Surging, bucking, sorry acceleration.

[itiswhatitisa5]

I own a 96 5sfe a/t with 170k.

And I've had this problem for a while, now it just seems worse.

At higher rpm's my engine tends to lose more power. It wont rev past 4k sometimes 3k. And when I'm merging from a ramp to highway, the car really doesnt want to go and it will jump from somewhere around 4200 to 3900 rpm. It almost acts as if there is a rev limiter there.

Also when I'm just cruising doing 45 or 50 mph, the rpm's will change from 1900 to 1800 rpm's in a up and down motion.

Has anyone experienced these problems and would know what it is.

Im not showing any check engine lights. I'm kind of baffled and I lost confidence with this situation

[bigbird]

sounds like a possible fuel problem, injectors maybe. have you tried running a fuel cleaner through to see if it helps?

[fenixus]

i would say it's a tranmission problem with higher gears not engaging or slipping ... might be wrong though ... at least your description fits to what was happening to my old '90 ford probe, it wouldn't ever go above 70mph as tranny was locking on 3rd gear (1st gear was not working either lol)...

what color is the tranny fluid ? anything like black ? when was it drained for the last time ?

[Stillrunning]

Could be fuel starvation or bad coil under load. Forget the expensive stuff for now, just replace the fuel filter first and see if that solves; if not then look for more complicated stuff. You won't be able to diagnose unless you have access to a dyno and scope.

[itiswhatitisa5]

I've added a quater can of seafoam to this tank of gas. Tranny fluild is dark red to brown. I need to change it and the filter. Fuel filter has a few thousand miles on it.

I know that my distributor shaft is leaking because of a bad o-ring. Could that effect the coil?

[itiswhatitisa5]

drove the car today in some good stop and go traffic, engine was warm and so was the tranny.

once warm, it would be more difficult to get up to speed. but once there, it was okay. loss of power after 3k rpm.

engine clanks from a start, bad valve seals, but sometimes it doesnt want to get going.

[itiswhatitisa5]

well last night i narrowed it down, i reved the engine and felt the fuel line to see if it got any softer after the fuel fliter. fine

today i unbolted the o2 sensor from the exhaust manifold, the 1st one, and started her up.

she reved sooo smooth even past 5k rpm. now i must figure it its the first or second cat. lol

enjoy guys

michael

[fenixus]

for starters maybe replace that upstream o2 sensor if engine runs good without it ti means it could have been feeding fake/bad info to the ECU and in return the ECU was starving the engine of fuel at some condition.

narrow band o2 sensors are cheap, new Denso OEM is like $40 on ebay.

[BMR]

Originally Posted by itiswhatitisa5

today i unbolted the o2 sensor from the exhaust manifold, the 1st one, and started her up.

she reved sooo smooth even past 5k rpm. now i must figure it its the first or second cat.

Plugged cat??? An exhaust shop can check it by drilling a small hole upstream from the cat, and with the engine running, monitor the pressure while revving the engine. If the pressure builds quickly on rev-up and slooowwwly drops, the cats are plugged. That's what they did to verify the cats were bad on my F150 anyways. When they're done, they just weld the hole back shut. Shouldn't cost much.

[itiswhatitisa5]

What i did was remove the first upstream o2 sensor and reved the engine...it reved great

i then bolted the o2 sensor and removes the exhaust from the first upstream cat converter...it ran like shittttt

so, i punched the upstream cat converter, the big one off the header that costs 500 bucks. psshhhh,

[fenixus]

Originally Posted by itiswhatitisa5

What i did was remove the first upstream o2 sensor and reved the engine...it reved great

i then bolted the o2 sensor and removes the exhaust from the first upstream cat converter...it ran like shittttt

so, i punched the upstream cat converter, the big one off the header that costs 500 bucks. psshhhh,

so wait, you ran engine without the o2 sensor at all thus opening the exhaust before upstream cat, right ? and it ran good. nice troubleshooting!
i think you found the guilty part, so the cat got clogged and was restricting the exhaust gas flow ?

[BMR]

Originally Posted by itiswhatitisa5

so, i punched the upstream cat converter, the big one off the header that costs 500 bucks. psshhhh,

What does that mean?... you punched out the ceramic honeycomb material inside the cat and removed it? Yeah, that would fix any blockage!

The emissions control system ain't gonna like that at all! The CE light will almost certainly light up. You gonna replace it?

BTW, the guy at the shop who fixed my F150's cats told me cats don't die, they're killed. Burnt oil smoke in the exhaust stream, running too long with the CE light on, etc., etc.. In the F150's case, it was running for a coupla years with the CE light on when my son owned it.

[itiswhatitisa5]

fexinus;

the clogged cat was the culprit. fixed the exhaust blockage. thanks


bmr;

sounds great, runs great, not going to replace it and my check engine hasn't turned on. it loves it

[Stillrunning]

I commend itiswhatitisa5 on some clever troubleshooting, but BMR is right that CATs don't die they're killed, usually by oil burning, and 170K on a CAT is not really that much. He will not a get a check engine light unless there is a post CAT O2 sensor that measures CAT efficiency. Punching out the ceramic honeycomb is a good way to get you going, but not a good long term thing for the environment, although I don't think itiswhatitis5 cares much about that.

[BMR]

Originally Posted by Stillrunning

He will not a get a check engine light unless there is a post CAT O2 sensor that measures CAT efficiency.

I assumed there was one. My bad. My '92 Camry's got one but I keep forgetting that was a Cali-only thing back in '92. When did it become standard for the whole USA?