Joe C

update: well. I finally fixed the idle issue. as suspected, it turn out to be an injector problem. I took advantage of FIC's Columbus day discount on another set of bosch3's ($155 shipped) - installed, and problem solved. happy camper! my original injectors ohm'd OK - 15 ohms +/- .5, and they chattered OK, so i'm assuming the solenoid internals were good. only thing I could figure is a flow issue. i'm going to try to rig up something to flow test #3 to confirm my suspicions. anyway, smooth idle, and no low end pulsing on acceleration -

Dt86

Glad you got it fixed. Nice price on those Bosch 3's.

ddahlgren

Disconnecting the injector does not tell you it is bad but it tells you something is in that cylinder is wrong if no rpm change.

Joe C

that maybe right, and not trying to be a wise ***, but why? seems to me if you stop the fuel source to any cylinder, it will effect the idle quality. I suspected a flow issue and swapping out the injectors did significantly improve my idle quality. i'm by no means a diagnostic expert, and my knowledge in these areas is mediocre at best.

aklim

Once in a while, I do try to get my buddy to let me use the injector flow bench at a local tech college he works at. I do it in 2 sessions. First to verify what is being sent out, the second to verify that what I sent out was fixed. I don't always do it but enough to know that FIC does report what I see and when it is done, it is really done.

Without a flow bench, the most the rigging can do is give you an approximate of what it might be depending on the limitation of your imagination.

Red1990VT

When it was time for new injectors, I checked with a reputable Corvette shop, and they suggested sticking with the OEM Delphi Injectors, same as the factory installed ones.

They particularly noted that going with aftermarket injectors can cause rough idle. This is because the car fuel injection system was calibrated to those particular injectors, and different injectors can have slightly different behavior, even if both are rated 22 pounds.

The Delphi OEM injectors are about $500 for a set, and you may not want to go back, take out the aftermarket ones, and put the OEM ones in. But from what I was told, it would likely solve your idle problems. I suppose alternately you could get the car recalibrated for the aftermarket injectors, but that's probably as costly as putting in the correct ones.

Also, my 1990 has a rock steady 20 vacuum not 18. Aside from the aftermarket fuel injectors, you may have something else going on too.

Red1990VT

And by the way, ignore the nonsense about Delphi injectors from 1990 not handling ethanol fuels - ethanol was long in use by then, and my original injectors lasted 26 years before having a problem.

aklim

Who are these people? I have seen a lot of other shops that also go the other way including LPE and TPIS, etc, etc. As to the calibration, I would say they are going to have to be more specific than what you have said. I'd really like to see some objective data as to how much of a difference and be better able to see if it is within the ECM range of adjustment. I honestly do not believe the calibration is as precise as a nuclear reaction where every little bit counts.

aklim

Interesting you should say that. Even GM has a TSB concerning the fuel cooled pre 94 Multec 1 injectors. They tell you not to clean it because of the windings being susceptible to corrosion from your additives.

As to ethanol being used in fuel, how long has it been in use? IIRC, back in the 90s it was harder to find fuel with ethanol. Today, thanks to the govt, it is everywhere except in Marinas or a few select places. Back then, the probability of getting a tankful of ethanol was slight. Today, you can't swing a dead cat without hitting a pump with ethanol as the saying goes.

Joe C

you haven't followed my post - with the new bosch3's, PROBLEM SOLVED! no other changes were made to the engine.

re-read;

as for the reputable Corvette shop's expertise, I can not comment on the calibration thing. all I can say is this was my 4th boschIII install in L98 C4's (plus, one in an 96 LT1). aside from one slight idle issue, with one set in my (current) 90, I have not had any other problems. there are probably a hundred members here as well as the third-gen Camaro forum that have gone with boschIII's - haven't heard much negative feedback.

"reputable shops" is one reason why I do my own wrenching!

Red1990VT

Glad you got your problem fixed, and were able to do it with the injectors you preferred. It's too bad you had to put in a set, take them out, and put in another set (having changed injectors in my 1990 I know how involved this job is). But all is well that ends well, and I guess that could happen with injectors from any manufacturer including the OEM ones.