Indycam

How would a carbon canister cause a motor on cold start up to not fire ?

altarchsa

Had the engine out, again, unfortunately (see previous post), and took the opportunity to clean the idle solenoid valve thoroughly. Don't know if that's what did it, as I performed a lot of other work on the engine, but it starts immediately now and I think it was a dirty ISV that caused the difficult starts. Thanks for those suggestions.

Now I have a completely different problem! The car idles really, really rough, like it has a hot cam in it. As I said above, it now starts quickly, idle speed is well controlled, and it seems to run great above 3k rpm. Initially it seemed like a spark issue, but I disconnected the coils individually with no change in symptoms. Now I'm beginning to think maybe it is running rich. Would an air leak in the intake below the MAF cause these symptoms?

While I had the engine out this time, I disassembled the intake system completely and cleaned the shrapnel (per my previous post), so that's why I'm thinking it may be an air leak and mixture issue.

I also had 3 new intake and i exhaust valve installed + all new intake valve guides and had spring height checked. But that work was by a really good machine shop. Also, I double and triple checked cam timing and distributor position when reassembling, so I think those options are out. I don't have a code reader and the two shops that have hammers are not good options for me.

Please continue to help! I feel like I'm so close to a perfectly running engine, but I am at the end of my rope!

celal

air leak cause that kind of problems and if you have an air leak then your car is start to run rich

Indycam

I would look for a misfiring cylinder .
Run it on one set of plugs and then pull one wire at a time off of the cap and see if pulling one wire has no effect .

altarchsa

Thanks guys.

I pulled the wire on each coil to make sure I did not have a bad coil or wire or wires crossed, but I had not tried checking for each cylinder yet. will do that next.

I'm not sure where I would start to confirm an air leak or to locate it.

springer3

This is old school and I have done it may times on pre-electronics ignition systems. I still have a plastic tool designed to pull spark plug boots and keep hands clear of the high voltage. This is not a good idea on high-energy ignition systems. The plug gap fires at @ ~ 4 kV. Open circuit the high-voltage side, and the voltage will climb many times higher as the system tries to fire the "bad" plug.

Depending on the humidity and the integrity of your HV insulation, you can draw a spark to your body or to ground on the car. You will not soon forget a spark to a body part, assuming you survive. The extreme high voltage generated when you open the HV circuit can damage the ignition system electronics and insulation.

There are many posts on how to disable one system on the low-voltage side. That should detect a bad plug or a bad system. If you really need to disable one cylinder at a time, it is better to disconnect the electrical connector at the injector and then start the car. You will have a dead miss on the fuel-starved cylinder. A better way to troubleshoot an ignition problem is to find an ignition scope and compare the waveforms to the standard troubleshooting guides.

Geoffrey

I would check the cylinder head temperature sensor.

darth

"I'm not sure where I would start to confirm an air leak or to locate it." Another method besides using a hose type stethascope or visual inspection is to use your gas barbecue propane tank and with propane coming out of the hose follow the vacume lines. When a leaky vacume line pulls in the propane, the engine will run smoother. You can imagine the potential danger if you don't regulate it properly by having a cloud of propane build up. Do it in a well ventilated area outside.

Bill

Indycam

I suggested that in post number 6 of this thread , back in 2009 .

Indycam

If its done right its no problem .

And if you look you will see I wrote more than a few of them .

We are not looking for a bad plug or system .

Why do that when the spark plug wire is faster and easier ?

Finding an ignition scope isn't needed to find a dead cylinder .
A simple quick non dangerous test is all that's needed .
If a dead cylinder is found , that cylinder can be looked at closely .

Indycam

Do you know how to do this test safely ?

If you do the spark plug wire test and you find a dead cylinder then you can check the intake on that cylinder for a leak / loose clamp , etc etc etc

altarchsa

Thanks Geoffrey, sprnger3, darth and Indycam. You've given me some great help to diagnose this.

I'm very familiar with the high voltage hazards and I'm very cautious. I don't need to get zapped again (happened many years ago) to remind me. Yes, Indycam, I can test each cylinder safely. My process is to pull one lead at a time with the engine off, safely locate the lead away from grounds and sensors and restart the car. I've been doing this long enough to remember the days when you could just pull and replace the leads with the engine running. But I appreciate your cautious approach to advice, not knowing whether I'm a novice or experienced "mechanic".

Re: misfiring plug one cylinder, I thought by pulling the coil wires separately, I had not only checked those systems separately, but also ruled out a bad spark in one cylinder, assuming I would not have a bad spark in only one cylinder on both circuits. I'll pull the injector connectors one at a time to test cylinders separately that way.

Not sure I want to try the propane test. Sounds a little dangerous, but I'm fast approaching the point where I might be ready to blow up either the car or myself!

Head sensor is a good suggeston I think, since the engine's been apart several times and that wire seems to get a lot of abuse in just moving it back and forth during disassembly/reassembly. I'll check the books for testing it. Per my previous post, I was unsure about which connectors matched up for the left side ping sensor and the head temp sensor, as my labels came off in the rebuild process. I found some old number markings on the connectors and I'm pretty sure I have them right, but can anyone confirm which is the appropriate connecter for the head sensor? A pic would be very helpful.

I feel like I owe each of you guys a spin in this thing once it's right. I think I'm so close to getting there, and it's frustrating to not be there already!

Indycam

The test for a dead cylinder isn't a test for a bad plug or no spark .
You could have two good sparks going to a dead cylinder .
A. If you have a good cylinder with two sparks going to it and you pull one spark , you have good cylinder firing on one spark , maybe no change to the smoothness .
B. If you have a good cylinder with one good spark and you pull the spark ,
then the motor should show that one cylinder that was firing is no longer .
C. If you have a dead cylinder with one spark and you pull the spark ,
nothing will change . The motor will run the same same . You have found the dead one . Now you can look into why that one is dead .
Air leak ?
Bad injector ?
Valve not closing ?
Valve not opening ?
Rag in intake ?
etc etc etc .

altarchsa

[QUOTE=Indycam;7396130]The test for a dead cylinder isn't a test for a bad plug or no spark .
You could have two good sparks going to a dead cylinder ....QUOTE]

Thanks Indycam, got it. I see your point, I was checking for spark. I'm planning to work on it tonight. Maybe I can make some progress with the advice that's been offered.

springer3

This is not a good idea. Unless you ground the spark plug wire through a spark gap, the system will generate extreme voltage trying to fire the "bad" plug. That puts a lot of voltage stress on the electronics, the coil, the high-voltage wiring, and the gaps inside the distributor cap. If the cap insulation is weak or humidity is high, you could get a cross-fire to the wrong plug, and that would leave a carbon trace that will cause problems.

It is also not correct to say an ignition scope does not diagnose a bad cylinder. Low compression, lean mixture, rich mixture, dirty injector, HV insulation breakdown, and high resistance all change the pattern on the scope in ways that are easy to recognize. The spark gap in the plug is quite sensitive to off-normal cylinder conditions at CTDC.