That Sky Guy

So the issue is this: When I accelerate, it's nice and steady, consistent sound/RPM until I hit around 35-50 (it differs sometimes). When I hit that speed area, the RPM shoots down to 1000ish and it sounds a lot quieter, and acceleration goes into the toilet unless I floor it. Haven't had this issue and am wondering what could cause it?

I haven't encountered an issue like this before. However, it's really bothering me and I want to fix it as soon as possible.

OrangeBird

iTrader: (1)

Hi Sky Guy ,

I believe from your description that your engine is fine .....

Now , with that said , I also believe your transmission is going into and staying in top gear and this is the reason for the RPM drop + lack of acceleration , that it's in top gear at 40 MPH and not downshifting when you step on the gas .

Your first check here is gonna be to make sure the transmission's throttle position cable is still properly attached to the throttle body . If that cable is disconnected , usually from the little plastic clip being broken , the transmission will always "think" that your only lightly stepping on the gas and as such it will hold itself into top gear because it doesn't "know" your actually stepping on the gas trying to accelerate .

IF , in fact the plastic clip has broken and the cable is now disconnected from the throttle arm , you have 2 "DO NOTS"

First , DO NOT go out and buy a whole new cable ! If it's only the plastic clip , those clips can be purchased from any reputable transmission parts retailer without buying/replacing the whole cable for around 2 or 3 dollars .

And second , DO NOT drive the car till that cable is put right . It is WAY more than just a "kickdown cable" , it also regulates "transmission line pressure" meaning that if it is disconnected , and you do step on the gas to accelerate , your clutches will not have the required fluid pressure , will slip , and be destroyed in short order . Yes indeed a $2 piece of plastic really CAN ruin your transmission due to it's breakage and putting this right , if indeed the cable is disconnected , will take all of 30 seconds when you have the replacement clip in hand .

Best of luck here and please report back your findings ......

That Sky Guy

That's both a relief and extremely worrying (because it means that yet another shop here in my city has damaged my car) but it makes sense. I will go check it out and report back later today.

That Sky Guy

So, pretty sure this is bad news. Here are some pictures.

OrangeBird

iTrader: (1)

Hmm , that little black plastic clip looks fine and so does the cable it's attached to . And yet it sounds from your description that it's acting as though that cable has become disconnected (or perhaps broken further down , near the transmission maybe ?) . There is a proper set procedure for that cable , it's not so much as an "adjustment" as it is a "setting" and if you search "TV cable set procedure" you should come up with the proper way to set it (although there really is no good reason for it to become "unset" unless someone tinkered with it ?) . If going through the set procedure* doesn't make the transmission kick down to a lower gear when you punch the gas then yea , bummer as it sounds , something deeper is amiss ...

* You may try to disconnect that plastic clip and carefully pull on the cable , if it only pulls out a couple inches and it feels like an internal spring is wanting to pull it back in , then the cable is likely ok . if it pulls right out then of course you'll have found the problem in a broken cable and that while being a bit of a PIA to change , isn't really a big dollar fix .

PS , and fix that fugly vacuum hose block off .... Fugggly !

Tootie Pang

iTrader: (2)

Just FYI. That vacuum hose is not plugged. Screws do not work. The air simply follows the spiral thread down into the hose.

That Sky Guy

I'm new to the mechanical restoration world. What exactly am I looking at, and how do I fix it? Does it plug in somewhere?

That Sky Guy

I am brand new to the mechanical restoration world, still a novice wrencher. What exactly am I looking at?

Also, how do I fix that hose you were talking about? What is it/what does it do?

Tootie Pang

iTrader: (2)

For that, I would buy a small hose cap kit from any of the major auto parts stores. $6-$8 for a variety of caps. It will have one you can slip over the hose and make a nice seal.

As far as WHAT that is, I'm not sure. If it was a TPI V8 I think that is the EGR feed. Mine had broken so I capped it and fed the EGR off of a closer vacuum port.

That Sky Guy

Update: Correct you are. That line with the screw does indeed feed into my EGR. There are a couple other lines as well, this is the only one disconnected. What do you recommend I do?

Interestingly enough, I'm currently having an EGR issue. Service Engine Light came on after my headers were installed, error code 32 (EGR). Never had the issue prior. I have a more in depth thread in the ECM forum.

