Help engine problems!
09-06-2011, 10:58 AM
#1
Cruising
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Help engine problems!
I just bought my first Vette(1986 Yellow Convertible). I new it had some problems when I bought it. It ran very rich, missed bad and backfired. Brought it home and did a basic tune up. Found that the rotor had the metal melted to the plastic. Put nrw injectors in it. Also put it on a scanner and read MAF sensor bad. Put new Maf in it, new IAC. Started it up and ran ok for a couple of minutes then started running rich,missing bad and backfiring. Then it would not idle unless I diconnected the MAF sensor. It idled then but still ran horrible. Somtimes when I start it would rev to high rpms stay there for a couple seconds before slowly comming back down and stalling. Getting frustrated, any help would be greatly appreciated. Could it possibly be the ecm I checked and it has the original in it.
09-06-2011, 11:21 AM
#2
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I just bought my first Vette(1986 Yellow Convertible). I new it had some problems when I bought it. It ran very rich, missed bad and backfired. Brought it home and did a basic tune up. Found that the rotor had the metal melted to the plastic. Put nrw injectors in it. Also put it on a scanner and read MAF sensor bad. Put new Maf in it, new IAC. Started it up and ran ok for a couple of minutes then started running rich,missing bad and backfiring. Then it would not idle unless I diconnected the MAF sensor. It idled then but still ran horrible. Somtimes when I start it would rev to high rpms stay there for a couple seconds before slowly comming back down and stalling. Getting frustrated, any help would be greatly appreciated. Could it possibly be the ecm I checked and it has the original in it.
coolant temp sensor can cause rich condition. 14 or 15 I believe. but not backfiring. that sounds like timing, or plug wire issue. is it thru intake or in the exhaust system?
fuel pressur regulator can leak into the vac line which comes from plenum, I think would show as rich condition too.
start with codes and get back.
jc
you set the TPS I assume, if you replaced iac. affects idle but not rich.
Last edited by stoydido; 09-06-2011 at 11:22 AM. Reason: spell
09-06-2011, 11:55 AM
#3
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Backfiring thru intake. Set timing. No fuel in regulator vacumj. Did not reset iac. Showing no codes. I did find a broken plastic vacum line near firewall on drivers side, cant find where it goes.
09-06-2011, 12:32 PM
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that can explain the idle issue, possibly the backfire if intake gets leaned out, may be wrong there, as the o2 sensors would try to compensate.
might wind up rich.
these c4's can get complicated!
a struggle just to hold stuff in your brain.did it ever run ok after injectors installed?
09-06-2011, 04:16 PM
#5
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may be an accumulator line that serves several lines, one is from the vac cannister, also serves the MAP on 91 models, your version of MAF, maybe the fuel reg also. definitely need to find the other end of it which will be a leak source.
that can explain the idle issue, possibly the backfire if intake gets leaned out, may be wrong there, as the o2 sensors would try to compensate.
might wind up rich.
these c4's can get complicated! a struggle just to hold stuff in your brain.
did it ever run ok after injectors installed?
that can explain the idle issue, possibly the backfire if intake gets leaned out, may be wrong there, as the o2 sensors would try to compensate.
might wind up rich.
these c4's can get complicated!
a struggle just to hold stuff in your brain.did it ever run ok after injectors installed?
09-06-2011, 04:32 PM
#6
Burning Brakes
before the ecm I would find backfiring as ign issues, crossed wires, arcing in dist cap, whatever. or lean air/fuel mix.
have to locate the missing vac line, because it won't run well without it connected. I am not familiar with the 86 enough to suggest what to look for. other than check the ones you removed in the inj change.
09-06-2011, 04:43 PM
#7
Race Director
the fan only comes on at 248* or so, or until you jumper it as you did.
before the ecm I would find backfiring as ign issues, crossed wires, arcing in dist cap, whatever. or lean air/fuel mix.
have to locate the missing vac line, because it won't run well without it connected. I am not familiar with the 86 enough to suggest what to look for. other than check the ones you removed in the inj change.
before the ecm I would find backfiring as ign issues, crossed wires, arcing in dist cap, whatever. or lean air/fuel mix.
have to locate the missing vac line, because it won't run well without it connected. I am not familiar with the 86 enough to suggest what to look for. other than check the ones you removed in the inj change.
