Why will car not idle?

Unfortunately, there are 13 variations for this engine and year. Was this truck sold or modified for high altitude? Was it sold in California or modified to meet the CA emission standards? Does it have a manual or auto transmission? After narrowing down based on answers to these questions, there are still alternative configurations depending on the particular equipment, so look carefully at the diagrams to see which components are used on your engine. Sometimes you can match the 3 letter code for the diagram to letters in the VIN or a sticker in the engine compartment. Please let me know if you have questions.

Fig. Fig. 49: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with automatic transmission

Fig. Fig. 50: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with automatic transmission alternate

Fig. Fig. 51: 1984 305 (5.0L) V8 engine-4bbl federal and high altitude with automatic transmission

Fig. Fig. 52: 1984 305 (5.0L) V8 engine-4bbl federal and high altitude with automatic transmission alternate

Fig. Fig. 53: 1984 305 (5.0L) V8 engine-4bbl federal and high altitude with manual transmission

Fig. Fig. 54: 1984 305 (5.0L) V8 engine-4bbl federal and high altitude with manual transmission alternate

Fig. Fig. 55: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with manual transmission

Fig. Fig. 56: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with manual transmission alternate

Fig. Fig. 57: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with manual transmission alternate

Fig. Fig. 58: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with automatic transmission alternate

Fig. Fig. 59: 1984 305 (5.0L) V8 engine-4bbl federal and high altitude with automatic transmission alternate

Fig. Fig. 60: 1984 305 (5.0L) V8 engine-4bbl federal and low altitude with automatic transmission alternate

Fig. Fig. 61: 1984 305 (5.0L) V8 engine-4bbl federal and high altitude with automatic transmission alternate

I believe they make 4 versions of that truck,as far as
emissions go,for different states

You may now need to have either a sensor changed
for the altitude or the pcm/ecm reprogramed

I would start by asking a dealer & check their
bulletins on that subject

A local repair shop may be a better place to actually
get the changes done

Fig. 30: 1985 2.8L engine with manual transmission - federal and low altitude




Fig. 31: 1985 2.8L engine with manual transmission - federal and low altitude alternate




Fig. 33: 1985 2.8L engine with automatic transmission - federal and low altitude




Fig. 34: 1985 2.8L engine with automatic transmission - federal and low altitude alternate


Hope this helps (remember to rate this answer).

Could be the radiator is full of bugs or normal road filth that accumulates. How is the coolant level in the radiator. Fill it if low. Were you stalled in traffic? Were you at high altitude, like in the rocky mountains or appalachian mountains. Check radiator cap. They are relatively in-expensive considering the job they do. The cap pressurizes the fluid in the radiator and prevents it from boiling out at higher altitudes or higher temperatures.

HI,

Freeze Plugs AKA. Expansion Plugs are needed on ALL vehicles. They keep the coolant inside your engine. Yes you need them in all climates.

Get a PCM test for fault codes. It could be an oxygen sensor or MAF sensor. Free test at AUtozone if check engine light is on.
Clean MAF sensor heated wires with carb cleaner by spraying seveal times. Do not brush it. Disconnect battery for 2 hours and then drive for 10 miles after hook up.

SERVICE TIP MASS AIR FLOW (MAF) DISCUSSION MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows. If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads. One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle. NOTE: THE FOLLOWING PROCEDURE MAY ALSO BE USED TO DIAGNOSE VEHICLES THAT DO NOT HAVE FUEL SYSTEM/HO2S SENSOR DTCs. Symptoms

• Lack of Power
• Spark Knock/Detonation
• Buck/****
• Hesitation/Surge on Acceleration
• Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0171, P0172, P0174, P0175 may be stored in memory

OBDII DTCs

• P0171, P0174 (Fuel system lean, Bank 1 or 2)
• P0172, P0175 (Fuel system rich, Bank 1 or 2)
• P1130, P1131, P1132, (HO2S11 lack of switching, Bank 1)
• P1150, P1151, P1152, (HO2S21 lack of switching, Bank 2)

