Siggie88

I just joined this forum and I did that because this forum is great.

I would appreciate some guidance on a problem -- it is surely a newbie question.

I own a 1988 Corvette with a 1227165 ECM. I just learned how to scan using an ALDL cable and ALDL software.

The car's engine has been thoroughly gone through, but never tuned (=ECM parameters were changed). It is bone stock otherwise. The problem is this: The 1988 Corvette is designed to idle at a very high speed -- up to 1100 RPM until coolant temp rises. Putting the car in gear at that idle speed jars the drivetrain and it results in poor driveability.

Is it possible to edit/reprogram the PROM to calm down the idle on a 1988 TPI engine? I read that prior to 1990 you can't "tune" a Corvette engine.

Thanks for any responses in advance.

Vanilla Ice

Yes you can. Look into Prom burning. At the top of this very forum are many FAQs concerning tuning.

Orr89RocZ

iTrader: (20)

Yes as stated above but a high idle could be too much base timing, or throttle screw is to far opened as well

I agree start up when cold is designed to idle higher. You can command lower or wait a few min before driving to let it calm down

Siggie88

Thanks -- I hope it didn't come across as a lazy question. I wanted to know if it was possible to do at all on the 88 Corvette before learning how to do it. Like I said, this forum is great. My previous information was apparently wrong. Thanks a million!

Siggie88

According to my information (Heh! Heh!) the car is normal when running at that idle speed. After CTS approaches 180F it calms down and idles at ~600RPM. Ihave a long list of adjustments and part changes (including every sensor except the knock sensor -- and I do mean every sensor, fuel pump, regulator, vacuum hose and on and on).

I set base timing to 6BTDC and even moved it around in experiments. Seems like Corvettes love to idle while cold at those high speeds. I must correct this.

Vanilla Ice

If it's that jarring in a stock car/tune there's a mechanical issue and I disagree with changing the tune to hide the issue. OEM set up that speed at that ECT and it shouldn't be an issue. Maybe there's too much play in the drivetrain?

Orr89RocZ

iTrader: (20)

If its a loud bang jarring type sound to go with the strong lurch forward or reverse depending what gear it could be a tranny mount or engine mount. Or maybe ujoints but i havent experienced that. On fbodies a bad torque arm mount could do it but you dont have that

A stock converter and high idle rpm can be pretty jumpy. My 305 car is the same way at first start. Let off brake in gear and jumps forward. It needs more stall speed

Street Lethal

iTrader: (16)

I'm looking at the bin now and it is showing nowhere near 1100-RPM just prior to 180* for quite awhile. Also, you said your engine eventually settles at 600-RPM when fully warmed up, are you driving a manual transmission? You stated you changed practically every sensor, so just to confirm you changed the IAC sensor, correct? Because it sounds like the IAC is sticking. If changed, then as mentioned above, check behind the fast idle screw on the throttle body to see if the cap was removed because someone might have raised the torx screw a little bit for whatever reason, and this would create a higher than normal idle during Open Loop, but then would settle down when Closed Loop is triggered...

By the way, that isn't Bruce/Caitlyn Jenner in your avatar is it, hard to tell?

Siggie88

That is the inimitable Jennifer Capriati. I chose that avatar because of the mood she conveys and the fact that she was an amazing athlete.

These are great responses and should help some others who have this problem.

A few other pieces of data:

First of all, according to information on the internet (which is always correct ) the 1988 Corvette should idle up to 1100 RPM on cold start. That's what led me to explore tuning that design defect out of my car.

The car is an automatic.

If I need to go to work, i can't wait 3-5 minutes for the car to warm up and settle down. When I put it in gear at anything over 850 RPM, there is no metal clang, bang, or other such noise. It is more like a "thunk" sound accompanied by a lurch. It seems very normal because the car is idling too fast. My worry is that long term, that will do damage. In a parking lot, or at a crosswalk, I have to really hold brake because the car will take off. I can do 10-20 MPH with the car in gear idling. It's a bad design.

I own the FSM and have meticulously followed the base idle adjustment procedure. I've even tried setting below and above 450 RPM to see if the problem goes away.

