After 25 years of faithful service, it seems my Cavalier's throttle body decided to take the summer off last year. It began running poorly, would start hard, and putter under load as if there was a vacuum leak (there isn't). I also had issues with it hesitating under load, even with a tune up and new fuel filter. It sat for the winter and I finally backed it out of the garage the other day to troubleshoot. I plan on replacing the original rubber fuel lines and some other things, but after reading one of Ron Love's old posts on the fuel injector replacement I decided the likely culprit was either a bad fuel pressure regulator or injector, Either way I'd have to pop off the TB. So off came the Rochester 500 series throttle body and off I went to grab some parts. I plan on updating this for folks who haven't dove into this rebuild yet.
It wasn't too hard to remove, just the two fuel lines, the throttle cable, shift cable, and vacuum hoses & electrical connectors. There's only three bolts that hold it onto the intake manifold.
This doesn't look too carboned up so I guess that means all that great BP gas I've been paying extra for has helped. That's what I'm telling myself at least. The first thing I noticed was there was barely a seal on the TB gasket. It came off easily and the gasket material was really crumbly under the metal base. It may just need a gasket replacement and that could fix it. But as long as its off...
The injector, screen, fuel pressure regulator diaphragm, and all gaskets wil be replaced. I also plan on throwing a new IAC valve in it. TPS voltage check and we should be ready to rock & roll.
Speaking of rocks, RockAuto.com had a closeout on gasket sets for the Rochester 500, and injectors from Kemparts. I'll see what happens here, but the prices were so cheap I figured I'd give it a shot and see how they are. I'll update this as I go, and if anyone else has been down this road feel free to chime in with suggestions / advice. Thanks folks!
To be continued...
Daryl, is it the same for an 84 Cav with the 2.0. and 5 spd. Mine runs like crap until it warms up. Changed plugs wires and fuel filter and it has been like this for years but seems to be getting worse.
John I would say yes.I rebuilt my tbi couple years back and did a new injector,full kit,and harness was replace that connects to the injector.I would have to surf back in the post to find my write up on the work I did to let u see the info,not sure if I did pics but do have them.
Thanks for updating your tbi post from a few years back, Ron. That's what helped me track down some valuable info. I always appreciate your tech knowledge and writeups. I figured with my new phone I can take pictures while I'm working and maybe help document this stuff. If nothing else it will help me put it all back together! Plus its nice to have some more knowledge for us all to draw upon for our cars. Thanks again.
Anytime! It was a few minutes to find it here and revive.I did go dig thru my old parts specific to the tbi to make sure I listed the part #s and so forth being we have a newer group on here who may not have the info to get them started on fixing stuff like this.
FedEx came today and brought me some goodies...
Complete rebuild kit includes all gaskets, and a fuel pressure regulator diaphragm. Looks like lots of small springs & stuff to lose if I screw up.
Here's the new injector to feed the beast.
And I'm putting a new IAC valve in there since mine is carboned up. I could clean it, but while its out I have access to it so what the heck.
I'll get started this week and document stuff. I hope to have this puppy running by Saturday so I can take the convertible to a cruise-in at the riverfront. We'll see what happens. Wish me luck!
Good fun for you.Always nice to get a package full of parts for the old cav.I would love to start on my cav,however tieing up some other odd jobs first,before tearing into the front end work,resto project.
Part Two: Disassembly
I got all my parts in for the TB rebuild, and after dinner I was feeling anxious to tear into this project, so I started carefully removing parts and documenting them as best I could to help me later on. Here goes nothing.
I started with removing the 5 (T20) screws that held the injector & pressure regulator assembly to the base plate. This came off nicely, and I documented the areas that had gaskets in place as you'll see.
Next, I had to remove the return fuel line fitting before the base plate could come out from the throttle body. There's a small washer that sits in between this fitting and the base plate, so be careful to keep track of it once the fitting is removed.
Then there's 3 (T20) screws that hold everything down to the throttle body itself. Remove those, and everything is free.
With this out, and a gentle pry with a flat blade screwdriver, the lone injector is able to pop out. Its original GM, so its definately due for a cleaning & flow test. I'm just throwing in a reconditioned one to save money and time. I will hold onto this original though.
