My son bought an '89 'Vette; obviously a L98 engine. It was missing on at least one cylinder, so we threw plugs/wires at it which helped (one plug's ground electrode was touching the center electrode), but it still has a hard miss on cyl 4....in fact what's odd is that when I disconnect #4 inj plug, it idles better! -smoother/higher. (?).

I hypothesized that inj 4 may have been stuck open (car last reg'd in '20) and flooding #4, thus the better running when unplugging it? (burns up the fuel w/o further flooding?) But tested and no fuel pressure leak down at all, after key off. So no leaking injectors. We pulled #4 plug and it looked like it came from the box, so then I wondered if #4 inj was stuck closed, or mechanical prob? Compression tested #4 and got ~145...good enough to fire.

Pulled one runners, plenum and fuel rails to watch inj's fire. Cranked engine....no inj fire. WTF? Some times, I get the slightest "shot", at the onset of cranking, sometimes at the termination of cranking....but mostly I get nothing. No inj shot at all. Not that it should matter, but every sensor and actuator on the engine is still connected. This engine was running today. When the distributor rotates, the injectors should fire. They aren't firing. Why.

 

I'm going to ask this even though I know you don't agree with me about the RP Multec injectors but does his Corvette still have RP Multec injectors in it?

 

It does. I can fire them all with a power source/ground. They'll fire...and it was running today. I don't think all 8 died while we took the plenum off. I don't think....

 

I assume you have a set of 8 known good working injectors you could use?

Swap all 8 electrically, swap 1 into the fuel rail leaving the other 7 RP Multecs as block off plugs. Test again.

 

Yeah....alright. I'll post back.....

 

You ever get the problems with your son's 89 Vette figured out?

 

Nope. Went Mountain biking all weekend, instead.

Did quickly ohm the injectors....5.5 to 18 ohms, so that doesn't look good.

 

Well mountain biking all weekend with your son sounds like it could be more fun than being bent over in the engine bay of a C4 chasing down problems, but that can also be a fun father and son project too.

Yeah with Ohm numbers like that it doesn't sound good for the RP Multecs. Still might not be causing the problem though. Multiple things can be bad at the same time.

Fun fact on 89 to 92 Vettes with a ZF6 manual trans you can hear bad Multecs injectors causing the gearset in the trans to rattle at idle. If there is any miss at idle the gearset will rattle. Even if you can't hear the miss to just being able to barely notice a miss. Rattle, rattle, rattle. Plenty of other things can cause a miss too but if it ain't any of those other things and you change out some suspect Multecs that seem to run fine and that rattle, rattle, rattle will go away or get way more quiet. Also applies to any 93 to 96 C4 with a ZF6 manual trans that has any amount of a misfire at idle.

I know it sounds crazy but it's true.

 

Oh, I totally believe that! For sure. I think we'll get back after it, this coming weekend. I think

 

No it doesn't !!

 

I had a issue forever ago where all 8 injectors were fine driving around town and wot, but take it to the drag strip where it could launch, hard ish. since tires back there didn't hook like today haha. but a 1.9 60 was great. and it would miss on that one back cyl all the way down the track, messed around and sprayed it with a 150 shot and kill a piston. replaced piston, bought a new injector plug and butt connected it to the plug next to it.

never had a issue again. the whole bank is in parallel if I remember right. Just swap plugs and see what happens if injectors don't fix it.

 

Which injectors are they?

 

Are you asking me? They're originals. New ones on the way.

 

Which ones you all get?

 

I'm not sure. Son bought 'em...they'll be here this coming week. I told him all the good vendors that I am aware of....I guess that I'll see what he went with, when they arrive.

 

Son came down last night, I helped him put the new injectors (Bosch 3) in, and we fired it up last night. Nice smooooooth idle. Moved vehicles this am and took it out and it ran flawlessly. Killer throttle response, good power, ran great*. So yep. After 35 years, and sitting for 5 years, these Multecs were dun for.

He drove it home this AM, about 1.5 hour drive and the trip computer showed him 28 mpg, so things appear to be working pretty good.


