Duck Ryder

I have exhausted my patience with this car and running out of things to test/replace. So I am putting it out to the Z community for assistance.

Problem description: No power under load. Little/very minor 'burps' at idle. Basically, rpms won't climb, pressure will go to about 0 gauge, but wont increase. stuttering.

Vacuum at idle: 15inHg
Fuel pressure at Idle: ~34 psi (a little low but gauge could be off)
Fuel: 3 years old...
Compression: If I remember correctly, I get about 145 psi after the third stroke on a cold engine. Gets up to about 160 after a couple more strokes
Spark: I have a adjustable spark tester, but haven't done yet.
Spark timing: Idle ~22 degrees before TDC (this is a turbo) Does advance further with RPMs but goes off scale...
Coil tested within range per the FSM
CHTS: Tested as per the FSM, resistances within range
AFM temp sensor: tested only at ambient air temps, within range.
AFM & TPS resistances tested per the FSM at the part itself, not at the connector for the ECU, all correct.
Cam clearances: If I recall correctly, within spec for the couple I checked when the engine was cold.
Wiring harness has been completely removed and inspected, I did find some wires that had the insulation rubbed away from where it passed through the firewall. It has been fixed.

What I have replaced:
O2 sensor
New connectors from Fricfrac for the injectors: AFM, CHTS, Idle air control valve (forgot acronym)
All new vacuum lines
New cap and rotor
New spark plugs
Replaced ignitor with HEI control module


Currently the AC is removed and the belt to the power steering pump is removed. Also the fuel injector cooling fan is removed.

For those that like to know what was happening before: I started taking the car apart when a exhaust leak made it impossible to breath inside the car. Once I took off the intake and exhaust, it became a slippery slope from there. I took out everything from the engine compartment except for the engine and steering. Both wiring harnesses, brakes, intake, cooling, hood and bumper came off. I cleaned up some rust and replaced the timing chain, guides, tensioner, and gears. Before the exhaust leak nearly killed me, I was experiencing a loss of power when trying to go up hill. (Same as current issue, but less pronounced).

Any help or advice would be greatly appreciated.




I've included some thumb links to high resolution pictures of the spark plugs. They are organized from left to right to represent cylinders 1-6 in that order.

Cylinders 1-3 on black background


Cylinders 4-6 on black background


Cylinders 1-3 on white background


Cylinders 4-6 on white background



Edit (Corrected Idle Vacuum from 25 to 15 inHg

rogerz

can you borrow an ecu from someone? Not much left you have done most of the testing. thermotime switch possible problem? Is your battery and cables good. low voltage will cause zx to do funny things. Weak battery corroded cables bad. ground cable going straight to starter and not to a bolt in the body first. this is not a reliable ground. at times we ingore the obvious (we have all done it).If you can't find an ecu you might get in touch with the Portland guys for help - we get together with them from seattle time to time. a good bunch and knowledgeable. Northwest Z - NorthwestZ Home. there is a link

Duck Ryder

Unfortunately the only other s130 Z owner I know long replaced his ECU with a self learning one.

As far as I understand the thermotime switch just controls the idle air valve and sends the signal to the temp display. I am sure that both the thermotime switch and idle air valve are both functioning properly as the car exhibits normal warm up behavior with the idle.

The grounding cable from the starter could be an issue... afterall, part of the rust I cleaned up was the removal off the rusted up battery stand. So currently the starter ground goes straight to the negative terminal on the battery. There is a small cable going from the ground on the batter to the chassis.

Will have to figure something out and test

Thanks

Genewiz

1. Check good ground to chassis

2. Warm up car. pull wire off cylinder 2. Any difference in problem? Put it back on.

3. Pull wire off cylinder 5. Any difference?

If you do not notice a difference then that/those cylinders are not hitting and it is an injector problem. Since 2+5 do not appear wet, I would say that you are getting spark to them, however I do not see slight ashing on the electrode.

4. Retard timing down to 8-10 BTC. Does this help? Yes it is suppose to be 20-24 BTC.

5. Still have the problem? Pull Harnesses at CPU and run down Air Temp, AFM, CHTS, throttle position sensor as described in FSM with a good ohm meter. I have found that small paper clips work well to probe the harness. I know that you repaired the harness but sometimes a small nick can lead to corrosion and breakage of a small wire, especially on one 30+ years.

6. Still a problem?, swamp out CPU

lifegrddude

How is the fuel pressure? Does it drop when the stuttering occurs? Could be a worn out fuel pump or maybe there is some debris in your gas tank clogging up the pump when climbing a hill.

FricFrac

Did you get rid of that three year old fuel?

