I finally got back from Las Vegas, so here I am in SoCal, still trying to troubleshoot my engine stumble.

BTW: TPS is disconnected, and I have pinched off the cold start valve fuel line.

My engine seems to do well when the engine has cooled. By cooled, I mean for about five minutes or more, say at a gas station. For the first five minutes, the engine runs OK. After about five minutes of driving, the engine misses pretty badly whenever I let up on the gas. During acceleration it feels strong, but once I let of the gas to maintain driving speed, the stumble - missing returns.

So I drove my car for a while to make sure the engine was warm, and returned to my garage. I unhooked the CHT, and the engine was unable to start - engine flooding. That makes sense to me. I grounded the CHT wire from the wire bundle to the ground of the battery and drove for another ten minutes. No change.

I re-attached the CHT and decided to see what was really happening (which I should have done at the start). At idle, if I disconnect the number 1 or number 4 spark plug, no difference in the engine idle. When I disconnect either 2 or 3, the engine barely runs. As I reattach #1 and #4, I see spark. So it would appear to me that cylinders 1 adn 4 are not getting fuel?

Since I have spark to cylinders 1 and 4, this would normally lead me to the triggers. But the triggers fire 1&3 together and 2&4 together. So that makes no sense to me either. Add to that a FI injector grounding issue should affect a single side, which would be 1&2 or 3&4.

So what would cause this issue? Any thoughts?

Eric Read

Correction:

I let the engine cool for about 15 minutes. WHen I start it up after it has cooled, all four cylinders are firing. Now when I pull any of the spark plug wires, the engine slows.

So the problem with #1 and #4 seem only to be an issue when the engine has warmed. Back to the spark portion of the Dizzy? Or does it still seem like a FI trigger issue?

Eric

BUMP

Any thoughts out there???

Eric

Checked your spark plug wires????

I had one that measured great, and turned into an insulator after about 5 minutes of operation. When cool, it was great, when hot, it didn't conduct. Timing light with the sensor near the plug works for me in ID'ing a bad wire. Check each wire when cold and when hot to see if that is the problem.

Pulling plug wires disconnects the electrical spark from a cylinder. It has nothing to do with the injection of fuel at that cylinder and will not indicate a fuel injection problem. It merely confirms that the cylinder with the removed wire is not operating properly and is a test to locate the problem cylinder/s

You should investigate both spark and fuel once the problem child is identified.

I had a VERY similar issue when I still had stock Djet. After screwing around with it and giving up, putting aftermarket FI on, I found (with the laptop plugged in to the new FI) that the head temp sensor was going full open when it got hot. No resistance at all. Once it cooled enough to check it, it would show ok again. Might just try a 1K ohm resistor to ground on it and see if it changes.

Kenny;

Good thinking. I never even though of that

Anyway, I hooked up the timing light and voila, I found a random firing problem with #4. After changing the dist cap - no change. After changing plug wires - again no change. So my distributor is randomly not sending spark to cylinder #4.

Any ideas on why/how the distributor would/could do this? All my other plug wires look really stable according to my timing light.

What happens is the the strobe shows regular signals for four or five seconds, then a very irregular pulse including complete signal failure for up to four or five seconds. I watched it for a number of minutes and could not detect any patterns.

Any ideas???

Eric Read

Try changing the spark plug they will break down with heat.

Eric,

That's weird. Were the plug and cap new?

Tried the a new cap and wire together?

I always save the old cap, rotor, and longest spark plug wire for troubleshooting tools. They might not work the best, but can work well enough to troubleshoot.

If your cap is old, I'd suspect a possible burn mark on the # 4 copper contact that extends into the cap and gets the zap from the rotor. Check the rotor for burn marks and the inside of the cap for a crack or arcing marks. Sometimes with an old cap, a conductive carbon arc trail forms inside the cap so look carefully for that. Try cleaning the inside of the dizzy and cap and rotor with carb cleaner and re-greasing the point contact block. Sometimes a film builds up inside.

Try looking at the running engine in the dark to see if the insulaton on the spark plug wire is broken and casing a spark to jump.

D-jet injectors are paired diagonally, 1/4 versus 2/3.

How are the points? What about the cam in the distributor that the points ride on?

If you have a points replacement, then how is it doing?

