Corvette Forum : DigitalCorvettes.com Corvette Forums banner
1 - 20 of 37 Posts

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #1 ·
Okay, here are the specs:


383
2.02/1.60 valves on hogged out iron center bolt truck heads
flat tops forged pistons
1.6 full roller rockers
Crane 2050 compucam see specs here: http://www.cranecams.com/master/apps/chevy5.htm
Hooker long tube headers
30# Accel injectors
BBK adjustable regulator
hogged out stock TPI and stock throttle body
stock ignition
ADS strip chip
2600 stall
3.07 gears

Problem is, it wants to run lean and ping unless I crank the timing 10 degrees or so AFTER tdc.

I also have a freak idle problem. 75% of the time it idles fine, then it goes into surge and hunt mode until it stalls.

I just upgraded from 10 year old 24# Accel injectors with minimal improvement.

NEW: Delco fuel pump, regulator...etc.

Ideas? Or the first $5,800 can just drive her home!!!!!!!
:spanked:
 

·
Registered
Joined
·
8,067 Posts
Most of what you have spec'd is over my head however (humor me here) is it possible that your fuel pump isn't delivering enough fuel due to the lope? Would you benefit from an electric fuel pump? Is there an optional, larger size fuel line?
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #3 ·
stilcrazee said:
Would you benefit from an electric fuel pump? Is there an optional, larger size fuel line?
Good question/guess. The thing is, it already has an electric pump, and it is putting out more than enough pressure. My 69 VETTE has EFI with 468 cubes, and feeds just fine on the same size line.

I am thinking the car has a problem in the harness, or programing on the chip. It could be a fuction of the 85 MAF computer system. I don't know if it would be better to wire up a speed density system. :huh:

Maybe I should go for the reprogram, but I don't know start.
 

·
DC Crew
Joined
·
53,226 Posts
Grumpyvette or -=Jeff=- could shed some light on this, I sent them PM's to come look at this thread.:thumbsup:
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #5 ·
Patrick96LT4 said:
Grumpyvette or -=Jeff=- could shed some light on this, I sent them PM's to come look at this thread.:thumbsup:
Cool! I chatted with Jeff about it just before I tossed the 30# injectors in. I talked to Grumpy a number of months ago (via phone) about the Stealth Ram. In that case specific, I have to make the car run and idle off the stock manifold, before I add another monkey wrench to the Frankenvette mix.

I am going to see if I can dig up the stock chip so I can mail it to Jeff for program changes....but where do we baseline it????
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #6 ·
one other thing.... I can unplug 3 injectors while it is idling normal before it starts to stumble (at idle only).

Back when I owned this car before (1996), it did not have these problems. I sold it, bought it back with the engine in boxes, slapped it together...and I have these problems. The guy that bought it and sold it back to me blew the engine twice. Once while playing submarine, and the second time it leaned out and melted #7. He had an MSD 6AL on the car with adjustable timing. I removed that as I questioned his wiring..etc.
 

·
Premium Member
Joined
·
10,489 Posts
Hey 69MyWay,

Do you have any codes?

I am wondering if maybe the Injector Drivers are going bad, not sure the drivers could act that way.

Maybe a MAF problem? if it is the Burn off Module, I would rewire the for the 86-89 ECM and then run 89 Code in the ECM.
If you find that the Harness is bad and need one, I have an 85 Engine Harness, but the Knock sensor Plug has been cut off. other wise it is in good shape.

if you find the Stock PROM, I would start with it as a BASELINE, in fact plug in a stock Chip to see how it acts.

Hope this helps
 

·
Super Moderator
Joined
·
8,548 Posts
WELL in the order of likely to less likely

(1) VACUUM LEAKS ON THE INTAKE GASKETS

(2) BAD MAF or CONNECTIONS TO THE MAF

(3) TPS OR IAC BAD OR MISS ADJUSTED

these top three are likey

(4) badly clogged EXHAUST (CATS?)

(5) badly timed cam or miss adjusted valves

(6) BAD/DEFECTIVE/fried ECU chip (ADS strip chip) or CHIP thats come loose from its socket

(7) fine rust or other crap in fuel clogging the indivdual injectors
 

·
Banned
Joined
·
591 Posts
isn't there a wire you disconnect to time an 85 ?
there is on my 86
did you disconnect that wire ( if applicable) ?
 

·
Registered
Joined
·
2,151 Posts
A few questions
1) are you SURE cam timing is and valve lash are correct
2) are there any codes
3) are you sure theres no air leaks between the throttle body & MAF
4) are you sure the TDC mark on your balancer is correct
5) what is fuel pressure doing when the idle is hunting and stalling
6)what is the GPM reading for the MAF at idle
7) if you REMOVE your O2 sensor(s) does it run better
8)Do you have a full 12V or more and a good ground to your ECU, Coil, fuel pump
9)are you sure your injectors are for the factory ECU? what fuel pressure do they require?
Sounds like this problem has been giving you fits for awhile, I can help you find it but we need to eliminate possible causes one at a time
If your car was mostly stock with no codes I'd suspect a blockage in the fuel return line or in the fuel rail at the regulator Or a major air leak.
You can E-mail me at [email protected] or I'll reply on here
Best of luck,
John
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #11 ·
Let me see if I can go through these