I layed everything out, separated each gasket, and snapped a picture to help with reassembly. Most gaskets came off perfectly, and I was suprised at how easily this went.
Now I was able to remove the TPS, IAC valve, and work towards the fuel pressure regulator assembly. There's 4 (T15) screws that hold this assembly to the bottom of the injector housing.
Once Inside you'll find the spring, and regulator diaphragm. Mine was VERY thin and stretched out. I'm not sure how much slack there should be in the rubber, but mine felt thinner in the middle near the metal bushing than anywhere else. Here it is in all its glory...
And that's where she sits tonight. I hope to start cleaning and reassembling the whole enchilada in the A.M. so I'll rest up, and let you know how it goes tomorrow. If the weather holds out, we may even get a chance to drive her around a bit this Memorial Day weekend...but I don't want to push it.
Cheers.
JOHN MASSON wrote:Daryl, is it the same for an 84 Cav with the 2.0. and 5 spd. Mine runs like crap until it warms up. Changed plugs wires and fuel filter and it has been like this for years but seems to be getting worse.
John, sorry to leave you hanging. Ron answered your question, and I agree I think its the exact same TBI setup. I believe most Cavaliers got EFI beginning in '84, and the Rochester 500 series was what they ran on the OHV motors. Ron's other post has more detailed information on units and the history breakdown by model year.
Part Three: Cleaning & Reassembly
I know there's lots of different ways to degrease fuel system parts, and asking 3 different people will get you 3 different answers. That's why I decided to trust my instinct and go with the most nasty-smelling, carcinogenic, non-EPA friendly solvent made by Berryman's. The legendary B-9 Chem Dip. Its good with whiskey, too.
This stuff is great for removing nasty carburator grime and throttle body goo, and mine has it. After removing all the plastic parts and anything I didn't want to disolve, into the pool they went for 10 minutes each. Here was my workbench..
Following the directions, I poured a tub of hot water (blue tub above) so I could rinse the Chem-Dip off the parts after cleaning. A little touch-up with a toothbrush and everything came out beautifully. All the plated parts remained intact, which is a good thing since this stuff can eat them if left to soak for too long. Here's a shot of all the cleaned parts after I blew them dry with an air gun.
*Now I layed parts out with the new gaskets and began throwing it all back together. You'll want to make sure your fuel pressure diaphragm goes back in the same orientation as it came out. Here is a new one next to a used one. You can see where it baloons out. Its worse on the other side.
Then its time to reinstall the spring, diaphragm, and fuel meter & base assembly. Here's a trick: Use a kit that provides dowels like these so you get everything lined up nice & straight. If you don't have them, you could use fine threaded dowel rod...but it makes life easier. Compress the spring and get the two T15 corner screws on opposite corners first. The kit provided Loctite threadlock #262 and said to use it on all screws. So I'm doing that here.
Here's the finished product...
*Moving right along, we start on the injector. This is pretty simple, and installs with the little metal tab in the recessed notch inside the injector housing. A filter screen & o-ring go on the bottom of the injector, while a metal washer and larger rubber o-ring are installed in the housing up top. I used a little lithium grease on the o-rings to make life easier. The injector then is pressed into place.
Using the dowels again, I lined up the injector housing cover with the holes in the two gaskets underneath...and installed the screws. Remember the two short ones go on the sides next to the injector, while the three long ones are to behind it.
Lastly, the three larger T25 screws and a new gasket help to complete the reassembly. The entire assembly now attaches back to the throttle body as a unit. They have a torque spec...but I snugged mine down until it felt right. Not real precise!
Now its time to reinstall the TPS, IAC, return fuel line fitting, and throttle cable bushings. I made up a new one since my original nylon one was stretched beyond belief. Here's the finished product.
And here is what it looks like back on the car. Its the nicest looking engine component now! Ready to carry us many happy miles....
nice. Now the important question... how does she run??
"85 raw horsepower"
lol, glad it runs. sounds really good.
Thanks, I appreciate it. I reused my original fuel injector since the replacement one wouldn't fire at all. Not sure what happened there, but I'll send it back for another. But everything went back together nicely and I'm proud I didn't lose any small pieces. That's usually my thing.