*Ya know what's fun about old cars, that new cars won't do anymore? FULL POWER UP SHIFTS! (Auto trans). MAN! The "kick in the boot" on the 1-2, and again on the 2-3....that's fun, and it feels GREAT! None of this spark retardin', throttle closin', laggy-laggin' BFShifts....just a nice, firm "WHAM", into the next gear. I miss that, when driving today's (last 20 years) auto-throttled **** boxes.

 

I'm glad you all got it fixed up and running great now. Those Bosch D3 injectors have a nice spray pattern and atomize the fuel very well. C4 Vette's can get some awesome gas mileage out on the Interstate cruising at the speed limit. His car a 2.59 or a 3.07 geared car?

Can't stand the new car slush box shift feel either.

 

30-35 years of life on the Multecs is GREAT in my world. I think if you get that out of any injector you can be very happy.

I agree on the shifts too. I hate the laggy throttle response and shifts on all the new cars Ive been driving last 10 years or so. Drove my 1987 Camaro into town today and just had to stomp the throttle a few times, partly because I love that solid and quick shift into next gear.

 

Totally. My wife has this Porsche Cayenne S. It's nothing special, performance wise...I think it does the 1/4 in mid 14's? But it IS 385 hp and it makes good power up to it's 7k redline. Anyway, when driving it, when you exploit that power and RPM range....it feels/sounds pretty good. SOTP, power seems to build w/RPM and it surges toward that redline with increasing muscle and urgency. It would be pretty great if it WHAM'd that next shift, as a "grand finale" for each gear....but it doesn't. Instead, it lays down, lags, executes a slow, lazy shift, then rolls the throttle back on in a soft, lameassed way. Talk about disappointment! This is in max-performance mode too, BTW. It's SO weak, and totally wrecks the experience.

A few years ago, I had HS friends out visiting from Mass, for a family ski trip. Mom/dad (both classmates of mine in HS) and their kids, then late teens. One night we ran an errand and I took my friend, and three of his kids for a ride to do the errands in our CTS-V (manual trans). As we got near the highway, my friends daughter asked me, from the back seat, in the most timid way, "Um...Tom....can you uh, shift this car, like, um...really fast?" I replied that I thought so, and I was just leaving an intersection from a stop so I came off the clutch nice and easy, rolled on the throttle gently, brought it up to about 1500 RPM, and "banged" it into 2nd gear.
I said "like that?". My friend laughed out loud -we had both understood what she was asking but I was busting her chops. She said, "No, um....I mean...can you rev it up really high, and then shift it really fast?". I said, "Maybe....Let me see what I can do here", just as I was pulling on to a straight, flat on-ramp that is probably just about a 1/4 mile long. I finshed the turn, then stopped the car. Turned "everything off", and then proceeded to basically execute a typical (for me) drag track pass; Good launch w/just a scratch of wheel spin, followed by 3, flat-foot powershifts just below the 6500 RPM cut off, resulting in three head-snapping events for my riders. They thought it was awesome. Now, the acceleration phases in each gear were not likely the "awesome" part; the CTS-V with 5 people in it, at 7000' elevation is probably a high 14 second car. It was the shift events that made it an experience for them -maybe the launch too, but mostly the head-rocking shifts; they'd never experienced a car shifted like that before.
We skied Sun Valley, Jackson Hole, Snowbird, Alta, Deer Valley, Park City Powder Cats, and Telluride that week -and had Fresh powder for all of it. A pretty OUTSTANDING skiing experience, if you ask me. The next summer, we were visiting them in Mass and I asked them what was the best part of the trip? I thought for sure, they'd say the Cat skiing at PC Powder Cats -that is the big bowl, powder skiing that all people want in an "out-west" ski trip. Their answer? "The ride in the Cadillac!"....and that apparently, was for real.

So for sure....shifts matter to the experience, they matter a lot. Cars today completely miss that part of the experience. It's a big let down. Glad to see that some others' agree, and could relate to the fun I experienced, driving my kid's older car. It was a "throw-back thrill", for me.



Yep, thanks and thanks for your inputs in this thread. I knew you were right when you first brought it up. His car has the "hi-po" 3.07 gear. You're right about the mileage. With a steady foot and steady speed, the '90's (LT1's) can go over 30 pretty consistently.

That turned into a novel^^