92 Camry 4cyl Hesitation

[dbassett74]

After the car has gotten out of it's cold start high idle routine, the car

will start to hesitate. It's not constant though. Here is the best way

that I can describe it. At idle, in Neutral or in gear the car will all of

a sudden drop rpm and the computer seems to compensate for it right away by

revving it a bit, then it returns to normal. This sometimes repeats 2 or 3

times in a row pretty rapidly and then it's fine for the next 30 seconds to

a minute then repeats. So it seems like the car is hiccuping or something.

Prior to a few weeks ago, this problem presented itself only at idle.

Accelerating and at speed were fine. Then, it started affecting

acceleratoin once in awhile in that the car would bog down when accelerating

from a stop, but not all the time. One time it sounded like it back-fired

when it bogged down. So I changed the spark-plugs and the bogging down seem

to have disappeared for awhile, but the hesitation I described earlier still

remains. The spark plug tips were very light brown in color. I just did

the rotor as well. I kept the old distributor cap cause it was pretty new,

but the problem still exists. I didn't do the wires because they are only

about 5,000 miles old, if that. The distributor had been replaced about 10

to 15,000 miles ago so I didn't think it could be that. I also replaced the

fuel filter, but still no luck.

The car has an automatic and has 180,000 miles on it. The problem does not

seem to be affected by weather.

Could it be the fuel pump? Wouldn't that tend to go completely dead though?

Any help would be appreciated.

[Joe W]

This seems like a sensor problem.Has the check engine light come on?Are you able to check the vehicle for computer codes?

[dbassett74]

The only code it gave was for the coolant temperature sensor. That was broken, so I replaced it, but didn't fix the problem. I just spent a lot of money on replacing the fuel pump, distributor coil and fuel filter. None of which solved the problem. What else could it be? What I don't understand is how it's not constant. You would think if there was a problem, it would be constant. It either works or doesn't right?? But I not this time. I just can't find any rhyme or reason to this.

[Joe W]

The coolant temp sensor does alot of weird things when it's bad and I would have put money on that being it.But it was't,so one suggestion is to disconnect the EGR valve and see if there is any difference.

[dbassett74]

When you say disconnect EGR valve, do you mean simply pull off the vac hose to it? I did that, no difference... I even took off the throttle body and cleaned it. There was a lot of black guck in there. Also, the EGR opening in the intake manifold was completely clogged with a large ball of this black guck. I cleaned it all out, the car seemed to run much better and didn't hesitate. Went around the block (about 1 mile total) got back in the drive way, left it idling, then wamo, it start hesitating again. I just can't imagine what this thing is? I did a vacuum check and it's stable. Can you think of anything else??

[Joe W]

A few thoughts.The comment "after the car gets out of it's cold start routine" points to an O2 sensor,because after the car warms up is when the computer reads off of this sensor.Maybe there is more black guck in the manifold.And yes I did mean to disconnect (and plug) the vacuum line.Good luck.

[dbassett74]

Turns out it was the ignition coil... Popped a new one and and wamo, problem solved!

[jho8]

Hi,

I have exactly the same problem as you described. I then propped in an ignition coil as you did, but my problem is not solved. I have already replaced the EGR valve, vacuum hoses, fuel filter. The car just has a RPM drop 2-3 minutes after it started cold. When it first started, it is good for 2-3 minutes, then this RPM drop when idle which makes the car shakes. Then it gradually goes back to normal as the car is warmed up to its regular operating temperature. I am very frustrated with this since I have tried to fix it for a long time. I was adjusting idle speed but nothing works.