new injectors ready to go back in. When I was removing the fuel rail, I discovered that 3 of the 16 rectangular gaskets on the injector connector were missing from a previous service. I have checked around a few sources and cannot find these. How critical are they? Any ideas on a substitution. Was really hoping to get this back together today.

Vette Daddy

Google - Jerry's Gaskets

msmoore

Tried him. He's only got a few from an old harness for private stock.

msmoore

I typically don't do a lot of wet weather driving so it may just have to wait until the next time I go in there.

Vette Daddy

Can you make new ones?

msmoore

Probably. I'll have to obtain the proper stuff to make my own. I called FIC and was told no big deal and not to worry about it.

Z51JEFF

I think Kurt White might have these.Since the injectors are also used in the L98,might just find these at a Corvette salvage yard.

mike100

Those are just bosch style square rubber seals on every injector from the 80's and early 90's. I scavenged a few from the junkyard as a couple inevitably fall into the valley abyss when you take off all 16 clips and plugs.

not ZR-1 specific at all.