Wade Nelson

Did you try running it with the gas cap off yet?

Try running it with the gas cap off and see if you have the same problem.

This is a classic voltage drop problem. Turn on the headlights. Now measure the voltage across the battery. Should be 12.4-12.6 volts or so, engine off. Now measure the voltage AT the headlight itself. Chances are you'll only see 11.5 or so. So you're missing around .9Volts. That is a voltage "DROP" The trick is to find where you're losing that voltage; in a dirty relay contact, at a poor ground, in a poor crimp. One of those is adding resistance to your circuit, and when the headlight current flows through it, well, V= IR, the resistance times the headlight current equals around .9 volts of "drop" You can lose voltage on either the ground side OR the positive side of the headlight circuit. Start by running a wire from battery ground directly to the headlight connector. Does your bulb suddenly get a lot brighter? Then you probably have a bad ground; paint underneath a ring terminal, whatever so your headlight isn't seeing zero volts like it should. Next run a wire directly from battery plus (B+) to the headlight connector? Does it get brighter? Next, using your meter trace back through the relays, switches, connectors, fuses, till you find where the voltage is getting dropped. A little corrosion, a very little resistance (as little as 1/10 of an ohm) and you can create a significant voltage drop that will make headlamps dim.

Anyone got a source for these? I"m so tired of wind noise! Is Nissan still selling them? Thanks! Wade

The hardest part of "I spy a Z" is conducting a successful search to FIND this forum. Apparently "Spy and Z" are too short for the search engine. Ideas, anyone? Ok so down at Panera Bread, on Airport Road, Huntsville Alabama, a nice 240Z with an air dam and a missing grille. Nice paint job, decent original interior. Some decals on the rear hatch, Redstone Arsenal sticker on the windshield. Tires / wheels not so pretty.

'Rarest of the rare': 500 unsold, vintage Chevrolets on sale - San Jose Mercury News Wow. I'd love to just go look at them or sit in on the auction.

Is the tow rope included?

Time to get back to basics. You SAY good compression, what are the #'s, dry and wet? If you spritz starting fluid / faux fuel, does cylinder #1 start firing? Then it's a fuel / injector problem. When you pull the wire off the plug do you have spark? Then it's an ignition problem. If you put a stethoscope on the injector, can you hear it clicking?

As an electrical engineer I've got to call b.s. on this "theory" A fuse may have corrosion on the outside that adds resistance to the circuit, and dims the lights, but the fuse itself is either 0% or 100%. No cigar.

No, unless someone replaced them, they're not stainless steel. Suggestion; take this to a muffler shop where they have a rack and air tools and just have 'em fix it. Unless you like grinding and drilling lying on your back underneath a car and getting crud in your eyes. You'll probably break a drill bit or two in the process; have spares.

Gradual contamination of the AC charge with water results in the production of acids within the system. Those eat the core and the condensor from the inside out. TIG weld one hole closed and you'll have another one next week. Suggest you replace both, get a good system evacuation, and then recharge the system. Holding the system under vacuum for a sufficient amount of time will "boil out" any water in the system. A good AC shop is invaluable; honestly, there are LOTS of shops who have an "AC machine" but the techs don't have a clue what they're doing. I know, caused I worked at several of them. You want a guy who's been working on AC systems SINCE the R-12 days...

Same here.

D'oh! Because if you don't pass the inspection they don't give you your license plates / sticker.

Throw out an anchor instead of using the brakes?

Restriction in the T-valve, perhaps?

There are a couple of easy solutions to the "urethane squeek." One is a louder stereo. Another is a header and lo-flow exhaust. Even just a new subwoofer may do the trick. Last, but not least, are earplugs. Don't worry after awhile you won't even hear it. You can also remove the bushing and wrap teflon (plumbers) tape around the rod. If your'e going to try the aerosol and little red tube technique, I'd suggest white lithium grease instead of WD-40,

This thread brings up a similar question for my 280ZX. On the rear of the head there is an octagonal stud that sticks out that the heater core plumbing attaches to. Actually two hoses attach to it. One that CONNECTS to ANOTHER ONE from the front of the engine, at a T-fitting, (bypass??) and the one that actually goes into the heater core. Is that just a solid, metal stud, with a connection between the two nipples, or does coolant flow out of the engine/head THROUGH that stud. (Making it a 3-way of some sort...) If it's a 3-way, is there a check valve or restriction in the system somewhere? Like at the T-valve? If not it appears hot coolant could choose to completely bypass the heater core. Anyone know the theory on how this plumbing nightmare (rivaling a Jaguar) is intended to operate?

I suggest you first learn how to PROPERLY set your Z to the factory recommended timing, Leon. Get in the factory service manual and see what the procedure is --- it may involve disconnecting the vacuum advance, plugging that line, etc. You'll need a timing light. You'll probably have to do some scrubbing to see the timing marks. Then go drive it. If the factory setting is 8 BTDC, now re-set it to 16 BTDC and go drive it. Lug it (4th gear, low rpm's) up a hill and you'll hear it pinging. Now dial it back to say, 10BTDC, and go drive it again. Try it on regular and then premium gas. The more timing advance the higher octane fuel you need to avoid pinging. Generally you can "get away" with an extra couple of degrees of timing advance (further BTDC) without a lot of pinging. Depends on your altitude, the grade of gas you normally run, humidity, lots of factors. You do NOT want to be pinging ALL the time, although "just a touch" when accelerating up a hill means you're set just about perfect. Any less and you're leaving performance on the table.