09-06-2011, 05:01 PM
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I took pictures of the vacum lines before replacing the injectors. I have them in the right place. I found this one after. Im thinking it may be the cruise control line.
09-06-2011, 05:06 PM
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I did plug it. Could it be the ignition coil causing it to backfire and not idle. I noticed a screw missing on the cover today and noticed some rust on the metal plate surrounding it.
09-06-2011, 05:31 PM
#11
Burning Brakes
the issues are rich, not idling, backfire. not sure the coil is the first place to look for either of those. don't see how we can ignore the iac.
09-06-2011, 05:56 PM
#12
Burning Brakes
also, unless you marked/numbered the dist ends of your wires, it is possible one is crossed. happens a lot.
another also, plugging a vac hose is fine IF it is the end that goes to the vac source.
it is so easy to overlook some little thing so I have to mention them. the backfire look like ign, timing, whatever. spark fires while intake is open.
joe
another also, plugging a vac hose is fine IF it is the end that goes to the vac source.
it is so easy to overlook some little thing so I have to mention them. the backfire look like ign, timing, whatever. spark fires while intake is open.
joe
09-06-2011, 06:39 PM
#13
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also, unless you marked/numbered the dist ends of your wires, it is possible one is crossed. happens a lot.
another also, plugging a vac hose is fine IF it is the end that goes to the vac source.
it is so easy to overlook some little thing so I have to mention them. the backfire look like ign, timing, whatever. spark fires while intake is open
joe
another also, plugging a vac hose is fine IF it is the end that goes to the vac source.
it is so easy to overlook some little thing so I have to mention them. the backfire look like ign, timing, whatever. spark fires while intake is open
joe
Have anything to do with my problems?
09-06-2011, 06:42 PM
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09-06-2011, 06:50 PM
#15
Burning Brakes
only by adding another problem to the several you have.
it starts, alternator resupplies voltage, starts again.
that's all the battery is expected to do. the engine should run fine with battery disconnected.
coolant temp sensor can fail, if reading is -49* the ecm will add fuel, engine runs rich. generally, code 14 would set.
it starts, alternator resupplies voltage, starts again.
that's all the battery is expected to do. the engine should run fine with battery disconnected.
coolant temp sensor can fail, if reading is -49* the ecm will add fuel, engine runs rich. generally, code 14 would set.
09-06-2011, 06:53 PM
#16
Burning Brakes
it has to be adjusted. no fsm or haynes? there is a documented procedure on the "sticky's" on discussions forum. check it out. I am almost certain the engine will not idle without it being set.
*** we are talkin' Idle Air Control, not ICM, engine module. correct?
*** we are talkin' Idle Air Control, not ICM, engine module. correct?
Last edited by joe paco; 09-06-2011 at 06:55 PM. Reason: add***
09-06-2011, 06:55 PM
#17
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only by adding another problem to the several you have.
it starts, alternator resupplies voltage, starts again.
that's all the battery is expected to do. the engine should run fine with battery disconnected.
coolant temp sensor can fail, if reading is -49* the ecm will add fuel, engine runs rich. generally, code 14 would set.
it starts, alternator resupplies voltage, starts again.
that's all the battery is expected to do. the engine should run fine with battery disconnected.
coolant temp sensor can fail, if reading is -49* the ecm will add fuel, engine runs rich. generally, code 14 would set.
09-06-2011, 06:58 PM
#18
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Yes the IAC. Just bought a Haynes going to try and reset thanks.
09-06-2011, 07:00 PM
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09-06-2011, 07:03 PM
#20
Burning Brakes
the IAC is simple with the haynes, that may cure the idle issue. I would verify all the ign parts if it was mine, wiring, plug wires, if it runs, the module and pickup coil are ok.