I don't even know if I want to call it a high "idle" problem. At cold start, the engine revs itself up to 3000 rpm, as if the throttle is stuck. Putting the truck in gear brings it down to roughly 1500rpm, but as soon as you take your foot off the brake, it takes off as if you're standing on the pedal. Most of the time this will calm down a bit once the truck warms up, but not always.
Today I almost rear-ended someone in traffic because the truck tried to outdrive the brakes. Sometimes I can get the problem to clear up by turning the key on and off a few times before starting, but not always. The truck usually has to be warmed up a bit for that. En route to work(after my near-wreck experience), I put the truck into neutral while cruising down the highway, and the idle ran itself all the way up to 3500 rpm(!!), then it dropped down to a loping ~1500rpm "idle". At other times, I have been able to get the idle to drop down by jiggling the relays, though that's not a consistent thing. I have also been able to do it by disconnecting the IAT sensor, but the idle fluctuates so much that the truck is undriveable.
Things I have done:
*Cleaned and added grounds. I added two large ground cables, one running from the battery to the firewall, and one running from the firewall to the passenger's side of the engine. Battery ground cable is brand new OEM. Battery terminals have been cleaned and checked.
*Cleaned and dielectric greased sensor connectors. TPS, IAT, o2, IAC, CTS, and other connectors have all been cleaned and greased. The knock sensor is brand new.
*Cleaned and greased relay connections on the passenger's side of the engine bay. Replaced LATCH relay.
*Checked and adjusted TPS to 0.827 ratio. This has been checked numerous times.
*Cleaned, checked, and lubed IAC valve. Twice.
*Checked plugs, wires, cap, and rotor - all are in near-new condition.
*Replaced ignition control unit(under the coil) for an un-related(at least I assume) problem.
Other problems I'm having that may or may not be related:
*Hesitation and near-stall(sometimes it does stall) at throttle tip-in. It's fine if I don't touch the throttle, and it's fine if I gun it, but if I apply very light throttle(think of sitting in stop and go traffic), it stumbles and tries to stall. It's twice as bad going in reverse(backing out of a parking space, for instance).
*Intermittant power loss, usually clears up at about 3000rpm. This has gotten better since I cleaned the engine bay connectors up, but it still does occur.
*Occasionally backfiring, severe power loss. 2 days ago, I drove to work, and the truck was fine(aside from the inital high idle problem of course), but when I got off the highway, the truck tried to die every time i pushed the gas, backfired through the intake, and just generally ran like shit. Cleared up after I stopped, turned it off, and re-started it.
I'm open to suggestions at this point, but I'd really like to get to the bottom of this so I can enjoy my truck again. I don't trust it enough to let my wife drive it out of fear for her safety.I'm open to suggestions at this point, but I'd really like to get to the bottom of this so I can enjoy my truck again. I don't trust it enough to let my wife drive it out of fear for her safety.
Thanks in advance for any suggestions!
Today I almost rear-ended someone in traffic because the truck tried to outdrive the brakes. Sometimes I can get the problem to clear up by turning the key on and off a few times before starting, but not always. The truck usually has to be warmed up a bit for that. En route to work(after my near-wreck experience), I put the truck into neutral while cruising down the highway, and the idle ran itself all the way up to 3500 rpm(!!), then it dropped down to a loping ~1500rpm "idle". At other times, I have been able to get the idle to drop down by jiggling the relays, though that's not a consistent thing. I have also been able to do it by disconnecting the IAT sensor, but the idle fluctuates so much that the truck is undriveable.
Things I have done:
*Cleaned and added grounds. I added two large ground cables, one running from the battery to the firewall, and one running from the firewall to the passenger's side of the engine. Battery ground cable is brand new OEM. Battery terminals have been cleaned and checked.
*Cleaned and dielectric greased sensor connectors. TPS, IAT, o2, IAC, CTS, and other connectors have all been cleaned and greased. The knock sensor is brand new.
*Cleaned and greased relay connections on the passenger's side of the engine bay. Replaced LATCH relay.
*Checked and adjusted TPS to 0.827 ratio. This has been checked numerous times.
*Cleaned, checked, and lubed IAC valve. Twice.
*Checked plugs, wires, cap, and rotor - all are in near-new condition.
*Replaced ignition control unit(under the coil) for an un-related(at least I assume) problem.
Other problems I'm having that may or may not be related:
*Hesitation and near-stall(sometimes it does stall) at throttle tip-in. It's fine if I don't touch the throttle, and it's fine if I gun it, but if I apply very light throttle(think of sitting in stop and go traffic), it stumbles and tries to stall. It's twice as bad going in reverse(backing out of a parking space, for instance).
*Intermittant power loss, usually clears up at about 3000rpm. This has gotten better since I cleaned the engine bay connectors up, but it still does occur.
*Occasionally backfiring, severe power loss. 2 days ago, I drove to work, and the truck was fine(aside from the inital high idle problem of course), but when I got off the highway, the truck tried to die every time i pushed the gas, backfired through the intake, and just generally ran like shit. Cleared up after I stopped, turned it off, and re-started it.
I'm open to suggestions at this point, but I'd really like to get to the bottom of this so I can enjoy my truck again. I don't trust it enough to let my wife drive it out of fear for her safety.I'm open to suggestions at this point, but I'd really like to get to the bottom of this so I can enjoy my truck again. I don't trust it enough to let my wife drive it out of fear for her safety.
Thanks in advance for any suggestions!