Help Troubleshooting

[Rich76_911s]

As we all know I recently rebuilt this engine. It was running fine, then started missing and it got progressively worse.

I checked my fuel pressure settings. AFR's were in a decent range while I was driving.
I checked my fuel pressures today at 18 degrees C I had:
Cold Pressure: 1.4 Bar
Warm Pressure: 3.4 Bar
*this is an '87 engine that has had the frequency valve deleted by Brain at Rarlyl8. So I've leaned towards setting the fuel closer to a 930/66 engine.

The cold setting is a bit high on the range for 18C, but is still within the gray area on the chart.

I also took a look at the ignition system. I have a distributor and permatune ignition system.
1. I checked my spark plug wires and they have between 4 and 4.15K of resistance on each.

2. My green wire had between 6-18K of resistance depending on where I put the probe into the socket. Jiggling the green wire did not impact resistance at all. The ground wire sheeting had no resistance at all. I think when it's fully contacted the 6K of resistance is probably about right.

3. I put new NGK BPR8ES spark plugs in it. I previously had non-resistor plugs in it. I also have a set of the bosch w3dpo's on the way.

4. Put a new Rotor and Cap in, as in I had new ones when I rebuilt the engine, then I put another new set in. The newest rotor was slightly different than the older one. Had a much wider contact point. Anyone know which is correct?

New:


Old:


What else can I check? Are the spark plug wires an issue with 4-4.15K of resistance?

Want to be driving this like 2 months ago, so any help would be appreciated.

[Rich76_911s]

This is how it was running before the rotor and cap replacement. I don't have a video of it, but the car is running better now with the new rotor and cap, but still not running right.

[Porsche 935]

Is it low on power because it does not sound like it is running on all 6.

[Rich76_911s]

Yes no question it seems to be down on power.

Also when you depress the gas pedal it would stall.

[Porsche 935]

Pull plugs and look for one that may be gas fouled.

[IMR-Merlin]

Sounds sick for sure. have you done the preliminary stuff like check for spark on all 6 cylinders?

Try pulling one plug wire off at a time to see if idle drops... also, check to make sure to check for correct firing order.

Do you have a pyrometer? Check exhaust header temps on each tube for temp changes.

[turbobrat930]

Find your dead cylinder. Either by pulling the plug, or checking with an I-R meter (as previously stated above). Then find out why its not operating correctly. Do you have spark at all
on the one cyl? Are you getting fuel, or a good, full spray pattern of fuel on that one cylinder? How is the compression? is a rocker arm broke, or shaft cracked and maybe loosened up on you?
Has the idle screw been touched at all? vacuum leak?

[IMR-Merlin]

And I think we met at turbopalooza 2 years back and we played with some electrical

[Rich76_911s]

I haven't pulled the injectors to see what kind of spray pattern I am getting. When I pulled the spark plugs they all smelled of fuel.

I also have not pulled individual spark plugs and check to see if they are firing.

I ordered a pyrometer to check, not a bad tool to have anyway.

Brandon, Yes we did meet at Turbopalooza. My brake lights weren't working and we checked to see if it was bulbs.

Is the 4-4.15 of resistance OK for the plug wires?

[icemann427]

You can easily pull the spark plug wires off of the plugs, one at a time, to see if any individual cylinder isn't firing, properly. If one or more are not, you can then pull the plug(s) to see if you see a spark or not. This way you can start narrowing down the problem.

[Rich76_911s]

Thanks guys. I'll try pulling plug wires and see if it makes a difference.

So replacing the plugs, rotor, and cap has me getting a little closer to proper running. Even when I apply gas it sounds much better, but still feels like a cylinder isn't firing.

[jsveb]

Are the plug cables properly seated at the distributor?

[Rich76_911s]

I'm pretty sure the cables are connected properly.

[kevin930t]

Rich check to see if you have all your manifold nuts tight.I also would pull out your spark plugs to see if any are fowled.My car ran excactly the same and turned out that it was the combo of air leek at the manifold and fowled plugs.

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[Rawknees'Turbo]

Originally Posted by IMR-Merlin

And I think we met at turbopalooza 2 years back and we played . . .

???

!!!




Rich, anther thing you you can to narrow down "spark or not" on each cylinder is to take a spare spark plug, attach one of the spark plug lead to it, ground the plug against a nearby metal component and the run the engine (or just turn it over with the starter if you have someone helping you). You would do that, one at a time, for each cylinder.

[Rich76_911s]

Thanks for the ideas. I'll be checking them over the weekend. Kevin I'll look at the intake manifold, and check for air leaks elsewhere.

Ronny- we actually played with a power probe!! An awesome tool I want to add to my garage.

[Rawknees'Turbo]

^^^

Rich, is that different than the power probe you were born with?!?!


PS - is there a way to troubleshoot the Permatune? I know that they had a negative reputation in the past for reliability (don't know if that is still the case, however) . . .

[kevin930t]

Originally Posted by Rich76_911s

Thanks for the ideas. I'll be checking them over the weekend. Kevin I'll look at the intake manifold, and check for air leaks elsewhere.

Ronny- we actually played with a power probe!! An awesome tool I want to add to my garage.

Rich is this the pwr probe u were using???Unlike Rawknees little tykes probe.

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[kevin930t]

This probe is called the hook

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[kevin930t]

I play with mine at least twice a day.Haha

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