1988 350 not running quite right

[jkien88]

Ok, so, I have am 88 suburban, with a freshly rebuilt 350, about 10k on it. A couple of weeks ago I was driving home and everything seemed to be ok. I was going up a hill and stepped on it abit, it stumbled twice while going up the hill and I remember thinking "that's not right". So I keep going and its starts backfiring thru the exhaust and losing power. I pull over obviously. it was running rough in OD, wanting to stall when I stepped on the throttle. I dropped it down a gear and it idled a little better. started going, hit a light and it died. I had to get it towed home as it wouldn't start again. Fast forward a bit. I replaced the fuel filter, plugs, coil. The guy at the parts store said it could be the pick-up coil. So I replaced that and it fired to life.

But its still not quite right. Its hesitating on shifts from 1-2, and 2-3. I can step on it and it just goes along and then bam it takes off. Its idling ok. I timed it the best I could with a timing light, but its not perfect. The hesitation is my biggest concern, as it didn't do this before it broke down.

Also as I was under it changing the fuel filter I noticed that my muffler has a pretty good sized hole in it. Could the lack of back pressure be causing this hesitation? I have read a bit here and it could be one of the sensors. The SES light comes on once in a while. Not every day and after I got it running again it took 3 days for the light to come on. Im out of ideas.

Anyone got any advice?

 

[Boone83K10]

anytime someone says it idles fine and runs like poo when accelerating.. I immediately think a faulty exhaust.

If you have a vacuum gauge, hook it up to manifold vacuum and throttle it up to around 2 grand. A healthy exhaust will hold high vacuum, a faulty one with go up while raising the RPM and then go to zero once you are holding it steady at 2000.

 

[jkien88]

I have heard that a clogged Cat Converter will make it run like crap, so that makes sense too. I will have to pick up a vacuum gauge.

Oh I wanted to add that this is a TBI with HEI. If that helps.

 

[Jims86]

I have heard that a clogged Cat Converter will make it run like crap, so that makes sense too. I will have to pick up a vacuum gauge.

Oh I wanted to add that this is a TBI with HEI. If that helps.

By all means, check the converter.
You may also want to freshen up the throttle body with a rebuild kit,that comes with a new fuel regulator. Check the codes to see what the intermittent light is, it will still be in the ECM Memory even though the light went out.
Dont get caught up in the "backpressure ids required for the engine to run right" bs....you only need a little exhaust pressure to operate a backpressur EGr valve, and even that works just fine with a single 3" magnaflow exhaust.

 

[jkien88]

I found the link in another thread on how to check the codes. I will be doing that this weekend. I will look into the tbi rebuild kit as well.

Thanks for the input. This issue is over my head as far as what the problem is, but all info is greatly appreciated and I will look into it.