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85 Engine project: The break-in phase

Ken

Gone but not forgotten
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Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Oh man, I like the '67! :cool

attachment.php
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
We all have one we wish we kept, that was it.....the 67 Camaro behind it was an 67 SS 4sp. Friend of mine , in a parade going to a local car show.
 
Joined
Nov 15, 2003
Messages
160
Location
pennsylvania
Corvette
stroked 85 blkrose coupe
maxrevs85 said:
Which way do you turn the adjuster on the reg and is that a vac port coming off the side of it? Also I have the distrib turned so the cap connectors are counter cockwise toward the fire wall. Car is idler high at 6* advanced .Tps is at .64. HELP
this wil help you out. might be a little late though

How to Adjust your Early C4 TPS and Idle Speed
by Lars Grimsrud
SVE Automotive Restoration
Musclecar, Collector & Exotic Auto Repair & Restoration
Broomfield, CO Rev. New 6-15-00
This tech paper will discuss the procedure for correct adjustment of the Minimum Idle Speed and for adjustment of the Throttle Position Switch (TPS) on the early C4 Corvette TPI systems. These steps apply specifically to the 1985 model year, and in general to other years. Later model years do not have adjustable TPS's.
General
Idle speed and off-idle throttle response on the early TPI systems is determined by correct adjustment of the minimum idle speed screw combined with a correct setting of the TPS. I've seen many of these cars that have had their idle speed "corrected" by well-intentioned mechanics and owners by simply screwing the minimum idle speed screw in a few turns. This really messes up the settings, and will not make your car perform properly. Doing a correct setup of the TPS is one of the easiest ways to make your car feel and respond better. To maximize the benefit of this procedure, I recommend that you first remove your Throttle Body (TB), disassemble it (it's incredible easy - there are a total of about 5 pieces in it…), clean the TB up really good with some spray carb cleaner, and put it back together. A nice clean TB will really put an edge on the performance improvement you will get by doing this procedure.
The Service Manual has instructions for doing these operations, but the directions are scattered through several sections of the Manual. Here is the complete, step-by-step process for doing this (not including TB rebuild). All specs and steps are taken directly from the Manual (all 3 different sections), and this process is absolutely correct.
Tools & Equipment
You will need the following tools and equipment:
1. A set of Torx wrenches. You can buy a complete set in a nice, genuine plastic pouch at Sears.
2. A good digital voltmeter that will read voltages less than 1 volt.
3. A paper clip.
4. A small screwdriver.
Procedure
There are two electrical components on the TB that you will be working with: The TPS and the Idle Air Control Valve (IAC). Make sure that the connectors for these two components are easily accessible and that you can easily disconnect the IAC.
You will also be playing with the diagnostic connector under the dash. Remove the cover (if it's still in place). Bend your paper clip into a "U" shape. You will be playing with the two top right hand terminals ("A" and "B") in the connector.
First step is to set the minimum idle speed. If nobody has messed with this on your car before, the set screw will be covered by a pressed-in plug. It's located on the driver's side of the TB. Remove this plug if it's there.
With the IAC connected and the ignition "OFF," stick the paper clip into the diagnostic connector from "A" to "B." This grounds the diagnostic lead.
Turn the ignition to the "ON" position without starting the engine. Wait 30 seconds.
Now, with the ignition still in the "ON" position, disconnect the IAC connector at the IAC.
Remove the paper clip from the diagnostic connector.
Start the engine and allow it to reach normal operating temperature. The idle speed will probably be really low, and you may have to coax the engine a bit with the gas pedal to keep it running for a while.
If your car is an automatic, set the parking brake and put the transmission in "DRIVE." If your car is a manual, leave it in neutral.
Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.
Shut off the engine and re-connect the IAC.
That's it for idle speed. Now on to the TPS.
There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires. You can either buy a special harness connector that breaks these wires out (from Mid America), or gently pierce the insulation of the wires with the pointy prongs on your volt meter. You can also stick a paper clip into each of the two top locations of the connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.
Turn the ignition to the "ON" position without starting the engine.
Loosen the TPS Torx adjustment screws.
Set your volt meter to a low scale DC volt setting that will accurately read less than 1 volt.
Measure the voltage between the two top TPS wires.
Adjust the TPS by rotating its position until you get a reading of .54 volts.
Tighten the Torx screws and recheck the voltage. Re-adjust if necessary to make sure voltage is right at .54.
Turn the ignition "OFF."
You are now in perfect adjustment on idle speed and TPS output. Start the engine. It may take a few seconds for the car to "catch on" to its new settings.
Questions, Comments & Technical Assistance
If you have questions or comments regarding this article, or if you notice any errors that need to be corrected (which is quite possible since I'm writing this from memory…), please feel free to drop me an e-mail. Also, if you need any technical assistance or advice regarding this process, or other maintenance issues, feel free to contact me:
lars.grimsrud@lmco.com
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Hi Plumcrazy, I cant recall for sure , but I think I did use this procedure in the beginning, but its been awhile and I appreciate the feedback. As a matter of fact I plan on revisiting this as soon as I check a couple others things.You got me thinking again .
The idle speed that was written kinda made me chuckle though. I'm not sure with the cam and mods I have that its abtainable (450). It likes to be about 700. Thanks for printing that I will use it soon as a referance.
BTW, any feedback is accepted and considered. I WILL WHIP THIS THING!! :)
Thanks,
Dave
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Man, you guys really had me confused there for a minute. :crazy

