1986 L98 weird stuff
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From: Canisteo NY
1986 L98 weird stuff
Ok so i had another post but it's gone some how.
I have a 1986 C4 L98 with 700R4 Trans. First time vet owner.
Was running weird acted like it had a miss fire. Changed all plugs and cap rotor and wires. All the plugs i pulled looked the same. Was throwing a code for MAF so changed the relays (yes both of them) then the MAF. Put a new O2 sensor in and coolant temp sensor in. Converter was clogged on drivers side so had both front converters cut off and pipe put in place.
Couple of issues. Coolant temp on dash just says LO. Coolant temp sensor (2 wire) and coolant temp sending unit (1 wire for gauge) have been replaced. Fan has not come on and was ran up to temp.
Runs weird like has a vibration. Checked compression and good. Checked fuel pressure and was around 40 psi even under a load.
Ohmed the injectors and they are all good. No vacuum leaks as tested with propane. Checked all wires and connectors to make sure they were ok and they are. Timed the car as well with the EST unhooked. I also adjusted the TPS to .54 v and reset the IAC. It is not throwing any codes. Does everyone elses C4 shake? It's almost like it has a cam in it.
I have a 1986 C4 L98 with 700R4 Trans. First time vet owner.
Was running weird acted like it had a miss fire. Changed all plugs and cap rotor and wires. All the plugs i pulled looked the same. Was throwing a code for MAF so changed the relays (yes both of them) then the MAF. Put a new O2 sensor in and coolant temp sensor in. Converter was clogged on drivers side so had both front converters cut off and pipe put in place.
Couple of issues. Coolant temp on dash just says LO. Coolant temp sensor (2 wire) and coolant temp sending unit (1 wire for gauge) have been replaced. Fan has not come on and was ran up to temp.
Runs weird like has a vibration. Checked compression and good. Checked fuel pressure and was around 40 psi even under a load.
Ohmed the injectors and they are all good. No vacuum leaks as tested with propane. Checked all wires and connectors to make sure they were ok and they are. Timed the car as well with the EST unhooked. I also adjusted the TPS to .54 v and reset the IAC. It is not throwing any codes. Does everyone elses C4 shake? It's almost like it has a cam in it.
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From: Summerland B.C. Canada
If you jump A+B on the ALDL connector(ign on), the fan should run.
Fan info and diagnostics http://members.shaw.ca/corvette86/Co...%20Control.pdf
There is some diagnostics for temp gauge in here
http://members.shaw.ca/dankai/Instru...%20Cluster.pdf
Fan info and diagnostics http://members.shaw.ca/corvette86/Co...%20Control.pdf
There is some diagnostics for temp gauge in here
http://members.shaw.ca/dankai/Instru...%20Cluster.pdf
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From: Canisteo NY
Fan runs when connector is unplugged from CTS. I think it's a relay.
It runs really weird. It acts like it's firing with valves open or something. Motor vibrates like it's miss firing or something. Again have checked timing and distributor placement. Could the valves be out of adjustment?
It runs really weird. It acts like it's firing with valves open or something. Motor vibrates like it's miss firing or something. Again have checked timing and distributor placement. Could the valves be out of adjustment?
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From: Cincinnati, Oh USA
At night in a dark place, turn off the underhood lights and look for sparks along the plug wires. Replace any missing or broken plug wire looms, the plug wires should not touch metal! Also, I would run a compression test and write the compression down on each cylinder.
An ohm test is almost worthless on injectors. Injectors get pulses and an ohmeter cannot detect a turn to turn short in a coil which will cause injectors to not work properly. Ohmeters will find gross coil errors only. It takes an impedance bridge that measures the inductance and coil Q. Also, coils aren't always the fault in injectors, the pintle and the oriface can prevent proper spray. The best test of all is to watch the injectors spray fuel.
An ohm test is almost worthless on injectors. Injectors get pulses and an ohmeter cannot detect a turn to turn short in a coil which will cause injectors to not work properly. Ohmeters will find gross coil errors only. It takes an impedance bridge that measures the inductance and coil Q. Also, coils aren't always the fault in injectors, the pintle and the oriface can prevent proper spray. The best test of all is to watch the injectors spray fuel.
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Joined: Apr 2009
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From: Canisteo NY
At night in a dark place, turn off the underhood lights and look for sparks along the plug wires. Replace any missing or broken plug wire looms, the plug wires should not touch metal! Also, I would run a compression test and write the compression down on each cylinder.
An ohm test is almost worthless on injectors. Injectors get pulses and an ohmeter cannot detect a turn to turn short in a coil which will cause injectors to not work properly. Ohmeters will find gross coil errors only. It takes an impedance bridge that measures the inductance and coil Q. Also, coils aren't always the fault in injectors, the pintle and the oriface can prevent proper spray. The best test of all is to watch the injectors spray fuel.
An ohm test is almost worthless on injectors. Injectors get pulses and an ohmeter cannot detect a turn to turn short in a coil which will cause injectors to not work properly. Ohmeters will find gross coil errors only. It takes an impedance bridge that measures the inductance and coil Q. Also, coils aren't always the fault in injectors, the pintle and the oriface can prevent proper spray. The best test of all is to watch the injectors spray fuel.
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From: Made In America
St. Jude Donor '10-'11
Does your exaust/cat glow? Sounds like a clogged cat. Maybe a tune up would help the "shaking/cam feeling"? Tune up helped mine alot. I still think you have a clogged cat...
