Reds4Indiana

Hi Guys. New to the forum although I have had several 928s over the years. Anyway, hope someone can point me to some insight and help here.

My car is a 89 928S4.

I have changed timing belts in several 928's as we as my f355 ferrari, so I am a decent backyard mechanic, with I think good common sense... Although this one stumps me.

The belt change went well, no surprises, changed water pump, all pulleys, tensioner, etc. Found the hall sensor plug cracked and damaged and replaced with a new one.

New cap / rotors
New beru wires
new plugs

After got it all together, when you turn the engine over it starts and dies a couple times, (expected, I had the fuel line off the front), and when I gave it a little throttle while turning it over it started. Runs rough. Takes some coaxing to get it to rev up, but it will and smoothly in higher rpms. If you goose it quickly it falls on its face ands many times will die.

I have plugged the noid light into each injector and confirmed its not in limp home mode. Also have put a timing light on each plug and confirmed each plug firing.

Confirmed twice the timing marks with light and visual that cam belt is correct position.

Confirmed 15 times the plug wires in correct order. The order determined by the cam cover on the respective side.

I am told the rotors cannot be in the wrong position, but have not tried to move them around to make sure. (Feels electrical to me)

Again stating the plug wires are correct... i will look again today to make sure elves didnt switch them on me in the middle of the night, known to happen in indiana... goes with our weather.

I even changed plugs to make sure I got good ones... ok ok who has really bought new bad platinum plugs?? desparation.

Yes, it ran great before, and only sat for about 3 days during this process.

One of my suspects, but cannot confirm anything, so this is my question. The 14 pin connector on the pass side has some corroded wires. We of course moved the connector out of the way for the belt change, so am wondering if there is anything in that connector that would alter fuel management or ?? I know it has starter wires, I think A/C, etc.. but didnt know what else was in that connector. I just wonder if bending a twisting it to get it out of the way it is my culprit. Everything else went so easy that I just cannot think of anything i missed. Seems like I have missed something major, but cant finger it at all...

Also, i have started it with and without MAF, and it make zero difference .... ?? Maybe the 14 pin plug supplies power or linkage to maf? I dont know... drawing blanks guys... help??

Reds4Indiana

I also changed valve cover gaskets, and painted the valve covers during this process. Maybe the car doesnt like its new ferrari red valve covers??? I wanted to add that, but nothing really moved to my knowledge during this process. Just trying to think of anything else that could have been missed.

Also the battery was off during this whole process, wanted to add that as well.

Mrmerlin

Also, i have started it with and without MAF, and it make zero difference .... ??

What does this mean??^^^^

I would say its possible either the coil wires are dirty and or shorting , are both of the coil grounds installed? one to each coil mount screw then to each head?
You do know the firing order starts with 1 to 4 on the passenger side.then 5- 8 on driverside
Please post a picture of the crank damper at TDC could you have it flipped around? you should be able to read the #s while facing the engine.
The firing order sounds like the most likely culprit, but since it was running fine before you started then it must be something you touched.
I would also reverify the timing marks.
NOTE the rotors can only be put on one way so if all 3 screws are in then they are on correctly they both point to about 3 o clock when the engine is at TDC while facing the engine.

Use WR7DC Bosch supers for the plugs Azone has em about 1.99 use part # 7900 to find them

atb

I would guess the LH took a bad reset when you reinstalled the battery. Disconnect for30 min , rehook it, and if its running better take it for a drive.

Bill Ball

That's a big clue. Most likely a short in the MAF plug wires under the aged rubber-turned-to-plastic boot.

Unplugging the MAF puts you in limp home mode (LH fires the injectors at only a couple of RPM-dependent fixed pulse widths). If you see no difference when you unplug the MAF or plug it back into the harness, then the MAF is not working. It could be a bad MAF, but the harness plug is the first suspect. Usually this happens after a intake manifold refresh as there is a lot of harness manipulation. Not sure why it happened now.

Reds4Indiana

the dampener is correct. verified that rotors point towards 3 oclock when at TDC. The MAF unplugged versus pluggged in makes zero difference in the running. The plug is in good condition. The intake nor any wires around it were really moved or touched. I agree its something I touched, but just cant find it... will keep looking. The drivers side coil ground on the clamp was missed but has been bolted on now. Same results.

does the 14 pin connector have any bearing on this situation? Lots of corrossion due to probably missing cap / cover. Maybe i need a harness etc there...

I have not removed battery for a reset, thats next, but have the connector apart at the moment.

Other thoughts?

Reds4Indiana

ok, battery had been off all night, (unhooked completely)

Same exact results.

okbarnett

I think you painted yourself into a corner. You did so many things now it could be anything in the world that causes a problem. You have to go over and over it.
First idea, wrong notch for the belt on one of the timing gears, second, you blew the fuel module some way

Reds4Indiana

here are pictures of the timing marks. they are dead on i believe and the rotors are not exactly at 3 oclock. the left one appears to be, the right one is more at 2. how can this be if the timing marks are exact?

Reds4Indiana

Did so many things? Simple timing belt and water pump change. valve covers do not require removal of any wiring, etc..

Reds4Indiana

Do the rotors have any adjustment? I have not read much into the cam gears and what aligns the rotors. It would appear that the oval shaped port that is in the timing gears would allow for some adjustment in some fashion, though maybe not... drawing straws here. one lines up with 3 other is slightly more around 2. The little not or cut out on the BACk side of the cam gear exactly lines up with the cut out as it should. Photos didnt make it that clear...

Reds4Indiana

So i found on another thread, the rotors have marks on the timing cover to align with, aside from only fitting one way. The left rotor is at 3 oclock, and the right one is slightsly higher, maybe call it two oclock. the timing cover indicates this is correct, so this should eliminate timing issues. Now I am back to the other side of things... why wont it run... arrrggghhh

Hilton

Change out the new platinum plugs for Bosch copper ones (WR7DC+).

Seriously - a search here will bring up a fair few posts where the issue is the lower conductivity of platinum plugs giving a worse spark, leading to rough running.

Stromius

Reds - The MAF boot may look good but the wires under it can be dried out and touching. I replaced mine with a kit (availalbe from 928srus.com or other sponsors) after I opened mine up. How is the TempII boot/plug?

Your cams look to line up good. Have you adjusted them for timing? Liftbars.com has a nifty tool that makes this check/adjustment easy.

dr bob

Start with the easy stuff--

VERIFY that both coil wires are firmly seated in both the coils and the rotors. Then check the LED on the ignition safety relay, located on the LH/EZK bracket on the right side of the passenge's footwell. Carpet cover there comes off, relay is on the left face of the bracket. Ignition failure on one coil/distributor shuts down the fuel supply to the affected cylinders. There's a telltale LED that lets you know that the protection is active. Red for one distributor, green for the other.