Chris White

A couple of things to think about –
The original post mentioned #2 misfiring and now its #3 & 4 – sounds like its moving…
You said you worked on the engine over winter – that means you had to move the wiring harness around a lot.
If you are running the stock injector drivers 2 & 3 and 1 & 4 are tied to the same drivers – but you are experiencing misfires not in that pairing – so the injector drivers in the DME are still OK .

Sounds like we have ruled out a mechanical problem internal to the engine as well as the DME….that pretty much leaves wiring harness or ignition. Since the problem has moved from cylinder to cylinder we can rule out plugs and plug wires. The repeatability of the #2 misfire rules out the coil….so we are back to wiring….

The non technical thing to do is to shake the harness (try many different places but start by the injectors) and see if the problem changes.

newkie

Additional information. Plugs look about the same. Cylinders #3 and #4 are wet and smell alcohol. This makes me believe it's the ignitionsystem... I will check the injector harness though.

mikeyoman

1280cc injectors ! Is that for e85 ?

newkie

Yes... E85 requires 30-40% higher flowrate.

Amounts to (1280 / 1,35) = 948cc on regular 98 octane gasoline...

With 80% duty cycle around 760cc

newkie

So after alot of work this evening it turns out my not so old (20 miles) ignition wires are worthless. Car runs fine with the old cables...

newkie

Turns out the car only ran fine with the old cables if the engine is warm. So i finaly went to the pump and got 20 liters of fresh e85 and bought 100 miles old Lindsey 8 mm cables at a discount.

Now it runs alot better. Don't mind the belt noise since i allreday corected it.

http://www.youtube.com/watch?v=bg7jiJLg6UA

Thanks for all the help guys...

reno808

nice

newkie

Well..

Sadly im not out of the woods yet. The car ran great that night (on idle). I have since taken it out on the road. The car runs rough and is really weak down low. I have some popcorn action going on aswell. Boost is intermitttent at best. Didn't dare try it more then once and only for a few seconds.

Finaly got a hold of a compressiotester.

1: 10.5 bar (Plug is gray and dry)
2: 9.9 bar (Plug is slightly darker and damp)
3: 10.9 bar (Plug is gray and dry)
4: 10.9 bar (Plug is gray and dry)

Just installed my Wideband O2. Car seems to run fine about 30-60 seconds after start. Looking at the AFR it shows around 10 (e85 is supposed to run around 9.7 AFR). Then it goes bananas, the car starts idling rough and AFR shoots up to almost 20. As the enginge gets warmer it settles at around 16-17.

Pressure test done and i didn't find anything. Hooked up after the turbo so i guess a leak in before could be possible although unlikely.

I took the FPR out and found a metalshaving covering the hole for the hose. No change though. I guess fuelpressure is good place to continue.

newkie

Well.. To recap and add information.

I did find a large vacume leak and fixed that. It did not fix my problem. On idle one of the cylinders still wont fire propperly.

Car is stronger under load now then before i fixed the leak. But, it still hesitates and stumbles alot under 3000 rpm and it still feels weaker the a functioning car. AFR is still high, around 14-15 (should be 10).

Under higher load, AFR is spot on, all the cylinders are firing and the car pulls hard under boost. Boost lands around 0.7 bar overpressure. The wg-spring should hold 1 bar... strange.

I now have no air leaks what so ever between the MAF-sensor and the vavles. It holds pressure during pressure test. Fuel pressure is around 2,6 bar with runing engine.

Finaly got a hold of a compression guage.

1: 10.5 bar (Plug is gray and dry)
2: 9.9 bar (Plug is dark and damp)
3: 10.9 bar (Plug is gray and dry)
4: 10.9 bar (Plug is gray and dry)

If i pull the injector cable from cylinder #2 the car runs less bad... ?! Moving cable 1 to injector 2 does nothing. 3 to 2 does nothing.

Moving injectors or cables around does nothing.

Pulling the O2 sensor makes the car run even more lean. It is probably not as lean as it says, guess one cylinder not doing anything messes with the value.

Plugs are brand new NGK BPR8ES, 0,5 mm gap. Cables are lindsey racing 8 mm cables. Distributor and rotor are brand new. Coil gets 12 volts. No startingproblems.

It seems what ever i try, it's in acceptable condition..

Im out of things to try here.. Any ideas?

Ronin-951

Theres been a fair amount of discussion about spark plugs and wires on the forum, so do a search and compare your problem to theirs. IMO, bad wire and maybe one bad plug. Porsche used a resistor in the plug boot so all wires have equal resistance, others depend on resistive wire so length becomes an issue. It was also noted that aftermarket assembly of the wire sets left room for improvement. In your case it sounds like a bad connection at one or both ends of #2. Once a plug has fouled, their never quite as good as new no matter how well cleaned so throw a new one in. Also, pop the cap and look at the posts, is #2 showing an arc? I have seen caps not centered or loose that cause a misfire. Another cool test for the ignition system is to spray a fine mist of water on the spark plug wires with the engine running in a dark garage or at night. Any voltage leaks WILL be apparant.

newkie

Doing new plugs today. One step warmer and bigger gap, have ,5 mm (,019 inch) now...

fast951

It takes 30-60 seconds for the O2 sensor to gets hot and for the ECU to start operating in closed loop. Does anyone see anything wrong with this picture?

fast951

Since you are using 1200+cc injectors, at low RPM the injectors duty cycle gets so low that the injectors become uncontrollable. All injectors have a minimum duty cycle below which they become uncontrollable.
We solved this issue by changing the software to operate in semi-batch mode when necessary.

Have you seen anyone else with the same configuration as you are running (injectors, E85, chip) not having similar issues?

newkie

Pulling the O2-sensor and runing in open loop, makes no difference though

I can look around.

If the car would be driveable i wouldn't mind a rough idle but nothing but stumbling and missfires under 3000 rpm (under load)?! I could change to gas and run smaller injectors to test it out.

But i doubt this is the problem. I ran the same setup last year and the problem, although pressent then, was not nearly as bad as now. And it's always the same cylinder doing the missfiring. Know any good tests for the injector harness?

fast951

Apparently you have multiple issues. The comments I made in earlier posts affect Idle and PT light load or the transition between light/heavy load.

The missfire on a single cylinder can be many things: injector malfunction, cap/rotor/plug wire/plug or a bad cylinder.