Loose MAF boot will leak like a bastage.

Interesting that the wires have been replaced already - wonder if someone was trying to fix the misfiring issues? Either way, unplugging all the connectors on the plug leads and checking for moisture/corrosion is a good idea. The leads are probably ok themselves given they've been replaced.

If you unplug the MAF, does it run the same, better or worse?

If the same or better, try cleaning the MAF hotwire - CRC make MAF Cleaner spray, or you can use something that won't leave a residue (e.g. CO Contact Cleaner) Don't use Carb cleaner.

Taking the dist caps off and checking the caps and rotors is worthwhile too.

Might be worth just buying some new spark plugs as they're cheap (like 2-3 bucks a piece cheap). Bosch WR7DC are OEM spec - single electrode copper. Correct gap is around 0.8 mm for S4 (exact figure is in the WSM).

If lead connections, rotors, caps and spark plugs all check out, then if you know someone with an S4 locally, try plugging your LH brain into another car and see if it's good.

As for the vac leaks, you probably need to do a full intake refresh - 928 specialists (928gt.com) have a handy page to order all the bits at once, or 928srus will be able to put together a package of parts.

You say the car doesn't have cats - does it have an O2 sensor fitted? There'll be a lead through the side of the tunnel into the passenger footwell if it is connected. (Some countries didn't get cats and O2 sensors until the '90s - my '89 S4 doesn't have 'em).

The other thing that could be causing issues is the LH brain - testing yours in a known-good car would be a good way to make sure its ok. Its an expensive option for replacement unless you know its bad.

You are doing what I would do, the injectors may not be flowing. Flow matched refurb is what you want. A diesel shop that does Bosch charge about $160 for 8 inj.

I bet you have one below 90% flow. Best one is maybe 92. Need all 8 @98 or above.

My red nology wires and coil work great with any plug, have plat 1 now on 944T. You have S4 which is more like 2 16v 944S2 engines in v8.

928 is sensitive to knock O2 sensor, new one is about $200 on that car.

Switching from the stock plug often causes problems.

I tend to agree on the injectors, flow matched set is best since ours are bank fired.

Knock sensor off I think a 944 works fine with a bit longer cable is all, ebay about $50.

Get new wires now. The location of the coils is poor, and leads to deterioration of the primary wires. Spend the money.

Also, look into what the guys are telling you about the flex plate and the driveshaft. Too much pressure on the thrust bearings can ruin your engine, if it is an automatic. Ruin, as in destroy the block and crank. I don't think you have this problem, but check it out and you can prevent it.

http://cgi.ebay.com/ebaymotors/Porsche-928-32V-Ignition-Wire-Set-Complete-Set-BERU_W0QQcmdZViewItemQQcategoryZ33692QQihZ008QQite mZ180336325508QQrdZ1QQsspagenameZWDVW

$300 what is cost me for S4 wires. Magnecor boots are too soft and tear off and get stuck, they are gummy boots. Beru and Nology have solid boots, won't tear up. Coils rarely fail. Consider Nology pairs with their coil, should have both.

I recommend Beru w/ your restoration headache.
Get a box of torque tubes, you will start snapping them when you get straight pipes, 111oct, chips.
Turn the shift firmness up on knob , under hood.
Get GTS cams, lighten crank, mill head.

Poor gas can foul the injectors and DME. $300 service charge.
Fuel press reg may be done, its 3bar stock Bosch

Pcar Tech Mechanic will recommend Beru ONLY , made in France :(

Several of the 928 vendors offer an economy set of wires without any frills, ie you reuse your old boots, and loom parts.

Ok I purchased all the tools and vac tester today.

Going to replace the spark plugs... check the tension on the flex plate and such tomorrow morning.

Question. What is the process one must follow to do the vac testing? Are there on line numbers that each section of the engine should hold? Presure... or such?

I know I am sounding like a dope here but I have never actually done this before. I have just replaced lines on my 924 and solved the issues. I have never had to vac test anything before. Guidelines?

Oh also I recall reading a post about where to shoot the WD40 to help lube the TPS? No I can not find it. I thought for sure it was in this thread. Could be the Captains not helping but which vac line was it again?

Thanks everyone. I think I am getting to tbe bottom of it. I have the idle down to 1000 to 1100 that is better than it was before. So eliminating some small leaks at least.

Best

Eric

I don't use WD40 to lubricate anything, it attracts dirt and doesn't last. TPS on my 83 are a pair of micro switches, best to just clean the contacts and leave them alone if they are properly adjusted.

No special value for the vacuum as long as it holds that value without leaking.

MityVac can be used to test actuators, see if they move or valve opens etc., but no leaks is where you start.

When you replace the hoses to the fuel injectors thats a great time to also pull the injectors and replace the orings.

Ok I am getting closer.

So this weekened I replaced the vac lines from the intake to the bake booster. Also replaced the plug that goes into the booster.

I replaced the spark plugs. The old ones were not gapped at all.

Also two or more of the plugs holes had quite a bit of oil down inside them. Hmmm.

Then release the tension on the spring plate... so you all can relax. There was really no tension on it anyway but I went through the motions. No I did not have time to do the check on the play. Only so much time in the day and I needed the car today.

Oh also sealed up the air pump valve. If you recall from another post I said it was bypassed? Anyway it was still fed by a small and large vac line. So I made sure all was well there.

I also found an interesting thing. The tube that runs down to the x-pipe just behind the O2 sensor... well it was just open up in the engine bay. I figured maybe that was screwing with the O2 sensor a bit... so I closed it up with a plug I created just for the occation.

So all this work... and.... well no more misfire. :) but only got the idle down from 1150 to 1050. A bit better but not all the way there yet.

Hey have any of you ever heard a kind of chirping noise from the fuse/relay area...?

Hi Eric,

Here's the info on where to spray the WD-40 for a sticking Idle Stablizer Valve (ISV) on LH-jet equipped cars:

http://forums.rennlist.com/rennforums/928-forum/376389-new-start-stall-issue-ideas.html

The reasoning behind using WD-40 is that you can spray it in there in a couple of minutes, versus removing the whole intake, fuel rails, injectors and throttle body to get at the ISV directly. It is however at best a temporary fix, although some have reported it working for 12 months or so.

Other places to check the vacuum lines include the 7-way connector under the airbox, on the driver's side under the fuel pressure damper - it often cracks and leaks, and you can also test each of the lines branching from it to make sure the other ends hold pressure (except the larger line off the end that is open to the throttle body).

Would you happen to have a link to a picture of the 7 way connector? :confused:


I was looking in that location this past weekend. I came across a 4 way but not a 7 way. Must have been close to it though.

Early cars just have a 4 way IIRC.

It could be right - my car had a 5-way (4 branches plus the main line to the throttle body), but my understanding was that only manual cars had those and the auto cars had the 7-way so there was a line to the transmission, although I haven't ever had that close a look under an auto's air box.

Here's a photo of the connector I meant, from my own intake job last year

http://forums.pelicanparts.com/uploa...1237996972.jpg

Yes that is it. Funny... I have no idea what I am doing but when I tried the VAC pump on that... I got no pressure. I pulled the line coming from the brake booster I think.

So one runs out back to the transmission?

Maybe that one got cooked when the tunnel area got real hot on the ride home.... hmmm. Have to check that out!

Thanks!