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Hey guys, figured Id update you on the latest with my Blazer. After putting in a new ported vac switch the truck seemed to behave much better. I now have heat coming out of the defrost. However I still have a heck of a time getting air out of the vents. When I put it on AC after awhile I can get air out of the vents.
I discovered someone “capped” a vacuum line with a screw, Im not sure why this occured as I cant find any port near the line for it to plug into.
The SES light is intermittent. If it does come on it takes quite sometime for it to come on tho it still shows the same code 44.
I was driving home tonight when the transmission started shifting rough and then after a stop at a traffic light it wouldnt shift out of first gear at all. I tried shifting manually (putting the shifter into first gear and shifting up manually) but that didnt work. It still goes into drive and reverse just fine tho which has me stumped. I checked the fluid and although its a bit dirty its at a normal level and doesnt smell burnt. Im owndering if it lost vacuum altogether.
After getting it home and parked I checked my TV cable and tried driving around the block but it still wont shift tho oddly enough the SES light has not come on since I came home after the shifting issue.
Another curious thing Ive noticed is I discovered my PCV valve is bad which Ill replace tommorow, and my “snorkel” going from the crankcase to the heat stove in the air cleaner snorkel has tore.
After getting the truck home I do hear a hissing sound similar to a vac leak but my hoses are still good and tight
Any advice would be greatly appreciated.
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Hey Chris. At this point, I don’t have much to offer without having the vehicle in my hands. I would follow the ‘plugged’ vacuum lines towards the HVAC controls, and see how and what they are supposed to control. You also need to get your eyes on the mode door actuator to see what it’s doing when you switch positions. The door itself may be sticking, or the actuator may be bad. This will most likely involve tearing into the dash, which is never fun. You should get your hands on some kind of service manual that has vacuum line diagrams to assist you. There should also be a diagram on the underside of the hood or somewhere in the engine compartment itself that may help you. I’m just now seeing that I’m suggesting what my boy Dreamer already has, so I give him a (ugh) +1. Good luck bud. 🙂
I replaced the PCV valve, and checked the fluid still fairly clean and at the right level but no change in symptoms
Just curious guys would a faulty TPS cause this problem? I havnt gotten any codes for it but Ive heard the TPS can sometimes cause transmission problems
If the transmission wont shift, you may have to test the line pressure. It sounds like the transmission may need a rebuild.
Did you try serving the fluid and filter yet?
Also, i think i suggested in one of your other threads to use a vacuum gage and find some vacuum diagrams from your HVAC system.
Thanks Dreamer and Matt. I think Ive eliminated the vac leak issues. I do think that the one capped vac hose is probably the hose that supplies pressure to the heater door actuator (sp?) as for the trans I dont have a line tester to test line pressue. So Im thinking about taking it to a shop and see if they can diagnose it or see if I can find more research material directly related to my particular tranny. I know my skills are limited. Outside of a filter change or TV cable change I wouldnt want to mess with any tranny components.
It would actually be very helpful if you could keep things on the original post, when you do it this way it’s hard to follow what’s going on so please in the future post any updates to the old thread instead of starting a new one, this will make my life a lot easier thank you.
Don’t get all bummed out man. I agree that you are probably dealing with multiple issues. I doubt the trans issue is related to the HVAC issue. Just post them as separate threads. It is hard for us to go back and forth between your threads, because 30,000 people have questions, and it’s rough enough as is.
Lol Ive noticed that too. Ive green lighted the SES light threads because like I was saying the SES light now only comes on intermittently and my main focus for now is the transmission
Well I tried pulling the TPS and MAP sensors both together and seperately. With the MAP off the truck seemed to not want to rev above 4000rmp. When I unplugged the TPS it hesistated more often at takeoffs and when first started didnt want to idle without dying. Im stumpred to me the trans acts like its in limp home mode but Im not sure if there is such a mode for the THM700-r4. I know there is for the 460le which is a newer version of the tranny. The ECM as far as I can tell has not gone into limp home mode (SES Light blinks once in key-on, engine off posistion and I can still pull codes). Ive read if the underhood transmission fuse pops it could cause the same symptoms but if it goes it also takes out the MAP and O2 sensor which throws more codes. I havnt been able to locate this fuse as thee is no underhood fuse box.
Im getting pretty stumped on this
Well I took the truck to a shop. Without a detailed look the tech did say it has gone into a limp home mode but the problem is finding out why. Theyd have to drop the pan and see what the computer says or if it went into limp home mode because the transmission is failing
Hey guys another question. I read that the transmission can lose electrical power via a blown fuse and go into limp home mode. I checked all of the relevant fuses under the dash but Ive read there may be an inline fuse or a fuse for the transmission somewhere under the hood. Would any of you know where to look? I dont have an under the hood fuse box. But I do know relays live there
I don’t know of such a fuse but I would also check all the fuses under the dash. It would be even better if you could get your hands on a factory service manual, perhaps you can find a PDF for cheep online as this would not only show you where the fuse was but also how to go about diagnosing the problem that you’re having.
The truck is a 1988? It has the 700R4, which is not electronically controlled. I think you are getting snow-balled honestly. If your engine issues are cleared up, and you are still having trans problems, then the problems are inside the trans itself, or with the TV cable. The 4L60E, which as you noted was the electronic version of the same transmission wasn’t introduced until ’92 or ’93 I think.
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