total frustration
Thread Starter
5th Gear
Joined: Jan 2005
Posts: 5
Likes: 0
total frustration
Having a miss problem with my 1990 L98 for over a year and a half. Car was running fine until alternator failed while I was driving it . I did not notice the problem until the car completely drew down the battery and stalled. Had to connect jumper cables to recharge battery enough to restart the car in order to get home. Ended up having to do this four times to make it home. Replaced the alternator restarted the car and that is when the miss showed up. Repalced plugs with Bosh + 4s, plug wires with Accel 8mm and installed a new rotar in distributor. Restarted the car the miss was still there. Ended up taking it to a mechanic to have it looked at,found no codes,scoped it and found no ignition problems,checked for any vacuum leaks,checked injectors found nothing.Took it to another mechanic and had the same results,found no problem.Need help big time on this one! Anyone have any ideas.
Race Director
Joined: May 2006
Posts: 10,691
Likes: 71
From: Phoenix Arizona
Wow, two mechanics? Then the obvious is probably out! I wouldn't think then that your present problem is related to the alternator problem. Did you change the cap? The Module? The fuel filter? You could also check you engine wiring to make sure you don't have an arching wire, or aloose conection on the injectors or other parts. A steady or random miss? Check the knock sensor wiring on the block by the starter, I've had that bite me.
Instructor
Joined: May 2005
Posts: 132
Likes: 0
From: Torrington CT
Try pulling off one injector plug at a time while the car is idleing. Do any make no difference connected or not. Did either mechanic do a compression check. If you have compression, fuel, ignitionn, should have 8 cylinders
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
How bad is the miss, and in what RPM range? A bad coolant temp sensor can cause a miss....without throwing a code. You can also get a noid light a to make sure all injectors are recieving their signal. To many things on our vettes can and will cause a miss without throwing a code. Did they check the TPS voltages?
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
How are these items looking and when were they checked?
Fuel presure?
Fuel filter?
Intake air temperature sensor?
MAP sensor?
O2 sensor?
Alternator voltage?
Coolant temp sensor?
Knock sensor?
TPS working and within voltage spec?
Throttle body nice and clean? (including IAC path)
Is the issue constant or follow temperature?
Does the issue remain under all loads and RPMs?
Is the ECM wiring connected tightly as well as nice and clean?
Is the chip in firm and clean?
All sensor connectors nice and tight and clean?
See what you have left after that.
Fuel presure?
Fuel filter?
Intake air temperature sensor?
MAP sensor?
O2 sensor?
Alternator voltage?
Coolant temp sensor?
Knock sensor?
TPS working and within voltage spec?
Throttle body nice and clean? (including IAC path)
Is the issue constant or follow temperature?
Does the issue remain under all loads and RPMs?
Is the ECM wiring connected tightly as well as nice and clean?
Is the chip in firm and clean?
All sensor connectors nice and tight and clean?
See what you have left after that.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
bad news is that when your old alternator died, it probably threw a ''spike'' at the ecm on its way out...not enough to smoke the ecm completely, but subtle trauma that will cause problems.
good news is that the -727 ecm used in your vette is the most common one at j-y supply(hordes of v-6's use the -727).... should be able to find one locally for $40, maybe less, ground yourself to the water faucet and change your vette prom into the j-y ecm....lots of ecm's here if you can't find one.
good news is that the -727 ecm used in your vette is the most common one at j-y supply(hordes of v-6's use the -727).... should be able to find one locally for $40, maybe less, ground yourself to the water faucet and change your vette prom into the j-y ecm....lots of ecm's here if you can't find one.
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Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
if you are normal, you often carry a static elec charge on you that is sufficient to fry an integrated circuit on discharge...the same thing that sometimes gives you a jolt when you touch the car door handle...while the ecm prom pins are shielded somewhat by the plastic body, it is still possible to destroy the prom, or the ecm, if you are ''sparky''...touching the water faucet will USUALLY discharge the static charge, won't if all your pipe are plastic.
Intermediate
Joined: Aug 2005
Posts: 28
Likes: 0
From: fargo nd
How do the plugs look? After a tune up I did last year I had a miss. After double and triple checking everthing else, 
, I pulled the plugs and put back in NGK's, and the miss was gone. Everyone of the +4's were gas soaked, almost like not hot enough. I'd take a look at those. That was the first and last time I used bosch plugs. AC Delco or NGK is the way to go.
, I pulled the plugs and put back in NGK's, and the miss was gone. Everyone of the +4's were gas soaked, almost like not hot enough. I'd take a look at those. That was the first and last time I used bosch plugs. AC Delco or NGK is the way to go.
Thread Starter
5th Gear
Joined: Jan 2005
Posts: 5
Likes: 0
Originally Posted by 85 Z-51
How do the plugs look? After a tune up I did last year I had a miss. After double and triple checking everthing else, , I pulled the plugs and put back in NGK's, and the miss was gone. Everyone of the +4's were gas soaked, almost like not hot enough. I'd take a look at those. That was the first and last time I used bosch plugs. AC Delco or NGK is the way to go.
, I pulled the plugs and put back in NGK's, and the miss was gone. Everyone of the +4's were gas soaked, almost like not hot enough. I'd take a look at those. That was the first and last time I used bosch plugs. AC Delco or NGK is the way to go.
Thread Starter
5th Gear
Joined: Jan 2005
Posts: 5
Likes: 0
Originally Posted by redrose
bad news is that when your old alternator died, it probably threw a ''spike'' at the ecm on its way out...not enough to smoke the ecm completely, but subtle trauma that will cause problems.
good news is that the -727 ecm used in your vette is the most common one at j-y supply(hordes of v-6's use the -727).... should be able to find one locally for $40, maybe less, ground yourself to the water faucet and change your vette prom into the j-y ecm....lots of ecm's here if you can't find one.
good news is that the -727 ecm used in your vette is the most common one at j-y supply(hordes of v-6's use the -727).... should be able to find one locally for $40, maybe less, ground yourself to the water faucet and change your vette prom into the j-y ecm....lots of ecm's here if you can't find one.
Thread Starter
5th Gear
Joined: Jan 2005
Posts: 5
Likes: 0
Originally Posted by zr1fred
Wow, two mechanics? Then the obvious is probably out! I wouldn't think then that your present problem is related to the alternator problem. Did you change the cap? The Module? The fuel filter? You could also check you engine wiring to make sure you don't have an arching wire, or aloose conection on the injectors or other parts. A steady or random miss? Check the knock sensor wiring on the block by the starter, I've had that bite me.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
Originally Posted by walnut pony
Allready headed in that direction. Have in hand a #1227727 but having a hard time locating the EPROM.The ECM that I removed from the 1990 was a remanufactured #16197128 with a AOS Super Chip #9023A for 1990-1992 350 TPI manual transmission. Compatability issue there Im thinking. Anyway trying to find EPROM that is compatable with #1227727, which I have traced down to be AC Delco #16137184 = EPROM, ECM ( code 7185ARFP) (usage: Y 6-speed - Manual /Trans. (ML9), 5.7-8 (L98)
hate to tell you, but the ign mod in the dist, your headlite module, wiper control, radio...all could be either fried or headed for early graves from an alternator spike or jump start spike--lets not panic tho.
Last edited by redrose; Aug 10, 2006 at 05:11 PM.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Check the button for the rotor on the distributor cap to make sure it is in good shape and it is not broken or any insulation carbon tracked. Also, that the order of installation of the parts are correct. Has been a source of strange running and missing in the past. Best of luck. 
Last edited by pcolt94; Aug 10, 2006 at 11:04 PM.
