Long time problem. Sputtering/ vibrations

[Bugman114]

Hello everyone. I've been having an issue with my 100% stock 95 safari. It has the 4.3 vortec OBD1 with a 4l60E trans. The problem is that it has this hesitation, almost like its mis-firing, on acceleration. It seems to dissapear on the highway from 70-80 mph, and drives perfect. Otherwise it's hesitating and vibrating. When stopped at a light the whole thing shakes, and on very rare occasions it will shut off when taking off. If i floor it, it takes off fine with no hesitation. It also seems to smoke everynow and then. usualy white smoke. and also it has a really bad exhaust smell. when u stop and have the windows open, u can smell it. its not rich fuel as it doesnt smell like that nor does it make your eyes burn (i have carb'd VW's, i kno what rich exhaust smells/ feels like, XD. I've replaced the TPS, plugs, wires, the entire distributor (brand new not rebuilt), MAP sensor, both knock sensors, the computer, the spider injector thing and all the intake gaskets while i was at it, the coil, the EGR valve, replaced ALL vacuum hoses, just about every sensor cept for the air diverter thing on top of the manifold (can't find it anywhere). I just can't seem to get it to run normally. It's been doing this for about 6 years now. I've tried spraying starting fluid on the motor while it was running to see if it will idle up to check for vacuum leaks, and nothing (a quick spray every few minutes to let it evaporate, I kno guys, I'm not gonna blow myself up, XD). I just can't seem to figure it out.

Also, I live in GA where it still needs the old skool style emmissions check where they put it on a dyno, and a hose on the pipe to read the exhaust and it always passes with flying colors. None of the numbers are anywhere near close to failing. IIRC last year there was one reason that allowed over a thousand, and I got like 12. Even tho it running rough, it's still passing perfectly.

I'm sure I've forgotten a bunch of stuff, but if u have any ideas, I'd greatly appreciate it. Thanks

[Leeann_93]

White smoke is coolant.

Possibilities: head gasket/s (since you said you did the intake gaskets - was there much pitting around the sealing surfaces and did you use the plastic-coated metal felpro upgrade gaskets?) or the oil cooler tank in the radiator has cracked and you've got coolant in your oil - and vice versa.

Of course, it's possible you have a cracked or warped head, but let's start with the easier ones.

[Bugman114]

Thanks for the quick reply . There isn't any coolant in oil or vise versa. I've had to replace the radiator twice since its been doing the problem. Right now it has about 100K miles on this motor (200K on the body). The problem started around 130K miles we had an overheating issue at about 160K that turned out to be a clogged radiator, but we thought may have been head gaskets/ heads, so we actually bought rebuilt heads, and new gaskets. But the hesitation problem still persisted. And yes , when I replaced the spider fuel injector thing (bout 170K miles), I used the metal gaskets. One thing I noticed was the upper intake was NASTY. I can't quite remember exactly what it was coated in, but I wanna say carbon. I just remember taking a wire brush to the thing, trying to clean it off as best I could.

As far as the smoke goes, sometimes it's white or like a grey color. It didn't quite seem to smell like burning antifreeze (the first motor blew at 98K miles and that was one of the things it was doing). It doesn't have that odd sweet? smell to it. Just a funky exhaust smell.

[cowboydan]

My definition of funky leads me to believe that it could be bad catalytic converter smell. Being that the old engine blew and the new engine seems on it's way out also, says it's not the engine that is the issue. Changing the cat and o2 sensors should resolve your issue...imho. Plugged cats will cause overheating issues, and more. For now, I would drill a reparable hole in the exhaust pipe in front of the cat. If it runs better.... refer above. white smoke can be caused by a large amount of moisture built up in the pipe. It's typically what happens when you lose exhaust velocity. You can pass emissions with no catalytic converter.

[Leeann_93]

It's a Federal crime in the US to remove a cat. Doesn't matter if your state does emissions testing or not. Just FYI.

It's much easier to unscrew an upstream O2 sensor if available (late '95 should; don't know about early) and see if the van runs better than drill a hole, too, unless you have access to a welder.

[chevymaher]

It's a Federal crime in the US to remove a cat. Doesn't matter if your state does emissions testing or not. Just FYI.

Reckon just poke the insides out then. It empty but she is on there.
Yes sir I just following the letter of the law. No matter how badly it is written.

[cowboydan]

Sorry, I wasn't recommending the removal of the cat, rather simply stating that you can pass without one.

[ishort18]

Sorry, I wasn't recommending the removal of the cat, rather simply stating that you can pass without one.

as far as i know, you can't pass without one. I know in PA anything older than 96 is a "visual" check. Which means the cat has to be there and that's all they check. Doesn't matter if its hollow. So long as there is one there.


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