Surfnazi

Is there water in your battery

Skatetrainer

Sorry, old battery is gone. New battery working great. The old battery never did turn the starter quickly. I don't have any guess why the stumbling went away but coindentally the battery makes the car start better - and the stumbling appears to be gone. Cleaning the throttle bodies was good but didn't solve the problem. Your results may vary.

ezbme

I saw a video on Amsoil Powerfoam, pretty interesting. I am thinking of getting some when I buy some oil. How about cleaning the maf sensor? I am new, I haven't even looked to see where my maf it, probably right after the air box. You wouldn't need to unplug it to get to your throttle bodies, but why wouldn't you want to unplug it?

Skatetrainer

update 12-2016: Only a hint of a stumble, very infrequent, but the stumble hasn't completely gone away. Saga continues....

ezbme

Found out that Amsoil's Power Foam and Liquid Glass aren't allowed in CA, due to CA resources board. Sucks.

DC makes headers for our cars and historically makes imho the best headers. They make the most consistent power. They don't have a carb #, but perhaps I can sneak some on. I wonder how difficult is a header swap on these?

I wonder how long the coils will last. My bmw had its factory coils at 225k, I figure mine will need to be replaced when the spark plugs are done again.

Skatetrainer

Update 2/19/17: Stumble is back - worse than ever. Doesn't appear to be battery related. It still starts well. I drove the car on a long trip and it is stumbling at many different speeds and OAT. It was noticeable the most at highway speeds around 75. OAT-35F at 8AM; bad stumble. OAT-55F at 3PM; bad stumble. It doesn't appear to be OAT-dependent at least within this range of temperatures other than to note that a warm spell could cause some condensation in the fuel from the supplier.

Observation: The first couple hours was spent with a full fuel tank and getting down to about 1/2 tank. I've noticed lately that the stumble happens frequently when the fuel gauge gets down to about 1/2 tank Since the cruise control was on and the highway was fairly flat, the throttle position was fairly steady at 75mph. When the fuel got down to 3/8 tank the stumble went away, or at least I didn't notice it anymore.

Questions: Really? What in the world does a fuel gauge or float or pick up have to do with fuel delivery? I've never seen a fuel gauge sender affect the actual fuel pump or pressure regulator. Does this car have a fuel pick up in the tank or a tank design that could pick up water at 1/2 tank when the water collects at the bottom of the gas tank? Could there be an electrical connection that is failing inside the tank?

Will post updates....

Surfnazi

Fuel pump might be going out should be float arm

Skatetrainer

Update: 8-2017 Changed the plugs at 86K. One of the plugs had a large gap but for the most part the color on all plugs looked good - light golden. One of the plugs did have a small amount of oil on the threads.

I still get the intermittent stumble bumble. No noticeable repeatable pattern. No CEL. No codes pending. Still waiting for a failure....

ezbme

Did you clean your TBs?

Skatetrainer

Yep, did that. Earlier post. No change. Next up is likely a COP. Which one??

Skatetrainer

Update 9-14-2017: Car is now showing signs of more frequent bad idle stumble and poor acceleration stumble. It doesn't matter if its in gear or not. It doesn't matter what the position of the throttle is or not. It still stumbles. One outing I had the window open and a very loud and distinct backfire, spitting, kicking, no acceleration just violent protest from the motor. A brief CEl came on and went away. Had to pull over, shut down, restart, back to only minor misfire. Put on the analyzer and no stored code So, hopefully it will completely fail soon. I'm suspecting a coil pack.

Update 9-27-17: I placed the OBD analyzer on the port. The LTFT was showing -10 on both banks so it appeared to be running rich. I also started monitoring the ECU voltage. The ECU voltage appeared to be very low; around 13.2V using live data the modulation was around 500mV. When starting the car the ECU voltage was at 11.7 and dropped to 9.2 and then up to 13.5 for about five seconds. Then the modulation kicked in and the ECU voltage dropped to 13.2 with the modulation of around 500mV. I drove with the analyzer on the port. After about five minutes the ECU voltage dropped to 12.2 and the car started stumbling. It jumped to 12.8 and bounced in between the two with the modulation. I placed the analyzer on a friends G37 - his ECU voltage was solidly between 14.0 and 14.4V. I'm going to replace the alternator.

Replaced the alternator. What a PITA. Removed the radiator fans and then the alternator out through the bottom. Battery charge voltage back up to 13.5V. However.... The ECU voltage is still reading between 12.2 and 12.8V. The stumble is very consistent. No CEL or pending codes. Disconnected the battery so it may take a while to relearn the settings. It doesn't appear to have been the alternator but I will see if the battery is just low from always having a low charging source.

OMG: Battery at 14.0V. The battery appears to turn the car over well now. BUT.... the engine started running rough, coughing, spitting, no acceleration, and then died. When I started it back up it is clattering. It sounds really loud. This is not good. Will check the oil pressure at idle. Will try to isolate the clatter but is sounds more like valve train than bottom end. Will check the compression and the plugs for indicators. sigh.