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From: Canisteo NY
Cats are removed. Today this is what I did. Complete compression check again. All ranged from 95psi to 120psi and held the compression. Plugs are not fouled out but it looks like the complete right hand side (passenger side) is not firing. All of the plugs on that side are soaked in gas while the other side looks normal. Ignition timing is correct with the EST unplugged. IAC and TPS have been set to factory specs. Cap and rotor are good and the coil ohms out correctly to specs. Ignition module has been tested and that is also good. Cap rotor and plugs are all new as well as wires. Has new CTS installed and a new coolant temp sender. New MAF and relays. All valves are adjusted properly as I checked today when I did the compression.
I also checked the distributor to make sure it was pointing to number one at tdc and it is.
It runs as if it is not timed correctly or is out of time. Like I said it's like the complete RH side is not firing at all. O2 sensor is also new.
I also checked the distributor to make sure it was pointing to number one at tdc and it is.
It runs as if it is not timed correctly or is out of time. Like I said it's like the complete RH side is not firing at all. O2 sensor is also new.
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From: Cincinnati, Oh USA
Measure the fuel pressure and see how long it holds pressure with the ign off. If it drops rapidly, you definetely have one or more leaky injectors on the right side. Spark plugs should not be wet with gasoline. 86 vettes batch fire injectors, all injectors on each bank fire at the same time and one leaking will make a too rich mixture on one side and cause shaking and raw gas smelling exhaust. Buy a noid light or use an LED (light emitting diode) and a 680 ohm series resistor and check that the right side injectors are being pulsed. A defective ECM that holds injector/s on can cause your symptoms but would be rare. I believe you have a leaky injector/s on the right bank.
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From: Phoenix AZ
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I would pull the plug wires on the side that is not firing one at a time, and put a used spark plug on each, and see if they are firing. If they aren't firing, I would guess that the module in the distributor is at fault.
It really sounds ike the injector driver for that side is not working, but you have fuel on the plugs, so tht isn't right.
I would also check to see tht the right side intake runners haven't ingested anthing that might block the runners somehow.
Pull the injector connectors, and put a meter on the plug, and watch the needle. don't use a digital. If the voltage stays on all the time, it might be the ecm.
It really sounds ike the injector driver for that side is not working, but you have fuel on the plugs, so tht isn't right.
I would also check to see tht the right side intake runners haven't ingested anthing that might block the runners somehow.
Pull the injector connectors, and put a meter on the plug, and watch the needle. don't use a digital. If the voltage stays on all the time, it might be the ecm.
Last edited by coupeguy2001; Apr 25, 2009 at 11:01 AM.
Le Mans Master
Joined: May 2007
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From: Valparaiso
i had a similar problem and all the injectors seemed to work ok but they were not !
ok do this :
get the car running ,and remove one injector wire at a time while idling,if the idle is affected,then,that injector is working,plug it back,and go and disconnect the next and so ....if the idle is affected,then,that injector is working if its not affected at all,you catched a bad injector and to make sure,take off the spark plug and smell it,if there is zero trace of gas,you got a bad injector or maybe 2.-
let me know
ok do this :
get the car running ,and remove one injector wire at a time while idling,if the idle is affected,then,that injector is working,plug it back,and go and disconnect the next and so ....if the idle is affected,then,that injector is working if its not affected at all,you catched a bad injector and to make sure,take off the spark plug and smell it,if there is zero trace of gas,you got a bad injector or maybe 2.-
let me know
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From: Little Rock AR
yeah i got that same problem on my 86 it shakes alot, when i finally get my engine to idle, but i think mine is only because its having a rough time idling and i have to start mine 4 - 5 times before it finally idles at 800 rpms, which i dont think its the norm.
Drifting
Joined: May 2006
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From: Chewelah Wa
There are 2 fuses in your fuse block.....INJ1 and INJ2, and they control each bank of injectors. Check each one and wiggle them around...I would say there could be a dead circuit to the one side that is not firing. It did the same thing to me once on my 85.
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From: Canisteo NY
The po said he put a brand new computer in it. I even changed the distributor today as the pick up wasn't ohming out right. Maybe the other side isn't getting gas so the other is getting to much. I'm going out to look at the fuses now. I'm so stumpted and ready to give up!
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From: Canisteo NY
Ok fuses are good. Started car up and pulled injector wires on left hand side and it ran worse. Pulled injector wires on right hand side and didn't do anything at all. Still ran the same. Why is that side soaked with gas though?
Le Mans Master
Joined: May 2007
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From: Valparaiso
are you sure the p.o. swapped computers ? never believe what the ex owner says
never,that's why im replacing everything and i did a complete rebuild of my engine
now i know exactly what i have ,every bolt of it.
ok you have your spark plugs with gas but no fire ...then you have an ignition problem!
never,that's why im replacing everything and i did a complete rebuild of my engine
now i know exactly what i have ,every bolt of it.
ok you have your spark plugs with gas but no fire ...then you have an ignition problem!
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From: Canisteo NY
are you sure the p.o. swapped computers ? never believe what the ex owner says
never,that's why im replacing everything and i did a complete rebuild of my engine
now i know exactly what i have ,every bolt of it.
ok you have your spark plugs with gas but no fire ...then you have an ignition problem!
never,that's why im replacing everything and i did a complete rebuild of my engine
now i know exactly what i have ,every bolt of it.
ok you have your spark plugs with gas but no fire ...then you have an ignition problem!
The ignition control module has been tested and is good. The distributor is brand new and I checked all wiring. Coil is new as well as plugs cap rotor. I'm confused.
Could be ECM?