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Chugging, hiccuping otherwise runs fine no codes?

Posted By: Edy

Chugging, hiccuping otherwise runs fine no codes? - 05/25/08 02:11 AM

I have a 98 2.7 liter, 5speed. For several months now I have had a symptom that I thought was water in the gas. At any given moment under load but often when you ease up for a moment and then give more throttle. The truck will cut out for a second. It could be a soft hiccup or a sharp jerk. Sometimes it comes in multiples. Never really stalls but it sometimes feels as though it might. I used alchohol and "HEET". Sometimes it seemed better, sometimes worse. Today I dropped my gas tank, emptied it and dried it and put in fresh gas. It still does it. Any clues?
Posted By: kewlynx

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/27/08 02:01 AM

When's the last time the fuel filter was changed? I'd also check the TPS adjustment and inspect the spark plugs to see if they tell a story.

Might also try and drive it with a loosened gas cap and see what it does. Don't know if that'll throw any codes for ya, but you can rule out if the tank pressure is okay.

Just a couple thoughts.
Posted By: john_luttrell

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/27/08 03:04 AM

Sure sounds like a bad TPS to me.............
Posted By: Edy

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/28/08 03:53 PM

Got a TPS link for the 98 3rZ? (the search function on this board is pretty useless IMHO)

I've had the fuel filter done before I dropped the tank. Should've waited 'til after. Did the plugs and wires yesterday. Plugs were text book perfect light brown to tan. Filled the tank up with fresh gas. Was terrible right after the tank drop so I let it sit a couple of days and made an appointment with a mechanic. Broke down and did the plugs and wires. Drove it 25 miles and it seemed better but still did it. Maybe it is ignition but it sure feels like fuel. Will let you know how it goes.
Posted By: Dandeman

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/28/08 10:13 PM

Quote
Sure sounds like a bad TPS to me.............



ditto.. no experience with the 2.7 TPS, but on an older Camry we have with a manual tranny, when the TPS is not adjusted right the symptoms as described above are what I get...

Quote
At any given moment under load but often when you ease up for a moment and then give more throttle.


I'm interpreting the above to be happening under light throttle conditions i.e. just slightly off the idle stop.. If it's happening at heavy throttle, then ignore the following, guess I should have asked first... <img src="/forums/images/graemlins/shiner.gif" alt="" />

TPS adjustment for manual transmissions are a lot more tricky.. it has to be right on not have the dropouts and jerking you mention.

One of the functions the TPS controls is the so called "fuel cut".. that is on trailing throttle conditions, the fuel injection system cuts off delivery of all fuel to the engine (i.e. when coasting). When this happens at too high a butterfly opening (due to misadjustment), you get the drop outs in power and jerks as it starts resupplying fuel when operating at close to closed throttle conditions. Other symptoms can be wrong idle speed as well as an oscillating idle.

Have you ever adjusted what looks to be the idle stop adjustment screw on the throttle body?

Some people still think this is an idle speed adjustment.. It's a minimum clearance setting to hold the butterfly slightly off the throttle body wall, that in turn is the base setting for the TPS switch..

It won't affect idle speed (as any changes in the resting butterfly position will be overridden by the servo operated idle air bleed valve controlled by the ECU). But moving the adjustment screw will sure screw up the TPS settings, can cause the above mentioned problems, as well as possibly causing the butterfly to stick (too little clearance) as the throttle body cools down after driving.

My recommendation would be to check, and readjust if required, the initial butterfly minimum clearance setting, then the TPS switch clearance settings using a feeler gauge as described in the procedure in the Factory Service Manual.
Posted By: Y2KTaco

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/29/08 02:06 AM

Another thought might be to check your converter, I was told if your exhaust can't get out it might act like you described.
Posted By: kewlynx

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/29/08 03:41 AM

Edy, remember there's a sticky here for FSM's-- go for it. I use it all the time.
Posted By: Edy

Re: Chugging, hiccuping otherwise runs fine no codes? - 05/29/08 05:32 PM

Finally sounds like we're on to something. And finally got a FSM downloaded that will work for me. (Unless the '96 2.7 TPS is different from the 98) Will get to work on the TPS adjustment soon. Luckily I do electical work on the side (I'm retired) so this is up my alley. (Not that it's that hard to read and ohm meter) Will let you folks know how it goes.
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