Duck Ryder

Disconnecting any of the injectors has a noticeable effect on the engine idle.

For the grounding issue, If I have time this weekend (I have to work on a house project) I plan to run three separate grounds from the battery to the ECU, Ground connections on the intake manifold and one to the HEI ground connection. If there is any grounding issue, this should take care of it.

The fuel pressure does adjust with the manifold pressure, however I've only tested this with the car parked and revving the engine. As for the old fuel, I am slowly siphoning it out and sharing it with my other car. The car unfortunately had nearly a full tank when I parked it...

I am contemplating building a fuel injector flow tester. I've seen some DIY where you use a compressor to provide the pressure and some beakers for each injector to visually inspect the spray pattern and volume flow rate. If I recall correctly, the injectors are low impedance, so I hook them up to a resistor and then to the battery and using a momentary switch, fire the injectors. I will leave them on the fuel rail. And there is a little 'tank' of fuel in which the compressor puts air pressure on the top side. The pain in the *** part is where does one find beakers? Or graduated cylinders...


I want to note that until recently, this was a time dependent issue. It used to be that the engine ran Ok while it was 'cold.' By cold I don't mean before it reached operating temperature, it still ran Ok when it reached operating temp... but the longer it ran, the worse the issue got. But now it seems to be almost immediate, last time I tested, the car had warmed up for about 5 minutes before I tried to drive it down the street... didn't get very far before it bogged down.

FricFrac

What is the condition of the turbo system? Does the wastegate work properly? Are you getting any boost leaks?

If you want to test the injectors you already have a "test system" setup. Get some longer fuel line and pull the whole thing out of the car using the longer fuel line as an extension cord. You can either open the injectors with a 9V battery since it will limit the current going to the injector or run an injector in series with a power resistor to limit the current. That way you can test the whole system as it would be running in the car including the fuel pump, filter, pressure regulator, rail, injectors, etc... You can get a graduated cylinder from a chemical supply store or use a pyrex measuring cup.

A star ground like you've described is a good idea for each individual system. The ECU and the sensors, however, are their own single system so you should go from the battery to the ECU then from the same point at the ECU to the plenum where most of the sensors are. That will prevent ground loops. That's not likely your problem but that's the proper way to do it. SOunds like your electronics are testing out OK. When you checked the AFM did you move it through it's full range of movement?

Duck Ryder

I have not tested anything with the turbo. I am lacking in knowledge in this area, any advice/reading material/direction would be great.

Thanks! I will do that instead. When I tested the AFM, I am sure I moved it through its full motion... as best as I remember.

lifegrddude

Since you're also using an HEI module as your ignitor, is it in an area to get a sufficient supply of air, and does it have any heat sinking fins on it? I recall several people on Hybridz having issues due to the HEI module overheating and causing what you're experiencing. However, I still think it more fuel related though. Another thing to check is when the car starts to sputter, try wiggling the ecu connectors and see if that clears it up. 30+ years and the wires tend to go bad. I had to swap out my entire harness to a Z31.

If you do get the opportunity, I recommend having a wideband air/fuel gauge installed so you can tell if the mixture is lean or rich to help clue you in some more.

Anyway, hope you can make some progress, and I'll see if I can find my old notes on my Z to see if there was anything similar I experienced.

Duck Ryder

I have mechanically cleaned all the connectors by hand, but if pins are bent/out of shape, then it can still be possible that there is a loose connection. I was going to check spark strength this morning... but ended up breaking the wire from the coil to the dizzy........ something else to buy now

This is how and where I have the HEI mounted:

Duck Ryder

So lets say I've tried this and the car runs better, a little rough at idle, a little rough during acceleration... but it will accelerate!

I'm guessing this means bad fuel. The octane level has dropped too much and the fuel is igniting faster/sooner than it should (lower octane ignites easier).

The car is down to a 1/4 tank of gas, I can't seem to siphon anymore out as the tube will not go in any farther into the gas tank.

rogerz

did you take the oil pump off whilst doing other stuff? IF not installed right will throw the timing off. waste gate stuck open? put mechanical boost gage in the system don't depend on the electric in the dash. you say you have a vacuum reading - did you not use a boost gage for that? boost gage is called a compound gage in the real world measures negative(vacuum) and positive pressures. If not getting any boost you are essentially driving an n/a car which is not tuned for that

Genewiz

If you want to get rid of the rest of the gas, then pull the line where it attaches to the fuel filter and splice in a longer piece you can run into a bucket/can. By turning the ignition switch on, the pump will charge for a few seconds then shut off. Dont turn all the way to start. keep flipping on and off. It will take a while but then you will know that all that crappy gas is out of the system.

