UR2H

Sorry but what's a BCDD? I know I replaced my air regulator not too long ago because my start up idle was really low.

I have a 77 280z with an unmodified F54 block and N47 head. I get right around 17 Hg vacuum at idle (~800 RPM) and remains relatively steady (tested the vacuum at the intake manifold at the brake booster hose). There is very slight fluctuation in the vacuum between 1 maybe 2 units but it seems to follow the idle, the idle isn't perfectly smooth but not that bad. So my problem is, after I rev the engine up, the RPM's when returning to idle, will drop down to ~500, stutter for a second then climb back up to ~800 RPM. It does this after I drop the clutch when I'm in gear driving as well, like when I'm coming to a stop. The engine has never stalled but it does feels like it's right on the verge every time. Anyone have an idea why it does this?

Oh you mean the same thing we've been discussing for the last dozen post? WOW! I feel :stupid:

Hey what's a CTS?

I don't have an aftermarket fuel pump but when my car is warmed up I do notice more gassy fumes. Whenever I can I will pull over to check if I'm leaking fuel somewhere in the hoses but it never is. Maybe my FPR is doing the same thing? Hmmm....maybe I'll look into replacing it with an adjustable one too.

I got .285 when warmed up and .8 when cold so the resistance did decrease as the temperature increased. It was just weird that the longer I kept the prongs touching the connectors the resistance kept dropping. I'm at a freakin' standstill. According to the FSM, my resistance seems within range. My spark plugs are consistent with each other and don't look like the fuel is rich. I still don't understand what all that soot is? My fuel pressure is solid at idle and under throttle and increases accordingly to the loss of vacuum at the FPR. I had new injector connectors installed a couple years back. I replaced all the fuel hoses under the hood. Yet I'm barely managing 12mpg without ANY aggressive driving...and the mechanic I consulted with used a machine to read my exhaust (kinda looked like the machine used when doing a smog check, but it wasn't) confirmed I am running WAY too rich. Seriously I don't get it.

So I got a few readings. I didn't get the readings from the ECU though, was having trouble removing the connector. But at the bullet connectors I got a reading of.285 when warmed up. For some reason I couldn't get a reading with the engine cold so I ran the engine for maybe 1 minute or so (~100 degrees) and it read .8. One thing I noticed is when I was getting the readings, the numbers kept dropping. Is that normal? So when I got the .285 reading, it then read .284, .283,.282, and so on.... I should also mention, the bullet connectors looked very clean. So I was going to hold off on asking this until this situation at hand was figured out but I'm thinking that it may pertain to the problem. So I notice the idle drops to around 500rpm them stumbles back up to 800rpm whenever I come to a stop or press the clutch. The engine never dies but it does do this practically every time. Is this something that would be affecting my gas mileage?

The fuel pressure increased to 38psi with the vacuum hose removed. I guess I didn't get too good a look last time.

My multimeter didn't come with a manual but I did look over the one this link provides - http://atlanticz.ca/zclub/techtips/electricalchecks/cp7678.pdf Also when touching the probes together I get a very low reading and apart gives an infinite reading so the multimeter seems to be working fine. I just don't get why I didn't get a reading when I was testing at the bullet connectors. Maybe I just need practice? Well I will give it a go on my next day off which is Thursday unfortunately. Thanks again to everyone for the advice. Really appreciate it.

The mechanic I saw had a machine that measured CO and my CO% form the exhaust was very very high. He said that is caused by running rich. I think I will hold off on the AFM adjustment for now since there can be other possible reasons. I don't drive hard...sometimes but hardly especially these days. When I'm cruising I try to stay right around 2500-3000rpm and I shift around 4000rpm. Like I said I'm, usually never at WOT.

When I removed the vacuum line I leaned over to look at the gauge and saw it was close to 45-50psi but I kinda got scared so I hurried and plugged it back rather than checking to see what the exact reading was.

My fuel pressure sits just slightly under 30 psi when warmed up nice and hot at 800rpm. The fuel pressure gets really high when I remove the vacuum to the FPR. I was told that is how to test for a faulty FPR.

So I am a bit embarrassed to ask but how do I test the resistance? I found the bullet connections for the water temp sensor but what do I do from there? I have a multimeter and I read the link "common automotive electrical testing" found at the bottom of the electrical section on the Atlantic Z site but apparently I still don't seem to understand. I apologize but I'm new to testing anything electrical. However I did try though. So my thoughts was that since I need to check the pins on the ECU, that I would have to unhook the ECU meaning the battery ground should be disconnected before doing so. So in essence testing the resistance at the bullet connectors would involve the same process. So with the battery ground off, I unplugged the bullet connectors and tried getting a reading but I got nothing. Did I test correctly? Like I said, I am new to testing anything electrical.

I pulled off each plug and they all looked relatively the same to one another. The insulator's color at the tip was similar to the picture of the toasted marshmallow. However the prong and the ends of the threads were sooty. I didn't do the test pulling off each connector one by one to see if there was a drop or change in idle. Since the plugs all look the same, this would indicate each cylinder is getting equal fuel right?

Again I will post what I record, which will probably be tomorrow. Thanks.

