94 Camry hesitation

[Donald]

If I am going 55 mph, take my foot off the gas to slow down a bit, then step back on the gas, I feel hesitation and a slight thump. Engine runs smoothly and transmission shifts smoothly. If I do the above very carefully and slowly I can avoid most of the hesitation. 4 cyl.

Ideas?

I was thinking EGR related??

 

[porcupine73]

Is this vehicle an AT or MT?

I experience the same thing in many AT vehicles. Typically it's because at that speed the torque converter is locked and there isn't really anything in the drivetrain to absorb driveline shock so you'll feel a little shudder when getting back on the gas after coasting, unless you do it gently as you say.

 

[Donald]

its an AT......maybe I notice it more as I have just fooled with (but not yet replaced) the front engine mount. But I did not think it happened much a few months ago. Car does have roughly 150K miles.

 

[Donald]

So any other things to look at with respect to the engine?

 

[Quest]

You mentioned that you have just replaced the engine mount recently, haven't you?

How does the old one(s) look like? Are they cracked?

If you happened to install a harder engine rubber mount, there will be a slight thump when you suddenly close the throttle (deceleration) and then try accelerating again. This is normal for most of the aging Camrys inc. my wifey's 93 Vee6 (more pronounced than yours, but with over 220,000kms on the original drivetrain, I have no complaints).

 

[Donald]

Actually I removed old front engine mount, installed a new one, found new one defective during the install (some metal broke off around the machined threads), and reinstalled the old one. So I have been in that area, had a jack on the engine (with 2x4 of course).

 

[Quest]

ok...so that eliminates the possibility due to questionable engine mount.

I guess my next guess would be that during your servicing of engine mount(s), did you bump or "disconnect" some sensors or cause some sort of intermittent electrical sensor connections? There are quite a few sensors around the engine mount areas you know (been there, done that with my wifey's Camry Vee6, but not so much as to remedy the "thump" problem).

 

[Donald]

I had also changed the dist. cap and rotor recently. I looked around the engine mount area and dist. cap for a loose electrical connector or vacuum line and did not see one. The only sensor I might have banged into while doing the engine mount was the secondary air sensor and it looks fine.

 

[quintdiesel]

I have a '96 LE w/ 2.2L and had a bad hesitation. It was really bad at stoplights, sometimes dying. The knuckleheads at our local stealership charged me $95 and told me they didn't know what was wrong!?! It was the EGR valve, it wouldn't always reseat. A new one fixed the problem, but it is a PITA to change as it faces the firewall and has very little clearance

 

[Donald]

The hesitation and/or "thump" seems to have gone away or maybe lessened when I replaced the front motor mount. The old mount leaked hydraulic oil when I turned it upside down, so I guess it was not in good shape. Or maybe I am use to this thump and the motor mount did not help.

 

[Donald]

quintdiesel - could you have cleaned the EGR valve with something like carb cleaner or throttle body cleaner? Or did it need to be replaced? Its not cheap, maybe over $100.

 

[quintdiesel]

Maybe, but it would be a PITA. I bought a new one at Auto Zone for less than anywhere else. I've found that cleaning EGR components are a very short term fix.

 

[unDummy]

You're feeling your TC unlock. When you get back on the gas, the TC needs to lock back up, hence the thump.

Flush your transmission fluid to smooth the shifting and TC lockup.

Give the engine a good tuneup up, and test things like TPS, o2, MAF,.......

 

[Donald]

The transmission was flushed less than 10K miles ago and filled with Amsoil synthetic ATF.

 

[Donald]

I looked up a new EGR valve at NAPA and it was $187. A lot for an EGR valve for a 12 year old vehicle. I was thinking of trying to clean the EGR and see what happens. The new gasket was only $1.00. Maybe its not the valve, but passages leading to the valve.