Back in a Porsche but need a little help

[jslo]

Bought this car (86 944 NA) last fall and have been working on it over the spring to bring it back to life and eventually use it for 944-spec/cup. Finally got it road-worthy a few weeks ago. Had the confidence to try and open it up the other day and noticed a serious lack of power/bogging/misfire over about 5k rpm/WOT.

Then once you do let off the idle/throttle is very rough until it finally tries to even itself out or you gently give it gas and slowly let off.

Car has new wires, new alternator, 2 degree timing advance, chip. Does this with or without any combination of the above. I did read somewhere that it could be a bad alt, but I haven't had a chance yet to remove that from the equation as the clutch master & slave are rapidly failing and I don't want to test without and be stranded with no alternator OR clutch.

Here's the video of the behavior:
https://www.youtube.com/watch?v=BHEnB7ZWe3U

After filming the first vid, I noticed a puff of smoke about the 5k rpm spot as well, here's a video of that as well. It's not much:

https://youtu.be/0e46wZ7RqFg

At the end of the second video you can see me turn my hands up because the car returned to normal idle after sounding like a Harley at idle for about a minute.

I've replaced plugs, wires, new alternator, checked compression (155,160,162,152 dry). Mileage unknown.

Thanks in advance for any advice.

[jslo]

Sorry for the double post . . ..

[fiily]

Too rich, black smoke, unburnt fuel. Check to see how much soot you have at the taipipe, if there is a exorbitant amt. of black soot there and by the bumper, then too much fuel is being dumped into the engine @ higher rpms.

You might have a bad afm(air flow meter), that is where your airbox connects to the throttle body. Sounds like not enough air and too much fuel, then black smoke appears when your car is running too rich at higher rpm's and the afm cannot keep up, then stumbles to maintain idle.

You're close, I have a spare afm. A couple of minutes to swap it to see if it fixes it.

[Jfrahm]

This is often a blown FPR or damper diaphragm. Pull the vacuum lines to these and check for fuel leaking into the vacuum line.

[jslo]

Originally Posted by Jfrahm

This is often a blown FPR or damper diaphragm. Pull the vacuum lines to these and check for fuel leaking into the vacuum line.

I recently replaced those vac lines, but for fun I checked again. No leaks.

Originally Posted by fiily

Too rich, black smoke, unburnt fuel. Check to see how much soot you have at the taipipe, if there is a exorbitant amt. of black soot there and by the bumper, then too much fuel is being dumped into the engine @ higher rpms.

You might have a bad afm(air flow meter), that is where your airbox connects to the throttle body. Sounds like not enough air and too much fuel, then black smoke appears when your car is running too rich at higher rpm's and the afm cannot keep up, then stumbles to maintain idle.

You're close, I have a spare afm. A couple of minutes to swap it to see if it fixes it.

Not much soot, but I really just started driving it, so it's possible it hasn't had time to accumulate. I will run through AFM testing, but I may very well take you up on your offer to borrow one for 5-10 minutes and see if that helps. I have to return my buddy's welder and he's in Merrimack off of Amherst Rd. You may get a PM soon . . .

[fiily]

No problem, hopefully it get's a bit cooler out, working on anything outside in 95 deg. with 72deg. dew point weather is not a pleasant experience.

[Jfrahm]

Cap and rotor should be checked and the spark checked with a spark checker (for strength).

If you can get it to idle badly shut it down and see if any or all of the plugs smell like gas. One or more of the injectors might be sticky and hosing at higher duty cycle. If you plan to go racing you'll want them renewed as best you can anyway so it might as well be now.

-Joel.

[jslo]

Originally Posted by Jfrahm

Cap and rotor should be checked and the spark checked with a spark checker (for strength).

If you can get it to idle badly shut it down and see if any or all of the plugs smell like gas. One or more of the injectors might be sticky and hosing at higher duty cycle. If you plan to go racing you'll want them renewed as best you can anyway so it might as well be now.