OBDI DTCs

• 181, 189 (Fuel system lean, Bank 1 or 2)
• 179, 188 (Fuel system rich, Bank 1 or 2)
• 171, 172, 173 (HO2S11 lack of switching, Bank 1)
• 175, 176, 177 (HO2S21 lack of switching, Bank 2)
• 184, 185 (MAF higher/lower than expected)
• 186, 187 (Injector pulse width higher/lower than expected)

NOTE: DO NOT DISCONNECT THE BATTERY. IT WILL ERASE KEEP ALIVE MEMORY AND RESET LONG TERM FUEL TRIM AND BARO TO THEIR STARTING/BASE VALUES. THE BARO PARAMETER IDENTIFICATION DISPLAY (PID) IS USED FOR THIS DIAGNOSTIC PROCEDURE. ALL OBDII APPLICATIONS HAVE THIS PID AVAILABLE. THERE ARE SOME OBDI VEHICLES THAT DO NOT HAVE THE BARO PID, FOR THESE VEHICLES OMIT THE BARO CHECK AND REFER ONLY TO STEPS 2, 3, AND 4 IN THE DIAGNOSTIC PROCEDURE.

1. Look at the BARO PID. Refer to the Barometric Pressure Reference Chart in this article. At sea level, BARO should read about 159 Hz (29.91 in. Hg). As a reference, Denver, Colorado at 1524 meters (5000 ft.) altitude should be about 144 Hz (24.88 in. Hg.). Normal learned BARO variability is up to ±6 Hz (±2 in. Hg.). If BARO indicates a higher altitude than you are at (7 or more Hz lower than expected), you may have MAF contamination. If available, Service Bay Diagnostic System (SBDS) has a Manifold Absolute Pressure (MAP) sensor that can be used as a barometric pressure reference. Use "MAP/BARO" test under "Powertrain," "Testers and Meters." Ignore the hookup screen. Connect GP2 to the reference MAP on the following screen. NOTE: REMEMBER THAT MOST WEATHER SERVICES REPORT A LOCAL BAROMETRIC PRESSURE THAT HAS BEEN CORRECTED TO SEA LEVEL. THE BARO PID, ON THE OTHER HAND, REPORTS THE ACTUAL BAROMETRIC PRESSURE FOR THE ALTITUDE THE VEHICLE IS BEING OPERATED IN. LOCAL WEATHER CONDITIONS (HIGH AND LOW PRESSURE AREAS) WILL CHANGE THE LOCAL BAROMETRIC PRESSURE BY SEVERAL INCHES OF MERCURY (±3 Hz, ±1 in. Hg.). NOTE: BARO IS UPDATED ONLY WHEN THE VEHICLE IS AT HIGH THROTTLE OPENINGS. THEREFORE, A VEHICLE WHICH IS DRIVEN DOWN FROM A HIGHER ALTITUDE MAY NOT HAVE HAD AN OPPORTUNITY TO UPDATE THE BARO VALUE IN KAM. IF YOU ARE NOT CONFIDENT THAT BARO HAS BEEN UPDATED, PERFORM THREE OR FOUR HEAVY, SUSTAINED ACCELERATIONS AT GREATER THAN HALF-THROTTLE TO ALLOW BARO TO UPDATE.
   

tune up-read your plugs and then check your timing. use timing light and double check with scan tool-most 91 305's were high outputs which
requires higher octane than regular (fuel grade revelatnt to compression ratio and altitude) you may want to check fuel pressure could be a clogged filter or bad pump.

the carb is dirty, high allitude yields less air and more fuel, a richer mixture, overhaul the carb.

1st off your car doesn't have a carburetor, it is fuel injected and will compensate for any altitude change up to 5,000 feet, here is what u need to do.
Here is the most common cause of surges and stalls at stops and low erratic idle speed and rough idle, it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.