Carpokes Porsche Forum

I've searched for a thread specific to the '85 32V Throttle linkage, so I apologize if there is already a thread for this that I missed. My 1985 928S 32V turns over and fires but immediately stalls.

Here are the events leading up to this:

• The car started easily at any temperature and idled smoothly. However, the original linkage connecting the gas pedal, automatic transmission kick-down, and cruise control cables to the throttle body control rod was binding, causing a sticky throttle while driving.
  I sourced a N.O.S. assembly and installed it (see picture below). I adjusted the throttle body rod clockwise so that the socket would fit over the ball of the new linkage. The car started and idled without issue, and I could drive it.
  Not realizing the throttle body end of the rod uses reverse threads, adjusting it clockwise to make it fit on the new cable connectors unknowingly back it out of the ball socket connected to the throttle body. Luckily it came undone in my driveway.
  I removed the center manifold tube to access the throttle body plate and reconnect the ball socket to the rod and throttle body.
  With everything back together, the car turns over, fires, and immediately dies. Adjusting the rod only forces the engine to start at high revs, and even then, the car will not idle on its own without throttle input.

I need help with two things:

• What could be causing the non-idle problem? Before anyone asks, the car benefits from a fresh fuel filter, good gas, and a year-old tune-up (plugs, wires, rotors, and caps).
  Is there a thread detailing how to adjust this vintage of cable connections? The '87 S4 Bowden Cable thread is a completely different design and does not apply.

Thank you in advance for any help you can provide.

P.S. If you're not familiar with my car, I post all of my videos on the work I'm doing on my car, "Project Risky Business," on my YouTube channel. Here's the link to the Playlist: https://www.youtube.com/playlist?lis...TPj1MpAtylOVly

Thanks!

Rudy

Welcome to Carpokes! While waiting for 928 experts to offer better-informed help (paging @dr bob et al), I have a question. If you moderate the throttle carefully, will the engine run at idle speeds, or does it simply die no matter what you do with the throttle below a certain rpm? If it simply will not run at lower rpms, I'd wonder about the mixture and vacuum leaks -- is there any chance that coupler tube isn't seated and sealing? If you can control the throttle to have it run at idle speeds, I wonder if the idle stop screw is out of adjustment? (Seems unlikely since it was ok before, but perhaps the linkage was keeping it open rather than the stop screw?)

You are probably searching for an air leak, or for damage at the electrical connector at the MAF.

The throttle body connects to the 'belly' of the intake with a boot and clamps. Easy to get the boot folded or not fully engaged. False air entering there below the MAF will present the symptom you described.

The original wires at the MAF connector are pretty crispy by now, and prone to damage during MAF removal for the work at the throttle body below it. Carefully pull the cover off the back of the connector, and inspect for insulation damage. I've seen some hack repairs using liquid goop "insulation", and don't recommend that. The connectors are first-gen Amphenol or "amp" "junior timer" connectors, and you can get replacement shells, pins and inserts for them. Shop carefully, as the later-style pins don't work in the early connector bodies. If there's a question, get the late style housing as a kit with matching pins and a new boot.

More: If the hoses under the intake are original or old, they are a risk of splitting and allowing false unmetered air into the intake. The crankcase vent system has oil-soaked and cooked hoses that connect at the cam covers and the oil filler neck to fittings on the intake section below the throttle. Air that leaks in offers a lean mixture that won't keep a cold engine running.

The idle speed is managed by an electric idle air control valve that lives under the intake. The signal comes from the LH controller by similar crispy wires. The air for the valve comes from a fitting on the boot between MAF and throttle, and feeds to another fitting in the intake below the throttle. The hoses there are subject to rotting and failure from oil and heat.

The idle air control valve itself wears and gets tired/fouled with age. The common failure mode is sticking and poor idle speed management. Some folks claim that running WD40 through them is enough to make them work again by dissolving the oil crud inside (from the crankcase vent system fumes?). My later car has a slightly different idle control valve, but I decided to replace it when I had the intake off for an everything refresh and refinish project at just shy of 100k. I didn't relish the idea of doing all that work again for the piece I didn't replace. So do it like you mean it once you are in there.

A local high desert PCA member here with your car and most of your symptom found the idle air control valve hoses split. We first tested his MAF on my car and it worked fine, so he went back in to find the actual problem. Know that the MAF units doe get tired with start/stop cycling, and can be rebuilt and recalibrated for a fraction of new replacement costs. Rich Andrade at Elektronic Repair in Phoenix is a long-time 928 owner and enthusiast, and offers MAF, LH and LHA services plus S4+ fan controller service to keep our car driving well. Anyway, the MAF is the same on '85-'95 US cars, so easy enough to just swap yours onto another car if there's a doubt about it working. Rich will test yours for functionality and give that evaluation if you don't have a test car available local to you.

I've made a couple plumbing fittings and adapters to support slightly pressurizing the intake to help identify leaks. I have both compressed-air and shop-vac versions that cost under $20 to make way back when. MAF comes off, the PE drain pipe adapter goes on. Connect some air, rotate the engine to -45º so no cylinders have all their valves open at the same time. Air to one or maybe two PSI or connect from the shop vac discharge, and listen. A smoke machine is also an option if you have access -- leaks are pretty obvious. Hint: A "vintage" Maxwell House coffee-can used a plastic cap that fits perfectly over the MAF if you decide to start smoking. To keep the smoke from leaking out there.

Let us know what you find!

Here's more than anyone ever wanted to know about those connectors.

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