Troubleshooting Guide — 18 Surges While Cruising (continued)
F2-51flowchart18 Surges While Cruising (steps 6—12)
1
STEP 6: Is throttle linkage correctly installed and does it operate freely? (page F2-96)
No
As required, correct, clean, or replace any binding or damaged linkage, and adjust cable deflection at throttle body (page F2-96)
Yes
2
Go to next step
3
STEP 7: Is intake manifold vacuum correct at idle? Vacuum: More than 450 mmHg {17.7 inHg}
No
Check for air leakage of intake air system components
Yes
4
Go to next step
5
STEP 8: Is air cleaner element clean? (page F2-70)
No
Replace air cleaner element
Yes
6
Go to next step
7
STEP 9: Connect System Selector to data link connector and set Test Switch to "SELF TEST"; is ignition timing at idle correct after warm-up? (page F2-70) Ignition timing (BTDC): 9—11° {10 ± 1°}
No
Adjust ignition timing (page F2-70)
Yes
8
Does ignition timing advance during acceleration? If it does, go to next step. If it does not, replace ECM (page F2-141)
9
STEP 10: Is fuel line pressure correct at idle? (page F2-113) Fuel line pressure: 260—310 kPa {2.6—3.2 kgf/cm², 37—45 psi} (vacuum hose to pressure regulator disconnected)
No
Low pressure — Check fuel line pressure while pinching fuel return hose. If pressure quickly increases, check pressure regulator (page F2-113). If pressure gradually increases, check for clogging between fuel pump and pressure regulator. If hose is not clogged, check fuel pump maximum pressure (page F2-110)
Low pressure — Check fuel line pressure while pinching fuel return hose. If pressure quickly increases, check pressure regulator (page F2-113). If pressure gradually increases, check for clogging between fuel pump and pressure regulator. If hose is not clogged, check fuel pump maximum pressure (page F2-110)
No
High pressure — Is fuel return line clogged? If it is not, replace pressure regulator (page F2-115). If it is, replace it
Yes
10
Does fuel line pressure decrease during quick acceleration? If it does, check for fuel pump maximum pressure (page F2-110). If pressure is OK, check fuel line and filter for clogging. If it does not, go to next step
11
STEP 11: Check if exhaust system is restricted (page F2-121)
Yes
Repair or replace
No
12
Go to next step
STEP 12: Try a known good ECM and check if condition improves (page F2-141)