3.2 60 days sitting, bad miss under load

[198491132]

Good Day, I am reposting, lost my original post. My 1984 3.2 was running great in December. I filled up the tank in early December, added Stabil, and ran it down to about 50%. The car sat with one start in January. It now has a severe mis, back fire and unable to drive issue. Starts fine, idles good at 800, under throttle, will behave fine for two or three revs. The third or fourth time under throttle, I get the huge mis issue.

I have added a bottle of red line fuel cleaner and five gallons of fresh gas. The car is now down to a quarter tank, same issue.

Done so far:

Listened to the injectors, all six sound the same.
Tapped injectors to free up
Verify all wire connections from sensors
Changed dme relay, for kicks and giggles
Checked battery voltages
Unscrewed oil cap for vacuum check, ok
Secured plug wires
Viewed cap and rotor, slightly worn but car idles and revs 2-3 times before issue
Pulled air cleaner, look fine
New air flow meter 1k ago

Some folks got back to me with injector ideas. I am going to change the fuel filter shortly, as I have a spare, just to see.

Full pump is new with only a few thousand miles on it. Sensors have been changed out about 15k ago. Temp sense and O2 also newer.

I am thinking bad fuel, but would like your thoughts as well. I only have a quarter tank left, should I run it down or add a few gallons of fresh?

I made a video, but Pelican will not take my post.......if interested please let me know and I can send it to anyone that wants to help.

Thanks, Dave

[Spumato]

I know that gas is not made the same as it was even 5 years ago, but sitting for just 60 days doesn't seem right! When you open the fuel fill cap, can you smell it?

If it has gone bad, will you be able to drain it in your garage? My thinking also is that if it has really gone bad, you are likely going to have to start over and clean the entire system from front to back.

[198491132]

Pulled plugs 6 and 2 also layed plug 6 on intake manifold. Saw yellowish spark. Changed coil with old black coil on shelf. Still have mis. Pict of plugs attach ed

[198491132]

Hi Ryan, gas smells ok to me. I just changed the fuel filter with no luck. Plugs do not look the best, going to order plugs, rotor and cap....needed them anyway, but still not sure they are the issue. Checked injectors for "ticking" all sound good. So still may be clogged/ dirty injectors. Just not sure why sitting just a short time would cause this.

[Flat6pac]

The injectors will gum up in just a short time. With the car running, tap the injector.
Bruce

[198491132]

Just tapped each injector firmly.
..no change. I did notice that the connectors seem to spin a bit on several. Is this normal?

If I take my fingers I can move the connectors back and forth.

What is consistent is that the first time full throttle is applied, I get full revs. Then after that, mis fires.

[rick-l]

Originally Posted by 198491132

Starts fine, idles good at 800, under throttle, will behave fine for two or three revs. The third or fourth time under throttle, I get the huge miss issue.

Do you know anyone that has the fitting to hook up to the fuel pressure test port?

[198491132]

Rick, I do not. I was wondering how to measure. I would need the fitting and gauges. What are you thinking may be the cause?

[wayne robson]

Dave , just in case this helps, that top plug is to dark ,not good, your best solution is
to fit a full set of correct new plugs,the other plugs could be the same or worse.
What can happen is you stated that ,you started car once after sitting in storage,then later started again with bad miss,.When using Stabil and storing, should never start car
unless it is driven to until normal temps are obtained. While changing plugs check inspect
your leads ,and use correct Bosch WR 7 DC copper . hope you get her running great again.

[Spumato]

I will repeat myself again, I have just resurrected a vehicle that sat for 18 years. Sitting at any timeframe is death to the Porsche engine. Whether it be 60 days or 18 years. Time still is time still. And gas has increasingly become less stable than it was even 5 years ago and separates. Seals dry out, and things gum up. This is a slippery slope that cannot be stressed enough. I know that the OP is having issues, but let the rest of the forum take note... Porsche's are the best engineered motors known to man, and they yearn to be driven and driven hard at each pass. Run them often, drive them more. Bury the tachometer to the red line at each and every shift, and she will reward you back. I have learned this the hard way and wish the OP and all many happy miles of smiles!

