Car not running right its missing CLUELESS
10-31-2009, 03:58 PM
#1
Nordschleife Master
Thread Starter
Car not running right its missing CLUELESS
I'm about to part this car out im so sick of it. I just got done doing a huge amount of work to this car and now its running like crap. It was running great for a bout a day than just started missing and won't idle. Sounds like it has a dead cylinder. Here is what I have done so far.
1. Swapped both coils for good working ones.
2. Swapped MAF with known good one
3. Swapped Plug wires and coil wires with known good ones
4. Swapped Cap and Rotor with known good one
5. Checked all Vac Lines and all are good
6. Checked Compression on all cylinders and there all around 200psi =- 5psi
7. Spark Plugs are less than 6 months old so assumed these were good.
Any ideas?? I'm completely stumped!
1. Swapped both coils for good working ones.
2. Swapped MAF with known good one
3. Swapped Plug wires and coil wires with known good ones
4. Swapped Cap and Rotor with known good one
5. Checked all Vac Lines and all are good
6. Checked Compression on all cylinders and there all around 200psi =- 5psi
7. Spark Plugs are less than 6 months old so assumed these were good.
Any ideas?? I'm completely stumped!
10-31-2009, 04:03 PM
#2
Team Owner
recheck the ignition wires I would bet that you have one crossed then run the car in the dark and see if you can find any fireflies
10-31-2009, 04:09 PM
#3
Rennlist Member
Rennlist Site Sponsor
Determine if this is a miss on one cylinder only. If so, determine which cylinder is misfiring by checking exhaust manifold temps, checking spark plug appearance, etc. Stan's suggestion to check the firing order is excellent, and should be the first thing to do!
Once you know which cylinder to check, go back to basics, and see if you are missing:
- Fuel (faulty injector or connection to that injector, or vacuum leak affecting that cylinder).
- Fire (no spark on that plug, faulty plug, etc.)
The consistent and high compression should indicate that valve timing is not the issue, and ignition timing is not adjustable.
If it is not a single-cylinder misfire, start checking for vacuum leaks, faulty coil wires, etc.
Once you know which cylinder to check, go back to basics, and see if you are missing:
- Fuel (faulty injector or connection to that injector, or vacuum leak affecting that cylinder).
- Fire (no spark on that plug, faulty plug, etc.)
The consistent and high compression should indicate that valve timing is not the issue, and ignition timing is not adjustable.
If it is not a single-cylinder misfire, start checking for vacuum leaks, faulty coil wires, etc.
10-31-2009, 04:27 PM
#4
Nordschleife Master
Thread Starter
Believe me the ignition wires are correct. When you rev it up to say 3k and hold it there it smooths out but if you gun it from 3k it spits and sputters. I will try and get a you tube video up so you can see what im talking about, maybe that will help. At idle it acts like it has a big cam and rocks and shakes like crazy.
10-31-2009, 04:40 PM
#5
Team Owner
look for ignition wire leaks, esp around the coil wires, they like to short out on the chassis and you might try putting the original coils back in one at a time
10-31-2009, 05:22 PM
#6
Rennlist Member
Rennlist Site Sponsor
The engine will run smoothly on six cylinders at 3,000 RPM - with no load. That is not any indication that the plug wires are correct...
10-31-2009, 05:32 PM
#7
Nordschleife Master
Thread Starter
I know for a fact the plug wires are correct. Because the car was running great a few days ago than all of this happened. So I started switching stuff. It's running exactly like it did when it started failing a few days ago. All the good parts I pulled from my low miles 928 did nothing for this car. I have also tested the ignition parts from this car in my other 928 and it fired right up and idles smooth as silk. At this point im taking a break until tomorrow. I'm on the verge of doing something stupid...
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10-31-2009, 06:05 PM
#8
Team Owner
open the hood and wait till night then start it
10-31-2009, 11:57 PM
#10
Racer
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My 91 was running like that, crap at idle but ok at higher RPM, replaced coils, caps, rotors, checked for fire flies, no luck. Then one day I happened to disconnect the EZK, LH and O2 connectors from the computers, reconnected and problem went away for a bit. Used CRC electronic contact cleaner on all of the connectors. Reconnected and disconnect about a dozen times to have the contact wipe themselves. Problem has been gone for a month, including a 1000 miles round trip to Sharktoberfest.
On my 91 the rough idle would get worse until at some random point the engine would go into 4 cly mode. Your 87 won't do this.
Also, the whole time I had the problem the AFM meter was not hunting as usual, and indicating lean after warm-up. I think it was running open loop.
After the contact cleaning the AFM is back to working normal, idle is glass smooth, no more 4 cyl mode, life is good. Not sure which connector had the problem, it just runs right.
On my 91 the rough idle would get worse until at some random point the engine would go into 4 cly mode. Your 87 won't do this.
Also, the whole time I had the problem the AFM meter was not hunting as usual, and indicating lean after warm-up. I think it was running open loop.
After the contact cleaning the AFM is back to working normal, idle is glass smooth, no more 4 cyl mode, life is good. Not sure which connector had the problem, it just runs right.
11-01-2009, 12:11 AM
#11
Chronic Tool Dropper
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Check/replace the plugs. Simple. Cheap. Good chance to see if any are wet with gas, oil fouled, or washed white from coolant in the cylinder. My too sense.
11-01-2009, 08:19 AM
#13
Nordschleife Master
Thread Starter
I had the 02 sensor replaced when I did the torque tube. Also I pulled all the plugs when I checked compression. All of them were slighty wet. (plugs have less than 3k miles on them) I have some friends coming over today and were gonna dig into it more. I will disconnect the computers and try that.
Thanks
Thanks
11-01-2009, 08:43 AM
#15
Nordschleife Master
The car is just mad your lady didnt show it any skin!
And I would recommend confirming fuel pressure and a replacement fuel filter.
When a filter starts to get clogged it will stutter at the upper RPM. At 3000RPM with the car not moving, you will be having a much lower fuel demand than after you punch it.
And I would recommend confirming fuel pressure and a replacement fuel filter.
When a filter starts to get clogged it will stutter at the upper RPM. At 3000RPM with the car not moving, you will be having a much lower fuel demand than after you punch it.