85/86 sensor differences
Thread Starter
Drifting
Joined: Jan 2002
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From: Las Cruces NM
85/86 sensor differences
I know the maf is a diff design between the 85 and 86 cars, but what about the manifold air pressure sensor and the throttle position sensor? The reason I ask is that I have a service engine soon light that intermittently appears and the code was code 54, which is either the map, tps or the pcm. I don't think its the pcm being that the car seems to run fine, actually really well. Also, the reason I ask about the two years is that my car is an 86 and I got an 85 parts car in the deal with the car.
Thanks.
Chris
Thanks.
Chris
- 1986 Original Owner -
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Re: 85/86 sensor differences (okinawa86vette)
Chris,
I'm not sure where you're getting your info, but on an '86, Code 54 is FUEL PUMP CIRCUIT (LOW VOLTAGE).
I'm not sure where you're getting your info, but on an '86, Code 54 is FUEL PUMP CIRCUIT (LOW VOLTAGE).
Melting Slicks
Joined: Aug 2001
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From: Lockport NY
Re: 85/86 sensor differences (Ray Quayle)
Also, your '85 should be TBI; the '86's have TPI. Different systems, almost certainly different sensors.
*Definately* different ECMs with way-different BINs.
Best to get a shop manual for the car you intend to restore. Put the TBI setup on eBay. Store the spare 4+3. (You'll need it eventually!)
*Definately* different ECMs with way-different BINs.
Best to get a shop manual for the car you intend to restore. Put the TBI setup on eBay. Store the spare 4+3. (You'll need it eventually!)
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Re: 85/86 sensor differences (Rich B.)
Also, your '85 should be TBI; the '86's have TPI. Different systems, almost certainly different sensors.
Melting Slicks
Joined: Aug 2001
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From: Lockport NY
Re: 85/86 sensor differences (Ray Quayle)
The '85 is TPI. It was the first year for it.
My parts book shows -
Sensor, Mass Air Flow (1985) - part # 14081243
Sensor, Mass Air Flow (1986) - part # 14094712
Sensor Kit, Throttle Position (1985-1989) - part # 17111606
I don't believe the '86 or '85 had a MAP sensor...That didn't start until 1990, IIRC - Speed Density system...(I could be wrong...again...) :crazy:
[Modified by Rich B., 12:27 PM 1/20/2002]
Thread Starter
Drifting
Joined: Jan 2002
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From: Las Cruces NM
Re: 85/86 sensor differences (Rich B.)
If code 54 deals with the fuel pump, what would cause this? The car probably needs a new fuel filter badly, but I haven't had a chance to get one being that I'm in Japan. Would it probably be a problem with the fuel pump itself?
I got the info from the book that came with the scan tool. Didn't even really need the scan tool, but I wanted the book for the codes.
Chris
I got the info from the book that came with the scan tool. Didn't even really need the scan tool, but I wanted the book for the codes.
Chris
Thread Starter
Drifting
Joined: Jan 2002
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From: Las Cruces NM
Re: 85/86 sensor differences (okinawa86vette)
As far as the map sensor, I don't think it did either, but that's what my little handy dandy, may be wrong code book listed. It's for a range of years of different GM vehicles.
Le Mans Master
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From: Kempner Texas
Re: 85/86 sensor differences (okinawa86vette)
I just had an intermittent code 54 problem last week I replaced the fuel pump relay; problem solved.
BTW, there is no manifold pressure sensor on the 86, there is a manifold air temp sensor though, located on the underside of the plenum near the distributor.
Hope this helps.
Jake
[Modified by JAKE, 11:40 PM 1/20/2002]
BTW, there is no manifold pressure sensor on the 86, there is a manifold air temp sensor though, located on the underside of the plenum near the distributor.
Hope this helps.
Jake
[Modified by JAKE, 11:40 PM 1/20/2002]
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Re: 85/86 sensor differences (okinawa86vette)
Chris,
I'd agree with Jake. Try the Fuel Pump Relay first. The ECM monitors the Fuel Pump voltage to alter the fuel delivery if system voltage drops. The code sets if the ECM sees < 2 volts for 1.5 seconds. This typically happens when the Fuel Pump Relay is bad or lazy (doesn't energize immediately). There are other causes, but this is usually the scenario - insert key, turn fully to start, engine cranks, but because Fuel Pump Relay doesn't energize, the Fuel Pump doesn't get power until the oil pressure comes up to about 4psi, if this takes more than 1.5 seconds (and often does) code 54 will set and the SES light will stay on until ignition is switched to OFF. This also obviously results in longer crank times.
Try switching the ignition to ON, not START and listen for the Fuel Pump buzz coming from behind your right ear (pump is in the tank). It should run for about 2 seconds. If it doesn't replace the Relay. It's the cheapest place to start. If you're having trouble getting parts, I can send you a relay from my APO to yours. Just let me know.
I'd agree with Jake. Try the Fuel Pump Relay first. The ECM monitors the Fuel Pump voltage to alter the fuel delivery if system voltage drops. The code sets if the ECM sees < 2 volts for 1.5 seconds. This typically happens when the Fuel Pump Relay is bad or lazy (doesn't energize immediately). There are other causes, but this is usually the scenario - insert key, turn fully to start, engine cranks, but because Fuel Pump Relay doesn't energize, the Fuel Pump doesn't get power until the oil pressure comes up to about 4psi, if this takes more than 1.5 seconds (and often does) code 54 will set and the SES light will stay on until ignition is switched to OFF. This also obviously results in longer crank times.
Try switching the ignition to ON, not START and listen for the Fuel Pump buzz coming from behind your right ear (pump is in the tank). It should run for about 2 seconds. If it doesn't replace the Relay. It's the cheapest place to start. If you're having trouble getting parts, I can send you a relay from my APO to yours. Just let me know.
Thread Starter
Drifting
Joined: Jan 2002
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From: Las Cruces NM
Re: 85/86 sensor differences (Ray Quayle)
Thanks for all the help. I do have longer than normal crank times too. Where exactly on the car is the relay located and would it be the same off an 85?
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Re: 85/86 sensor differences (okinawa86vette)
Chris,
The relay should be the same as the '85. May be part number 14078915. This is a common relay and is used for many things. Mounted on the firewall just inboard of the brake booster. If you have the manual trans, there will be two of these relays mounted on a bracket. One is the manual trans overdrive relay and the other is the fuel pump relay. They should be the same part number and will be interchangeable. Just swap them and see if it helps the long crank/code 54. You will then probably find your OD doesn't work. If you don't have the manual trans, there will only be one relay there and as I said, the one from the '85 should be the same.
Good luck.
The relay should be the same as the '85. May be part number 14078915. This is a common relay and is used for many things. Mounted on the firewall just inboard of the brake booster. If you have the manual trans, there will be two of these relays mounted on a bracket. One is the manual trans overdrive relay and the other is the fuel pump relay. They should be the same part number and will be interchangeable. Just swap them and see if it helps the long crank/code 54. You will then probably find your OD doesn't work. If you don't have the manual trans, there will only be one relay there and as I said, the one from the '85 should be the same.
Good luck.
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,606
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From: Las Cruces NM
Re: 85/86 sensor differences (okinawa86vette)
I checked the part numbers on the actual relays with my parts car and my driver, and they turned out to be the same. I grabbed the parts car one and went to install it and low and behold, the one in my car wasn't plugged in. I plugged it in and the car now runs good. Much better than before but the computer is still learning the curves since I reset it to erase the codes. Thank you for the help.
Chris
Chris
