High Idle Problem TPS voltage test procedure

[hpbadger]

Originally Posted by Aurora40

I would think the high idle is more likely caused by a leak somewhere than by an improper TPS. But I could be wrong. I'm not sure how a high-reading TPS could actually cause the motor to run much faster since it needs air to do that.

Did you clean the throttle body when you replaced the IAC?

I haven't clened the throttle body other than spraying the IAC hole with cleaner like crazy when I replaced it.

I replaced the TPS....the original was set to .34 but it was probably good. Checked for vaccum leaks and could not find any.

Got a QDM1 fault YES on the scanner. Noticed a hard to reach throttle cable stop but I don't want to mess with it.

Wierd thing is the speedometer is always reading 60mph to 220mph.

New TPS set to .54 did not fix the problem. I drove for 1 hr and idle suddenly came back to about 650 where it is supposed to be but I expect it to be high again when I start engine today. Real mystery. Hope I don't have to change the ecm.

hpb

[bldavis11]

Originally Posted by hpbadger

I haven't clened the throttle body other than spraying the IAC hole with cleaner like crazy when I replaced it.

I replaced the TPS....the original was set to .34 but it was probably good. Checked for vaccum leaks and could not find any.

Got a QDM1 fault YES on the scanner. Noticed a hard to reach throttle cable stop but I don't want to mess with it.

Wierd thing is the speedometer is always reading 60mph to 220mph.

New TPS set to .54 did not fix the problem. I drove for 1 hr and idle suddenly came back to about 650 where it is supposed to be but I expect it to be high again when I start engine today. Real mystery. Hope I don't have to change the ecm.

hpb

I have nearly the same problem as you and spent the my entire 3 day weekend working towards solving it, though I changed a ton of other things as well.

My problem is a faulty PCV valve connector tubing. The paired PCVs connect into a piece of rubber tubing about 10" long that runs along the rear of the block. You'll see if when you find the PCV valves.

After taking the tubing off, I could see that there are a number of very very small tears that are likely the source of my vacuum leak. A replacement house made from silicone is available from White Racing Products.

I also removed the plenum to check for vac leaks, removed the coil packs and starter to clean out the crap down in the valley, then cleaned everything well. In hind side, I'm glad I did all of this as there were clearly some mouse/rat droppings by the starter and my little friends had clearly been eating at insulation to the starter!

Replace the PCV valve hose and you'll be set. Watch out though. That little hose is over $150! I also rewelded the braces that connect to the aluminum tubing which connects to either end of this PCV tubing. One was snapped off and I didn't want to even think about how much it would cost to buy it new.

[hpbadger]

Originally Posted by bldavis11

I have nearly the same problem as you and spent the my entire 3 day weekend working towards solving it, though I changed a ton of other things as well.

My problem is a faulty PCV valve connector tubing. The paired PCVs connect into a piece of rubber tubing about 10" long that runs along the rear of the block. You'll see if when you find the PCV valves.

After taking the tubing off, I could see that there are a number of very very small tears that are likely the source of my vacuum leak. A replacement house made from silicone is available from White Racing Products.

I also removed the plenum to check for vac leaks, removed the coil packs and starter to clean out the crap down in the valley, then cleaned everything well. In hind side, I'm glad I did all of this as there were clearly some mouse/rat droppings by the starter and my little friends had clearly been eating at insulation to the starter!

Replace the PCV valve hose and you'll be set. Watch out though. That little hose is over $150! I also rewelded the braces that connect to the aluminum tubing which connects to either end of this PCV tubing. One was snapped off and I didn't want to even think about how much it would cost to buy it new.

Thanks a lot..I will take a look back there and see if the tubing is faulty and report what it is.....also the QDM 1 fault I found out is for a Quad Driver Module.....not sure what it is so am researching....just know it is in the ECM.

hpb

Originally Posted by hpbadger

Thanks a lot..I will take a look back there and see if the tubing is faulty and report what it is.....also the QDM 1 fault I found out is for a Quad Driver Module.....not sure what it is so am researching....just know it is in the ECM.

hpb

Quad drivers are what control the injectors. Hopefully the QDM is not bad as these are not cheap! They are located on the drivers side of the car. One is mounted to the rear inner fender panel. The second is mounted on the firewall by the battery.

[hpbadger]

Originally Posted by Jeffvette

Quad drivers are what control the injectors. Hopefully the QDM is not bad as these are not cheap! They are located on the drivers side of the car. One is mounted to the rear inner fender panel. The second is mounted on the firewall by the battery.

Thanks very much for your help. I will try to locate the quad drivers. Is the rear quad driver mounted to the rear surround?

hpb

[bldavis11]

Originally Posted by hpbadger

Thanks a lot..I will take a look back there and see if the tubing is faulty and report what it is.....also the QDM 1 fault I found out is for a Quad Driver Module.....not sure what it is so am researching....just know it is in the ECM.

hpb

I had to remove the hose to see where the problem areas were. Even with a flashlight I wouldn't have picked them up. The whole hose needs to come off the car and be inspected. Personally, I would just replace the sucker while you're at it. It's going to go bad at some point and likely sooner rather than later.

Originally Posted by hpbadger

Noticed a hard to reach throttle cable stop but I don't want to mess with it.

Do not touch the throttle stop screw. These came preset and Mercury Marine never adjusted them either. If you do adjust it you are masking the real issue.