The IAC was replaced and the printle was adjusted. 40 counts according to the latest scan. In the year I've owned this car and fixed PO issues, this is just some of the engine work that I've done (I've also had a Corvette mechanic check my work):

New Delphi injectors from Fuel Injector Connection (leak tested also)
Cleaned fuel rail
Tried 2 new fuel pumps -- including an AC Delco, new relay.
Tried 2 fuel pressure regulators
MAF sensor -- 2 new units tried, Of course both relays were replaced
New plugs (Iridium) wires, cap/rotor, ignition module, coil
Tried 2 coolant sensors
New manifold temp sensor
Meticulously cleaned (twice) plenum and throttle body
Vacuum leak check 3 times (including smoke test)
New intake manifold gasket (see leak check)
All new vacuum lines
Base timing multiple times including experiments with various settings
Of course, all filters replaced
New old stock cold start valve (also leak tested)
New fan switch
New EGR (leak tested also)
New thermostat, radiator
Compression check (>170lbs)
New O2 sensor
Tried two new TPS's -- Set at 0.54V (latest scan shows some error - 0.57V)
New ECU (remanufactured)
Checked harnesses/wiring
Dozens of scans -- no codes currently
New EGR temp sensor

Of course, this work was not all motivated by the idle behavior. I've restored (and painted) the car. (don't get me started on the interior work i did ) Some of the item replacements were done multiple times because of bad parts (especially fuel pump related parts).

Throughout all of this, the high idle behavior stays constant.

I could change out the IAC again (3rd IAC) but can you confirm that the idle should be lower? I'm learning the subject and am not sure what BIN you're referring to.

(sorry for the long post)

One other piece of data: The PO did adjust the idle screw, and as described above, I reset base idle multiple times. My mechanic pointed out that the screw seems to screwed in much deeper than he's seen on other cars. But, it is adjusted to a 450 RPM base idle. I even tried to back it off and the car won't hold idle if I try to retract it.

Street Lethal

iTrader: (16)

I guess I used to watch tennis for a whole other reason, Anna Kournikova for one (holding back from posting a picture of her lol). When I was a little kid it was Sampras and Agassi bonking heads, loved when those two went at it. They made tennis fun to watch...

Aside from the smoke test, have your mechanic run another vacuum check during idle, if its' reading lower than a normal stock reading you more than likely have a vacuum leak somewhere, in turn raising your idle RPM during Open Loop, but then being corrected for during Closed Loop. The IAC steps during idle will confirm everything...

Edit: I see you edited your post while I was typing mine; 40 steps for the IAC is a little too much, it needs to be closer to 25 steps during idle. Your said your running new injectors, what size are they? Are you running 43.5psi of fuel pressure with the vacuum line on, or off? Where is your base timing, 6*...?

Street Lethal

iTrader: (16)

Hmm, let me retract that, $32B is actually calling for 65 steps at 176* degrees, as well as 575-RPM with an auto. Back off the fast idle screw until you see 65 steps during idle, then make sure your Base timing matches Initial timing at 6* with the EST disconnected. Also confirm 43.5 fuel pressure with the vacuum line disconnected, as well as 23# injectors...

Siggie88

Anna? Google Andrea Petkovic. You'll find new reasons to watch.

Well, in the Bay Area of California, there are three mechanics who would work on a 28 year old Corvette and know them all. And they know my credit card number.

As of now, I am, as augmented by this august forum, my own mechanic..

As mentioned above, the car was leak tested thoroughly. Vacuum leaks were my first thought. I even plugged off vacuum sources. No change. I have a vacuum gauge and could measure, but I'm not confident I'd know how to use the data. In fact, what should the value (psi) at what idle speed?

FIC stated that they were stock 22lb replacements. No other information was available.

Base timing is 6 BTDC.

I regularly measure fuel pressure and it is 38-40. I'm not sure what you mean by measuring with the vacuum hose off.... BTW, the car takes 5 long starting bursts to start in the morning. After 3 fuel pumps (two from FIC), it still does not hold fuel pressure. Clamping the fuel pump line arrests the pressure drop. I have an external fuel check valve on the way from Jegs this week that will hopefully solve that problem. C4 Corvettes are notorious for fuel pumps with bad check valves (that, according to my experience and comments made to me).

My understanding is that there is no preferred value for IAC counts. Any value from 20 to 144 is valid. The ECM resets the IAC each shutdown anyway. If, I wanted to reduce to 25 from 40, is that a printle adjustment?

Siggie88

Here we are. At the edge of my understanding of tuning. This must be how James T. Kirk feels when he enters the neutral zone.