-Joel.

I had the injectors out not that long ago. #1 seal was leaking so I replaced all the seals. I do notice just a hint of wetness around the base of #3. I mean barely a glimmer. The problem was occurring before and after I pulled injectors and replaced seals, but it could be that one (#3) still isn't sealed properly I suppose. For the price of another set of seals, it may be worth going through again. Thanks for the food for thought.

[Jfrahm]

Seals and pintle caps won't fix a bad, sticky, clogged injector. You may need to have them serviced or at least clean and backflush them yourself although testing them properly takes some rigging.

[thomasryan]

under hood fuel leaks can be disastrous. you may have a leak in the injector housing.

[jslo]

Originally Posted by Jfrahm

Seals and pintle caps won't fix a bad, sticky, clogged injector. You may need to have them serviced or at least clean and backflush them yourself although testing them properly takes some rigging.

I should have mentioned that I did indeed clean and backflush them when I had them out.

[fiily]

Jason, how does your cap, rotor, and plugs look?

[djnolan]

Injector bodies have been known to leak. Small slick spot will show.

[jslo]

Originally Posted by fiily

Jason, how does your cap, rotor, and plugs look?

no crazing, scorching, carbon or cracks that I can see. I did replace plugs the other day. Here's what the one's that came out looked like:

[Tom944]

I can't really tell from the picture if any are too black. I had one plug blacker than the others and it turned out that that injector was leaking. The injectors had recently been refurbished. If the plugs are different colors then the mixtures are different so likely an injector issue.

[jslo]

Originally Posted by Tom944

I can't really tell from the picture if any are too black. I had one plug blacker than the others and it turned out that that injector was leaking. The injectors had recently been refurbished. If the plugs are different colors then the mixtures are different so likely an injector issue.

Ya, picture probably isn't the best, but they aren't black, just a bad photographer. One is actually just a little cleaner than the others. Fiily and I took a look at it last night and tried another AFM, but that didn't do it. Going to try and swap out a loaner fuel pressure regulator and/or damper and see what that gets me. Fiily is a man of much knowledge (and spares) and showed me that I'm definitely rich at high rpms.

[jslo]

Going to test fuel pressure this weekend and try swapping loaner parts. I like Fiily's theory that the pressure damper or regulator is either bad or not correct for the car. Would not be surprised to figure out that someone replaced the 2.5 bar regulator with a 3 or 3.5 bar (bigger is better, right?!)

[fiily]

No problem with using spares to see if it fixes you issue, and I hope it does and then you'll know what to replace without spending a fortune or chasing your tail with throwing new parts at the car.

I turned into a hot mess under that hood dying from the heat, man it was hot! Let us know how it turns out, and if you need any other stuff on loan for testing, let me know via PM or Text.

[jslo]

Well I haven't tested the fuel pressure yet, because the wrong adapter was shipped. The correct one won't be here until some time this week. I did swap over the loaner fuel rail - after having to replace the starter - I went to start the car so I could pull the fuse and empty as much fuel out of the lines as possible and nothing. Just a tick. I just had the starter out like 2 days before to replace the clutch slave and of course it couldn't have failed on me then. Pulled it out again, tested it and sure enough it was really weak. Fortunately Autozone in Manchester had one in stock.

So after I replaced that, I swapped out the loaner rail, fpr, fpd, etc. Still having the same issue. Over 5k she's rich and stumbles. I pulled the loaner off and re-cleaned the injectors before re-installing my rail just to be sure.

I also see a balance shaft seal replacement in my near future. Good times. I guess it's to be expected with a car that sat for probably close to a year (maybe more) from the time the PO parked it and I finally got it back on the road.

[jslo]

Originally Posted by fiily

I turned into a hot mess under that hood dying from the heat, man it was hot!

Can't thank you enough for sweating it out and taking a look for me. I owe you one, probably two.