No power in low RPM range...

[WVU91Camry]

91 Camry, 3SFE, 5 speed....

Let me preface by saying that the compression is good (168-180 psi) and the plugs, dist. cap and button all looked fine 2 months ago.

My car seems to "fall on its face" in the low RPM range, especially when shifting from 1st to 2nd....

I cleaned the throttle body and finally got a muffler installed, and it helped a little bit, but the problem is still there.

I did notice when I was crawing in stop-and-go traffic the other day that it seemed like the car was missing....when in 1st gear trying to hold 8-10MPH, the car would surge and hesitate, giving me the impression that it was missing.....but not the "dead cylinder" type of miss, more like a rough idle where there is no pattern.

My question is: Does this sound more like a fuel problem or an ignition problem?

I've heard that the ignition coil is weak in these cars, so that is one thing I'm looking at. Also, when I cleaned the throttle body, it was EXTREMELY dirty, which also leads me to believe that one (or more) of my fuel injectors are partially to fully blocked.

I don't want to spend lots of $$ replacing things that don't need it just yet, especially near the holidays, so any previous experience with this sort of thing would be greatly appriciated.

[Doctor J]

Bad secondary ignition components such as coil , wires etc, are causing misfire under load.
The problem sounds to me like throttle pos.sensor, or cleaning residue after TB cleaning have found its way to idle speed control valve.

[WVU91Camry]

Originally Posted by Doctor J

Bad secondary ignition components such as coil , wires etc, are causing misfire under load.
The problem sounds to me like throttle pos.sensor, or cleaning residue after TB cleaning have found its way to idle speed control valve.

I had this problem before I cleaned the thottle body....

[timebuilder]

I'd look for codes before going any further.

You could need a coil, but without a diagnostic machine, it's not easy to tell. You could install a spark gap tool and power brake the engine and see if the spark breaks down, but that's not something you can do by yourself. And please, block the wheels, pull the parking brake on hard, and don't stand in front of the car!!! I worked ina shop with a guy who died at home in his driveway on a Sunday afternoon because he wasn't using safe practices. If you need help, find an experienced motorhead or two to help you. A sick spark under load means a new coil should be installed.

One dead-on test for fuel system performance (besides the rated pressure) is the ability of the system to deliver a full pint of fuel in 30 seconds. I have never, ever seen a properly functioning fuel system take longer than that to produce a pint. Average time for a pint is 12 to 25 seconds.

Drawing the fuel after the filter will show you if you have a filter problem, as well. If you are not happy with the volume after the filter, then put a hose on the metal line that connects to the filter inlet and check the volume there. If you still can't make a pint in 30 seconds, it's time to install a new pump.

I would also take the advice above and re-clean the TB and the IAC passages.

It's easy to make sure enough air can get into an engine, but it's more difficult to make sure that the air can get "out" of it. An exhaust restriction is not beyond the realm of possibility. If the same symptoms happen with the computer in open loop (before it warms up, after starting) you could remove the 02 sensor and see if performance improves. If it does, you may have fractured pieces of catalyst blocking the outlet of the cat or stuck in the muffler. Check everything else first. While far from being an everyday occurrence, cats do break and cause havoc once in a while. And, don't try this with the engine warmed up, or the ECM will assume a very lean mixture is being detected and start adding fuel. Do it when it's cold.

Gentle tapping on the cat with a rubber mallet can reveal the sound of loose pieces of cat bouncing around inside. A good cat will have no rattle (as long as its a honeycomb cat).

So:

re-clean the TB and IAC passages

spark under load

tap on the cat

a pint in under 30 seconds


Let us know what you find.

[fredk]

check the big intake hose for getting loose or cracks and check for a vacuum leak

[ironpig]

I second pulling the codes first before anything. I doubt the IAC would be dirty enough to cause your problem but couldn't hurt.