1. cam degreed with new high quality timing chain (crane specs)
2. vavles were cold set the same way I always do them
3. I traced out and replaced all the vacuum lines to the fuel canister, and verified they were correct per the emissions routing.
4. tested for vacuum leaks on the manifold, and even replaced suspect runners a few months ago.
5. NO CATS, wide open exhaust with cross over
6. I did install a heated 3 wire O2 with no real change in things.
7. Cleaned out the fuel system when I installed the new injectors. (found no debris in the inlet of the old ones.)
8. I am not 100% sure about the tdc mark, as it is running a high dollar fluid dapner, added by the last owner---it apperead accurate when I was building the motor...but who knows???????????
9. These injectors are designed to work with an 85.
10. Yes, I disconect the brown wire for base timing.
11. CODES---none after the injector swap---I have been getting a MAF burn off relay, but only the first time you crank the car cold. It is gone after you warm it up. Could we be on to something here???????????
12. I have also seen an ESC code, but that cold be where I have set the timing.
13. I don't know the fuel pressure under a load, as I have not rigged up my gauge where I can see it while driving.
************
I have a decent scanner, and access to a snap on. What data should I capture?????????

Jeff, the harness sounds great, but let's try to nail down the problem before I go to that extreme. I really like the MAF re-wire idea. We can do that when we burn a chip...right?

Thanks guys. Since my Dad died, I don't have him here to bounce stuff back and forth until it is fixed. He was the master at solving these kind of problems.
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #12 ·
EGR????????????

This is the only thing that really changed after he blew the engine with his submarine run. He yanked it and created a block off plate.

My brother is a master tech, but does not touch modifieds. He said the EGR block off is messing up the fuel mixture, and causing ping?

Should I slap a vavle in it?

Make sense?

Remember it is the oldest of the old TPI systems, and it did not do this when I owned the car years ago. In fact, it ran 13 flats in the 1/4 on 7 second 1,8 miles and lightening quick 60 foots. Right noe it may not squeeze off a 14 second run when it gets into this freak ping mode.
 

·
Registered
Joined
·
2,151 Posts
The EGR is closed at idle so i don't think that's your idle problem...
I'd sure like to know what your fuel pressure is doing
I don't know what a snap-on scanner reads but you should compare the maf readings between normal idle and when it's hunting
 

·
Super Moderator
Joined
·
8,548 Posts
SWAP THE M.A.F with a KNOWN GOOD ONE. IM BETTING THATS THE PROBLEM!!
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #18 ·
Details after ALL day with this monster.

I got my hands on the GM repair manual and started tracking down grounds...etc. My brother came over to help.

Ended up replacing the computer...OH, the HEATER CORE RUPTURED WHILE ALL THIS WAS GOING ON!!!!!! ARGGGGGGGGGGGG!!!! YES ALL CAPS, I AM YELLING!!!!

I was getting freak mode readings off the O2. It was shooting straight to 1.000 (1 volt), and beyond while sitting at idle. So, we back tracked grounds, jumpered the wires, and tested the O2 with a volt meter while running seperate from the computer. BAM..it was reading right?? Hmm?, so we figured the computer was fried, thus we replaced it.

Sooooo, we pop the new one in, and get started. Boom, the O2 readings climb to 1 PLUS volts..Impossible you say???

So, while I am messing around I find the PCV is bad. With it in, the IAC is running at ZERO steps. I plug it off, and the IAC drops into play, between 18 and 25. So, I will get a new one tomorrow.

Finally..and here is the freaky part. I get a code for over volts. While running, we disconnect the alternator feed. Low and behold...the O2 starts to read normal signal, and the idle starts to drop down smooth. Hook it back up, and the O2 goes nuts, car gets stupid.

We end up jumping the main feed to the exicter harness back to the charge lead. For some reason, this now allows the car to run, and not send the O2 off the deep end. It was getting late, and it will hit 29 here in Florida tonight. We shut it down to think it over.

It appears that the alternator feed is sending a strange signal down the harness that is causing false readings that is back feeding through the system and putting it out of sink.

The MAF readings are all within normal spec.

We could not get the car to go into closed loop however. The MAT is reading on target, etc, but no closed loop.

So, the car was actually running normal at idle (also put in new plugs as it had gotten so rich it was fouling it all out), but could not drive it with the heater core ruptured, etc, and not hitting closed loop, there was no point.

Back to the drawing board tomorrow after Church.

Keep the ideas coming..........
 

·
Premium Member
Joined
·
10,489 Posts
Chris,

I wonder if the Harness is shorted somewhere. do you have a DVM to check continuity and also check for shorts and opens? if so, now is the time to get it out and start checking wires.

As for the Heatercore, don't sweat it too much, the 85-89 heater core is easier to swap then the 90-93

Good Luck, and let us know how it turns out.
 

·
DC Crew
Joined
·
4,751 Posts
Discussion Starter · #20 ·
Yep, got the DVM. I may need that harness from you after all.

I swapped the heater core on my 90 Vette. It blew the day I got the miniram motor in the car!

Right now I only have one good arm, after having the right arm shoulder surgey. Don't think I can tackle the heater yet.

Short, or no short, it is so strange that the alternator when hooked up normal causes the O2 to run off the scale.

I have to wonder if I am dealing with a bad reg, or just a wire unshielded sending voltage into the O2 wire.

Still does not explain the lack of closed loop operation, even after running at temp for 30 minutes.

Maybe I should just set it up like this

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6783&item=2445614667

Nahhhh, not that desperate yet!
 
1 - 20 of 37 Posts
Top