2000 Camry I4 Hesitation on Acceleration

[wubstyle]

Hey everyone, I've been lurking for about a week now. Got a 2000 Camry I4 Automatic 143,xxx miles with some hesitation problems on acceleration.

Upon looking at the great write-ups around here, I cleaned the TBI, and ran a can of seafoam through the tank. I figured that would cut it. The air filter is clean, plugs and wires are in good shape.

When I cleaned the TBI and put the seafoam in the tank I didn't get ANY black smoke from the tailpipe as I expected. Followed all the instructions on the write-up in the DIY section to the T. And I'm still getting hesitation.

Thoughts? My only other thought is that it could be the trans, but I'm hoping it's something else.

[wubstyle]

Just checked the codes: Multiple cylinder misfires and a bad catalytic converter. I think the cat is causing the problem.

[Camry LE 94]

I didn't get smoke after cleaning my TB either. The brake booster vacuum line is a totally different story. You WILL get smoke! I had a bad hesitation problem upon acceleration once before, and I changed the fuel filter, hoping it would solve the problem, but it didn't. The problem was actually one of those very small and thin TB vacuum lines with the plastic over it, which had a hole in it where the end connects to the air port.

[Mike Gerber]

Originally Posted by wubstyle

Just checked the codes: Multiple cylinder misfires and a bad catalytic converter. I think the cat is causing the problem.

It's probably the other way around. The misfires probably ruined the cat by allowing the unburned fuel from the misfiring cylinders to travel out through the exhaust valves and down through the exhaust system, including the cat converter. Solve the misfire problems first and then replace the cat. Check the plugs, plug wires and the coils on your car first.

Mike

[wubstyle]

Originally Posted by Mike Gerber

It's probably the other way around. The misfires probably ruined the cat by allowing the unburned fuel from the misfiring cylinders to travel out through the exhaust valves and down through the exhaust system, including the cat converter. Solve the misfire problems first and then replace the cat. Check the plugs, plug wires and the coils on your car first.

Mike

Makes sense, but I'm still leaning towards the cat being the first culprit. At the beginning of the summer the cat threw a code before any cylinder misfires. Plugs, wires and coils are in good shape.

[carldyck]

I started noticing significant loss of power on my 2000 Camry 4 cyl (300,000km) several months ago. The problem was mostly rough and sporadic power while accelerating, with significantly less torque at low RPM than it had previously. Idle was occasionally rough, but no stalling problems. The CEL would only come on showing code 303 (cylinder 3 misfire) if I matted it at low RPM (making it run really rough) for 5+ seconds

First thing I did was to check the spark plugs, and re-gap (they weren't terribly worn, the centre post was quite an oval) and then run some detergents in the gas/oil. No noticable improvements.

I then started messing around with the EGR/VSV/Modulator system, but ruled it out by testing a blind gasket between the EGR and the throttle body. Good thing I cleaned out the throttle body, since I found a plugged vacuum hose along the way, anyways this wasn't the solution so..Moving on...

I bought a ELM 327 reader to log my engine parameters to laptop under load and trolled through the forums. I managed to rule out the O2 sensors, since the problems only really manifested themselves when the fuel injection system went into 'open loop' operation (ie under full throttle). At least my efforts and the $25 cable paid for themselves by saving me an O2 sensor or two.

I then figgured I'd just replace part by part everything closest to the combustion. Bought and installed in this order:

fuel filter ($20) Obviously not the solution but I figgured a good time to remove the original before changing injectors.

re-manufactured injectors ($140) these actually seemed to have a detrimental effect. The old ones weren't visibly clogged or damaged. I just changed them 2 days ago, but starting the car definitely takes a couple more cranks with the 'new' ones.

OEM spark plugs ($40) Since they're the double-ground type its hard to check the gap but it seemed a little smaller than the 0.044" spec. Ohwell, put em in anyways and voila, feels like double the horsepower, and I'm back to burning my tires (as well any stock camry would) at will! She runs way smoother too.

NGK spark plug wires ($50) Since its already running well with the new plugs I cant tell if they help, but probably not a bad maintenance item at 300k.

Moral of the story: Don't try to re-gap old spark plugs! buy new ones!

[fullofzen]

Originally Posted by wubstyle

Hey everyone, I've been lurking for about a week now. Got a 2000 Camry I4 Automatic 143,xxx miles with some hesitation problems on acceleration.

Upon looking at the great write-ups around here, I cleaned the TBI, and ran a can of seafoam through the tank. I figured that would cut it. The air filter is clean, plugs and wires are in good shape.

When I cleaned the TBI and put the seafoam in the tank I didn't get ANY black smoke from the tailpipe as I expected. Followed all the instructions on the write-up in the DIY section to the T. And I'm still getting hesitation.

Thoughts? My only other thought is that it could be the trans, but I'm hoping it's something else.

I would be surprised if the transmission were the issue at only 143k. Is the fuel filter original? That your OBDII codes are showing cylinder misfires would not suggest correlation with poor fuel flow, but that is certainly one potential issue in cases of hesitation.