est module trouble code
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Joined: Apr 2007
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est module trouble code
I just ran a scan on my 87' with a scan tool, the auto x-ray 6000. The scan displayed a problem with my EST, monitor error code and MAF / MAP sensor, too high and MAF sensor, burnoff fault. The scanner gave me these three codes. The problem is the car will not start, and if I do get it started it will not run for no longer than a few seconds before it shut off. The scanner is showing me my tps sensor is reading .68 volts. I have set this sensor several times at .54 but it continues read higher everytime I attempt to start the car. It's a brand new sensor, just installed it and its set properly. Another thing my injectors are reading 11.2 ms on a three second run, is this correct. I thought the injectors read only around 4.4 after start up. Thanks guys for your help in advance. This problem has been haunting me for almost four months.
purplehayes
purplehayes
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
The TPS will read .68Vdc at normal idle if it was set to .54Vdc at base idle of 450rpm.
Sounds like your main problem is with the MAF, if replacing the relays doesn't do it, pick up a good used MAF from a mid '80s F-body car.
Sounds like your main problem is with the MAF, if replacing the relays doesn't do it, pick up a good used MAF from a mid '80s F-body car.
Team Owner
Joined: Jan 2003
Posts: 20,322
Likes: 248
From: Summerland B.C. Canada
Does it run with the MAF unplugged ??
I'll assume your lack of response to my question, is due to the fact you don't have a FSM.
Follow the flow charts
http://members.shaw.ca/corvette86/Code%2033.pdf
http://members.shaw.ca/corvette86/Code%2036.pdf
http://members.shaw.ca/corvette86/Code%2042.pdf
If you have had the EST wire unplugged recently, you will get a code 42 until the battery has been disconnected and all codes are cleared.
I'll assume your lack of response to my question, is due to the fact you don't have a FSM.
Follow the flow charts
http://members.shaw.ca/corvette86/Code%2033.pdf
http://members.shaw.ca/corvette86/Code%2036.pdf
http://members.shaw.ca/corvette86/Code%2042.pdf
If you have had the EST wire unplugged recently, you will get a code 42 until the battery has been disconnected and all codes are cleared.
Team Owner
Joined: Jan 2003
Posts: 20,322
Likes: 248
From: Summerland B.C. Canada
Never, ever, seen that on my vette, and I can't see why I would. The only difference between min idle and normal idle, is the IAC will bypass air to reach target RPM. The throttle hasn't moved, nor has the TPS, so why would there be a change in TPS value ??
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
No Map on an 87, disregard that one. What am I missing here as far as your injectors.....11.2 ms? and 4.4? Your injectors should ohm above 10ohms, per 87 FSM. My 87 injectors (stock) ohmed around 16. Most important is that they all ohm within + or -.5. You should also do a fuel pressure test.
I'm with 86 on the TPS setting, maybe 65Z01 can fill us in?
Another thing, take your ignition control module to AutoZone, they'll test it for free.
I'm with 86 on the TPS setting, maybe 65Z01 can fill us in?
Another thing, take your ignition control module to AutoZone, they'll test it for free.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
The throttle hasn't moved, nor has the TPS, so why would there be a change in TPS value ??
I just checked an old AutoXray scan and see .78Vdc at 660rpm.
Last edited by 65Z01; Aug 8, 2008 at 01:09 PM.
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From: Cumming Ga
No Map on an 87, disregard that one. What am I missing here as far as your injectors.....11.2 ms? and 4.4? Your injectors should ohm above 10ohms, per 87 FSM. My 87 injectors (stock) ohmed around 16. Most important is that they all ohm within + or -.5. You should also do a fuel pressure test.
I'm with 86 on the TPS setting, maybe 65Z01 can fill us in?
Another thing, take your ignition control module to AutoZone, they'll test it for free.
I'm with 86 on the TPS setting, maybe 65Z01 can fill us in?
Another thing, take your ignition control module to AutoZone, they'll test it for free.
ohms is the resitance of the coil.. two different things.
Team Owner
Joined: Jan 2003
Posts: 20,322
Likes: 248
From: Summerland B.C. Canada
I understand your logic and can only guess that the inflow of air at the normal idle is pulling the throttle blades open a tad. After I set my TPS to .65Vdc at min. idle of 450RPM I always see around .74Vdc at normal idle of ~700RPM.
I just checked an old AutoXray scan and see .78Vdc at 660rpm.
I just checked an old AutoXray scan and see .78Vdc at 660rpm.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
I could understand a change in the TPS voltage between engine not running/engine running - IF the voltage regulator/power supply circuitry built into the ECM was messing up, not providing the "constant" 5.0 volt reference to the TPS circuit.
I cannot understand why the TPS voltage would change with/without the IAC and ESC bypass connected (min idle/normal idle). Shouldn't be any difference.
I would suspect the measurement, first. If the voltage really and truly IS different then Something is going on in the ECM. Take the voltage measurement "manually" with a voltmeter by jumpering the wires out at the TPS itself, and compare the value to what the ECM is seeing and sending out on the datastream (read by the scan tool). They Ought to be the same...
I cannot understand why the TPS voltage would change with/without the IAC and ESC bypass connected (min idle/normal idle). Shouldn't be any difference.
I would suspect the measurement, first. If the voltage really and truly IS different then Something is going on in the ECM. Take the voltage measurement "manually" with a voltmeter by jumpering the wires out at the TPS itself, and compare the value to what the ECM is seeing and sending out on the datastream (read by the scan tool). They Ought to be the same...
Thread Starter
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Joined: Apr 2007
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I changed the computer, the car idles a little better. Whats going on, when the scanner tells you the "vehicle not responding" when you try to scan. All connections are good. A local shop informed me, if that happens the ecm is nomally bad and its not reading. I've also recieved anthor set of codes, 13,24,51,46,45,44,43,36,22,21,14. Whats stange is that the car never kick out so many codes before. All this happen right before the scanner was no loner able to read the ecm.
purplehayes
purplehayes
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
You either have Another bad ECM, or - more likely - a problem with wiring/grounds/power To the ECM.
You can chase individual trouble codes forever, but until you at least verify that the ECM has the power and grounds that it's supposed to have you'll be wasting your time..
You can chase individual trouble codes forever, but until you at least verify that the ECM has the power and grounds that it's supposed to have you'll be wasting your time..
