Rough Idle

97MKVIIILSC

97MKVIIILSC

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Guys,
My car (135,000 miles) has a rough idle that results in a rumbling / popping kind of sound coming from the air box. my mechanic installed new plugs and boots (together with a vc gasket) and while the pick up seems improved I still have a rough idle. Now he's suggesting a motorvac process to remove carbon build up. Any ideas, suggestions, comments experience of motorvac?
Thanks,
Phil.
 
Weird...

As far as the Motorvac process goes I'd just buy like three cans of Seafoam and do some carbon removal yourself. I have personally ran 2 can of Seafoam through my mark and noticed a large improvement in idle smoothness.
 
thanks for the seafoam tip - car idles at about 1200 on initial start and drops to 950 after about 20-30 sec warm up
 
seems a little high but not too bad. Try the seafoam, suck it throught the brake booster vacuum line and watch the smoke. !!:)
 
1200??

You have a vacuum leak, find it, fix it, enjoy. I would Seafoam it anyways though... it can never hurt, only help!

My car on start up revs to about 900 and then drops and stays at about 700ish.... Tommy spent a ton of time playing with his tune getting his car to start like that and he helped me out with it :D
 
did you have a cel when your inject was faulty?
 
It's funny I read the op and my first thought was seafoam, and then about 3 posts later everyone else said the same thing. If I were you I would seafoam the pcv valve vac line and put some in the gas tank as well. I read somewhere that the brake booster line doesn't feed all cylinders but the pcv does. Any truth to that? I've done this on both my LS and my Mustang and have been very pleased with the results.
 
If its a poping horn type sound from your air box..Thens its the IAC motor..Its gone bad ...Might get lucky with just a cleaning...
 
brake booster is were exactly on a 97 mark viii
help please cause i have the same problem
 
94BLU8 said:
brake booster is were exactly on a 97 mark viii
help please cause i have the same problem
Click to expand...

When looking at the motor it is to the right of the driver side valve cover on the fire wall. The brake master cylinder is in front of it will the yellow tank. The booster will have a gray round fitting pull that out and seafoam from there or from the pvc line.
 
kustomizingkid said:
1200??

You have a vacuum leak, find it, fix it, enjoy. I would Seafoam it anyways though... it can never hurt, only help!

My car on start up revs to about 900 and then drops and stays at about 700ish.... Tommy spent a ton of time playing with his tune getting his car to start like that and he helped me out with it :D
Click to expand...


Had the same problem on my '96. Installed new plug wires and had a terrible idle for a while. I thought I had crossed a couple of wires. When I removed the intake tube, I noticed that I had inadvertently knocked a vacuum line off. Reconnected the line and ran a can of seafoam through it. And all was well with the world.
 
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