Dave, you asked the question a little over two years ago - almost to the day!
maxrevs85 Adjusting fuel pressure and... 07-07-02, 08:12 AM

The dates were almost identical; that's why I was confused. :L

It's right below this post if you view it in the "threaded mode." I answered you in post #12 I believe it was. ;)
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
time for a change....kinda fed up

This project started over 2 years ago and i have realy never been satisfied with it. The mods tothe chassis are great . The motor is a great piece. The problem is the fuel injection. I'm just plane fed up with it. I can't get the bugs out of it , its inconsistant and it wants me to throw moey at it to add this new this and new that and go to this kind of control system and that. I didnt come from the computor age and maybe that the problem, or should have left well enough alone and went with mild mods. I've always been a hotrodder at heart and this aint getting it. Mayebe I should have bought a pre -putor car but I like the improvements of the c4 over the earlier models. I cant afford the mid 60's vettes that are my favorite . Sooo , I think the car is going to a carb setup. I'm thinking about gutting the exsisting wiring and guages and getting back to basics. It wont have air , it'll loose about 200 to 300 pounds and is going to end up being a hotrod with attitude. no air , no frills ....push button starter , roll bar and maybe racing seats. The dash will get modified and will be all business. kinda like a race car for the streets. The biggest challenge will get the wiring right and keep the main fuctions. Lights , blinkers horn, power windows and heater defroster. maybe its crazy , but I think its what I really want . Then somday I will have a pure stock vette to drive for pleasure and leave it that way. One for roddin , one for pleasure.
Any ideas on this venture are welcome and appreciated....Also , in the near future I will have a complete TPIS manifold, runners, plenum and TB for sale with extras.
I have a Torqer 11 manifold I might use and an 830 cfm 4150. Also i might try a dual plane . My engine builder wants to experiment with both at his cost. I think the sigls plane will work with the manual , but i think the dual plane will have less driveability problems. I will be using a MSD ditributor.

383 stroker.all eagle
6" rods Oliver billet splayed main caps
AFR 190 full ported heads
488 lift cam with 1.5 roller rockers
7qrt pan
balanced etc.
forgeed pistons
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Don't give up Dave, and don't give up on fuel injection yet either. I finally got mine to the point where it's behaving nice around town, while still kicking ass whenever it gets a chance to strut its stuff. :_rock

Your project is beginning to sound a lot like mine in that it's only a step or two away from being an all-out racecar. :bu

Hang in there man; it'll all come together soon. :CAC
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
Dave, I know your pain, and mine was relieved by a guy who could do a proper, custom chip, for MY engine; MY mods. I see guys who think they can do a few 'minor' things with ECM cars and have them run properly. Been there; doesn't work too well, and it is amazing how minor the things are that cause the smooth runner; to not be.

