jej3

Okay. Here's my update so far... regular life is getting in the way a bit.

1. Ignition Wires are in correct locations
2. Spark plugs are sooty again (see pic)



3. Temp II harness is a bit mangled (had silicone goop on it in place of boot and a bare part of wire was showing - see pic)



4. MAF harness is cracked at boot and wires are showing but no observed bare wire (see pic)



5. Battery Voltage is 11.8v at Jump Post when not idling and 13.8v when idling

6. Listened to each injector with Mechanics Stethoscope, each is clicking when idling, seems normal

7. Disconnected ground strap, disconnected Temp II, ran car - no change

8. Disconnected ground strap, disconnected MAF, ran car - idle stayed low (500-600) but no surging, touched accelerator, car cuts off

9. Disconnected ground strap, reconnected MAF, same results as 8 but hunting at idle.

10. Connected all sensors (MAF, Temp II and O2) after battery reset, car runs but first step on accelerator, car cuts off

11. Checked inside 14 point connector (I had already viewed prongs and put stabilant on each)



So, in my feeble mind, this leaves me with this list of suspects....

1. LH
2. MAF
3. Fuel Pump or Fuel Pressure Regulators
4. Ignition Coils

I need to test fuel delivery but do not have a pressure gauge for fuel rail.

I'd like to swap LH and MAF but need to find someone (not many Jacksonville S4's - but will start a new thread to ask.)

I probably should just order new coils as they are probably original to the car and it has 155K miles on it.

Looking forward to everyone's thoughts.

jej3

Bump

SeanR

How were the coil side of the coil wires? Not unusual for those to be corroded and cause something like this. Also, I'd not just toss parts at it but if you can borrow a good MAF from a local and try it. You are on the right track, keep it up.

jej3

Thanks, Sean. Coil wires (and all plug wires) are brand new. Coils are both getting 13.6ish volts on the positive terminal when running.

I really don't want to toss parts at it either I am just starting to face the financial reality that LH/MAF both probably are in need of a rebuild during my ownership.

I'm going out to test fuel volume per the WSM even without having a fuel pressure gauge. My gut is just telling me I'm getting a weak spark and the plugs are ending up fouled. Just my gut, no practical knowledge otherwise.

jej3

Checked the Fuel flow this afternoon.

Disconnected the return line at the top of the tank through the access hole in hatch area.

Connected an extended fuel line to run into a "Drink" container with 1l, 1.25, 1.5l, etc.. markings on it.

Jumpered Fuel Pump relay with inline switch to have exactly 30 seconds of flow.


Here's the flow results....

Run 1 - about 1.1 liters in 30 seconds



Run 2 and 3 - approximately same amount in 30 seconds.






The WSM I have says it should be 1.35l and I can definitely say I was below that number each time. What do my results mean... sub-par Fuel pump or is this "Close" enough"???

fbarnhill

Have you checked the fuel dampers? My 88 had a lot of the same issues. After replacing all the dampers/fuel pressure regulator, it ran perfectly. If fuel runs out of the vac line when you pull it off a damper like mine did, then it is dead, if you smell fuel in the vac line then I think that is also a bad sign.

Good luck,

bradartigue

Running rich and getting less than expected fuel on the return line I'd check that the cold start injector is not firing once the motor is warm. It should be off very shortly after the engine starts.

jcorenman

Trey,

I found your problem-- your ground strap is lying on the floor. Put it back in the car.

Seriously (but only for a moment): Fuel volume test is below spec, indicating a weak pump, partial restriction, or high pressure. But close enough, and not the cause of your current problem.

In more detail: The spec, according to the tech-spec book for the 90+ cars, is 1.25L in 30 seconds, measured at the return line at the tank (where you measured). That's the amount of fuel that the pump sent to the engine, minus what the engine used (zero, since it is not running), and got sent back to the tank. As long as the pump us supplying more fuel than the engine needs, everything is good-- fuel pressure will stay at the regulated 55spi (minus engine vacuum).

I think a 300hp engine running flat out will consume around 100L/hour, or 0.8-1.0 liters in 30 sec. The issue is not at idle, but under load-- starving for fuel at WOT. What we were looking for was a clogged line and a much-reduced delivery volume, where it couldn't even keep up with modest demand for fuel.

So your 1.1 liter in 30sec is certainly close enough, just make a note to buy a new fuel pump some day and save this one as a spare. It may be partially clogged with crap from the tank.

Have you checked the fuel pressure? If it is markedly higher than 55psi (engine off, pump jumpered) then the mixture will be rich. That is very unlikely with a stock regulator, but an aftermarket adjustable regulator will be mis-adjusted almost by definition.

As mentioned, check the vacuum lines for any fuel. Disconnect them and smell for fuel, should be just air.

Your MAF connector looks ugly but the wires appear OK, and ours looks just like that. Tape it for protection.

