Rough running
#1
Three Wheelin'
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Rough running
Have an odd rough condition in my motor now.. Car starts and idles just fine, plenty of power, pulls as hard as it ever has, or so it seems. But every once in awhile, the engine gets really rough and power is way down. Usually happens when going from a closed throttle, IE from a stop sign or after coasting with my foot off the go pedal. Then it goes away and everything is good again. Feels kinda like a fuel starvation situation or bad ignition timing. ARM1 is happily showing it's normal output during all of this. Haven't dug too far into it yet, just a cursory look over for the obvious.
Would appreciate any thoughts before I go nuts tearing into her.
Would appreciate any thoughts before I go nuts tearing into her.
#4
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Still have a problem.
The good:
- Starts right away
- Idles smoothly
- Exhaust sounds nice and even
- Intake R&R last year, 99% sure no vac leaks.
- New fuel filter.
- Check over ignition, caps fine, rotors fine, not pulled plugs yet.
- Don't know fuel pressure at the rails yet.
- ARM-1 always shows normal operation. Nice sweep.
The bad:
- Pulling away from a light, moderate amount of gas, engine splutters for a few seconds, then clears (1st gear)
- 4th or 5th gear, 40mph, > 25% throttle, Engine splutters and I think it stays this way, back off, down shift and easy on the gas and it's ok.
- Engine Hot, Cold, day or night.. deosn't matter it always there.
- My daily driver....
As long as I am easy on the gas pedal, the engine is perfect, as soon as I put it under a load, it starts to hesitate. Almost like fuel starvation. she has 160K on the clock so I know I need a fresh on my MAF but I would like to narrow down my options to fix this problem before I go nuts doing the old parts swap routine.
The good:
- Starts right away
- Idles smoothly
- Exhaust sounds nice and even
- Intake R&R last year, 99% sure no vac leaks.
- New fuel filter.
- Check over ignition, caps fine, rotors fine, not pulled plugs yet.
- Don't know fuel pressure at the rails yet.
- ARM-1 always shows normal operation. Nice sweep.
The bad:
- Pulling away from a light, moderate amount of gas, engine splutters for a few seconds, then clears (1st gear)
- 4th or 5th gear, 40mph, > 25% throttle, Engine splutters and I think it stays this way, back off, down shift and easy on the gas and it's ok.
- Engine Hot, Cold, day or night.. deosn't matter it always there.
- My daily driver....
As long as I am easy on the gas pedal, the engine is perfect, as soon as I put it under a load, it starts to hesitate. Almost like fuel starvation. she has 160K on the clock so I know I need a fresh on my MAF but I would like to narrow down my options to fix this problem before I go nuts doing the old parts swap routine.
#5
Rennlist Member
I had a similar intermittant prob: cruize at 65, shift to 4th and try to accelerate, or w/o shifting just try to accel in 5th, slight or wide open, it would veerrry slowly accelerate, but essentially no power. I had recently checked the belt tension, so the passenger coil wire had been disconnected. Re-insert. No joy. It was the other coil wire with corrosion in the boot. More likely to be your MAF.
#6
Rennlist Member
Hi NIck,
At cruise the O2 loop will try to compensate for the MAF if it is aged (and it will be if it has 160k miles on)
But when you hit the throttle, it goes off loop, and you are dependant on the correct signal coming from the MAF. Ageing makes it run much too weak under these conditions.
Regards
At cruise the O2 loop will try to compensate for the MAF if it is aged (and it will be if it has 160k miles on)
But when you hit the throttle, it goes off loop, and you are dependant on the correct signal coming from the MAF. Ageing makes it run much too weak under these conditions.
Regards
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#8
Three Wheelin'
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Originally Posted by Dave Howerdel
Nick,
I have a spare MAF you could try out.
I have a spare MAF you could try out.
If you wouldn't mind I would really appreciate it!
Sent you an email..
#9
Rennlist Member
Originally Posted by NickT
Have an odd rough condition in my motor now.. Car starts and idles just fine, plenty of power, pulls as hard as it ever has, or so it seems. But every once in awhile, the engine gets really rough and power is way down. Usually happens when going from a closed throttle, IE from a stop sign or after coasting with my foot off the go pedal. Then it goes away and everything is good again. Feels kinda like a fuel starvation situation or bad ignition timing. ARM1 is happily showing it's normal output during all of this. Haven't dug too far into it yet, just a cursory look over for the obvious.
Would appreciate any thoughts before I go nuts tearing into her.
Would appreciate any thoughts before I go nuts tearing into her.
My car had similar symptoms for the past year. Local Porsche Dealer had the car for two weeks, charged me $600.00, said it was fine. Picked it up - NOT!
I had bought one new coil about a year ago while accumulating new parts to install when I swap in my stroker. I was going away on vacation two weeks ago & figured I'd buy another coil & put them in before I go & hope for the best. I GOT IT! Problem solved! No more sputter, miss, just smooth acceleration. Runs like it did when I bought it 16 years ago. Even chirps the tires when it shifts into 2nd. I do wholesale parts for a living so the coils cost me $45.00 each. If you can get them cheap it's worth a try - your symptoms sound just like mine. Good luck.
Hammer
#10
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Thanks so much to Dave for loaning me his spare MAF... Wish it fixed my problem but it didn't.
Did notice a bit of pinging though. Going to ohm out the coils next, see where they are...
Did notice a bit of pinging though. Going to ohm out the coils next, see where they are...