TTops

My 2002 Trans Am won't rev past 4K RPM. It runs great other than this issue. Happens at a steady acceleration or at WOT. No misfires, pinging, ticking, or anything out of the ordinary other than this issue. It just reaches about 3,600-3,700 RPM and then chokes, like it hits a wall. It will hang steady at around 4K and keep running just fine right there, but it obviously doesn't accelerate. It acts exactly as if I were purposefully trying to hold it at 4K, even though my foot is to the floor. I can only confirm it happens in 1st and 2nd, haven't been anywhere I could test 3rd and 4th without exceeding the speed limit.

NA99T/A

Did it just start doing this overnight? or did you do any mods/repairs then this problem started?

TTops

I don't regularly try to go over 4,000 RPM, so it's difficult to say when it cropped up. I noticed it today, was driving around for a bit and everything felt great, decided to romp on it on an empty road near my house and I discovered the issue. Revs pretty freely, seemingly just like it did before the issue, but hit 3,500 RPM and it's like the engine gets filled with syrup and then slowly plods to about 4,000 where it just sits

unit

How long have you owned the car and have you made any mods to the engine? If you have mods - what are they and when did you make them? Could be any number of things, such as clogged catalytic converters.

SheepDog209

iTrader: (2)

^^^ what he said... I've seen a clogged cat do that numerous times.. take a rubber mallet and tap the cat... see if it rattles... if so, replace it.

wph351

iTrader: (3)

Clogged cats.

TTops

Car is stock, no mods at all. I replaced the drivers side cat three months ago. I'll check the passenger side.

pantera_efi

iTrader: (1)

Hi TT, I would also check the FUEL FILTER.

Remove this, shake the filter, drain the inlet onto a paper towel.
I would check the fuel pump AND pump Fuse.
I would listen to the pump for "whine".

Lance

ddnspider

iTrader: (26)

Does it do it in neutral or only in gear?

pantera_efi

iTrader: (1)

Hi DD, yes good observation ???

The help, with report ??? = OK

Lance

TTops

Gearhead1

To save some coin, my Son tried a tank of regular in his SS. The computer wouldn't allow it to run over 4G until he got rid of the crap gas. You didn't, by chance, put the wrong octane gas in by mistake, did you ? It happens.....

2xLS1

iTrader: (25)

Sorry but no way just 87 octane gas by itself would cause that. I've done dyno pulls clear up to 6200 rpm on several LS1 cars that had 87 octane gas in them.

Gearhead1

......even with the stock tune ?

Bowtie316

iTrader: (1)

I had one do that when the fuel pump was dying. I would try to check fuel pressure during a pull.

Also, as stated, could be cats.

ddnspider

iTrader: (26)

Yes, stock tune will only pull out so much timing, but it'll still rev.

SheepDog209

iTrader: (2)

When you replaced the cat earlier, did it come apart? I've seen the internals plug up a muffler. Try disconnecting the exhaust, before the cats if possible, and drive it. See if it changes.

thunderstruck507

iTrader: (18)

as noted above it could be a fuel issue or a backpressure issue, fuel is probably easiest to check since you can rent a gauge from the parts store

don't know where you live but if the area has had a ton of rain its possible the gas stations in the area could have mud/dirt contamination in the fuel which will quickly clog the filter or injectors themselves

less likely since you say it does it at part throttle but if you keep turning up empty also check the MAF sensor by unplugging it to force speed density mode and see if it still occurs

2xLS1

iTrader: (25)

Yes, stock tune. You typically see about 20-25 less peak RWHP with the stock tune running on the low octane timing table values. But they still rev all the way to the stock 6200 rev limiter. Saw this on a C5 Vette one time on the dyno and when I asked the customer what kind of gas he had in it he proudly said 87 octane. That the salesman who sold him the car said it would run just fine on it so that is what he always used.