Formula94lt1

Hey all I was hleping out another board member mess with his car, 87 s4, and basicallly this is the run down... About 4 months ago he sprayed some wd-40 into a vacuum line thats leads right into the TB. Well it smoked a lot and ran rough, he took it to the dealer and they told him it needed a MAF and a fuel pressure regulator after scanning the car. That barely helped so he called 928 specialists to ask their opinion and they suggested replacing the O2 sensor and so he did. Well it still runs like crap, like not really drivable, up untill a few weeks ago when it got finiky about starting. Seems to be spewing fuel out of the exhuast and has fouled 3 sets of plugs in about 30 miles since this all started, THIS ALL STARTED WHEN HE PUT THE WD40 IN THE CAR. There is a vacuum leak under the intake that is rather large but it was more than likely there already when it was running comparatively well before, other than this nothing has been altered or is known to be wrong. The fuel pressure regulator that was replaced was on the back passenger side. He swapped some relays around to see if the fuel pump relay was the culprit of the no start. Well no matter if we had a known (brand new anyways) good relay or what in there the fuel pump would not come on. We jumped it with a paper clip and it comes on but the car still won't start. Tested cold compression and it was about 150 psi on the cylinder tested, it also is getting spark. I was going to try and test the injector clips with a test light but other than that I would like to get some opinions.

ErnestSw

Unplug the "new" MAF and see whether there is any change in how the car starts/runs.

Rich9928p

Many things can cause too rich of an air/fuel ratio.

- Temp II Sensor (LH thinks the engine is cold, enrichens A/F mixture)
- Leaking fuel pressure regulator, dampeners
- O2 sensor
- Failing MAF
- Failing LH module (over rich A/F mixture is one of the symptoms of failure)
- Fuel injectors, bad flow pattern, leaking, too high flow

I had an interesting problem with my S4, it idled very rough and would die but otherwise ran OK. My mechanic checked the air/fuel ratio and found that one side of the engine was lean, the other rich. When the exhaust was mixed, it netted out to be a bit lean so the LH was enrichening the mixture.

The first thought was unbalanced fuel injectors. I had them removed and cleaned. With over 100K miles on the engine, they did need cleaning and the screens replaced. However, the cleaning made no difference. After a lot of basic testing (it was the number 1 cylinder that was the problem). A smoke test illustrated that there was a leak in the intake gasket to the number 1 cylinder - that cylinder was lean from the leak but the LH was working to keep the mixture proper, so it was enrichening the air/fuel mixture to the other cylinders.

Charley B

Might wanna start there.

dr bob

I'd do as the others recommend, starting with fixing the known vacuum leak under the manifold. What seems like a rich condition is often a lean condition, where the mixture is so lean that there is no combustion and raw fuel and air are pushed out the exhaust. Plugs can be wet, etc, all pointing to rich mixture problems. The engine will support a rich condition and run sluggish, but a lean condition with associated misfires will exhibit the symptoms you describe. So fix the vacuum leaks that you know of before you start swapping in a bunch of [expensive] parts trying to mask the known problem.

The fuel pressure regulator and the two dampers operate on manifold vacuum, from the port on the throttle below the MAF. Is that where you were squirting the WD-40? Make sure that the hose was restored to the port-- pull a line from the front damper with engine running and verify that there is vacuum. If that hose is not connected, the regulator and dampers will be fooled into thinking the engine is always at full load, and will raise the fuel pressure accordingly to richen the mixture. It would not be out of line to actually verify the fuel pressure too, just to be sure.

The dampers themselves fail internally with a ruptured diaphragm that allows fuel to be drawn into the intake. Use a Miti-Vac to verify that each of the dampers will hold vacuum and not leak down.