92 Caprice Stalling/Erratic Hesitating Problems

92 Caprice, 305, fuel injection, overdrive transm.. Problem: car is very erratic/jerky whenever give it gas after a complete stop. Sometimes stalls, but not always. More erratic on starting out from a stop (very little noticeable while crusing at say 55mph). "Service Engine Soon" light only comes on sometimes (and usually not long enough to get a diagnostics test so that pretty much rules that out I guess). Also after car warms up the erratic start up from a stop seems to happen more. And sometimes while car sits in idle, the motor increases and decreases in speed.

What was done so far: replaced the plug wires, plugs, rotor cap, rotor "button", thermostat, cleaned the pcv valve that was full of grime but was not stuck, cleaned the air filter, and replaced a sensor(?-has a wire that connects to the top and bottom screws into top of intake, located to the left of the thermostat. that sensor seemed to take care of the erratic idle speeds at 1st, but now it does it again). sometimes smell of gas as if it's flooding, unless it's my imagination.

could it be, fuel filter? throttle sensor? tcc? idle air control valve? Any ideas and help appreciated.

Do a search here on how to get your computer codes. You should find many a post by myself that details how to get the codes. Even if the light goes out, you car has still stored a code. Get those and let's work from there.

Can you feel the car jerk/buck alot when you shift?

it has an auto transmission but yes while trying to give the car speed it does the stalling/bucking soon as give it gas, or while the trans. is tryng to shift gears. was able to finally get a chance to get a diagnostics done at the diagnostics port while the serv. engine soon light was on and they said codes 24, 25, 33, 36, & 66 showed up, with one of those codes kept showing up to somehow mean the computer is defective possibly. They also said one of the codes meant the air temp. sensor is bad (but just had that replaced recently).

thought someone said those same codes are saved in the computer for future reference, but I went out and re-checked the codes myself (after now learning how to do it- car was shut off for some hours, and serv. engine soon light doesn't come on now) and only codes 15, 23, & 44 only show up now (besides the normal 12 that shows up at the beginning and end of each full code cycle).

when light comes on again I'll re-check the codes again myself and post later.

Ok engine light came on again, checked the codes and they come up again only 15, 23, 44 (besides the usual 12's at the beginning and end). Any info on these woudld help. I still wonder if the throttle sensor is screwed. Thanks for any help!

All currently listed codes are from the 1989 B-car Service Manual. Why? Because that's what I have. If you have others that aren't listed or need to be added, just let me know.


CODE AND CIRCUIT POSSIBLE CAUSE

CODE 12 = System check
Indicates that the ECM is functioning.

CODE 12 = No Engine Speed Reference - VIN 'Y' CARB
Indicates an open or ground in the distributor reference circuit.

CODE 13 = OPEN Oxygen Sensor (O2)
Indicates that the oxygen sensor circuit circuit or sensor was open for one minute while off idle.

CODE 14 = Coolant Sensor (CTS)
Sets if the sensor or signal line are grounded for 3 seconds. HIGH Temperature indication.

CODE 15 = Coolant Sensor (CTS)
Sets if the sensor wires or connections are open for 3 seconds. LOW Temperature indication.

CODE 21 = Throttle Position Sensor (TPS)
TPS voltage of more than 2.5 volts for 3 seconds at an engine speed less than 1200 rpm. HIGH Voltage Signal.

CODE 22 = Throttle Position Sensor (TPS)
A shorted to ground or open signal circuit will set code in 3 seconds. LOW Voltage Signal.

CODE 23 = Manifold Air Temperature Sensor (MAT)
Sets if the sensor wires or connections are open for 3 seconds or Intake Air Temperature (IAT) LOW Temperature indication.

CODE 24 = Vehicle Speed Sensor (VSS)
No vehicle speed present during road/load deceleration. NO Vehicle Speed Indication.

CODE 25 = Manifold Air Temperature Sensor (MAT)
Sets if the sensor or signal line are grounded for 3 seconds. Or Intake Air Temperature (IAT)
HIGH Temperature indication.