[rick-l]

Originally Posted by 198491132

Rick, I do not. I was wondering how to measure. I would need the fitting and gauges. What are you thinking may be the cause?

The left fuel rail has a cap with a bearing in it to seal (Don't drop it).
I recall several cars of our vintage that the regulator sticks, the pressure gets real high after it runs a while causing the injectors to work funny.
Even if that is not it knowing the pressure while it stumbles will answer all your fuel delivery questions.

[brujo65]

Check your head temp sensor

[RedCoupe]

Check the spark plugs wires with an ohm meter, terminal to terminal. Of course. Likewise with the coil wire.

[198491132]

Thanks guys for the helpful responses. Just measured 4.9 ohms at 45 degrees on cyl head sensor. Within spec of Bentley manual.

[CCM911]

I am not believing that the car just went bad from sitting. Mine just sat from April until January, and after a few coughing fits, the engine ran just fine.

Before you do anything drastic, fit a new set of plugs and take it out for a 20 minute ride.

[brujo65]

How about the speed sensor and reference sensor

[Spumato]

CCM... Sitting is the worst thing you can do to a Porsche! These glorious machines were built to be driven, not be garage queens.

[Franks89-911]

FWIW - I inherited my Dad's 89 911 about 2 years ago. The service he did was spotty at best. From what I could reconstruct, he had replaced the spark plugs, dist cap and rotor only once in 26 years of ownership, and done a few oil changes. Wires were never replaced. When I got it and started driving it, it ran rough and stalled out on me a couple of times.

So I dived in on the simple things, myself: changed the oil and filter, changed spark plugs, spark plug wires, distributor cap and rotor. Got alternator rebuilt so that I had 14v going thru the car, not 10v from a dying & uncharged battery.

Point being, after doing those simple things, she runs like a dream now. Roars to life at every turn of the key - "drive me" she says. Ockam's Razor: sometimes the simplest explanation is the right one. Start with the simple things that make the engine go and see if that fixes your issues, before spending thousands replacing every "sensor" or relay - those may not actually be bad. At least test them yourself first. Lots of Porsche mech's out there only too willing to part you from your money because the car won't run and we're scared because it's German and say "I don't know why it won't go, just fix everything Hans, I don't care what it costs". I'm not afraid of doing work on the P-car like I used to be. (A $2500 mech bill cured me of that fear).

[198491132]

Good Day, thanks again for ideas and thoughts. Plug wires measured between 3k and 3.2k for cyl 1,2,3 and 6. Meaured 4.5k for cyl 4 and 5. Coil wire was 60 ohms.

Not liking the 4.5 readings.

Most plugs a bit black......new ones on order.

Flywheel sensors measure close to 4ohms, but it is a cool day here.

Dave

[scarceller]

Flywheel ref and speed sensor should measure 900-1100 ohms.

Spark cables on the RHS are longer, thus higher resistance is normal.

CHT sensor at 45F temp should be around 1000 to 1300 ohms (1.0 - 1.3 Kohm)

I agree with Rick that testing fuel pressure is in order. You don't need the exact fitting to put on the FP port. You can try adapting a hose from the gauge so that the hose just fits over the threads of the port tightly, then use a hose clamp to clamp the hose tight to the port.

With engine running at idle you should have 30-32PSI then while it's idling remove the vacuum line from the regulator and the pressure should increase to 36-38PSI
If indeed she's rich then it could be that the vacuum hose to the regulator does not have vacuum for some reason?

The other thought is maybe the carbon track in the air flow meter has failed? If this happens then the engine will be under fueled at those give air flow rates that the track is worn in. You can sweep test the AFM by pushing the barn door open while monitoring the 0-5vdc output signal. This test is done with engine OFF and key in 'RUN'

Finally, if you can borrow a DME for testing we would rule out DME issues. Or take your DME and test it in another working 84-89 car.