I have a reliable (usually) car that started to idle very badly, stumble
and shake. I also began smelling gas in the exhaust.
-No codes shown or in CEL memory
-Checked plugs and all 4 black sooted
-Oil smells of gas
-Borrowed a scanner and STFTRM was -34
-Fuel pressure in spec when checked
-Strong spark from ignition system
-O2 upstream sensor in spec when checked
-O2 downstream sensor out of spec when checked
It was then I checked the vacuum and it was very low, (8-10 in.) and then I
heard the telltale sound of the timing chain hitting the cover. My first thought
was the timing chain or tensioner was gone, which was sapping the vacuum and
that’s why the car was running rich.
Removed timing cover and tensioner was broken. Replaced timing gears, chain
and tensioner with OEM parts. Engine is transverse mounted so it was difficult to
eyeball whether the dots and tang on the tensioner lined up, but I was pretty
sure it was lined up.
Upon start up, idle improved and mostly stable but was still off. During the
first test drive, the car stumbled, and had no power at all and got worse when
it warmed up. Pulled back into garage and no codes when scanned.
-Vacuum 15 inches to 16 inches cold
-Timing wildly changing from -2 to -26 degrees
-At load timing a solid -15 degrees
-STFTRM still at -34
-Gas smell still coming from exhaust
At this point I didn’t know what to diagnose and fix first. I figured I would
try the fuel system. Mostly because I had already started diagnosing it.
-Replaced fuel pressure regulator
-Replaced Injectors and Seals
-Checked all sensors for in spec numbers, all were good
-Checked ignition system, all parts in spec
-Completely cleaned throttle body (no maf on this engine)
Dead end. STFTRM did not change, and still running rich. So, I decided to investigate
the vacuum system next, as it was probable at this point it wasnt a fuel system fault,
and maybe it was vacuum/timing related. At this point I kinda went nuculear. I checked
or bypassed any part even remotely connected to the vacuum system I could. (sans timing)
-New OEM manifold and intake gaskets
-Removed and plugged up EVAP system
-Removed electric EGR valve and added a bypass plate
-Smoke checked engine, no apparant leaks
-Checked brake booster for leaks, none found
No change to vacuum, so decided to diagnose at load with test drives. Attached vacuum
guage to manifold inlet and ran long hose so vacuum guage dial could be taped to the
windshield, and seen while driving. Engine left overnight to cool.
-Vacuum at idle: 15 inches
-Under load (1500 rpm/10mph) but cold vacuum: 15 inches dropped to 5 inches steady
-Warm engine at idle vacuum (160 degrees): 13 to 14 inches
-Warm engine tripped SES cel P1406 (egr code because of bypass plate)
-No power under load and at 5 inches vacuum (expected)
That’s all the data I have room to give, but its the most pertinent. I want to do an
open header road test next to check for exhaust restriction but I doubt that would help much.
Any input appreciated at this point.