After Cam Install: Injectors Shutting Down Causing a MISS! HELP!
03-02-2004, 07:14 PM
#1
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Location: Toledo, Ohio USA
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After Cam Install: Injectors Shutting Down Causing a MISS! HELP!
Ok now that I have everyone's attention I will continue. 
Before I get into it too much, here's the lowdown:
96 Formula Converted to OBD-I.
I have a friend who just installed a XE cam/Comp Springs into his car & replaced his Opti & H20 Pump. Now his car was tuned by PCM4Less also, but it has a REALLY BAD miss! I'm unsure if this is tuning related or not, but I have a feeling it's something electrical because in the LOG it shows the miss actually being lack of fuel by the injectors shutting down for about 1 sec...
It happened 3 times while logging and I don't know if this makes a difference, but the first time it happened the CCP DC% Dropped to 0 just a second before the injectors cut out, the log showed the injectors staying CLOSED for 3 seconds.
Now the second time it happened Bank 2 shut down first, but only by a mS.
All 3 times were on Deceleration and range from 2800-3600 RPM @ speeds of around 60 MPH.
No Knock Count, but Knock Retard goes up to 2.5 sometimes...?
PCM Voltage = 14.1-14.2v Isn't that high, my 93 is logging 12.7-12.8v...???
Any help would greatly be appreciated, is it possible he might have overlooked a small detail in the OBD conversion???
Before I get into it too much, here's the lowdown:
96 Formula Converted to OBD-I.
I have a friend who just installed a XE cam/Comp Springs into his car & replaced his Opti & H20 Pump. Now his car was tuned by PCM4Less also, but it has a REALLY BAD miss! I'm unsure if this is tuning related or not, but I have a feeling it's something electrical because in the LOG it shows the miss actually being lack of fuel by the injectors shutting down for about 1 sec...
It happened 3 times while logging and I don't know if this makes a difference, but the first time it happened the CCP DC% Dropped to 0 just a second before the injectors cut out, the log showed the injectors staying CLOSED for 3 seconds.
Now the second time it happened Bank 2 shut down first, but only by a mS.
All 3 times were on Deceleration and range from 2800-3600 RPM @ speeds of around 60 MPH.
No Knock Count, but Knock Retard goes up to 2.5 sometimes...?
PCM Voltage = 14.1-14.2v Isn't that high, my 93 is logging 12.7-12.8v...???
Any help would greatly be appreciated, is it possible he might have overlooked a small detail in the OBD conversion???
Last edited by ZPaul2Fresh8; 03-03-2004 at 06:01 PM.
03-02-2004, 07:21 PM
#2
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Location: Toledo, OH
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Few things...
I did the install, the rockers are adjusted properly, with polylocks so that is not part of the problem. The entire valvetrain was replaced, lifters, springs, pushrods everything.
The knock sensor was replaced by a 94 sensor.
Brand new GM opti and WP (dowel pin is right)
Stock injectors, looked like two had been replaced previously though, they looked newer than the rest.
I did the install, the rockers are adjusted properly, with polylocks so that is not part of the problem. The entire valvetrain was replaced, lifters, springs, pushrods everything.
The knock sensor was replaced by a 94 sensor.
Brand new GM opti and WP (dowel pin is right)
Stock injectors, looked like two had been replaced previously though, they looked newer than the rest.
03-04-2004, 11:48 PM
#6
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I could swear I answered this post yesterday on another board.
Entirely normal. When you snap the throttle closed and go into decel, the PCM shuts down the injectors. They stay shutdown until the engine reaches a certain RPM and/or the vehicle hits a certain MPH. With an M6, you can typically feel the injectors kick back on at about 1,500RPM on decel. This prevents the injectors from dumping raw fuel into the exhaust. I think its called fuel over-ride cut or something like that.
I think you are looking in the wrong place if you are trying to relate your miss on accel to the injectors shutting down on decel.
All 3 times were on Deceleration
I think you are looking in the wrong place if you are trying to relate your miss on accel to the injectors shutting down on decel.
03-05-2004, 06:13 AM
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Originally posted by Injuneer
I could swear I answered this post yesterday on another board.
Entirely normal. When you snap the throttle closed and go into decel, the PCM shuts down the injectors. They stay shutdown until the engine reaches a certain RPM and/or the vehicle hits a certain MPH. With an M6, you can typically feel the injectors kick back on at about 1,500RPM on decel. This prevents the injectors from dumping raw fuel into the exhaust. I think its called fuel over-ride cut or something like that.
I think you are looking in the wrong place if you are trying to relate your miss on accel to the injectors shutting down on decel.
I could swear I answered this post yesterday on another board.
Entirely normal. When you snap the throttle closed and go into decel, the PCM shuts down the injectors. They stay shutdown until the engine reaches a certain RPM and/or the vehicle hits a certain MPH. With an M6, you can typically feel the injectors kick back on at about 1,500RPM on decel. This prevents the injectors from dumping raw fuel into the exhaust. I think its called fuel over-ride cut or something like that.
I think you are looking in the wrong place if you are trying to relate your miss on accel to the injectors shutting down on decel.
You say it cuts off the injectors @ a certain RPM, but everytime it did it I was at different RPMs and came back on at different RPMS.
One cut out @ 3300 and didn't come back on until 2800!