Your temp-II connector looks worse, the green corrosion is a worry. I would recommended re-doing it (Roger has connectors and contacts I think), or at least do the resistance checks at the LH connector, described in the WSM.

You said "Disconnected ground strap, disconnected Temp II, ran car - no change". Which ground strap? Don't ever try to start the car with the engine ground-strap disconnected (under the car, passenger side)-- the starter current may try to use the electronics ground-wires for a few hundred amps of starter current.

No need to disconnect the battery ground strap while messing with MAF, temp sensors, etc-- those are all powered off completely with key off. I always disconnect the battery ground when unplugging LH or EZK boxes, just to be safe-- those connectors have constant 12v power.

And no change with temp-II sensor disconnected is odd... It should make a difference, a disconnected sensor is high resistance which means very cold, which means more fuel.

That could be a big red flag, an indicator of a broken wire or a bad sensor. Disconnect battery, unplug LH and do the temp-II resistance check, WSM page D24-17 (appended section 24-28). Send a PM if you need a copy of those pages.

Next step would be to beg, borrow or steal another LH and MAF.

jej3

Thanks, Jim. I really appreciate all of the sound advice. I now have a spare parts box from this exercis

When I mentioned Ground Strap Disconnected, I should have said Computer Reset because I disconnected the battery ground strap and reconnected it after removing the different sensor connectors.

I'll go back through everything and I'll send you a PM, too

jej3

More information...

Ran WSM resistance tests on the Temp II Sensor -

2.52 and 2.56 resistance at sensor
2.52 and 2.51 resistance at LH

Pulled Vacuum connectors of Fuel Pressure Regulator (at front of engine between rails right?) and Fuel Dampers (at end of Fuel Rail at back of engine)

Connector of FPR smelled slightly of gas
Elbows taken off of Dampers did not smell of gas

Applied Vacuum of 20lbs to each connection...Slow leak down at one of dampers (is this normal? I guess I need to read up on it and measure the speed of the leak down)

I need to get the new Temp II connector and Fuel Guage from Roger and will likely go ahead and order two new coils (because I then know the ignition system - coils, caps, rotors, wires and plugs are all refreshed)

I'm going to pull and clean the MAF for kicks with MAF cleaner bought at O'Reilly's

I am starting to think the MAF or LH are the issue But better in my driveway than on the road.

Any thoughts?

John Speake

The very rich running could be a fractured diaphram on the FPR or a damper. There's a diagram in the WSM of the fuel and vacuum paths, the unit at the front is a damper, there's a damper and the FPR at the back of the engine.

Try pulling the vac lines off all three and plug them, run the engine and see if any there's any race of fuel. As you'll need the engine airfilter box of for that test, also try switching on the ignition, and look into the MAF (engine not running) . Look to see if you can see the hot wire glowing. If it is, the MAF is faulty. I don't recommend cleaning the MAF, high risk of damage. Cleaning won't help the gross rich running you have at present.

You can eliminate the Temp 2 sensor by simply unplugging it once the engine is up to temp, the LH will revert to a default 80deg C setting.

jej3

Thanks, John. Did you mean any "trace" of fuel? How long should I run engine for?

Should I test the MAF Hot wire after running engine, before or does it matter?

John Speake

Yes, I meant to write "trace". The MAF test doesn't require the engine to have run before the test.

jej3

John - no hot wire after turning on ignition.

I did as you prescribed and I capped the vacuum lines to the dampers and FPR, no trace of fuel from running on any of the open ports. I further tested by restoring the vacuum connections and then using my mightvac to pull a vacuum on each of the FPR and dampers individually. No trace of fuel and no smell of fuel.

More testing....

I decided to do the following tests from the WSM:

Test Point 5 - Air Mass Sensor

a) Power Supply - I connected volt meter to the plug terminals 2 and 4 at the MAF - voltage was 11.65v

I then connected volt meter to the plug terminals 17 and 21 on the LH Control Unit plug - voltage was 11.65v

b) Checking Resistance of hotwire circuit at the MAF

I measured a resistance between terminals 3 and 5 with the ohmmeter and read a value of 5.1 (normal is 3.6 - 4.1) Is this an issue???

c) Checking the hot wire signal

Connected plug to the MAF, Took out the LH Relay (XXV) and bridged terminals 87 and 30. Connected terminals 6 and 7 and read correct voltage of 1.6v

Couldn't blow on hot wire to read difference in voltage reading but a couple of times when wind blew, voltage went from 1.6 to about 1.7 or 1.9.

Not sure where to go from here.

jej3

I should have also added that I went ahead and wrapped up the wiring with electrical tape on both the Temp II harness and the MAF harness. Since the measurements were consistent between Temp II at the sensor and at the LH harness, I'm going to forego focusing on replacing the temp II connector for now.