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My 1998 Nissan Altima has been idle hunting/surging at startup for a while, and also has a slightly high idle after highway driving. A mechanic told me not to worry. He said the engine wouldn't be hurt by a slight surge at startup, or by a slightly high idle, and that the motor seems to run great by the looks and sound of it.
I'm not so sure. I mean, he didn't even check for codes. I suspect he just didn't want to do a couple of hours of diagnostics only to find out it was a leaking vacuum line. The engine does run fine, so he's right about that. What do you guys think? Get it fixed, or stop worrying and enjoy the little scare it gives pedestrians when I start it up?
(Additional info: The engine revs to 1500 or 2000 rpm for 20 seconds or so at startup, then drops to 1000 for a sec, before the ECU pushes it back up to 1300, then 1000, then normal idle. This takes place over about five seconds. The surge only happens when the engine is warm.
Sometimes the engine won't surge, but then the tach stutters a little as it shoots to 1500 rpm. It's quick, but there's a jerkiness to it, instead of the normal smooth rise. When I step on the gas, it's smooth.
Have tried: starter fluid on vac lines, replaced vac lines, bled air from cooling system, cleaned and new gasket on TB, cleaned and new gasket on IACV, ran techron through the fuel system The engine runs great otherwise, with good mileage and rock solid idle.)
What the "mechanic: is really telling you: "I don't know how to fix this."
What the "mechanic: is really telling you: "I don't know how to fix this."
Don in Austin
See a couple of posts above. The mechanic DID know how to fix it. The same mechanic who told me not to worry also told me how to fix it a while later (when I bugged him about it again when I brought the car in for state inspection). First he checked for vacuum leaks - none. Then he asked me if I had sprayed the TB with carb cleaner - yep. Then he said, swap a used one it and you'll fix it.
So the fix was replacing the throttle body and TPS. Cleaning the throttle body by spraying carb cleaner on an old Nissan can mess it up, evidently.
What the "mechanic: is really telling you: "I don't know how to fix this."
Don in Austin
See a couple of posts above. The mechanic DID know how to fix it. I just had to bug him to get him to spend the time.
First he checked for vacuum leaks - none. Then he asked me if I had sprayed the TB with carb cleaner - yep. Then he said, swap a used one in and you'll fix it.
So the fix was replacing the throttle body and TPS. Cleaning the throttle body by spraying carb cleaner on an older Nissan (or maybe any...idk) can mess it up, evidently.
I have a 2001 Ford F150 xlt. after the engine is warmed up at idle the vehicle will hunt for a steady RPM. most times it will drop so low the engine will stop. Any suggestions as i think it will very expensive to have a dealer check it
My 98 Explorer does exactly what the OP described. Nothing has worked. All indications point to a vacuum leak but no one has been able to find it. Nobody mentioned throttle body though. I do get a lean code.
Throttle Body can do it, too.. But, "in general" you don't see it unless it has never been cleaned and you put about 100k miles on it.
The Nissan mentioned above.. I've never heard of simply cleaning the TB causing a problem.. The electronics are generally sealed up on them, so unless you submerge them or something..
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