CODE 32 = Exhaust Gas Recirculation (EGR)
OR Vacuum switch shorted to ground on start up. Switch not closed after the ECM has commanded EGR for a specified period of time OR EGR solenoid circuit open for a specified period of time.

CODE 33 = Manifold Absolute Pressure (MAP)
MAP sensor output too high for 5 seconds or an open circuit. LOW Vacuum.

CODE 34 = Manifold Absolute Pressure (MAP)
Low or no output from sensor with engine running. HIGH Vacuum.
CODE 35 = Idle Air Control (IAC)
IAC error.

CODE 42 = Electronic Spark Timing (EST)
ECM has seen an open or grounded EST or Bypass circuit.

CODE 43 = Electronic Spark Control (ESC)
Signal to the ECM has remained low for too long or the system has failed a functional check.

CODE 44 = LEAN Exhaust Indication
If voltage to oxygen sensor remains BELOW .2v for more than 20 seconds code is set.

CODE 45 = RICH Exhaust Indication
If voltage to oxygen sensor remains ABOVE .7v for more than 1 minute code is set.

CODE 51 = PROM - Faulty MEM-CAL or ECM.

CODE 52 = Faulty or missing CAL-PACK.

CODE 53 = System overvoltage
Indication of a faulty alternator or regulator. Camaro/Firebird uses a Code 53 for Vehicle Anti-Theft System (VATS).

CODE 54 = Low Voltage To Fuel Pump
Sets when the fuel pump voltage is less than 2 volts when reference pulses are being received.

CODE 55 = Faulty ECM

15. Low temperature indicated at engine coolant temp. sensor
23. Low temperature at intake air temperature sensor
44. Left oxygen sensor lean

Hope this helps!

thanks for the help on the codes. with the certain codes given, what does this all mean, and what do you think might need changed or fixed? was told might have to replace the throttle sensor for example, but I guess that's not even listed on the codes given by the car. any ideas?

Unfortunately these codes were not completely standardized by GM, they varied somewhat from different models, and different years.
For code 15 I would check for a 5 volt reference voltage with a digital voltmeter, if you do not have one they are pretty cheap, I have seen them for 5 bucks before, typically around10-15 for the cheaper ones. If you are not the correct reference voltage to the sensor you will not get a correct signal to the ecm. For a Code 23 you need to make sure what circuit the code is calling for. On some models a code 23 is a Throttle Positioning Sensor. You also want to check for a 5 volt reference voltage on that sensor, I would not worry about the code 44 until you get the other ones taken care of. It means the car is running lean, which is probably the result of the other two trouble codes. Hopefully someone can give you resistance values for the sensors soyou can check them out to

Hi I own a 92 caprice 5.0 L and i had the exact same problems as you discibed. now finding it was total blind luck and the lack of eletrical engine components to replace .... so i know how you feel .... that being said , the problem is simple and stupidly simple (anoying) insid your fuel tank there is a 1 inch piece of ruber tubing that conects the fuel pump to the fuel pump mounting asembly you will most likly find that there is a crack in that line .... due to the fact that it is inside the tank you will have to pull the fuel tank and disconect the fuel lines ... its not dificult to do this there are 2 clamps that mount the fuel tank to the car 2 nuts and the tank is loose then diconect the fuel lines and its out ..... your best bet to stop any futher trouble is to just buy a fuel pump kit it comes with a new peice of tubing and the pump itself ... slap it all back together and your problems should be over

this issue I'm sure was corrected,,,it is about 4 years old now....

this issue I'm sure was corrected,,,it is about 4 years old now....

We realize that, but sometimes as in this case, the thread can benefit from additional information and help. Especially if someone in the future does a search with the same issue, then they would have all of the options to solving that problem before them in these threads. That is why it was not closed . It is a goal of AF to present as much archived info as well as updates as they become available.

The 454 in my 89 pickup has some of the same symptoms. I think it is the EGR valve, at least it's the code that it showed.