Actually I just Google'd RedLine MT90 for images and the bottles come in quarts. They look like the same bottles I used. If that's the case, I'm good to go. But I wonder where I got pints from? Do they even come in pints? :stupid::stupid:

I wonder why me and the mechanic both thought it was full? This means it's just over half full... Thanks for the advice. I'll get to measuring the connections at the ECU, the sensor and the pigtails ASAP. I'll post what I recorded as soon as I do. However I won't have any time till probably Tuesday. Was gonna do some work on it over the weekend but things came up and priorities first...I wish my Z could be one my main priorities. Also sorry for the late reply. I really appreciate all the help I get from this site.

My 77 Z gets terrible gas mileage, somewhere in the neighborhood of 12mpg. A mechanic I know who had a CO measuring machine said my CO% were way too high and that I was running really rich. He measured my ignition timing at 9 BTDC. He also checked my vacuum and said it was okay, however I didn't check what his pump read and he isn't a Z guy so I don't know for sure if what he read is where it should be at. I do have all new vacuum hoses under the hood though. Also replaced my auxiliary air regulator not too long ago. So I was reading up on the AFM adjusting on atlanticz.ca and what exactly is the idle flow adjusting screw on the bottom right corner of the AFM for? It states it works the same way at the idle adjusting screw on the throttle body but which one am I supposed to adjust when I "lean out" the AFM? I fingered the wiper clockwise for a leaner mix like the site states to do causing the idle to drop a bit. Interestingly when I finger the wiper counter clockwise to "enrich the mixture," i get the same effect. Is it supposed to do that? Anyways so if I do rotate the black wheel clockwise and set it there, which screw (idle screw on the AFM or idle screw on the throttle body) should I adjust for the idle? Weird thing is my car was getting around 17 -18mpg before but all of a sudden dropped to the 12mpg range and has been this way ever since. I noticed my fuel hoses to my injectors were leaking so I replaced those along with all the other fuel hoses (on the rail, CSV, return hose, filter hose) under the hood thinking the weathered and damaged hoses were the culprit but even after changing those I still kept getting bad mileage. I then changed out the AAR but that changed nothing either, except for what it is supposed to do with the higher revs on cold starts. I should also note I have new injector connectors, which were put like 2 years back. I also have a fuel gauge installed right after the fuel filter and it reads ~29psi at idle and like 33ish on throttle. BTW on a different topic, I just recently did a transmission oil change. The FSM states the 5 speed, which is what I have, holds 4 and a quarter pints. I know I drained all the old oil out but I was only able to put in 2 pints before it started to overflow. Actually after I drained the oil I wasn't able to get the fill plug loose so I had to get the car towed to a shop where they got the plug loose. It was on there really good as they even had difficulty getting it off and they were using a breaker bar. And apparently the fill plug is tapered so I guess I'm kinda lucky the casing didn't didn't crack from the plug being on so tight, or would the casing not crack because of it's DATSUN strength? Well after they got the plug loose they made certain everything was drained before filling back up. But 2 pints? What gives? I used Redline MT90 and my shifts have never been smoother. I don't even get the occasional little grind I would sometimes get when racing the motor between 1st and 2nd. But 2 pints? Should I be worried? If you got this far, thanks for reading.

Castrol GTX 30 weight and I've been using the same stock one since I bought the car.

John, the weather has been slightly cooler this month but still relatively warm. FastWoman, the pressure does hold steady once I get around 3500rpm but it's around 70psi and around 25psi at idle. But after I drive the car around for 20 minutes or so the pressure drops back to normal, which is 55ish psi driving and 15ish psi at idle. Horsemann, I did the oil change not too long ago, maybe 1000 miles ago and I have always stayed on schedule with the changes ever since I've had the car, which has been about 5 years. I think I will change the oil out again soon though and run some of the gunk flush before I drain it. x

I will try that. Curious...if the relief valve was broken and not just gummed up, what kind of pressure would I be getting?

Yes it does. Once I start giving it some throttle the oil pressure increases, it's always consistent. It's basically 10-15psi higher. Weird thing is I found that after driving it for awhile, the oil pressure returns to "normal." When you say the oil pump is gummed up, can it be cleaned out or should I just replace it?

I installed new Auto Meter gauges all the way a few months back. I have the oil pressure gauge hooked up directly to the oil pressure sending unit. It reads fairly consistent with the old stock gauge I had before.

My 77 280z seems to be running high on oil pressure for some reason. The pressure was running 12-15psi at idle when warmed up and around 55-60psi when driving hard and around 40-45psi when cruising. Now it's at around 25-30psi when at idle and seems to climb to almost around 75psi when driving. The motor still runs as smooth as it was before the high oil pressure readings both at idle and in gear but now has a slight but distinct clanking sound that wasn't there before. I can't seem to figure where it's coming either from but it's best heard if I listen underneath the car. Only thing I was messing around with prior was the AFM but I wasn't even making adjustments, I was just fingering it to enrich or lean out the fuel/air mixture to see if the motor ran any differently, followed the directions on the Atlantic Z site. I'm getting really bad gas mileage. Anyways this wouldn't mess with the oil pressure right or could it? Other than that, haven't done any mods to the car except upgrade to a 280zx alternator. But the oil pressure was fine after the conversion. I know the oil pressure sending units go bad but don't bad sending units usually read low rather than high? But then again there is that noise.... Any suggestions on where I should begin diagnosing?

These are my readings- when warmed up at 800RPM ~14.8-15V at idle ~12.2-12.5V at idle with headlamps on when driving ~15.5-15.7V regardless if headlamps are on or off Are these with range?