Rough idle and vibrations
01-06-2008, 04:24 AM
#1
Drifting
Thread Starter
Rough idle and vibrations
I"ve had weird idle problems for a long time now. Before it used to idle fine at start up and then when it warmed up the idle would be too high or when I reved teh engine the idle would not come down to whre it was suppose to be.
other things I noticed was that the car would idle too low when it rained and not idle high like it did in the dry and hot.
now I got a different problem. Now all of a sudden the past week or so the car is idlineg low, sometimes I give it a tap of gas at the pedal and it revs up and the idle increases.
now I have to constantly do this at the stop lights, give it a bit of gas to get the idle up or it idles really rough with the whole car shaking.
at 1000 rpm it idles decently but still a bit of vibration, above 1000 and througout the rpms its smooth and no vibration.
I replaced both of my motor mounts 5000 kms ago with Mehle brand motor mounts from my porsche dealer, only ones they carried and they said that they have installed it on lots of cars with no problems. but hetn I looked at pelican and the Mehle are the aftermarket ones for 69 bucks, the dealer sold them to me for 190 each...... list price 215 so I thought they are decent. according to pelican CFW-Freudenberg is the OEM mount but too late now.
my belts were also replaced and I don't think my balance belt has skipped although it is very loose, it was retentioned a few months ago after the 2500 break in so I think it is fine as the porsche shop that works on a lot of 944s did the tensioning.
now about the idle falling too low, sometimes it goes to like 600-700 rpm and the engine shakes violently so I have to give it gas to raise it up and sometimes the idle stays up other times I have to hold the pedal to keep the idle up at like 1000 rpm
Some things I'm thinking of replacing:
1.) TPS
2.) Idle control Valve
3) DME temp sensor
4) oxygen sensor.
5) intake boot, vacuum hoses.
6.) spark plug wires.
but what is the most likely cause of this?
also where is the engine temp sensor and idle control valve located, I couldn't see them and how do you get to it.
I can see where the TPS is.
also is it okay to get the universal oxygen sensors and cutting the wires ? will it effect the performance?
I"m not really sure if I should start replacing all these parks as they are not really cheap and it might not fix the problem.
other things I noticed was that the car would idle too low when it rained and not idle high like it did in the dry and hot.
now I got a different problem. Now all of a sudden the past week or so the car is idlineg low, sometimes I give it a tap of gas at the pedal and it revs up and the idle increases.
now I have to constantly do this at the stop lights, give it a bit of gas to get the idle up or it idles really rough with the whole car shaking.
at 1000 rpm it idles decently but still a bit of vibration, above 1000 and througout the rpms its smooth and no vibration.
I replaced both of my motor mounts 5000 kms ago with Mehle brand motor mounts from my porsche dealer, only ones they carried and they said that they have installed it on lots of cars with no problems. but hetn I looked at pelican and the Mehle are the aftermarket ones for 69 bucks, the dealer sold them to me for 190 each...... list price 215 so I thought they are decent. according to pelican CFW-Freudenberg is the OEM mount but too late now.
my belts were also replaced and I don't think my balance belt has skipped although it is very loose, it was retentioned a few months ago after the 2500 break in so I think it is fine as the porsche shop that works on a lot of 944s did the tensioning.
now about the idle falling too low, sometimes it goes to like 600-700 rpm and the engine shakes violently so I have to give it gas to raise it up and sometimes the idle stays up other times I have to hold the pedal to keep the idle up at like 1000 rpm
Some things I'm thinking of replacing:
1.) TPS
2.) Idle control Valve
3) DME temp sensor
4) oxygen sensor.
5) intake boot, vacuum hoses.
6.) spark plug wires.
but what is the most likely cause of this?
also where is the engine temp sensor and idle control valve located, I couldn't see them and how do you get to it.
I can see where the TPS is.
also is it okay to get the universal oxygen sensors and cutting the wires ? will it effect the performance?
I"m not really sure if I should start replacing all these parks as they are not really cheap and it might not fix the problem.
01-06-2008, 07:59 AM
#2
Racer
Join Date: Apr 2005
Location: Tallinn, Estonia
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01-06-2008, 12:15 PM
#3
Addict
Rennlist Member
Rennlist Member
Hey;
I would start by doing the following;
- I would clean and lightly grease the connections at the Head Temp Sender and the AFM. The HTS is on the lower part of the head near the deck surface, below the intake, behind the upper hose outlet, in the area below spark plug #1. It has a 2-wire modular Bosch connector. The gauge sender is close by, but it much smaller and has a simple female spade, slip-on end.
- I would replace the plug wires. Low idle in damp conditions is a classic sign of failing wires. Wouldn't hurt to check the cap & rotor either. Plugs too. If you decide to replace the C&R, make sure to ask for the REAL Bosch parts. They are BROWN, NOT BLACK. There have been crazy problems with the "aftermarket" black Bosch rotors.
- You might want to check the TPS for adjustment. This will give you a chance to clean the throttle body too. They can get really crudded up, especially if your engine is getting a little tired and pushing oil into the intake tract. You'll be amazed how much smoother they work when tended to.
- Also, the TPS can get filled with oil (mostly on Turbos). I always clean them out with carb cleaner and compressed air.
- Check all the vacuum lines and connections. This includes the crankcase vent system. All the rubber hoses and fittings have been getting fried for years, and they are often brittle and cracked. You'll have to remove the intake to do this properly. Gives you the opportunity to clean everything and make it look nicer too!
This stuff gets to be cumulative. Suddenly you notice the car running like ****, but it's been going off for a long time. The TPS, HTS, C&R, wires, plugs... are not that expensive. Why not treat the old bucket to some new goodies?
I would start by doing the following;
- I would clean and lightly grease the connections at the Head Temp Sender and the AFM. The HTS is on the lower part of the head near the deck surface, below the intake, behind the upper hose outlet, in the area below spark plug #1. It has a 2-wire modular Bosch connector. The gauge sender is close by, but it much smaller and has a simple female spade, slip-on end.
- I would replace the plug wires. Low idle in damp conditions is a classic sign of failing wires. Wouldn't hurt to check the cap & rotor either. Plugs too. If you decide to replace the C&R, make sure to ask for the REAL Bosch parts. They are BROWN, NOT BLACK. There have been crazy problems with the "aftermarket" black Bosch rotors.
- You might want to check the TPS for adjustment. This will give you a chance to clean the throttle body too. They can get really crudded up, especially if your engine is getting a little tired and pushing oil into the intake tract. You'll be amazed how much smoother they work when tended to.
- Also, the TPS can get filled with oil (mostly on Turbos). I always clean them out with carb cleaner and compressed air.
- Check all the vacuum lines and connections. This includes the crankcase vent system. All the rubber hoses and fittings have been getting fried for years, and they are often brittle and cracked. You'll have to remove the intake to do this properly. Gives you the opportunity to clean everything and make it look nicer too!
This stuff gets to be cumulative. Suddenly you notice the car running like ****, but it's been going off for a long time. The TPS, HTS, C&R, wires, plugs... are not that expensive. Why not treat the old bucket to some new goodies?
