I have an 87 Camaro 2.8 injected(not sure which style)

I am noticing a hesitation (bogs down, but doesn't stall) when lightly pressing the pedal. When I press harder, it's fine.

I normally drive hard, so no issues for normal driving.
I normally only notice in my driveway or side street stop signs.

Any idea what to check first?


resent changes:
replaced defective non-charging alternator with working one.
replaced holey muffler. Still have slight leak between Cat and muffler.

 

Tps possibly

 

Also a leak in the intake manifold / small vacuum leak will cause this. Any sucking sound coming from the engine?


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I have a similar problem with hesitation and burbling when pressing on the accelerator. I cleaned the IAC which helped, but I'm sure the IAC needs to be replaced. I ordered an AC Delco IAC which I'm sure will resolve the issue (famous last words!!!).

Be careful you don't break either screw, if you decide to remove & clean the IAC. You may want to use a lot of PB Blaster and tap lightly on the screws with a hammer until they break loose. Trust me, it's real easy to break one. In addition, GM used star topped bolts (hate them). I used carburetor cleaner to clean IAC which did the job, but the IAC was just bad.

 

I'll check both.

It idles fine and revs fine without load.

 

99% you got a vacuum leak.

Is there a hissing sound behind yor dash in the area of the duct controls?

 

The reason it runs better with heavy throttle is because that puts it into "power enrichment" mode. It goes rich and ignores the O2 sensor.
Lighter throttle stays in the normal mode which tries to keep a stoich air/fuel ratio. That makes it more prone to stumble if everything isn't working perfect. For example, vacuum or exhaust leaks can throw off sensor readings which throws off the ECM.

 

87 2.8 does NOT have a bolt-on IAC. It screws into the throttle body.

OP, tune-up done recently, or at all? Did you check for vacuum leaks? Any other work done lately besides the alt and the muffler?

 

I have a similar problem with my 92 RS 3.1. Plus, it won't pass emissions - very high O2 levels. I have replaced EVERYTHING else - O2 sensor, Water Temp Sensor, Throttle Position sensor, spark plugs, wires, - and found (and corrected) a couple vacuum leaks. Still idles a bit rough (not too bad), but also stumbles on mild acceleration. Haven't gone back for the emissions, but want to do so soon (since my tag is now expired by over a month - been dodging cops!). Thoughts? Would the IAC affect O2 levels as well as cause stumble?