But, as we have seen, snake oil and such continues to sell.

Which do you think is cheaper; spending all that time and cash on rewiring and re-doing the plastic dash, or getting a proper chip?

My guess is the latter. :w
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
My .02..... Don't do it!


You will kill this car and turn it into nothing but a wanna be race car, that isn't a very good race car, or a good street car.

"IF" you are going this route first consider what you want to do with the car. For example SCCA, NHRA competition, etc. That way you build your cage and select your engine mods, etc. in such a way the car is legal to compete and still drive on the street. Otherwise you will have a raw highly modified C4 that is not legal to race anywhere, and with no a/c and a roll bar to climb over to get in....it won't be much fun on the street. Now a days, putting a/c on a car (especially an old car), is as cool as having 500 hp. Once you make those cuts that car will never return.

You don't have to get exotic, but I would consider a stand alone NEW aftermarket computer and harness at a minimum. The 85 Computer is too slow and won't compensate for all the mods very well.
 

maxrevs85

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Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Thanks a heap guys ....This is just what I needed. I feel like a quiter when it comes to giving up on the TPI.....Gotta leave for work . I will post some questions and maybe I can get thru this....

ttyl.....Dave
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Well guys, I'm going to dig in a little more and see what I can do to keep the TPI. First I'm going to pull the complete TPI and manifold and check for vacuum leaks.(high idle problem) and replace all the gaskets . Once confirmed to be ok , I will look in to a different computer and harness. Ken I see you have a 90ECM for sale and I believe a speed density and a harness .Is this what I need and what is involved ? I dont think my guages will work with this change will they ?
Chris I appreciate your input and you also Whale Pirot. I respect your experience with these set ups. And Ken it goes without saying what you have been thru. Man i just want to get this thing right. Thanks, Dave
More to come.;)
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
A vacuum leak was one of my problems - a major problem. Once I fixed that the driveability was very much improved, as to be expected. :eyerole

As for which computer is best, I'll have to defer on that question. I do have both computers, which are for sale, as well as the chips and the street rod wiring harness. I don't know how much good the chips will do anybody though. ;shrug

The gauge change-over for me was a personal preference. ;)

Hang in there Dave, you'll get there yet.
 

69MyWay

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Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
maxrevs85 said:
Well guys, I'm going to dig in a little more and see what I can do to keep the TPI. First I'm going to pull the complete TPI and manifold and check for vacuum leaks.(high idle problem) and replace all the gaskets . Once confirmed to be ok , I will look in to a different computer and harness. Ken I see you have a 90ECM for sale and I believe a speed density and a harness .Is this what I need and what is involved ? I dont think my guages will work with this change will they ?
Chris I appreciate your input and you also Whale Pirot. I respect your experience with these set ups. And Ken it goes without saying what you have been thru. Man i just want to get this thing right. Thanks, Dave
More to come.;)
There is no reason why you can't keep the stock gauges and overlay a new or replacement wireharness. It will require a couple of jumpers here and there, but is easy enough to figure out.

I remember when Ken had the 90 harness in his 87. His speedo would not work. Can't remember on the tach. It could have been fixed. The problem was the feed going to the speedo was not reconnected to the feed coming from the new ecm. If there was a difference in pulse speed between the two, dakota digital has that covered with a dip switch panel that can reset the calibration. Nothing to panic over right now.

I didn't go back and read the whole post with all the mods, but here are some guesses on what to do.

1. EGR? Do you still have one? Is it working? Did you simply cap it off. If you just capped it off, this is a big no-no on a stock 85 computer harness system. I would suggest reinstalling it and making sure it works properly.

2. Fuel pressure? Is you pump good? Regulator? Are you trying to cram too much fuel down the engine?

3. O2 sensor? Are you running a HEATED O2 (Three wire)? The stock one is a one wire. It is a neat and simple conversion to go to a 3. It makes a HUGE difference in getting the engine to warm up quick and stay in closed loop.

