Mechanics

ENGINE SPUTTER/HESITATION/NO POWER

1988 Pontiac Trans Am

Engine Performance problem
1988 Pontiac Trans Am V8 Two Wheel Drive Automatic 60000 miles

My 305 TPI is starting hard at times, but the biggest problem is that when I crack the throttle open the engine kind of " stalls" and then goes through a series of hesitation like symptoms where it is acting like it wants to rev up but can't. The problem seems to be better or at least less apparent after I have let the engine warm up real good. I have corrected a couple of vacuum leaks including the EGR and my Cold Start Injector, but no joy. I have ohmed out the plug wires and they are good. Engine vacuum is 21 in -Hg and steady and fuel pressure reads around 30-32 psi. I do have a video file I could provide that may help with showing what is going on.
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Jnbdykema
March 23, 2010.



Is the service engine light on? Read the codes Cross terminals A & B as shown with a piece of wire, then turn the key on. Count the flashes, a 22 will flash as 2 flashes then a short pause, then 2 flashes, if more than one code is stored, the pause will be longer. The codes will display three times and end with 12. Write them down and post here. This connector is right under the middle of the dash...


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Hesitation, Sag, Stumble 1. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Check for contaminated fuel. Check for sticking or binding TPS. 2. Check PROM or MEM-CAL for proper application. Check spark plug condition. Check vacuum hose to MAP sensor for damage. Verify alternator output voltage is between 9 and 16 volts. Repair as necessary. 3. Check for air leak between MAF sensor and throttle body. Check canister purge system and EGR for proper operation. Check MAP or MAF sensor. Check ignition timing. Ensure engine is operating at proper temperature. 4. Check HEI ground circuit. Perform injector balance test. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Rough, Unstable Idle 1. Check for sticking or binding TPS or throttle linkage. Check idle speed and IAC system. See CODE 35 CHART in COMPUTERIZED ENGINE CONTROL section. 2. Verify alternator output voltage is between 9 and 16 volts. Repair as necessary. Check P/N switch circuit (if equipped). Check ECM ground circuits. Check EGR system and PCV valve operation. 3. Perform injector balance test. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Check ignition system and ignition timing. Check fuel evaporative system. Ensure battery cables and ground straps are clean and tight. 4. Check A/C input to ECM. Check for vacuum leaks. Check for loose or damaged air duct between MAF sensor and throttle body. On 2.8L VIN S, 5.0L and 5.7L, check Air Injection Reaction (AIR) system. No air should exist at ports during closed loop operation. 5. On all models, inspect O2 sensor for contamination from fuel. Sensor is defective if coated with a White powdery coating. Disconnect MAF sensor. Replace sensor if condition is corrected. 6. Check for fuel in pressure regulator hose. Replace pressure regulator if fuel exists. Check cylinder compression. Cuts Out, Misses 1. Disconnect IAC motor. Start engine. Using insulated pliers, remove one spark plug at a time and note RPM. If RPM drops within 50 RPM on all cylinders, proceed to ROUGH, UNSTABLE IDLE symptom in this article. 2. Check ignition system and cylinder compression if no RPM change was noted or exceeded 50 RPM. Repair as necessary. 3. Disconnect all injector wiring connectors. Install Injector Test Light (J034730-2) between connector terminals. Note light while cranking. Test light should blink during cranking. Check injector drive circuit if light fails to blink. 4. Check for restricted fuel filter or fuel contamination. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. 5. Perform injector balance. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Check ignition system. Check for worn or damaged engine components.


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I show fuel pressure at 40-47 psi? If this is right, your fuel pump, or filter needs replacing.

Merlin2021
Mar 23, 2010.