On my other PC, right now, there is TunerRT installed. I opened it up twice and could not fathom how to use it. There was no documentation on how to use it. Instead I used WinALDL (that mysteriously stopped being able to log data today). My action item is to read the links pointed out to me to learn how to use this program.

It sounds as though this tool will make things easier. If I can perform an idle speed adjustment as you've described, I'll never go back to the old FSM procedure.

What I need to learn:

It sounds like a BIN is simply a file with a group of engine operating parameters that are intended to match a specific engine/chassis and tuneup. Amongst all of the "BINs" how can I be sure of which one to use? Do I need to read the ECM placard and match up numbers?

Which vacuum hose must be disconnected?

Can this program actually display timing? That would be a great benefit.

This is incredibly helpful. And educational.

Vanilla Ice

Basic Tuner pro setup info https://www.thirdgen.org/forums/diy-...ml#post6020869
More questions you will probably have are answered just above this post too.

Siggie88

By the way, this is the patient. Her name is Peggy. She thanks you all.

Street Lethal

iTrader: (16)

Very nice, I miss my last C4 Corvette. Eyeing a ZR1 for next Spring...

Siggie88

I'll be honest, the engine work I described was about 30% of the work I've done, from rebuilding the sport seats, fitting a double din Nav Receiver to bodywork. These niggling problems actually got me to log onto Craigslist on Monday.

My search terms:

For Sale
Cars/Trucks
Year: Blank to 1973
Keyword: Swap Trade

anesthes

iTrader: (12)

Climbing out of a C4 reminds me of 1st day of boot camp.

C6/C7 for me.

-- Joe

Siggie88

What's the connection? I'm fascinated to know how those two are connected. (and thanks for your service).....

anesthes

iTrader: (12)

The shape I'm in now, it requires about the same amount of energy to climb back out of a C4.

If the targa roof isn't off, getting into the thing requires contorting my body in ways that it shouldn't be bent.

Even my C3's are hard to get in and out of, but they don't have that gigantic rocker.


-- Joe

Orr89RocZ

iTrader: (20)

Depending on the bin check for startup spark advance vs coolant vs lv8. There could be 7-9 deg added there that bumps idle rpm when cold

Street Lethal

iTrader: (16)

I think I've plugged the EBL-P4 enough on this website during my time here lol, but here comes another one. Just looking through the limited XDF for $32B, I'm again very impressed with the XDF of the EBL-Flash/EBL-P4, the areas it covers, and the ease of its' navigation...

When Lou came over a few weeks ago to say what's up in his ZR1, as he pulled away I was looking at my wife who was looking out the window, and I gave her this look that I wanted one lol. She gave me a look back as to imply no way lol. When I took that video of him by the store after running into him again, after he pulled away, I again looked at her with that same look, and this time she just smiled. So it looks like a go for next Spring lol. I know I said 90's ZR1, but that was my way of drawing sympathy from her, as if to "settle" for an older ZR1 lol. I wanna get my hands on a newer one. The new ZO6's look like Imported crap to me though, IMO...

anesthes

iTrader: (12)

I know the EBL works on Crossfire C4's, but will it run the alternate dash functions in an 86-89 ?

I didn't care, but some people do. I ran "super" $8D on mine.

I would actually consider another C4, cuz they are cool cars, but I think I'd go with an LT1 car.


-- Joe

Street Lethal

iTrader: (16)

I'm honestly not sure about the dash...

I think it would boil down to three C4's; ZR1, LT4 & B2K. I FOOLISHLY let an early B2K pass me by at only $8000.00, it needed a lot of TLC, and I didn't want to invest in it. I wish I had the opportunity again. The '89 ZR2 "Big Doggie" 454 BBC Corvette was for sale too, but they were asking too much due to the history. Believe it or not nobody even put a bid on it when it went to auction. Kicking myself. But then again, these are all C4's that have sentimental value to us, a lot of the newbies could care less about those cars...

Off topic, but, do you guys see the pic in my avatar? It took me a long time to finally nab that old cartoon in full, one of the, if not the best cartoons ever released by MGM, and youtube pulled it harder than a raped ape. WTF, the damn cartoon used to be played when we were kids throughout the 80's and 90's all the time, these freaking people with their seven minute copyrights. I could understand if it were brand knew, but the damn cartoon is from 1952! Maybe they don't consider it to be politically correct, perhaps? Dunno...

