No freeway acceleration 1995 Tahoe

[jdwxly]

Finally had some time to look at it again. Drilled a hole ahead of the cat for a back pressure check and looked at that. Right after engine startup and after allowing it to warm fully I see about 1.5 psi of back pressure. That doesn't sound like a restricted cat or muffler. Next paycheck I'll swap out the O2 sensor and see what they does for me.

I also banged on the cat and heard no rattles or funny noises. WHile not a conclusive test, at least it helps eliminate an obvious problem

 

[east302]

Was that 1.5-psi at idle or at higher rpm...say 2500 or so?

Does your 95 use just one catalytic converter?


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[jdwxly]

Was that 1.5-psi at idle or at higher rpm...say 2500 or so?

Does your 95 use just one catalytic converter?


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1.5 psi at 2500 rpm. And yes, my Tahoe has the single cat at the end of the Y-pipe coming from the manifolds.

 

[jdwxly]

Installed a new O2 sensor today and went for a drive. No change :-( In fact, by the time I had driven 15 miles on the freeway the best the Tahoe could do was 65 mph. Turned around and headed for home. Ten miles later I was down to 40 mph, driving down the shoulder with the emergency flashers going.

I pulled off at the next exit and chugged into a nearby parking lot. Once parked I tried revving the engine to see if it would run cleanly with no load. It would not. It revved to 2000 rpm and then stumbled and bucked. If I backed off the throttle a little then accelerated again i could coax it to 2500 rpm. Then more stumbling. Repeat to get to 3000. That's all it would do. I shut if off and let it sit for half an hour, then tried again. It revved cleanly to 3500 in the parking lot so I got back on the freeway. It was still sluggish accelerating and could barely hold 60 mph by the time I got off 5 miles later.

The parking lot behavior now has me thinking this is ignition related, like something is failing when hot. I've pretty much eliminated all of the emissions stuff. So I guess we'll try a good tune-up and perhaps a new coil.

 

[YukonandtheHOE]

Try swaping out your water temp sensor?
Does your exhaust smell really rich?

 

[jdwxly]

Try swaping out your water temp sensor?
Does your exhaust smell really rich?

Water temp sensor was the second thing I replaced (bad thermostat was the first) so it should be ok. Exhaust smells normal even when it acts up.

 

[Baylee Brown]

I had same the problem on my 99 2 dr. OBS and after replacing the O2 sensor it had the same problem. After I replaced the throttle positioning sensor the problem was solved.

 

[jdwxly]

A friend suggested that I try removing the catalytic converter and seeing if that truly was the problem. I went to a local wrecking yard and picked up a Y-pipe from a '95 1/2 ton pickup. The collector was mashed where the cat had been cut out for recycling. A little work with an angle grinder, big hammer, and some adapters and I was able to cobble together a Y-pipe with a glass pack muffler on the end.

The test drive afterward proved that the problem has been the catalytic converter all along. The Tahoe pulled cleanly to redline and had plenty of power, even climbing hills when fully warm. Problem solved!

 

[qukon 95]

take 02 sensors out put a scope camera in to check the in ternals or a infared temp gun to check exhaust pipe temp before and after cat.