michaelathome

Well we got it back together.

Working under the intake was not so much fun, once we were done we went to fire her up and my battery was dead. It was a little to late to keep working on it so we called it quits. I will be replacing the battery sometime this week as I don't like 3-4 no starts in 6mos off of a 1yo battery.

I have a brand new alternator I will be putting in soon as well as replacing the AC pump/pulley hopefully in the next few months, gotta few other things to get done as well. Just to add, I have had no signs that my alt is not charging BUT since I have a new one I might as well replace it.

I can say this though. Before photos are critical to have when doing this kind of thing, last night it helped us find several things that we weren't exactly sure how they went and without another S4 around it woulda been a guessing game w/out the pics. Everyone take pics of your engine cause you will never know when you might need them.

Another thing was that when removing the manifold, we didn't get the intake/valve openings plugged real early on so I was a little concerned about having dirt or whatever having fallen in. We took a turkey baster and taped it to the shop-vac and stuck it down inside the and it worked great, we were able to pull some small pieces of powdercoat that had fallen off the old intake and foam from the fuel rail that had fallen in there as well during the removal process.

Hopefully I can get it re-tested by the end of the week.

Thanks again John and Jason for the help!

I'll get some "MORE" pictures up once I get a chance to clean it up a bit, everything looks great!

Michael

michaelathome

After sitting on a charger within about 10 cranks or so it fired right up. The battery was just too dead it seams. Also it looks like I missed tightening down the fuel rail fitting on the rear passenger side where it meets the reg/dampner and we had a little leak, Shut it right down and tightened the fitting, but I don't have time to try playing with it again today.

Will need a few tweeks I am sure but it runs. Thanks again everyone for your help.

Michael

JHowell37

I would still change the battery. Somethings seems very odd about its behavior.

michaelathome

Bump.

That's right I failed again this past wed with a new Temp II and what I was told was a known good MAF from another rennlister. I am still running rich.

Here are the #'s from back in Jan on page 1

Limit 15mph Limit 25mph
HC 55 239 100 296
CO 0.22 4.70 0.32 5.14
NO 720 66 700 65

I'll try to update this post with wed's numbers when I can later tonight but they are not too much different than what they were at the beginning of the thread. I have gotten some slight improvement but that could IMO be as simple as the outside air temp and the temp of the engine when I took it in. Last 3 tests were all performed by the same shop with car in 3rd gear with a hot engine.

So to sum things up,

- Bosch coppers, gapped and cleaned (2yrs old)
- New wires (2yrs old)
- New Bosch coils (2yrs old)

Since Jan when this started:

- New O2
- New Temp II
- Intake refresh
- New knock sensors
- New Flappy actuator
- Fuel Pressure Regulator checked
- Fuel Pressure Dampeners Checked
- Original fuel injectors were serviced during refresh
- Smog/Air pump "IS" working, there is a slight draw of air at idle not sure how much it is supposed to be.
- Fuel pressure in the rails are 45lbs and on throttle up to 55-58lbs

Passenger side CO test bung is missing and I don't know if it is capped, I have been told this would actually help a little by allowing fresh air into exhaust if it were missing/uncapped.

Currently the O2 is showing a reading of .82 at idle and higher 89-92 under variable throttle conditions.

Runs pretty good, no misfires, stalling, idle is strong. Vacume is strong. Plugs were "sooty" not a sight of oil. Just looked like it had been running rich.

I have emailed another lister to see if I can borrow his comp ( LH and/or EZK ). I am along with Flyingdog stumped as to what it is that I have missed.

We both have ideas but I for one could use the input.

Michael

dprantl

I didn't read this whole thread, but if you are running rich your O2 sensor or something along this line *must* not be working right:

- Check for any exhaust leaks before the O2 sensor (including the O2 sensor's seat). I'm not so sure extra air before the O2 sensor is a good thing; you want the sensor to get the exact picture of what the exhaust gas consistency is.
- Check the connections of the O2 sensor and examine its wires (sometimes the wires can melt if they are too close to the exhaust or routed incorrectly
- I know you say you replaced it, but maybe try a known good O2 sensor?
- Did you test the WOT switch on the throttle body?

