90 V8 Suburban is chugging when climbing inclines

My 90 V8 Suburban started chugging and backfiring when climbing inclines. I changed the fuel pump less than 500 miles ago and changed the fuel filter same time. I just changed the filter again and did not fix the problem. The engine has about 75K miles. I checked all cylinders and they run about 120 PSI and hold pressure, not burning oil. Any suggestion on what to check on?

I've given this similar answer a couple of times before, and I'll repeat it here only because it was a shock to me when this was discovered on my Suburban. But I was having power problems, overheating, etc.. was ready to sell the vehicle. Took it to Chevy dealer several times where they told me to replace this, replace that, fix this, etc.. but it never ifxed the problem. finally took it to a trusted independant mechanic of a friend, BAMM! he found that the little journal bearings on the distributor shaft were shot. he stated that the cylinders were firing as much as 12 degrees off. He should me the old distributor assembly, and those little bronze bushings were pretty much destroyed.

Funny thing was, as I was leaving the shop he warned me to drive careful because it would have more power than I was accustomed to. And he was certainly correct.

Good luck. could also be a vacuum leak, blocked exhaust, or something else... if that helps.

My 90 V8 Suburban started chugging and backfiring when climbing inclines. I changed the fuel pump less than 500 miles ago and changed the fuel filter same time. I just changed the filter again and did not fix the problem. The engine has about 75K miles. I checked all cylinders and they run about 120 PSI and hold pressure, not burning oil. Any suggestion on what to check on?

with 75,ooomi on the engine ??? distributor ???? I would guess that this is more like a fuel contamination problem . I would check for water and bad fuel.

also check for a restricted exhaust . this can be plugged cat converters or muffler or even a rats nest in the exhaust system. check for back pressure. remove upstream O2 sensor[s] and go for a test drive hole open .

the distributor bearing issue is with mileage over 150,ooo mi. starts with miss fire codes then gets gradually worse.

try to pull the DTC failures.

I agree that distributor bearings are usually 150K miles and up, but I was at about 90K when this happened. Just another possible thing to check.

Hey, which engine do you have Mr. Nichols45? (Mine is the 454).

One thing that Nichols45 states is the "backfiring", that is something I didn't have happen. But another time I did start having problems with the two injectors (TBI), if I remember correctly one of the injectors was sputtering the fluid instead of generating a nice connical spray.

Best of luck to Mr. Nichols45, please keep us posted.
Later,

Thanks all for you comments. I have a few things to check now. I have a 350 and I cut the Cat out this winter. Is their any way to change out the bushings or do I have to buy another distributor assembly? I will have to get in a dark area to check my fuel pattern. Living in Alaska has problems with lack of dark in the summer. The distributor assembly is the original and has over 150K. I put a crate engine in about 75K ago.

Thanks all for you comments. I have a few things to check now. I have a 350 and I cut the Cat out this winter. Is their any way to change out the bushings or do I have to buy another distributor assembly? I will have to get in a dark area to check my fuel pattern. Living in Alaska has problems with lack of dark in the summer. The distributor assembly is the original and has over 150K. I put a crate engine in about 75K ago.


since the distributor/vehicle has that many miles on it then the distributor/cam gear are a good possibility..I would replace the distributor. replacing the bearings , would not be the normal way this is repaired.

with the cat converter gone you can still have restrictions in the muffler. the baffles can break off and plug up the exhaust.

Hmmm... the distributor is look even more suspicious. If I can recall correctly, the mechanic replaced the entire distributor assembly, including the rotor and cap, as a complete unit from GM. And I seem to recall him saying it was on the order of under $300, saying "It's the best bargain GM offers". Keep in mind this was about 4 years ago.

Good luck.

did you fix it ?

Thanks for all the imput. It is still not fixed. I installed new injectors, dist. assembly and re-timed. I still get a chugging under load or up inclines. If the air breather is off I can hear it pop throught the throttle body.

Any other suggestions?