I am asking here because I trust the people here. My 97 Suburban 4x4 with the 5.7 Vortec acts strangely after extended highway use. At regular city driving right after being on the highway, it shifts hard from 1st to 2nd, and the Service Engine Soon light comes on. This has happened twice after driving up into the mountains, but it did it yesterday after I went to Spokane. The shifts smooth out the next day and the light goes off again the day after or the second day. Now that this has happened for the third time, I would like to know what I am up against. Is it just an oxygen sensor or is it something else?
My 4.3 vortec was doing the same symptoms and it was a short in the EGR control switch. Check your EGR circuits. There's something about it functioning above a certain speed (65mph I think) that's when mine would come on. I ended up getting it fixed when I smogged it and they put a new EGR valve in it, and fixed a short in the wiring...I think it was just the wiring, but they couldn't get $350 out of me for just fixing a wire. This switch is like a small plastic box just to the passenger side of intake near the EGR valve on mine (TBI) and the EGR vacuum hoses go to it pus the wires. Can't hurt to give it a look anyway.
Maybe the altitude is tripping the check engine light. I know my 350/700R4 would shift really weird when I'd go up into the mountains, Flagstaff is about 5500 ft higher than Phoenix and it just felt like a dog up there, and it would downshift hard when it didn't feel like it was supposed to. But, I never had a check engine light.
My brother's F-150 does the same crap after altitude changes. Service engine light and screwed up shifts. Goes back to normal after a day back at our alt. Also does it after towing a car on the freeway for more than an hour. Ford dealer says the computer & sensors are tuned for this altitude and nothing we can do about it. (Translation: He hasn't got a friggin clue!) "And if you believe that, you'll buy this watch!"
How many miles on it? My 93 acted similar, and I changed EVERYTHING related to the ignition, short of the computer. Then out of frustration, I just changed the whole distributor, even after "rebuilding" the old one. That did the trick. Other than that, I don't know what else I'd look at... if it's tuned up like it should be. Good luck, these newfangled contraptions will be the death of me!!! Jay
I drove at 75mph the whole way, I always do. My chevy has 86K on the clock. I guess I need to start pricing that silly assed stuff. I just wish I could get jobber prices.
El C, Check out Chevy talk. Lots of info on that over there. I just went through that on my 98 van with a 4L60E trans in it. Your probably getting an 1870 slip code when your check engine light comes on. It won't let your trans go into lockup.Mine eventually got to the point where the light would'nt go off after a few days. The boost valve gets stuck causing the hard 1-2 shift.There is a kit by Sonnax for the fix but requires a steel sleeve to be reamed into the valve body. I found a kit by Superior (kit4L60E-V comes with a new boost valve) that fixed my problem without the reaming. I was told to fix as soon as possible or you will burn up your converter. I could turn the van off and recrank and the harsh shift would go away until I spent some time on the highway but the convertor still does'nt go into a full lock up. Crosley on this board gave me alot of info about the problem. It's a very common problem on the 4L60E.You might check with him for a little more info. I used the Superior kit at the first of Sept. and so far everything is O.K.
To have a shop put the Sonnax kit in runs about $400. The sonnax and superior kits run around $40-60 for the kits. The reamer for the Sonnax kit is about $110. My nephew used to be trans tech and he recommended the Sonnax.Most of the transmission guys will. What he does now is takes everything apart and lets a trans shop put the sleeve in(about$65 in California) then does everything else himself. Also my van had about 85K on it. I've been told it can happen as early as 30K on them.
I wouldn't spend or fix anything till I had somebody scan it with a scan tool to read the codes...when you have the codes it will make the diagnosis much more reliable instead of wasting money trying to guess what is doing what...it could be a tranny problem or and engine problem....get somebody to read the codes then post em and I will try to watch and help....I am a drivability tech...fatchuk
ElCaballo, I agree with both 67 Imp & Fatchuk. You should get your vehicle scanned for codes first, but most likely have a 1870 code.We use both Superior & Transgo kits to cure this problem.The problem isnt the boost valve tho, actually its the convertor regulator & pulse valve in the valve body that we replace.The bore that the valve rides in wears.We prefer the Transgo kit because of the other good tech that comes with the kit. It goes for 45.00 around here & its a no brainer to install.Let me know if I can help you more. Dave
El C, here is an old post from back when I was doing mine. http://www.chevytalk.org/threads/showflat.php?Cat=&Number=547318&page=0&view=collapsed&sb=5&o=&fpart=all&vc=1
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