Duck Ryder

The car is running better, but still not right...

I have drained all the fuel out, added new fuel, drained that out and then add some more new fuel. Car ran much better, got on the freeway just fine, but after a mile I lost power and could only maintain my speed. On the surface streets home the car seemed to run fine. When I got home, I took a look at the FPR and it said I was running only 24 psi at idle. I put in a new FPR and the pressure is much better, but still off, so I am assuming my gauge is off a little.

The car runs better with the FPR, but still not right. On the freeway it will bog down, then release, bog down, then release and so forth. On the surface streets its similar to before, runs ok, but seems low on power and does not want to run WOT.

At this point I think I need to find out why spark plugs for cylinders 2 and 5 are different/darker. I am going to try swapping injectors around to see if the problem follows the injectors, otherwise I think it could be leaky valve stem seals.

If anybody has any other suggestions...

Thanks!

zedsdeadbaby

Are we 100% sure the VCM is a good ground? I thought it was rubber mounted.

Aside from that, everything you're saying leads me to believe you have a **** fuel pump.

PredatorZ

After all that bad gas I would change the fuel filter and use a fuel additive to help clean any sludge or glazing out of your system and injectors.

mrprofile

I didn't read all the comments so i don't know whether this was covered but, you obviously did some exhaust work, and the lack of boost, slow rpm climb and lack of power points to some kind of clogged exhaust to me, maybe a broken or clogged cat, stuck turbo wastegate, any number of things.
It's an easy test, turn on the engine and put your hand near the end of the exhaust pipe to feel for good enough exhaust flow out of it, if there is very little we may have found your problem.
also just FYI you want to check the valve lash while the engine is warm not cold

duckyz

Ok..Pardon me, I'm 1/2 in the bag....(I finally have a few days off, and I'm having a few beers, dammit!!!)

But, that damn Cylinder Head Temp Sensor (CHTS) is one SOB. It's located just under the #5 and #6 spark plugs and has a connection like the fuel injectors. IF that connection isn't right, all kinds of crap happens. Make sure the metal connections on both sides are clean and straight!

..ok... time for another beer!

PredatorZ

You pics are very low res, no links to better pics, this site will actually support pretty large pics. I wish I lived a bit closer to you, its a 7 hour drive from Boise to Beverton. I have an 81 zx with the original ECU, just a bit to far to do in a day. But it does sound like your getting some of your issues sorted out. As far as electrical goes, I'd talk to Fricfrac, have him send you a connector Kit, best $55 you will ever spend on your car. If you could eliminate about 95% of the connectors that cause issues you would be miles ahead of where you are now.

Duck Ryder

Update... the car passed emissions test, however that is only done at idle. But the car still does not run right.

Since my last update, I did swap my injectors around and the difference in spark plug color has now gone away. They are all white...

It seems I may have multiple issues, but to describe the problem over again:

At initial start, car will idle around 1200 RPMs, there is a consistent misfire during this stage that eventually appears to go away as the car warms up. At some point the idle will drop to about 1000 RPMs. I assume this means the air regulator is functioning. I currently have the throttle valve adjustment screw backed all the way off. Vacuum is still good.

The car at this point still hesitates and can bog down when trying to accelerate, giving too much throttle during this period will cause a pop through the intake. The bogging and hesitations happens during cruising and acceleration. 5th gear is nearly impossible to drive in.

There is a caveat to all this, the longer the car is driven/idles, the lesser the intensity of the issue. After being stuck in stop and go traffic for 20 minutes, I was able to just barely cruise in 5th gear.

It has been suggested that I may have a leak that is bypassing the throttle valve. I've also got a new CHTS coming, they were cheap so I ordered one. Another note, I have currently bypassed the coolant line that runs to the throttle body and air regulator.

Questions: Any suggestions?

Can anyone explain what the FICD, AAC and Vacuum Control Valve does?
I've also read about someone bypassing the VCM, but could not find further info on how to do this, can someone point me in the right direction?

Duck Ryder

I got my answer for the FICD, AAC, and Vacuum control valve from hybrid z

What is a AAC valve, F.I.C.D, Air regulartor, Vacuum control - Turbo / Supercharger - HybridZ

Duck Ryder

Fixed the drive-ability issue... Disabled the VCM and plugged the vacuum lines to it. Its disconnected from the ECU and the vacuum lines are disconnected from the manifold, AAC and the EGR. Vacuum went from 15inHg to 20inHg. Technically, I will fail emissions now... but since I just passed... I've got time to resolve it.

Still have the misfire during the warmup process, if anyone has any suggestions.

Thanks