The only other thing it could be is the brain is not working properly and is misinterpreting the O2 signal. Have you tried a known good LH and/or EZK brain?

Dan
'91 928GT S/C

michaelathome

With the O2 sensor giving a 0.82 or higher it is providing the correct input/output to the comp to lean it out. If exhaust gases were normal (not rich) it should be reading about 0.45



Wiring looks good



Same basic emission test results before and after swapping out my O2 Sensor and since I am getting 0.82 and higher readings isn't that telling me it is working?



WOT switch was not replaced or tested during the refresh. What sort of impact would this have on performance it it had failed or was faulty? IIRC the WOT map is used which is lean.



This is what I plan on checking next. IIRC from looking at the wiring diagrams the O2 sensor feeds directly into the LH so is that what I should replace/swap first?


Thanks for the questions Dan.

Michael

dprantl

Ok, so the O2 sensor seems to be in working order if it is telling you the car is running rich. But, does the value the sensor outputs oscillate between a low and high value many times per second? I bet it doesnt, right?

If the WOT switch is faulty and is always open, it will cause the LH to be in open-loop mode where it will run rich. In this mode it will *ignore* the input of the O2 sensor. I'm not sure what you mean by the WOT map being lean. It's quite easy to see this operation on a car that has a gauge connected to the O2 sensor. During idle and cruise operation the gauge flips back and forth between lean/rich. When the car is floored and the WOT switch is tripped, the mixture goes rich and stays there.

Yes, the LH brain takes the O2 signal directly, but as mentioned above, it will ignore that input if the WOT switch is on. I'm betting that your WOT switch is failed on.

Dan
'91 928GT S/C

michaelathome

Actually Dan it does vary, we were looking at readings from a low of 0.57 to a high of 0.94 but the readings most often fluctuated +/- 0.81 and on throttle +/-0.89


Two years ago when I first tested my car I was running really lean, NOX was in the 1000's and CO and HC were very very low. It was determined that the O2 sensor was unplugged. I was told that with the O2 unplugged that it would run in the WOT map. High NOX and low CO and HC is normally a sign that a car is running lean. I assumed that the WOT map was therefor lean and not rich.
We do however all know what "***-U-me" means though.

If in fact the WOT switch is faulty and is failed open, based on what you said, above the situation would not make sense.

No O2 sensor forces the WOT map.
Failed open (on) WOT switch ignores O2?

I hope I am getting it. I really need a better understanding of open-loop, closed-loop and cruise from the sounds of it.

Michael

rixter

don't assume this.. cap it off,
also, I have a known good maf/brains (chipped, but I have the original chips), etc in my 87

dprantl

The symptoms of running lean with a high NOx are not of a disconnected O2 sensor. I cannot explain why your car was doing this, but failure of the O2 sensor or running it disconnected on an LH injected car will cause a rich condition (otherwise called open-loop mode). In open-loop mode the O2 sensor voltage will not fluctuate and will read a steady value corresponding to an AF ratio below 14.7:1. This is one reason why running without an O2 sensor on a car equipped with a catalytic converter is a bad idea, because the prolonged rich running will eventually plug it up.

It's interesting that you see the O2 voltage fluctuating but you still run rich. The fact that it fluctuates indicates that the LH is receiving the O2 signal and is trying to run in closed-loop mode by changing the mixture, suggesting your WOT switch is working. I would try a known good LH brain in your car as the next troubleshooting step, then check the O2 voltage output with it installed to see if it is any different.

Dan
'91 928GT S/C

michaelathome

Thanks Dan, will give it a try.

Michael

Jerome Craig

Did you swap the MAF yet?

michaelathome

Jerome, just to give you a hard time my first sentence in post #49 was:

"That's right I failed again this past wed with a new Temp II and what I was told was a known good MAF from another rennlister. I am still running rich."




















Michael

JHowell37

I'll come over and let you borrow my MAF that was rebuilt about a year ago, and my car passed emissions perfectly.

fraggle

I sure hope mine goes smooth when I bring it out here. What a PITA.