LPDesRoche

Ok its been a while since I have been over in this section, but no stranger to working on the LT5 after owning one for a while. I am working on a friends 90, one owner car with 25K miles on it. Last year it started running very poorly and just progressively got worse over time. So bad that it wasn't making enough power to even get it in my trailer so that I could get it to my place to work on it. First thing I did was drain the fuel tank and the gas was bad for sure, no horrible smell but it was considerably darker than it should have been. I'm sure it was over a year old. Changed the fuel filter as well. Pulled the plenum and did a set of rebuilt FIC injectors (its what he had previously bought so I used what parts he provided) and all new injector O-rings. Did a little bit of cleaning and general checking of things while I was under there as well. All vacuum lines looked perfect like I would expect with a low mileage garage kept car. Swapped the MAP sensor for a new one and redid the vacuum line on that since it seemed a little looser than I was comfortable with. Also changed the plugs and O2 sensors. Put it all back together, it started right up and ran much better but still not right. It ran vary bad at part throttle, but ran great once the secondaries opened. Strange enough I figure out that the #5 primary injector is stuck wide open. Even open when no electrical connector is plugged in. Call FIC and they swap me out for another rebuilt unit. I just put that one in and it fires right up. Runs nice and smooth so I go for a test drive. After about 5 mins the service engine light comes on and it starts running bad again (mild stumble at light acceleration in the higher gears). So I was thinking fuel pumps, grab my gauge reset the ECM and go for a ride. Code clears for a bit and I get the secondaries to open up for maybe a 10 second blast. Fuel pressure stays above 50PSI then it sets a code and falls on its face once again. I reset ECM and tried this a few times with same result. Codes are 44, 45 and 55? I get the 55 but the 44 and 45? WTH? Could I have more bad injectors? None of them are stuck open this time because FP is rock steady with car off for over 10 minutes. But once the codes a cleared the car runs great for a few minutes no matter if driving normal or if secondaries are open, but once the code shows then it starts running poorly? It's like something changes then it runs weird. Sorry for the marathon post, but just trying to avoid all the usual stuff and get the real diagnosing. Don't think its a coil pack issue because it does run ok for a bit and not to mention when I put it together the first time with the stuck injector it ran great at WOT just couldn't compensate for the extra fuel at low RPMS. So with that said any suggestions, Im all ears.

zr-1 guy

injectors are dead, replace all 16 with stainless from FIC

LPDesRoche

They are brand new rebuilt injectors from FIC as stated above. They can't all be bad and I'm not in the habit of just throwing parts at a problem.

Vette Daddy

Strictly without using a scan tool.

I had an intermittent miss that drove me crazy. Ran great one time and had the miss the next time I drove it. It could change on a dime. Every once in a while it would fall flat on it's face while shifting to 2nd gear.

Ended up being a bad fuel pump. I changed both pumps and went with Bosch rotary pumps and it runs great.

Get a scanner and diagnose it.

erikszr1

yea....hmmm. i was gonna go with rebuilds....the fellas here swayed me away from them....not to say thats your issue but hey you never know. hopefully for you its not. as stated here, you might have a fuel pump issue although you did say it was tested....not much goes wrong with these cars except these items....im leaning towards those darn injectors anyway.....

LPDesRoche

Well I watched the gauge all the way up to redline I never saw a pressure fluctuation on the gauge. Hmmm.

Dominic Sorresso

Secondaries are shutting down because you are going lean. You can rebuild the mechanical part of the injector but not the coils that fire them.

LPDesRoche

Well thanks to the awesome customer service at FIC they are giving me full credit on the rebuilt injectors towards a set of the stainless injectors. Can't ask for much more than that.

ghlkal

That's impressive.

I'd be very interested in hearing if this is an injector problem. If so, I couldn't imagine anyone wanting rebuilt injectors (nothing like pulling the plenum multiple times to ruin the fun of troubleshooting)

Dynomite

I am thinking the same thing.......if you cannot rebuild/replace the coils of an injector as Dominic suggests, why rebuild the injectors. Or is the reason for rebuilding injectors always mechanical and never electrical?

I use RC SL4 205 Injectors

Harborbreeze

There are few changes for 2012, save the addition of a $1,495 “High Performance Package” (kind of a redundant name, no?) that includes Michelin Pilot Sport Cup run-flat tires. For the uninitiated, this is what enthusiasts call an “R-compound” tire, DOT-certified street rubber that resembles a racing slick but is legal for road use. It offers more grip than the ZR1′s base tire, which is both ludicrous and awesome. The only penalty is a homicidal lack of grip when wet or cold. This is not an exaggeration. Want to die cold and fast? Drive a Sport-Cup-equipped ZR1 on a wintry mountain road, in the rain, with stability control off. If you live, pat yourself on the back and start buying lottery tickets.

bb62

What scanner can one purchase to diagnose problems? And are these scanners useful in maintaining the car's tune?

Paul Workman

I went with an AutoXRay scanner with an "event" feature, which has paid for itself over use on 3 vehicles now.

In fact, on my 95 LT1 Vette, I had an intermittent problem with an O2 sensor. After taking my Vette to the dealer, only to be told, "No problem found", I decided to get a scanner myself.

The AutoXRay I bought has an active datalogging feature which allows me to sample some 42 parameters in real time, as well as screening for codes. And, with the "event" button, I was able to capture a series of samples before and after the "event", and then graph the data on my computer. That was how I caught the O2 shorting out (zero volts) falsely indicating to the computer that bank had just gone totally lean. The computer reacted by more than doubling the right cylinder bank injector dwell time compared to the left bank (at WOT). Without the scanner and datalogging, I might have thought I had an injector issue, when in fact the excess fuel was a reaction to bad signal from the O2 sensor. I keep the AutoXray in the car all the time now against eventualities something might jump up unexpectedly.

But, perhaps the better solution is one of the free tuner software programs out there and a laptop. Ask Dominic Sorresso for details.

P.

bb62

Paul,

Thanks. I will look into these scanners. My car runs fine right now, but I do want the ability to address issues when they come up.