p1518 code, car idles rough and shakes but goes away after 2 mins??

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vikingdiesel

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I have the p1518 code on my 98 Mark VIII and here are the exact symptoms.

I start the car in the morning and everything is fine, if I punch it, it will hesitate a little but will drive off nice and fast. Now when I shut it off and have it sit for more than 5 min and re-start it, thats when it will stutter and shake and when i give it gas, it bogs alot and stutters almost likes its gonna die, but as soon as I start driving away, it will clear up and drive normal again.
 
Run seafoam through the engine. It probably has carbon build up, the IMRC's are not opening or closing right whiich is causing the engine to stutter and shake.
 
ive ran seafoam on a different car in the fuel tank before, where should I run the seafoam on this one and how do I do it on this one? Also, is it true that seafoam isnt really good for Fuel Injected cars? The car sat for a few months before it started doing this, so carbon build up? The dealer also mentioned some box in the back that a wire could be disconnected from, not sure exactly
 
try the brake booster line. Have some one idle it up while you poor it in.
 
You can run Seafoam through it just fine and you also want to take a large vaccume hose off and suck some into the intake that way.
I would also take off the IAC and clean it out with that B-12 stuff or any good throttle body cleaner. I cant remember what code mine threw but the symptoms were the same when my IAC was sticking.
 
Good info LASERSVT but the problem is I need some pics of these things I have to clean... lol.. What large vacum hose? Where is the IAC located? Would putting seaform in the fuel tank make a difference or no? Also, after putting seafoam, after how long should I notice a difference?
 
vikingdiesel said:
Good info LASERSVT but the problem is I need some pics of these things I have to clean... lol.. What large vacum hose? Where is the IAC located? Would putting seaform in the fuel tank make a difference or no? Also, after putting seafoam, after how long should I notice a difference?
Click to expand...

Pour just over half the bottle in a half tank of gas then take the rest and pour it in the intake. In the following picture you can either disconnect the red line and pour it in there or disconnect at the blue circle and stick it in the bottle to let the car suck it in while having someone hold the car at 2000 rpm.
After its all in there shut the car off and let it sit for a couple minutes and then restart the car and drive it a bit. You will mosquito fog the neighborhood. :D

The IAC is the yellow circle. Remove it and place it upside down on a bench and fill it up with a throttle body cleaner and let sit for a half hour or so then dump it out and spray the leftovers out. Make sure to get a new IAC gasket first though cause chances are the one you have is dry rotted.
IMGP0390.gif
 
i will do that tomorrow, seems like pouring in the red circle is easier, should the car be running for the red circle or no? Also, after how long should I feel a difference. Also, my buddy who works at the dealer was told about some black box by the firewall with some wires possibly disconnected and is a common issue, familiar?
 
vikingdiesel said:
i will do that tomorrow, seems like pouring in the red circle is easier, should the car be running for the red circle or no? Also, after how long should I feel a difference. Also, my buddy who works at the dealer was told about some black box by the firewall with some wires possibly disconnected and is a common issue, familiar?
Click to expand...

Yes the car should be running while it sucks up the seafoam through it. Basically the idea is for the seafoam to remove the carbon that might be causing the IMRC to stick and not close or open. I would do two treatments of seafoam before you have to check the other stuff.

Yes there is a "Black" box that controls the IMRC's. you can follow the wires down to IMRC controller and see if its attached. When you rev the engine above 3,000 RPM and you should see the two wires move. (I pointed to the wires in the pic)

IMGP0390.jpg
 
ok, I did 1/2 bottle of seafoam and not really a big difference and today I dumped a whole bottle and waited 2 hrs and it definetely cleaned it out but still the code and it still has that bog, whats my next step?
 
I cleaned the IAC and the (2) wires with the black box do move when I rev them, could it have anything to do with my HYPERTECH chip?
 
If you have some t-body cleaner then pull out the MAF sensor and clean it with the spray. DONT TOUCH THE LITTLE WIRE WITH ANYTHING! just shake it out and let it dry. Also take the negative cable off the battery then get in the car and press the brake pedal (to discharge any capacitors) then go hook the battery back up. It will reset the computer just incase it learned some bad habbits.

If that dont work then remove the chip and see how she runs. If she runs well without the chip then you know the problem..... hey, you running 93 octane? Cause the chip requires it.
 
the car came from MINNESOTA so 92 octane was available, was that fine? I now only use 93 since thats what we got here. Also, if I remove the chip, what should I replace it with?
 
You dont have to replace it with anything. It should just be piggy backed on the ECM on the top. Just dissconect the battery and pull the chip. Reconnectthe battery and fire her up. It will be a bit ruff at first as it remaps itself (learning curve) and see if that cures the problem. I would still clean the MAF first though.
 
How long does the car take to remap itself after I remove the chip? It idled rough for a while. After the brake pedal thing after i disconnected the battery, the car drove extremely rough and actually wouldnt go away. I then took the chip off and it took a while for the rough idle to go, i waited 10min(it still somewhat rough IMO), i drove the car around and it felt a bit smoother however, I punched it from a stop sign and all it did was bog out. ANy other ideas, also the previous owner put a K&n intake which i dont think is the issue but he also put an 80mm MASS AIR FLOW, could that be the issue?
 
vikingdiesel said:
80mm MASS AIR FLOW, could that be the issue?
Click to expand...

I'm willing to bet that is one of your issues with the car. The computer isn't tuned for the 80MM sensor, what with no chip in it... if even the tune on the chip accounted for it to begin with.

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2nd post
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What year is your car? See if you can move the IMRC's by hand first, to dislodge any carbon that might be keeping the controller from closing them.
 
so I should put the chip back then? Its a 98 and the (2) wires in the black box do move when I rev the engine
 
The black "wires" coming out of the IMRC controller should not move. The black you see on them is the color the conduit that houses the actual wires that actuate the IMRC's.

Move the IMRC's by hand. Trace where the "wires" go into in the back of the heads and you'll see the IMRC cams the wires are attached to. Try moving those cams by hand.


Get some fine (FINE) sandpaper or a steel wool brillo pad, and lightly scuff up the contacts on the chip. I heard that can sometimes help with making a secure connection between the ECU and chip.
 
vikingdiesel said:
ok, I did 1/2 bottle of seafoam and not really a big difference and today I dumped a whole bottle and waited 2 hrs and it definetely cleaned it out but still the code and it still has that bog, whats my next step?
Click to expand...

I just had the same code and experience.

I would check the return spring first. It is pretty easy and can be done within seconds, without any tools. I have read a few posts were running the sea foam didn't work, just as you experienced.

Check here for a detailed explanation and pics:
http://www.lincolnvscadillac.com/forum/showthread.php?27020-Advice-for-Dealing-with-Stuck-IMRC-s
 
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