qquake2k
New Member
- Joined
- April 18, 2007
- Messages
- 7
- Reaction score
- 0
- City, State
- Northern California
- Year, Model & Trim Level
- '92 XLT
A few weeks ago my 92 Explorer started surging, and had an erratic idle. I replaced the IAC valve, and it was better. But all of a sudden last Saturday it came back, even worse. It doesn't do it when the engine is cold, just when it's at operating temperature. When I come to a stop, the idle dips periodically below 500, which affects the alternator output. So I put it in neutral, and the idle stabilizes (sort of) at around 600-700. Sometimes if I put it back in drive when still stopped, it'll stay at around 600, but other times it'll dip again.
When I'm driving at a constant speed, it feels like it's surging, but I think it's more that the engine speed is dipping. Seems to happen more, or it's more noticeable at lower speeds. But it happens at even freeway speeds. What's really weird, though, is it seems to do it more and/or worse when I'm stopped pointing downhill. It doesn't do it at all when I'm stopped in my driveway, which is slightly uphill. It also seems to do it worse in drive than in reverse. When I put it in neutral and the idle stabilizes, it still feels like it's idling slightly rough. It also seems like it's pinging worse, even though I have the timing jumper out.
Like I said, I replaced the IAC valve, and yesterday I replaced the MAF sensor. I've sprayed starting fluid around the vacuum tree, vacuum lines, and intake manifold, but can't find any obvious leaks. I've also disconnected each vacuum line at the tree, one at a time, and covered the port with a finger, but it made no difference when I plugged it. It would run rougher when I first unplugged a line, then go back to the way it was when I plugged the port.
It acts like an intermittent vacuum leak, but what could cause that? Help! I'm at my wits' end! Would a diagnostic at the Ford dealer tell me? I have a friend who is a service manager, so I know they wouldn't lie to me, but I hate to bother him with this. Any ideas from anyone out there? Something I've missed? Any and all thoughts and comments are welcome. Thanks in advance!
Jim in Northern California
When I'm driving at a constant speed, it feels like it's surging, but I think it's more that the engine speed is dipping. Seems to happen more, or it's more noticeable at lower speeds. But it happens at even freeway speeds. What's really weird, though, is it seems to do it more and/or worse when I'm stopped pointing downhill. It doesn't do it at all when I'm stopped in my driveway, which is slightly uphill. It also seems to do it worse in drive than in reverse. When I put it in neutral and the idle stabilizes, it still feels like it's idling slightly rough. It also seems like it's pinging worse, even though I have the timing jumper out.
Like I said, I replaced the IAC valve, and yesterday I replaced the MAF sensor. I've sprayed starting fluid around the vacuum tree, vacuum lines, and intake manifold, but can't find any obvious leaks. I've also disconnected each vacuum line at the tree, one at a time, and covered the port with a finger, but it made no difference when I plugged it. It would run rougher when I first unplugged a line, then go back to the way it was when I plugged the port.
It acts like an intermittent vacuum leak, but what could cause that? Help! I'm at my wits' end! Would a diagnostic at the Ford dealer tell me? I have a friend who is a service manager, so I know they wouldn't lie to me, but I hate to bother him with this. Any ideas from anyone out there? Something I've missed? Any and all thoughts and comments are welcome. Thanks in advance!
Jim in Northern California
