3.2 bogs down doesn't have full power

400orbust · 400orbust's Garage

So I've read through several threads about this and most don't seem to apply to my situation. The quick rundown: 1988 backdated 3.2. The car is new to me and I'm a new Porsche owner. Car ran great when I purchased it, drove it home 350 miles with no issues. I changed the oil cooler flexible lines, did a valve adjustment, changed the oil, filter, spark plugs and fuel filter, air filter, DME replacement (focus9 upgrade). The car has SSI exhaust and I found the O2 sensor unplugged when I was poking around so I plugged it back in. Shortly after doing the above maintenance the car seems to bog down or not have full power at times. The idle seems rougher to me too. While driving along at a constant speed the car will suddenly increase increase speed and run much better. To me it feels like a fuel supply or spark problem but, again, I'm a new owner.
Thoughts? Thx!

proporsche · proporsche's Garage

disconnect the oxy sensor

Ivan

cabmandone · cabmandone's Garage

Quote:

Originally Posted by 400orbust

So I've read through several threads about this and most don't seem to apply to my situation. The quick rundown: 1988 backdated 3.2. The car is new to me and I'm a new Porsche owner. Car ran great when I purchased it, drove it home 350 miles with no issues. I changed the oil cooler flexible lines, did a valve adjustment, changed the oil, filter, spark plugs and fuel filter, air filter, DME replacement (focus9 upgrade). The car has SSI exhaust and I found the O2 sensor unplugged when I was poking around so I plugged it back in. Shortly after doing the above maintenance the car seems to bog down or not have full power at times. The idle seems rougher to me too. While driving along at a constant speed the car will suddenly increase increase speed and run much better. To me it feels like a fuel supply or spark problem but, again, I'm a new owner.
Thoughts? Thx!

350 mile trip and no issues. You service and issues develop. You mention you replaced the DME, I'm assuming you mean the DME relay to focus9 solid state relay and not the DME itself? Anything that you changed (short of plugs and oil obviously) I'd back out and go back to what was in the car when it was running fine. As Ivan said, unplug the o2 sensor. If the DME was chipped it might not need the o2 sensor. Also check electrical connections. You might have bumped something loose while changing plugs. I bumped my cylinder head temp sensor connection loose while doing some work in the engine bay once. Not saying that's the issue but worth looking to make sure anything you might have bumped while changing plugs is still tight.

kach22i · kach22i's Garage

Quote:

Originally Posted by 400orbust

DME replacement (focus9 upgrade).

I've not seen this before.

Pelican thread on it:

Solid state DME Relay conversion ?
Solid state DME Relay conversion ?

Solid-State DME Relay 84-89 911
https://rennlist.com/forums/911-forum/947925-solid-state-dme-relay-84-89-911-a.html

Just tossing this out there, mismatched rotor as in using a resistor type when you need an non-resistor type because of aftermarket upgrade (MSD) is a common mistake.

Also not replacing the distributor cap and be a mistake, hairline cracks can form out of nowhere.

I don't know squat about this relay, but going back to what was in the car before sounds like a solid approach.

Wrong spark plugs, wrong gap, and or pulling on ignition wires and causing damage to them can happen even with the best of intentions and being careful.

I once chased a problem for a week on my S10 pickup truck, air intake hose slippage after air cleaner replacement, it can be the simple things.

proporsche · proporsche's Garage

if you have never adjusted your C/O level maybe you should go and have it checked...

Ivan

400orbust · 400orbust's Garage

Thanks all for the replies. Yes, I meant the DME relay...my original one died so I "upgraded" to the FT9 solid state one. I'm going to hope that is not the problem because I don't have another to swap in there. Good thought on the dizzy cap, I will get one of those and swap that our as well as the plug wires. Before doing those I'll unplug the O2 sensor. Also, I unhooked the battery last night as I read somewhere that might reset/recalibrate the computer. I'll report back once I go through these fixes. Ivan, what do you mean by the C/O level...carbon monoxide out the exhaust? Thx.

proporsche · proporsche's Garage

yes you fuel air mix ratio..C/O level..it could be rich ...

Ivan

400orbust · 400orbust's Garage

Alright! Just took the car for a 1/2 hour spin and it was fine! It was either disconnecting the battery for a computer reset or unplugging the O2 sensor. I'm going to guess the O2 sensor was the problem. So now, apparently the sensor is not needed? Any negative effects to just leave it unplugged? I don't have to do emissions testing or anything where I live.

400orbust · 400orbust's Garage

Also, how do I tell if the DME has been "chipped" and the O2 sensor is not needed? The previous owner didn't seem to know much about the car (based on a lot of "I don't know" when I bought it from him). If I had known more before I bought it I would've had an inspection done but the car looks awesome and, now, runs great and pulls hard.

cabmandone · cabmandone's Garage

Quote:

Originally Posted by 400orbust

Thanks all for the replies. Yes, I meant the DME relay...my original one died so I "upgraded" to the FT9 solid state one. I'm going to hope that is not the problem because I don't have another to swap in there. Good thought on the dizzy cap, I will get one of those and swap that our as well as the plug wires. Before doing those I'll unplug the O2 sensor. Also, I unhooked the battery last night as I read somewhere that might reset/recalibrate the computer. I'll report back once I go through these fixes. Ivan, what do you mean by the C/O level...carbon monoxide out the exhaust? Thx.

DME relay isn't the problem. Unplug your o2 sensor.

On a 3.2 it is more commonly referred to as the base idle mixture. But if it ran fine for a 350 mile trip, the base idle mixture didn't suddenly change.

cabmandone · cabmandone's Garage

Quote:

Originally Posted by 400orbust

Also, how do I tell if the DME has been "chipped" and the O2 sensor is not needed? The previous owner didn't seem to know much about the car (based on a lot of "I don't know" when I bought it from him). If I had known more before I bought it I would've had an inspection done but the car looks awesome and, now, runs great and pulls hard.

The PO would know if it had a chip in it. They would have sent it in or they would have opened the DME themselves.

Quote:

Originally Posted by 400orbust

Alright! Just took the car for a 1/2 hour spin and it was fine! It was either disconnecting the battery for a computer reset or unplugging the O2 sensor. I'm going to guess the O2 sensor was the problem. So now, apparently the sensor is not needed? Any negative effects to just leave it unplugged? I don't have to do emissions testing or anything where I live.

I was told not to run mine with the o2 sensor plugged in by the guy that did the tune for my car. That and the jumper under the seat needed to be unplugged.

mo-mon · mo-mon's Garage

I believe the ROW carrera did NOT have a O2 sensor. PO put it there.

400orbust · 400orbust's Garage

Interesting...the harness certainly looks original but I guess the ROW could've had the same harness and he just added the plug.

proporsche · proporsche's Garage

it all depends where is the car from ROW..mine is Euro model and it came with the catalyst and the oxy sensor.i do not use it at all i bypassed the circuit on my computer with a switch and remove the cat....if i go to France for smog test i put it on .....if you do not need it for your place where you live do not bother connecting it;-)
In France the ROW 911 have the cat and oxy sensor.....

Ivan