Pagosa Springs, Colorado Saw a gold? brown? ZX? eastbound on Highway 160 somewhere near City Market. Waved to no reply from my silver ZX.

The original question was "Why use back pressure instead of the AFM signal" to determine load, for purposes of enabling or disabling EGR. Can we agree that the AFM might output a similar signal for an engine at 2000 rpm, with the pedal floored, and, perhaps 4000 rpms with the engine loafing? So a "raw" AFM signal gives no direct indication of load. You'd have to compare RPM's versus AFM signal in some sort of a look-up table and go "Hey, this is a very large AFM signal relative to RPM's, so that PROBABLY indicates a high load. Except the L-Jetronic is analog, so a "lookup table" is beyond it's ken. I suppose some sort of slope comparator circuit COULD be devised to do it, but .. So for purposes of MECHANICALLY enabling/disabling EGR, exhaust back pressure gives a simple, direct indication of load with no "processing" required. And it's inexpensive. Maybe I'm EGR-dyslexic or something; sometimes my initial arguments are just wrong, but the feedback leads me to where I'm trying to go. Ain't that great? Love this place!

Hey, great summary of our discussion Capt. I think that'll really help other Z owners. As for AFM indicating load, this is how I think about it: Imagine you're in 5th gear at 2000 rpms, at an easy cruise. Whether you're on the gas pedal lightly or have it shoved to the floor, just about the same amount of airflow will be going past the AFM. At 2000 rpms the engine is going to pump virtually the same amount of air regardless of throttle opening. Opening the throttle up WILL increase back pressure, however, because you've reduced pumping pressure losses past a closed throttle, even though the volume stays ABOUT the same. The engine isn't having to SUCK the air in as hard, so it can use the same pump to EXPEL it harder.

We're BOTH right here, Captain. There is negative logic AND positive logic at play. At sufficient load (backpressure) the BPT indeed PASSES control vacuum. But at high throttle openings there is very low manifold vacuum so the EGR valve itself doesn't get pulled open even with the BPT wide open. If the engine is lightly loaded (low backpressure) you don't WANT EGR. EGR is for mid-to high loads, but NOT WOT. All engines - GM, Ford, Nissan, Toyota schedule EGR under pretty much the same operating conditions. The Toyota document shows a really informative graph of this.

Come-along AND park the dolly on a downhill makes loading a LOT easier.

Here's a case study about a problematic EGR system on a newer vehicle (Chevy Tracker). It incorporates ECM control of an EGR solenoid, but the key take-away is this: P0400 Exhaust Gas Recirculation (EGR) Low Flow "The pressure transducer regulates the amount of vacuum to the EGR valve depending on backpressure in the exhaust (engine load). Unless at wide-open throttle, the more the load, the more the EGR valve opens." Wide-open throttle = zero intake manifold... Another interesting EGR read: http://www.tomco-inc.com/Tech_Tips/ttt9.pdf

"I know what it does... It disables the EGR system if the exhaust backpressure is too low." I don't think that's quite right Captain. I'm pretty sure it disables EGR if backpressure is too high at low-to-mid throttle openings (high to middle intake vacuum). The Japanglish in the FSM may be a bit confusing here. If you've got a high backpressure (load) situation you don't want EGR "flooding" the intake manifold when it's most "vulnerable," which could cause a serious stumble right when you are calling for maximum power. EGR, in theory, when it's working correctly, should BENEFIT an engine with higher efficiency. How, you ask? EGR SHOULD allow increased spark advance without pinging at mid throttle and load levels. It should also decrease backpressure (ever so slightly), and reduce pumping losses. But here's the thing. I've seen hundreds of cars with inoperative EGR systems. In most cases it fails closed. And yet there's seldom any pinging, no noticeable loss of mileage, etc. Only in the few cases where it fails open and causes a rough idle or stumble on take-off does anybody ever bother to fix it. So what does that mean, really? That many makes of cars are leaving 2-7 degrees of spark advance (meaning power and MPG's on the table?) Perhaps. On the Z's, perhaps owners are compensating by running premium fuel where they might be able to get away with regular with a properly functioning EGR??? On Hondas in particular, EGR tends to clog individual passages in the intake manifold until a single cylinder is receiving ALL the EGR gas, causing a rough running situation. On older Nissans like the Z it's usually the EGR valve that sticks (closed) and no harm, no (apparent) foul. I've always wanted to "clean up" an EGR system on a car like a Z and carefully measure what sort of spark advance was tolerable, if any MPG improvement was discernable, etc. Never have had time to bother. Too busy driving it and having fun! Like air pumps, catalytic converters, and other pollution control equipment, a lot of owners consider EGR a boogeyman and immediately rip it off or disable it instead of going to the time and expense of getting it working properly. Pity. References: EMISSIONS SUB SYSGTEMS -- EGR Toyota Factory Documents http://dept.sfcollege.edu/InTech/AUTO/content/courses/AER2840%20materials/Toyota%20EGR%20systems.pdf So Why do we have EGR by Glen Beanard Better Breathing: EGR Improvements: Underhood Service EGR Systems - Operations & Diagnosis By Henry Guzman Australian 300ZX Owners Association Technical Library: Content / EGR (Exhaust Gas Recirculation) / EGR, what does it do?