Bad Idle
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Bad Idle
I'm working on a friends 1989 RS with a 2.8 V6.
One day, she went out to it to start it, and it cranked fine but when it idled, it had a miss and a sluggish idle.
The weird thing about it is, above 1200rpms or so, its fine. It has plenty of power, etc.
First thing she had done with plugs and wires, and she claims it made it worse. So I went to her house and replaced the cap and rotor, she said it made it run better, but like the day this all first started happening. Well it had some pretty bad oil leaks coming from the valve covers. She also maintains this car well, it has 98,000 miles on it.
I fixed the exhaust leak on the manifold by replacing the gasket, however there is a small exhaust leak on the EXHAUST side of the EGR, there are NO vacuum leaks that I can find, I have replaced the TPS, IAC Valve and PCV.
When I had the intake manifolds off, there wasn't any gunk build up in the head or valley. So all the intake manifold gaskets have been replaced with valve cover gaskets.
The only thing that I can tell is off is the timing, it stays dead on around 15*, and the hood says it needs to be at 10*. However, I can not get my 9/16" distributor wrench to fit on there! It is a huge pain in the *** trying to get a small 15mm socket (thats what will fit on there) with a U-joint trying to losen it with the plenum on.
If its not the timing, another suggested to me it could be the CTS or a leaky injector. Any ideas?
EDIT - Just played with the timing, seems to me that sweet spot is 12* and replaced the fuel filter. It idles better now, but no where near how it should. Its also got a sluggish throttle response, but once it gets going, it has plenty of power. When I had the intake manifold off, I cleaned out the gunk the best I could and ran it through the dishwasher twice, including the throttle body. The plenum is squeaky clean...as I said, TPS and IAC are brand new as well.
One day, she went out to it to start it, and it cranked fine but when it idled, it had a miss and a sluggish idle.
The weird thing about it is, above 1200rpms or so, its fine. It has plenty of power, etc.First thing she had done with plugs and wires, and she claims it made it worse. So I went to her house and replaced the cap and rotor, she said it made it run better, but like the day this all first started happening. Well it had some pretty bad oil leaks coming from the valve covers. She also maintains this car well, it has 98,000 miles on it.
I fixed the exhaust leak on the manifold by replacing the gasket, however there is a small exhaust leak on the EXHAUST side of the EGR, there are NO vacuum leaks that I can find, I have replaced the TPS, IAC Valve and PCV.
When I had the intake manifolds off, there wasn't any gunk build up in the head or valley. So all the intake manifold gaskets have been replaced with valve cover gaskets.
The only thing that I can tell is off is the timing, it stays dead on around 15*, and the hood says it needs to be at 10*. However, I can not get my 9/16" distributor wrench to fit on there! It is a huge pain in the *** trying to get a small 15mm socket (thats what will fit on there) with a U-joint trying to losen it with the plenum on.
If its not the timing, another suggested to me it could be the CTS or a leaky injector. Any ideas?
EDIT - Just played with the timing, seems to me that sweet spot is 12* and replaced the fuel filter. It idles better now, but no where near how it should. Its also got a sluggish throttle response, but once it gets going, it has plenty of power. When I had the intake manifold off, I cleaned out the gunk the best I could and ran it through the dishwasher twice, including the throttle body. The plenum is squeaky clean...as I said, TPS and IAC are brand new as well.
Last edited by Fredless; May 8, 2005 at 11:15 AM.
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I would have the ignition module tested. They run on serveral circuts- Low rpm,Mid rpm, High Rpm ect... The low rpm side might be going bad.
Most auto parts stores will check it for free, Not sure if you have an O'rielys near you but they will check it.
Most auto parts stores will check it for free, Not sure if you have an O'rielys near you but they will check it.
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Joined: Apr 2002
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Sorry to bring this back up, but the car still is not right!
I bought a new set of wires, used di-electric grease on all the points on the cap and on the plugs themselves. I also replaced the ESC module. The car actually downshifts right again, goes all the way to 6500rpm-ish at WOT and has MUCH more power now. It idles better, but however its still at 90% now.
Upon pulling all the plugs and regapping them to .045, the number 1 cylinder spark plug had a very small amount of oil on it. I think that was run off from when the valve covers were leaking before I replaced them.
Just for ****s and giggles, I bought a new MAF, but returned it as that did not make the car run any better. I am realizing how much I love OBD II now as the car is not throwing any codes.
What I find perplexing is when I disconnect the MAF sensor, the car runs no differently, but the SES light does come on at that point. Plug the MAF back in, no SES light on the next start up. Yes I've also disconnected the battery to reset the computer. Doing that MAF test is what led me to replace the MAF. It seems to be in limp mode, but if it was, would it still WOT and have as much power as it does? I really wish I knew what a stock 2.8 did because I've never touched one before and I don't know how much power they're supposed to feel like they have.
Somehow its in limp mode I think, but I've replaced everything under the sun I can think EXCEPT for the injectors and the ignition coil itself. It sems like a spark problem to me, as the miss is intermittant now...it will smooth out sometimes, and then you get on it again, it starts the bad habit back again.
Do ignition coils just go half way bad? I thought it was all or nothing with them?
I bought a new set of wires, used di-electric grease on all the points on the cap and on the plugs themselves. I also replaced the ESC module. The car actually downshifts right again, goes all the way to 6500rpm-ish at WOT and has MUCH more power now. It idles better, but however its still at 90% now.
Upon pulling all the plugs and regapping them to .045, the number 1 cylinder spark plug had a very small amount of oil on it. I think that was run off from when the valve covers were leaking before I replaced them.
Just for ****s and giggles, I bought a new MAF, but returned it as that did not make the car run any better. I am realizing how much I love OBD II now as the car is not throwing any codes.
What I find perplexing is when I disconnect the MAF sensor, the car runs no differently, but the SES light does come on at that point. Plug the MAF back in, no SES light on the next start up. Yes I've also disconnected the battery to reset the computer. Doing that MAF test is what led me to replace the MAF. It seems to be in limp mode, but if it was, would it still WOT and have as much power as it does? I really wish I knew what a stock 2.8 did because I've never touched one before and I don't know how much power they're supposed to feel like they have.
Somehow its in limp mode I think, but I've replaced everything under the sun I can think EXCEPT for the injectors and the ignition coil itself. It sems like a spark problem to me, as the miss is intermittant now...it will smooth out sometimes, and then you get on it again, it starts the bad habit back again.
Do ignition coils just go half way bad? I thought it was all or nothing with them?
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