Fuel Response Options

[6G96GT]

I had a diagnostic and full service inspection on my Celica done from a local Toyota Dealer. It passed with flying colors so I know there's no large concerns at hand that would cause my car to have a fuel issue. Anyway, here's my issue:


Whenever I am driving around (city driving that is), right after I shift and then press the accelerator pedal, my car lightly hesitates, it's not a smooth transaction kinda deal. It started happening about 3 or 4 months ago but now it seems routine. Doesn't matter what gear I shift into either. It's a very light (but noticeable) hesitation (under normal driving). If I were to accelerate it hard, there's no issue at all. Only when normally driving and shifting. By the way, I shift gears when I reach 2.5K - 3K RPM under normal driving.

I really don't want to pay a mechanic to spend hours troubleshooting if I can help it. What would cause this issue?

This post has been edited by 6G96GT: Sep 21, 2009 - 1:54 PM

[blu94gt]

You're shifting at 2.5k? That's too low, when you get into the next gear the motor will be lugging. Try using the same amount of throttle, but let the RPM's get up to 4-4.5k. I try to never let my car get below 2-2.5k rpms with the clutch engaged (other than starting in 1st gear).

[6G96GT]

Really? I've always shifted at that range. What is the optimal range stock??

Also, what about when you're cruising on some back road? When I'm in 4th at say about 40 mph, my rpm range is about 2K. What's yours at?

This post has been edited by 6G96GT: Sep 21, 2009 - 9:46 PM

[delusionz]

It depends on how heavy your foot is, ofcourse the engine is going to lug with a heavy foot when your gear change drops you below 2k.

Even my GT4 with its stupidly long gearing/final drive ratios (and turbo lag of a steel wheel) can still drive below 2k. And I bet you guys with the 5S-FE have alot more torque under 2k than I do and alot less weight and no 4WD.

Let the clutch out smooth, and ease onto the gas and you will have no problem driving under 2k (aslong as you're not going uphill)

If there's a hesitation then somethings obviously wrong. Check your oil, spark plugs & filters. Easy!

PS. Personally I wouldn't add anything to the fuel system. Some additives can block injectors and fuel filters. Go for premium fuel (doesn't have to be anything near race fuel, but something above standard unleaded is good). We have RON 91, 95 and 98 (100 is race fuel), 95 is what I would pick (I think you guys call it 92 or 93) for an FE head, and 98 for a GE head.

PPS. Does the hesitation feel like knock sensor at work? I don't know how I would describe this to you but you would get hesitation like you've described if you had a 3S-GE running 91 RON.

This post has been edited by delusionz: Sep 21, 2009 - 11:54 PM

[6G96GT]

Good info, thanks guys! Well, I run top grade fuel and have been since I bought it almost 2 years ago. My oil is at the correct level and my oil pressure is good. I have an SRI with a fairly recent air filter which is still clean. I haven't checked my spark plugs yet and it's been about a year since "I" did.

It only happens on the first press of the gas pedal right after I switch gears. Maybe a second long. It's not really a big issue but it's definitely one that bugs that he!! out of me. I did try switching gears at the rpm range that Blu94gt recommended and it does help but it still has a slight hesitation about it.

I also used Gumout Fuel Additive back in the early summer and then had a check engine light about a week later but my mech said it was questionably bank 2 oxygen sensor and so I replaced it and the check engine went away. It does come back on from time to time but never stays on for more than a couple seconds here and there.

This post has been edited by 6G96GT: Sep 22, 2009 - 6:41 PM

[rdaharry]

Have you looked in the throttle body for a build up? When I first got my 95 ST the throttle body was very dirty and I was having similar problems. Local auto parts store throttle body cleaner and an old toothbrush will do the trick.

[6G96GT]

I'm going to check out those spark plugs this weekend and the throttle body as well. Good tip, didn't think of that.

[alltracman78]

It might just be that your not smooth enough on the transition from clutch to gas.
If you "jolt" the engine instead of smoothly engaging it will run weak for a second before it catches back up.

Judging purely from what you've said, that would be my guess.

[delusionz]

I know what you're talking about alltracman and the effects of that aren't really felt in a FWD NA celica.

[domyz]

It's perfect to shift under 2500rpm what are you saying blu94gt... a daily drive shifting at 4000-4500rpm? I tought that only girls drove like that!!

My engine start hesitate under 1200rpm... over that you have a mechanical problem

[blu94gt]

It's perfect to shift under 2500rpm what are you saying blu94gt... a daily drive shifting at 4000-4500rpm? I tought that only girls drove like that!!

My engine start hesitate under 1200rpm... over that you have a mechanical problem

Most of my shifts are at around 4000, sometimes I take it up to 5k if I'm getting on the highway. Drive over 100 miles every day, car has 153k on it and no issues other than some slowly leaking valve seals, and I get around 30 miles per gallon. See no reason to shift so low when I can have some fun in the higher power range.

[6G96GT]

Well, I checked the throttle body, looks good. I forgot that I had it cleaned and serviced when I had the head rebuild. Spark plugs are good too. Could it be my clutch getting worn out? I haven't replaced it since I've owned it.

By the way, I haven't performed an oil change on my celica in over a year and can't remember if I am supposed to put oil in the new filter and then screw it on or don't put oil in it???

[supaneko]

Yikes...4,000rpm?!?! Is this something that applies specially to the GT's?

I too shift at about 2500-2900 RPM. I thought this was actually a good point to shift so you're not putting too much wear on your engine or clutch. Hmm...

Can an ST be shifting at 3000-3500 or have even more lead added and shift at 4000+? Sounds kinda scary.

This post has been edited by supaneko: Sep 29, 2009 - 9:25 AM

[delusionz]

Who has fun chopping their power down right when it starts to kick in?

[GriffGirl]

Well, I checked the throttle body, looks good. I forgot that I had it cleaned and serviced when I had the head rebuild. Spark plugs are good too. Could it be my clutch getting worn out? I haven't replaced it since I've owned it.

By the way, I haven't performed an oil change on my celica in over a year and can't remember if I am supposed to put oil in the new filter and then screw it on or don't put oil in it???

Over a year?! Woah. I take it this car isn't your daily driver?

I don't put oil in the filter when I change the oil - just rub some on the gasket ring around the filter to make a good seal is all, and after your oil change, drive the car around the block a couple of times to get it flowing through the filter, then check your level and make sure you're where you should be.

I'm gonna have to agree with the shifting being on the low-rpm side. I wouldn't take it up to 4k at all, unless you're fond of killing your gas mileage and racing your engine needlessly. I shift at around 3k or slightly over and don't have any problems with that hesitating you're referring to. When you shift, do you "snap" your foot off the clutch quickly once you've shifted? Maybe your timing is slightly off and it's not giving the gears a chance to fully engage before you push the throttle in.

[6G96GT]

I meant I haven't changed the oil in my car 'myself' in over a year. I usually pay to have it done. My timing's good, it was serviced in March/April this year and hasn't changed. I tend to let the clutch out a bit slow (but smooth) because I have always been that way. It runs very very good, the only annoyance I notice is the very light hesitating right after shifting.

What about the fuel filter? Would that potential cause this?