Cheers,
thanks for the informative post
I stumbled across while troubleshooting my 94 4.3L TBI sonoma. For what it's worth, I did a full clean and rebuild with new injectors like you. And I replaced the injectors with Delphi parts from Napa, they look just like the one you show. My truck ran like total dog crap, it would cycle between 1800 rpm surges and 200 rpm practically stalling. It was obviously rich from the exhaust odor and I was getting IAC counts way outside normal.
I spent several hours chasing every possible sensor and control issue, I have a scanner and got all kinds of confusing data but nothing obvious enough to identify a problem. Then I replaced the factory injectors and it runs great (better than before with all the other stuff I cleaned or replaced). Either the parts I was sold are the wrong flow rate or they are just total junk.
Did your car run at all with the new one you show?
Hi James, sounds very familiar to what I had dealt with. Glad you got your S10 running again. Those 4.3's are GREAT motors!
To answer your question about the injector, I FINALLY got my replacement shipped from Rock Auto yesterday. They apparently send returns via parcel post so it was a while before it arrived. I will plop it in this weekend sometime and report back. The 'new' injector would not even fire. It was in there in the right place, but was not flowing fuel at all. The fuel pump would just keep cycling and and the car would crank...but no fuel was spraying. Then I reinstalled the original one and it ran (just as it did before) with hesitation, and surging. The mist isn't a fine one, I can actually see it dribbling down the barrel, so I'm pretty sure its the injector...but at least it ran.
I'll report back once I get time to swap the new injector. Otherwise the original one is being sent out for ultrasonic cleaning.
Yeah the fine mist is what you want!My old one was let's say dieing dripping some,mist was shotty.Def kills the mpg,performance aspects.
I can't believe how many problems there are with parts that are "brand new". I had a brand new optispark distributor fail on my Camaro. It never made it off the ramps. The problem is it was 2 hours of labor and 2 gallons of antifreeze later...
I also had a "brand new fail" with the sending unti for the oil pressure on my 84.
I forgot to say "Sweet Post Daryl" - very detailed.
Always some drama with parts.I am obtaining some parts myself.
Paul94Z28 wrote:I can't believe how many problems there are with parts that are "brand new". I had a brand new optispark distributor fail on my Camaro. It never made it off the ramps. The problem is it was 2 hours of labor and 2 gallons of antifreeze later...
I also had a "brand new fail" with the sending unti for the oil pressure on my 84.
I'm guessing they say Made in China. The quality of alot of items these days, not just auto parts, seems to have gone downhill lately. For example I bought a Holmes window fan 10yrs ago and it still works like new. I've never had a single problem with it just clean it once every few months. We bought another Holmes window fan last year and a week later the one fan in it stopped and started on it's own and started smelling burnt. After returning it I checked that model # out online and found maybe 1 good review out of 20 bad ones on various store sites. Another example my dad bought an Apex dvd player back in early 2000's for $35 it finally bit the dust in 2009, he bought a Sony model for $60 tor replace it, two weeks after the "90 day warranty" the Sony wouldn't power on.
Pushing this post up front.I am getting some information together to do another video with a TBI.I have researched the parts and might this wk get a few new parts to prepare for my extra tbi and I am going different on soaking said part I will elaborate later once I try it and this is just my start.Idk just doing several projects and working on the easier things before I really dig into this loco style.Lawn mower work this wk grass is getting green,so car stuff kinda has to wait plus cost of parts.
After reading through this, it makes me wonder about mine.
The Hawk is such a dog in the cold weather until it fully warms up, I can't single out any one thing that would make it run so bad in the cold, but be fine any other time. During the winter, I dread starting it in the morning, and when the temperature stays below freezing all day, it's not the most fun thing to deal with when leaving work. It shakes a bunch and acts like a tired brat when I press the gas until full warmup.
Could it be time for a gasket in the TBI?
Mine was the same way (shake and stall) with the old motor and I do think that the TBI was the problem as it was 27 years old and had 167K on it. I am going to rebuild the TBI on the old block now that it is out of the car and if I screw it up I can always put the other one back in.