But you're saying the injectors are suppose to cutout?
?Why would that happen? Spark didn't cut out...
CAn anyone answer the PCM Voltage Question?
The alternator produces 14.2 volts, and the PCM reads the same. Doesn't anyone see something wrong witht that?
I know the PCM is responsible for regulating that voltage down for distribution...
Anyone?
03-05-2004, 09:12 AM
#9
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We need to get the datamaster log up on here first of all.
Second one thing i remember is that the O2s were reading way split, one up around 900+mv and the other in the 100s. The are 80k 02s so I dont know if that has anything to do with it, but its more of a sluggish feeling at lower RPMs now (it has gotten worse since the original post) up until about 4000 it is really sluggish, then it kinda kicks in and goes, but still doesnt feel like full power.
What are some symptoms of bad injectors for one?
Can that canister purge that evaporates all the fumes in the gas tank into the intake manifold have anything to do with this?
Second one thing i remember is that the O2s were reading way split, one up around 900+mv and the other in the 100s. The are 80k 02s so I dont know if that has anything to do with it, but its more of a sluggish feeling at lower RPMs now (it has gotten worse since the original post) up until about 4000 it is really sluggish, then it kinda kicks in and goes, but still doesnt feel like full power.
What are some symptoms of bad injectors for one?
Can that canister purge that evaporates all the fumes in the gas tank into the intake manifold have anything to do with this?
03-05-2004, 10:28 AM
#10
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Location: PHX,AZ
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hmm. my problem is close to that.
after cam install my car has shut down on me 2-3 times on WOT runs.
I have had a code 16 and 18 throwen.
hmm.. injector circut and a opti low res code.
hope this opti thing works out. alot of work for nothing.
I may need to get datamaster on it.
after cam install my car has shut down on me 2-3 times on WOT runs.
I have had a code 16 and 18 throwen.
hmm.. injector circut and a opti low res code.
hope this opti thing works out. alot of work for nothing.
I may need to get datamaster on it.
03-05-2004, 10:41 AM
#11
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Location: Little Rock, AR
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Originally posted by ZPaul2Fresh8
I had seen that. Well I don't know what else to say. You say it's normal, but I say it's not.
You say it cuts off the injectors @ a certain RPM, but everytime it did it I was at different RPMs and came back on at different RPMS.
One cut out @ 3300 and didn't come back on until 2800!
But you're saying the injectors are suppose to cutout??
Why would that happen? Spark didn't cut out...
CAn anyone answer the PCM Voltage Question?
The alternator produces 14.2 volts, and the PCM reads the same. Doesn't anyone see something wrong witht that?
I know the PCM is responsible for regulating that voltage down for distribution...
Anyone?
I had seen that. Well I don't know what else to say. You say it's normal, but I say it's not.
You say it cuts off the injectors @ a certain RPM, but everytime it did it I was at different RPMs and came back on at different RPMS.
One cut out @ 3300 and didn't come back on until 2800!
But you're saying the injectors are suppose to cutout?
?Why would that happen? Spark didn't cut out...
CAn anyone answer the PCM Voltage Question?
The alternator produces 14.2 volts, and the PCM reads the same. Doesn't anyone see something wrong witht that?
I know the PCM is responsible for regulating that voltage down for distribution...
Anyone?
When deceleration is rapid or for long periods, the PCM will shut off the injectors. It is sometimes called Deceleration Fuel Cut Off or DFCO. It does not happen at particular rpms, rather under certain conditions. The exact situation you are saying the injectors "cut out" has to be known to claim it as being abnormal. A data log would be the best thing.
01-07-2005, 03:11 PM
#13
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Location: St. Charles, IL
Posts: 643
Re: After Cam Install: Injectors Shutting Down Causing a MISS! HELP!
Ok, first off, the alternaror regulates it's own voltage. If you think there is a problem, take it in to Autozone and have it tested. If it works to hard you can blow the diode trio and the regulation will get all ****** up.
second. Injuneer is right. what your talking about is called DFCO on a stock pcm I believe it shuts off at 2500 and turns on at 1500. but it also requires a certain throttle percentage to activate. I would think a tune shop would lower the activation RPM not raise it. Unless you said you wanted a more gas efficient car.
When you say it happens at different RPMS, do you have a scanner log. or are you just reading the tac?
second. Injuneer is right. what your talking about is called DFCO on a stock pcm I believe it shuts off at 2500 and turns on at 1500. but it also requires a certain throttle percentage to activate. I would think a tune shop would lower the activation RPM not raise it. Unless you said you wanted a more gas efficient car.
When you say it happens at different RPMS, do you have a scanner log. or are you just reading the tac?
Last edited by Brent94Z; 01-09-2005 at 08:58 AM.
01-08-2005, 02:06 PM
#14
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Re: After Cam Install: Injectors Shutting Down Causing a MISS! HELP!
Quick question..... what purpose does it serve to dig up a 9 month old thread, and then break board rules by pushing the language filter?
01-09-2005, 09:00 AM
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Re: After Cam Install: Injectors Shutting Down Causing a MISS! HELP!
Eff, I've edited your post. Please don't over-ride the language filter. A good clue that you are doing something wrong is anytime you have to type different characters in order to make the word you want to type appear. It is best to just type out whatever you want and if it is a word that should be filtered, it'll be filtered. Thanks!