RBob

iTrader: (1)

The EBL Flash ECM supports the driver information center (DIC) on the C4. The EBL P4 does not as it is 8192 baud. This is one reason we suggest the EBL Flash with the Port Mod over the EBL P4 for '85 - '89 TPI setups.

RBob.

anesthes

iTrader: (12)

Sounds like that is what he should do then.

Does the 90-91 C4 have a relationship between the ECM and the BCM? If so, does the EBL P4 support that platform?

-- Joe

MrWillys

If you have Bosch Yellows from FIC you are running lean. Either 0280-155-700 or 0280-155-710 should not be used and do not flow 22 lbs. Change your flowrate to 20 and it will run okay!

Siggie88

I’m back from the woodshed.

I learned a lot.

I’ve built a lot of cars and read a lot about engine theory. This is an area I have never looked into and with what I know now, I think that understanding tuning is essential to understand my car.

I read every page of the sticky that was forwarded by Vanilla Ice (THANK YOU!) – and I read it several times. I started to prepare a one-page diagram that summarizes the information – but stopped as I started to dig into some of the links.

It’s dated.

This is going to take a lot more work to get a complete setup. My first move was to order a PROM eraser. Five minutes at Digikey and it’s apparent that those are becoming obsolete. I visited other sites –

basically, I prepared myself to INVEST in good software and equipment to scan and tune my 1988 C4 and this is going to take more time to find current components for that car.

And this: If (if!) someone wanted a “can’t miss” business idea, writing a definitive book on the subject (=aggregating, updating and cleaning up information on sites like this) would be a “first.” Of course, in the age of entitlement (“Why should I pay for music?”) it might not be a highly profitable business, but whoever does it will be known forever in the field of automotive writing.

I’d do it, but I’m still a dumb *** on the topic.

Not for long though….

Here’s what I think now.

1. You people are smart.
2. Anyone who has bought new fuel injectors for a 1988 Corvette should NOT be using $32B.

Especially me! I just ruled out the very last possible reason for the fact that it takes 5 long starting cranks to start my engine in the mornings. Every morning. Without failure. Even though I installed a fuel check valve, a group of neighbors watched me with concerned, sympathetic eyes as I cranked my car over before it caught.

I think I should use $6E. That car needs more injector pulse width, and or timing when cold.

3. I don’t need to tune for higher performance. I just need to tune to correct GM’s engineering mistake. As in, allow my GM car to start when cold. A useful thing to do.

The shopping list:

PC – I bought one that is dedicated for car tuning.
ALDL cable – bought
PROM read/writer – need to buy
Programmer software – need to buy
Spare EPROM – need to buy
EPROM eraser – need to buy
Editor software – need to buy
Bin – need to get (free)
Scanner – need to get (and donate – these guys need to be paid)
Carrier (Memcal) – need to buy

I’m budgeting ~$500. Maybe more, maybe less.

EBL-P4.

I read carefully. That is something I have not read or seen and I will research that. It sounds like I should buy that!

(thanks for being awesome -- all of youse)

Siggie88

John at FIC is a classic character and a guru. The injectors are Delphis and they are stainless bodies with no colorartion. There's not part number, paperwork -- nothing.

I asked, and they don't know. I described the problems I've been havibg and God bless him, he sent me a set of experimental injectors (with zero documentation) to try out.

That reminds me -- I need to send them back. Unopened.

I have two modes of dealing with people.

a) Trusting, friendly and considerate to a fault.
b) Questioning overseer manager

80/20% A then B.

Anyway, I'm sure the injectors are set up for 22lbs. They said they were.

Siggie88

I'll be damned!

Jennifer Capriati just lept out of my avatar and smacked me!

Why did she do that?

Rpicard21

You can adjust the idle with a volt meter and a Allen wrench it's not hard mine idles at 650

anesthes

iTrader: (12)

Well. Kinda sorta not really in a way.

You can set the minimum idle speed, but the ECM is going to control the IAC stepper regardless.

-- Joe

Rpicard21

Still if his TPS is out not set up with its optimal voltage the idle will be erratic and could run with an rpm in the 1500 range . If it was my car I would look at that first before screwing with the computer tune .

anesthes

iTrader: (12)

That's two different things.