4. Timing/knock sensor. I was having a TERRIBLE time getting my 85 383 to run right last year. After replacing almost every sensor on the car I found out the knock was bad. Believe it or not, it was killing virtually every aspect of the car. The scanner I was using was not properly reading 1985 data (I find out after the fact). Switched to a snap on scanner and located the freaky fault in the knock. The one on the engine looked fine. I think it had been overtightened upon installation. Long story short, the car ran like the wind afterwards.

5. SIMPLE MECHANICAL CHECK. Are your rocker arms too tight? It is a common problem. It will load the car up at idle and cause it to surge and or try to stall, etc.

Other than the 85 Computer being a bit slow on processing, the car should still be able to be tuned and run well overall. For maximizing the kick, you really need to look into replacing it. But for now, check these items out as well as any potential vacuum leaks.
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Ken , I remember your vac leak problem and went back and checked out the photos. I am real suspect on this since the high idle problem has been from day one.

To bring you up to speed on the mods Chris I'll list them.
Engine :30 over , 375" crank , 6" rods. balanced. Billet splayed main caps, Oliver.
Heads: AFR 190's full port and polish
Manifold: ported TPIS Big Mouth
Big tube runners , TPIS
Ported plenum
Throttle body: TPIS 58mm
cam: Comp. 224/230 - 488 lift hyd. flat tappet
Roller rockers 1.5
Accel 24lb injectors
Air pump eliminater
TPIS coated full length headers gutted cat and flowmasters.
There are no emission and the egr has been capped and the cold strart injector removed and capped. Has adjustible fuel reg @ about 45 psi .I had a TPIS stage v chip burned for this settup after much discussion with them.
The chip was awesome . I have to admit that i might just be feeling alittle frustrated do to my ignorance about these systems . The high idle , around 1600rpm is the main problem. The car runs strong . sometimes better at times then other times. One of the last times I drove it on a cool eve in ran so strong I was having truoble keeping it hooked up thru the first 3 gears . It wanted to be sideways . It actually scared me a little ( didnt let up though).
Oh yea on the EGR , I(when ordering the chip) told TPIS that I had no egr and let them know all the particulars on the engine. It actually was very close to one of there own.
Anyway , like I said . I'll get the probable vac leak squared awawy and go from there. I do mhave a scanner and it didnt show any fuel air mix problems other than maybe a little rich. But I would expect that on an HP motor.
As far as the guages go , like Ken i prefer the analogs and the tach would never keep up . Always about 2000rpms behind.:D
I'm sure there'll be more questions and I appreciate your interest.
Thanks again,
Dave
No heated o2 and I think the knock senser needs to be replaced .The plastic is broken.
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Welllllllll, here we go again.:D ...Its time once again folks to continue the quest for my ultimate Hot rod. :W

Today I ordered all new sensers and a DUI distributer, new fuel pump,heated o2 and new Bosch 30# injectors from TPIS. Also thanks to Ken I aquired a 90 ecm speed density and harness and all the stereo equip. Thanks Ken:upthumbs .
I have to remove the manifold and replace the gaskets do to a suspect vaccum leak. AAAND I oredered a new Richmond ROD 6 speed trans . I am geeked:D :D . Other plans are all new gages , wheels and tires. I will most likely be building my own exhaust, front to rear since I now have the equipment to do it and I think it would be cool to add my own touch to it. I,m also gonna take a look at a new brake system.
So, I will be busy again. I will try and keep progress reports as it moves along. Maybe next year, CRUISEFEST!!:w
Dave
maxrevs85
MAXIMUM REVOLUTION:lou
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Update- 7/15/05

Since the last update I decided to go with the MIni-ram from TPIS . I just recieved it along with all the new sensers and injectors etc. Also the Richmond ROD 6-speed arrived. Yesterday I removed the the 4+3 and associated parts and pulled the motor. I plan to change some wiring and tidy up the engine compartment. I will be ordering the new Gauges as soon as I figure out which ones I want electric or mechanical. The new ZR1 wheels came in too. So, plenty to do . It should help to keep me out of trouble on here too. :eyerole
 

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