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Hesitates at 1000rpm intermittently

 
Old 09-12-11, 11:41 AM
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mrmdubb
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Default Hesitates at 1000rpm intermittently

Hi, I have a '99 RX300. Every once in a while it hesitates between 1000rpm and 1400rpm. After that point it drives fine again. This never happens after I just started the engine cold. However, after I drive the car for 5-10 minutes the problem appears. It's especially frustrating because the hesitation won't happen every time. I'd say it happens 50% of the time after the car has been warm and driving for 5-10 minutes. I just accelerate out of the red light and I feel a couple hesitation/jerks in the engine until it passes 1400rpm. The rpm isn't skipping and catching so it doesn't feel like the tranny.

I recently changed the plugs, timing belt and do regular maintenance. My mechanic thought it was the throttle body so we replaced that yet it did nothing.. .huge waste of money. Anyhow, now the mechanic wants to actually open up the fuel injection/throttle system to clean it out manually instead of just adding an additive to try and clean it out. I've had the usual RX issues (IAC valve, MAF, o2) and this is definitely different from those so I'm out of answers.

Any experience with this? Thoughts? Suggestions?
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Old 09-12-11, 06:40 PM
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carguy07
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1st find a new mechanic! Check engine light on? What did you use for plugs?
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Old 09-13-11, 11:54 AM
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Originally Posted by carguy07 View Post
1st find a new mechanic! Check engine light on? What did you use for plugs?
I gave the mechanic an earful about the throttle body. He's cleaning out the injection for free and told me he won't charge me for whatever fix it takes. At least he's willing to go that far. Probably because his shop is near my office and I've referred many colleagues to him in the past. I agree with you though, eventually I should just take it to the dealer and have them do it right.

To answer your questions, no, there is no check engine light on. On top of that, the problem happens intermittently so the scanner doesn't pick up any errors when in the shop. I told the mechanic I'd drive around for a few miles until the problem starts to occur so he can jump in at that point and try to scan it.

I'm not sure what kind of plugs he used. I didn't ask for that kind of detail. Is there a certain type you recommend?
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Old 09-13-11, 01:46 PM
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hypervish
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For plugs, denso or ngk is recommended. (iridium)
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Old 09-13-11, 01:46 PM
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Any vacuum leaks?
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Old 09-14-11, 01:31 AM
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1st question is does it only happen under load?
Does it do it in Neutral?
Don't rule out the transmission it won't show errors it has several clutches so a lot can go wrong.
It could also be a sticky brake caliper causing the car to drag or a differential.
It also may be a lead a plug or as mentioned a vacuum leak.
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Old 09-14-11, 08:19 AM
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No, it doesn't do it under load or in neutral. I would best describe the driving feeling as not enough fuel getting into the engine for a couple split seconds between 1000-1500rpm. So it goes and "hesitates" for a second, then goes & "hesitates" as if the engine's getting gas then isn't.

This morning it didn't happen at all driving into work. I'm almost certain it will on the drive home. That's how odd this is. It's like my car is moody. I'll ask about the vacuum and the lead plug. Thanks for the feedback.
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Old 09-14-11, 08:55 AM
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What is the mileage? 2wd or 4wd? GL
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Old 09-15-11, 08:46 AM
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Originally Posted by Francis View Post
What is the mileage? 2wd or 4wd? GL
198,000. 2wd. The mechanic is searching for answers but told me, again, the financial burden will be on him. It sounds like he doesn't know what to do at this point. He said he may have to take it to the dealer and work with them on it.
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