You want to adjust your throttle stop to set the minimum idle speed. That's one procedure.

Then you want to adjust your TPS to set your closed throttle position, which for stock ecm's the typical target is .5 volts. (On aftermarket you usually take a closed and open reading).

-- Joe

Siggie88

This is not a lazy question -- I just spent the past 45 minutes searching: Does anyone know where instructions to use TunerPro may be found?

I've been using WinALDL. It has not been stable and I determined that it is not intended to work with my Win7 PC and an 88 L98. I've downloaded TunerPro and want to scan this engine.

The_Punisher454

Those 700's and 710's will flow 22 at 4 bar. just crank up the fuel pressure a little if you need 22lbs. Unlike old fat body injectors, the bosch designIII's are really happy at 4 bar and even higher.

edit:
ok just re-read this thread, your injectors may not be 700's or 710's after all.

also you really do need to check the fuel pressure with the vacuum hose disconnected. with the FPR diaphragm vented to atmosphere it will be at full pressure. sounds like you may have a leaky FPR (fuel pressure regulator) if you are having to re-prime the system at startup, assuming you have changed the fuel pump. And there is nothing particular to corvette about a C4's fuel system. Same as a camaro or firebird TPI AFAIK.

Siggie88

Thanks, 454. I checked it more times than the Phillies won games. I also installed a check valve to hold pressure. The FPR was replaced twice. Neither of these are the problem. It shouldn't require 4-5 long starting burts to fire an L98 motor. Think about cranking your motor 40 seconds on a 55 degree morning. Even after that long amount of cranking, it does not fire, it begins to catch, turning faster, gradually unloading the starer (but not quite running) for 10 seconds more. The motor starts like a B-17 Wright radial engine on a Westchester morning fog. The tuning is off. The PO did something to this car. I want to datalog and TunerPro has no documentation as to how to use it.

Siggie88

I tried logging using WinALDL again. Here is one of the displayed results pages...

Siggie88

And the raw data from WinALDL:

Siggie88

These data were generated an hour ago. The outside air temp was about 65 degrees. I started the car after it had been sitting for a week and took this data.

This data appears to be garbage. The car idled well enough (altough the RPM stayed way above 600 RPM.

Does anyone know of a working, functional, documented program that I can use to scan this car with? Forget about tune. I'd be happy to scan first. I need data to tell me what is going on.

If i can not get a scanner, i will simply go buy a $6E PROM from an 89 Corvette and do part substitution. (Future L98 engine owners with the same problem take note....)

91ragtopTA

Does your Corvette have the same 700r4 as 3rd gens? because my Trans Am used to jolt quite badly when I selected drive or reverse to the point it used to chirp the tyres, esp when cold. I resolved the problem by correctly setting the TV cable, after that it slipped smoothly into gear even when the revs where still up from being cold.

anesthes

iTrader: (12)

The case is different (no boss for a crossmember mount), tailshaft is different, and they randifferent servos. Otherwise it's a 700R4.

The throttle valve must be adjusted properly.

91ragtopTA

The throttle valve should be "set" as opposed to adjusted, makes a huge difference and easily overlooked, I thought I'd set mine correctly when putting the engine and transmission back in but I had'nt, caused all sorts of issues including what the OP described, I too was worried about the stress on the drivetrain when engaging D or R. so I went back and double checked and tried setting it again, got it right this time, different car!

gibbles

I had a similar issue with my C4, noticed after installing an ebl flash ecm.
After much reading and tinkering my car on a warm day idles high for about 5 seconds and the idle drops way down.

I recently boosted some pressures in my S10 and noticed a nice clunk when going into gear due to the high idle until warm

I took a crash course in transmission rebuilds this spring after an aftermarket TV cable on my C4 disconnected it self from my throttle body due to a poor fitting connector.

I learned that the clunk was a big issue for gm especially in the corvette.

In the end i removed much of the clunk by upgrading the reverse input drum, and paying special attention at the low/reverse clutch pack and case support for that clutch pack at the back of the transmission.

From what i learned if it's bad enough it can wear on the lugs for that case support.

Also for that case support area they actually installed from the factory a little spring "anti clunk spring".

I tried a few after market "case savers" that only made the clunk worse....
They make another part that clamps onto the case lugs and is sold as a case fix... I have thought about picking one up to try but its about $140 and requires a total disassembly of the transmission to install.