2000 Chevy Malibu acceleration issue

well that doesn't sound too pleasing

I really do hope its not a transmission issue.. fluid and filter was replaced about 40k miles ago.. I will say though, I do think I have some misfiring going on. I got a p0304 during this WOT test, the last time I tried to do it, IT STARTED BLINKING ( check engine light). It went from solid to flashing on the last WOT, which Almost reached 5k rpms. so needless to say, i stopped the WOT, now i have to figure out this p0304.

I know this engine needs a new fuel pressure regulator ( leaks fuel every key on ), new head and intake gaskets, as well as a new front oil seal. Really hope its not a tranny issue!

Also, by delyaed engagement, the car DOES respond to the gas, it just takes a little while before it gets up to speed but it does shift gears as it should.

Thanks for getting back to us with the capture! I'm kinda with Cheryl, the Load looked a bit low for a GM - I saw a max of 71%. I usually see that closer to 90%. But, the upstream O2 did go full rich, and stayed there during your run. That suggests to me that the overall fuel delivery is OK.

Also, glad to see you did a backpressure test. That answers a lot of questions about potential breathing issues.

The stuttering, flashing CEL and P0304 are definitely the direction to go, like you said. I saw that some ignition parts got replaced previously, but I think you've got to revisit the ignition system. I wholly endorse swapnostics at this point (moving coils/plugs/wires and rechecking codes) You could also use an incandescent test light to check spark strength at the coils, or wet the wires with water and look for arcing.

Tyler wrote: Thanks for getting back to us with the capture! I'm kinda with Cheryl, the Load looked a bit low for a GM - I saw a max of 71%. I usually see that closer to 90%. But, the upstream O2 did go full rich, and stayed there during your run. That suggests to me that the overall fuel delivery is OK.

Also, glad to see you did a backpressure test. That answers a lot of questions about potential breathing issues.

The stuttering, flashing CEL and P0304 are definitely the direction to go, like you said. I saw that some ignition parts got replaced previously, but I think you've got to revisit the ignition system. I wholly endorse swapnostics at this point (moving coils/plugs/wires and rechecking codes) You could also use an incandescent test light to check spark strength at the coils, or wet the wires with water and look for arcing.

This car had two bad plug wires, one of which was soaked in oil. Lot of brown powder on the ignition coils as well. new plugs and two wires, new fuel pressure regulator, fuel trims look a little normal now. I'll redo the test soon.. really gotta get these oil leaks fixed. On another note, the guy who did the tune up a long time ago was a fraud ( long story) judging by some of the plugs/ wires that I replaced, This job did not see its completion at the time.

Thanks fellas.

My gas leak is gone and there are no more misfires, engine is running smoother, And my fuel trims are almost perfect since changing the regulator, 2% LTFT at idle now opposed to -10 and even at times -24 trims.

Problem still largely persists. it is still hesitating upon acceleration, I'm not sure to classify this as a misfire or not, I usually have a difficult time differentiating between transmission slipping ( Not sure if I've ever felt a slipping transmission before), engine hesitation, and misfires. I know what a misfire feels like.

This happens under low and heavy load, usually under deceleration.

It resolves itself if I give it a bit more gas,. It doesn't happen every time and is very intermittent. Its as if the crankshaft is not spinning past a certain point when I want to go faster.- ;looking at the rpms while its hesitating, its jumping in between 2000-2200 rpms until I give more gas

Any other ideas?

Were you able to revisit the wot test now that the regulator has been repaired?
Also, I rember you mentioned the transmission has been serviced fairly recently. Have you checked the fluid level? Actually, can you check the fluid on this car or is there no dipstick tube in this transmission?

Donnyten wrote: My gas leak is gone and there are no more misfires, engine is running smoother, And my fuel trims are almost perfect since changing the regulator, 2% LTFT at idle now opposed to -10 and even at times -24 trims.

Problem still largely persists. it is still hesitating upon acceleration, I'm not sure to classify this as a misfire or not, I usually have a difficult time differentiating between transmission slipping ( Not sure if I've ever felt a slipping transmission before), engine hesitation, and misfires. I know what a misfire feels like.

This happens under low and heavy load, usually under deceleration.

It resolves itself if I give it a bit more gas,. It doesn't happen every time and is very intermittent. Its as if the crankshaft is not spinning past a certain point when I want to go faster.- ;looking at the rpms while its hesitating, its jumping in between 2000-2200 rpms until I give more gas

Any other ideas?

Glad to hear the overfueling got fixed! Making progress

Distinguishing between different symptoms like this can be tough. I can say that the behavior of the engine speed in your last capture looked pretty normal, but that isn't the whole story. Does the CEL still flash at times? I'm tempted to suggest chasing the P0304 for now, but you don't sound convinced that it's a misfire...

The engine speed jumping a few hundred RPM, then going away with gas sounds like a slipping torque converter clutch. But, the TCC by itself doesn't explain the rest of your symptoms, as it only locks in at steady cruise. I know you said the trans was serviced recently, but I say check the fluid level anyway, make sure it's in the right range at idle in park.

Noah wrote: Also, I rember you mentioned the transmission has been serviced fairly recently. Have you checked the fluid level?

Get out of my mind!

Im gonna recheck the fluid level soon, I can redo the WOT test if need be.

Sucks that theres no friggin dipstick on my transmission. I had to change it the hard way last time I serviced it * oil+ filter*

By the way, the misfire code is non existent and no more check engine light