--DD

The only cylinder that seems to be having a problem is #4. However, the problem stays with number 4 no matter if I switch wires, plugs, or change the cap and rotor. I am using a Pertronix Ignitor, and it seeming works great for cylinders 1,2 and 3.

Kwales suggested I track the prolem using a timing light in each of the plug wires. From that I can see where cylinder 4 randomly fails to get a spark from the distributor.

Hmmmm. I guess my only thought is to make sure there is a gap between the Pertronix unit and the center magnet when it turns to cylinder 4.

Eric

Maybe you can pull the magnet ring and rotate it 90 degrees? See if that causes the problem to move.

Or swap in points as a diagnostic step.

--DD

Dave;

Good thought. I'm going to swap the spark plugs between #3 and #4 first, to ensure this is not a result of a faulty plug.

Eric Read

Update:

I exchanged the plug in cylinder 4 with cylinder 2. The timing light test showed the ignition misses followed the plug, so I replaced the spark plug.

I take a short ride and experience the same issues. I re-test the plug wires with the timing light, and find missing ignition pulses one the wire for plug 1. I replace it. Now I re-test all the lines and they all show steady ignition pulses. Could I have had two, brand new, out of the box bad plugs?

I test drive it again, same problem. I had replaced the plugs about a week ago in trying to remediate this problem. Now I am thinking the bad plugs merely masked the actual problem...

Back at the garage, I re-test all the plug wires once more, and they all show a steady pulse. On to my next test.

At idle, I pull the FI plug at the #2 spark plug, engine almost stalls. I replace and pull the FI plug at #1 spark plug, no engine change. Repeat with #3, engine dies, and #4, no engine change.

So apparently, I am not getting fuel injection pulses to cylinders 1 and 4. So what do cylinders 1 and 4 have in common. Nothing.

But let's assume that for the past few years, I have been driving with FI plugs 1 and 2 exchanged (by the previous owner). I theorize that I wouldn't really notice it too bad, as the injection timing isn't exact. But using this theory, it would allow me to say that the FI signal to cylinders 2 and 4 have failed. That would point me directly to the FI triggers.

I see by the PO's past invoices that he replaced the triggers in 2005 with Trigger Points for a 914-1 1.7 (from Auto Atlanta).

1. I have put close to 45,000 miles on this car in the past 3 years, so in five years with daily driving, will a set of FI triggers wear out?
EDIT: Never mind this question. I realize now that the 1.7 and 2.0 triggers are the same.

2. Would a set of FI triggers for a 1.7 fit in the dizzy of my 2.0L engine? And how would that have affected drivability?

So what do you think? Am I insane and stretching the bounds of reason to justify my engine problem, or am I on the right track????? Do I purchase a set of FI triggers, or look elsewhere.

My thanks.

Eric Read

You could try changing the coil, they brake down in funny ways that will drive you
crazy when they get hot.

#1 & #4 are driven by the same trigger point. The trigger points are now suspect, as are the wires to and from them, and possibly one of the output stages in the ECU.

#2 & #3 injectors are opened by the other trigger point in the assembly.

The trigger points for the 1.7, the 2.0, and I think the Type III are all identical. Very possibly for other D-jet cars as well. Swap away as much as you like.


What the trigger points do is they short one of the outer contacts to the center contact, then break that connection, then short the other outer contact to the center contact, then break the connection.... Over and over again. Check to make sure that is happening when the distributor rotates.

--DD

Welcome to the real world of problems masking other problems.

It happens all the time with making products.

It's a lot like peeling an onion. Once you solve one problem, there is another beneath it and possibly another, and....

Glad you found out about the plugs. With two new ones bad out of the box, I'd be looking at another brand next time. It's the only way you can send a meaningful vote to manufacturers who decided to sell bad product.

I finally broke down and had a set of FI trigger points overnighted from AA.

After a thorough cleaning and reassembly (with the old FI triggers), as I turned the dizzy, I only heard a single click. Using an Ohm meter, I saw that one side of the trigger connector (sides of the three-spade connector are the positive pole, and the center is the ground) didn't cause any change in my meter readings.

Once I replaced the trigger, I distinctly heard two clicks (one for each side). The Ohm meter also demonstrated the expected result.

I replaced on my engine, hooked everything up, and performed a quick timing. On the road it ran soooooooo smooth.

My thanks to all that provided recommendations

Eric Read