Any thoughts on the strange engine issue?

That Sky Guy

Me, too! Have an update for you.

There's wiggle/play in that whole assembly. Nothing falls off or is detached, but it does have wiggle room. Should that be the case? Would that contribute to the issue? If so, how can I fix it?

Mark RWC

The small plastic tube with rubber piece that has the screw in it is supposed to go back under the plenum and connect to the egr solenoid via a T fitting. With the hood open there a label showing the vacuum hose diagram It is toward the passengers side of the open hood at about eye level.

Not having the vacuum hoses to the EGR will cause the error code and did on my friends 89 V6. I have an 88 V6 and it is very similar to 89 except no anti theft system.

That Sky Guy

If I have headers installed, will that change the location of the hook up/vacuum line?

Mark RWC

Headers being installed may when the vacuum line was disconnected. If Arizona has smog test you will fail unless the vacuum lines are hooked as per the diagram on the hood.
My friend 89 threw ERG CODES after a shop had done work on the exhaust manifold and left a vacuum hose to EGR DISCONNECTED.

Will try and attach photos so you can see what your vacuum hoses connect to.

That Sky Guy

I'll definitely have to give it a look when I have the time. Thanks for your help!

NoEmissions84TA

iTrader: (1)

GM got smart at some point regarding EGR being disconnected or bypassed.
They programmed the ECM to look to see if there was actually a change in the exhaust after the EGR was triggered. If not, then you get a check engine light.
My 1995 GMC truck is set up that way. I have a BB in the vacuum line going to the EGR valve. I get the CE light going down the highway. But I know what it is. When I go to emissions, I just remove the BB.

That Sky Guy

I am unsure if my '89 would be set up that way. I am definitely going to make an effort to investigate the vacuum tubes first, and then I'll ensure to inspect the rest of the system. Thank you!

OrangeBird

iTrader: (1)

The "wiggle room" is a kinda subjective quantity , and honestly I can't make an assessment based on that description .


And now my friend , it appears we're gonna have to have "the talk" ...

No , not THAT talk , the one about car modifications .

The computer in your car is looking to see that each and every one of it's "input and output devices" are in working order . In all cases , it'll "know" if an electrical device is unplugged or missing (like your possibly now missing oxygen sensor because of the header install ? WAS the O2 sensor preserved in it's functioning when the headers were installed ?) and when certain modifications are made (elimination of EGR , anyone ?) the computer will substitute a fixed value in place of the missing parameter and a certain amount of the system's built in "self tuning" ability is lost . This of course triggers the check engine light . Now , since you know things have been modified (the screw in the vacuum line being one Hell of a tipoff that at least one of possibly a few somethings are missing) there is no point in chasing a check engine light on a car that had had , for example , it's EGR removed .

All proper modifications are done with a deliberate plan as to not only make the modification itself , but also how to make the modification work well with all the other interrelating systems . "I'm gonna just rip out all that thar EEemissions crap and then it'll be a RACECAR" , this idiot mentality has likely ruined more of these cars than accidents & rust combined .

You have two paths forward here .

Path #1 ; put everything , and I mean EVERYTHING , back to it's factory configuration and the check engine light will no longer be a problem .

Path #2 ; build a killer V6 like some of the guys here in the V6 forum do , learn how to tune electronically through the new computer that your new killer V6 is gonna require , and then again the check engine light will no longer be a problem . PS , this path MUST be a self taken one , any notions of paying someone to totally build you a killer V6 from the ground up will be very quickly slain when you see the pricetag for such labor .

I wish you well on your journey ...

Tootie Pang

iTrader: (2)

Basically the ECU has a heat sensor just passed the EGR valve. If it calls for EGR and the heat sensor does not come back hot (meaning hot exhaust gases are not flowing) you will eventually get an EGR code since something is not working to cause the EGR valve to open when called.

I would just hook it back up and see what happens. It's not going to hurt anything.

Mark RWC

After pulling the plenum on my 88 firebird this weekend I realized the hose with the screw in it looks the right length to go to the fPR or fuel pressure regulator under the plenum. There are two plastic vacuum tubes that connect to the rubber block at the front of the plenum. One goes to the fuel pressure regulator and the other to the EGR solenoid or vacuum switch as it is referred to in the emissions diagram on the under side of the hood.