I ahve a tbi 88 sub that will bellow blue smoke after idleing for a couple of minutes. I have already put valve stem seals on it. When I first bought it it smoked bad on first start up so I put stem seals when i first got it. I am leaning towards a cracked intake manifold or bad intake manifold gasket. Anybody experienced this before? Thanks in advance!
CK5
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88 sub smokes only after extended idle??
- Thread starter bigjohn79
- Start date
Does the tbi run a PCV? I have a carbed 79 that was sucking oil through the PCV. Oil was being flung up through the baffles.
I changed out the valve covers with ones with tighter baffles. May be a long shot, but worth a quick check.
I changed out the valve covers with ones with tighter baffles. May be a long shot, but worth a quick check.
My S10 was burning oil in a similar fashion, it was the PCV valve causing it. Got a new one at the dealer for like 4 bucks.
Would it happen to have a th400 with a vacuum modulator?
Many "non factory" valve covers lack baffles for the PCV valve,and many dont even have a place to PUT one!..I have used the oil filler caps that twist-loc into the valve cover that have 2 prongs and a hole with a grommet for a pcv valve and is stuffed with breather element fitration stuff on those types of "custom" valve covers before..
The suggestion it might be a ruptured diaphram in the tranny modulator is something worth checking out--also see if any brake fluid is getting sucked into the power brake booster,I had a K5 that did just that and would start putting out white smoke after idling several minutes--like at a long stop light or at McDonald's drive thru's!..
The suggestion it might be a ruptured diaphram in the tranny modulator is something worth checking out--also see if any brake fluid is getting sucked into the power brake booster,I had a K5 that did just that and would start putting out white smoke after idling several minutes--like at a long stop light or at McDonald's drive thru's!..
Scratch that -- I just bought my Jimmy two weeks ago and it's been smoking. I took some advice in this thread and changed the PCV valve and it appears to have solved the smoking problem. Thanks for the great insight fellas!
Have you physically looked at PCV area of the valve covers? Is there oil flung up there?
Another method to see if oil is being drawn up is to pull the vacuum line running from the carb to the PCV valve. Pull the PCV valve off and blow some air through the line. Is the line wet from oil at the carb end? If it is, it is sucking oil through the PCV baffles and there is nothing that I am aware that will change that until the valve covers are changed. If it's completely dry - move on to other things.
The blue smoke after idling suggests something other than seals. I would expect blue smoke at start up for leaking seals/rings - but I'm not an engine builder either.
Have you done a compression test and is it holding compression?
Have you pulled the plugs? There will probably be evidence of which cylinder(s) is oil fouled/contaminated.
Another method to see if oil is being drawn up is to pull the vacuum line running from the carb to the PCV valve. Pull the PCV valve off and blow some air through the line. Is the line wet from oil at the carb end? If it is, it is sucking oil through the PCV baffles and there is nothing that I am aware that will change that until the valve covers are changed. If it's completely dry - move on to other things.
The blue smoke after idling suggests something other than seals. I would expect blue smoke at start up for leaking seals/rings - but I'm not an engine builder either.
Have you done a compression test and is it holding compression?
Have you pulled the plugs? There will probably be evidence of which cylinder(s) is oil fouled/contaminated.
Also,be sure the PVC hose to the valve and its ports are not clogged with carbon,you need a good strong source of vacuum to operate the PCV valve properly..if it cant greate enough vacuum to keep blowby from bypassing the rings thats just where it'll go,and cause smoke..I have seen some small blocks that had bad end seals on the intakes,and they didn't leak much oil,but the "open" area allowed vauum from the PCV valve to suck air in there,instead of "vacuuming" the crankcase as it should..
A crude test is to run it at idle and take off the oil filler cap,and block it with a peice of paper or your palm--you should feel suction after several seconds,or the paper be held in place by the vacuum..any other seal or gasket thats allowing air in,or oil out,will do the same thing too..(and may not nessasairly leak oil,due to the vacuum there!)..
A crude test is to run it at idle and take off the oil filler cap,and block it with a peice of paper or your palm--you should feel suction after several seconds,or the paper be held in place by the vacuum..any other seal or gasket thats allowing air in,or oil out,will do the same thing too..(and may not nessasairly leak oil,due to the vacuum there!)..
Most probable cause is loose worn out valve guides.
Sorry but valve seals do not "mask" a worn out guide.
Did you look at the heads when you had the valve covers off?
My old blazer used to have the oil drain holes filled up with burnt up oil/sludge. Cleaned out the oil drain holes, and then the thing stopped smoking at idle. The thing would fill up the valve covers with oil and the only place it could go was through the valve stem seals.
I'd also check to see if you are getting any vacuum to the PCV valve. Seen quite a few TBI throttle bodies plugged up with carbon and wouldn't have any vacuum to the PCV.
My old blazer used to have the oil drain holes filled up with burnt up oil/sludge. Cleaned out the oil drain holes, and then the thing stopped smoking at idle. The thing would fill up the valve covers with oil and the only place it could go was through the valve stem seals.
I'd also check to see if you are getting any vacuum to the PCV valve. Seen quite a few TBI throttle bodies plugged up with carbon and wouldn't have any vacuum to the PCV.
old thread, but I am having the same type of problems as the OP in this thread. Does NOT blow blue smoke on start up. That is totally fine. After warm, then when I let it sit at idle for a minute or so, will start smoking only out of the passenger bank (have true dual and can see it only smoking out of passenger side). And the smoke is more white then blue, which indicates fuel not oil to me (could one injector be pumping more than the other causing this?). I just changed the PCV hoping that would help and also checked to make sure it has good vacuum. I am hoping that I will hear something other than valve guides, but if anyone has any extra info, I'm all ears
FYI....It's an 89 TBI350 that I swapped into my 86 K5 and reworked the harness to work in my factory 86 system. Thing is running really good now. Idles well, runs smooth, just have this annoying smoking issue I would like to figure out.
Thanks
I'm pretty sure it's not coolant. You have a good point to check...and I will. But I am pretty sure it's fuel and/or oil
