Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 20 of 24 Posts

·
Registered
Joined
·
905 Posts
Discussion Starter #1
Could someone chime in and offer some advice? I've got a 383 with a custom TPI setup and I took it out for a test drive last night. I just got it running and am still working out new engine bugs. It ran great for the first 20 or so minutes. Then it started missing real bad unless I had my foot in it. I got it home and pulled the plugs. 7 of them showed to be running lean (real light gray) and # 6 was clean and black, even the insulator. I checked and it is getting fire. I then removed the valve cover and checked to make sure my cam hadn't wiped a lobe or two on that cyl. All good. Would an injector stuck make that happen, and if so how do I check it? Can you hear them click open using a screwdriver against your ear? Also, as far as the running lean, would upping the fuel pressure cure that? Right now it is at about 35 psi. When I first got it running my check engine light spit out a code for oxygen sensor rich and the pressure was at 45 psi. I lowered it and the code went away. Too far I guess/:huh: I'm going to change plugs after work and try again. Thanks, Art:cheers:
 

·
Banned
Joined
·
3,855 Posts
Art, IF you have headers on it, you may want to check spark plug boots arching to headers.....I went nucking futz for about 3 months finding #5&6 were INTERMITTANTLY breaking down on the headers....engine ran fine when cold, but after warmup, totally ran like crap....that AND I think I maybe well have had a wiring error in the computer setup from years earlier...this is the 4th wiring harness for my TPI setup in 12 years....

I just can't figger why it ran so fine when cold, and then the breakdown, I even went to running it in darkness a couple of times, hit it with windex spray looking for plug wires, NUTTIN'.....looked fine.....

and of ALL the damn things to happen, i'm leaning over the freeking engine with it running just hanging my head in frustration, and that damn #5 went SPARK right there in bright sunlight smack in front of my eyes.....
set of Jacobs spark plug boots and arc NOW, BITCH!!!!

that was allmost a year ago, then I went to a Mega Squirt computer which did not turn out at ALL well for me last Jan/Feb.....so I reinstalled the OEM style 1227730 computer, but had to redo the harness again....so when doing that, I noticed something about the wire routing....that is....

When looking at the wiring diagram of say a '91 F body/firebird using the speed density 1227730 computer or any other GM computer...
you will see the main grounds marked injector, sensors, system, etc...

they must all be INDIVIDUALLY GROUNDED....do NOT do what I think I did, that was tie some points together and run ONE ground wire to the engine/chassis/frame/birdcage/whatever.....I did have several ground wires, BUT from the old wiring remnants I suspect, but can not PROVE, that in fact I had a O2 sensor ground wired with a injector ground wire ......putting MV of pulses on that O2 sensor signal.....

all I do know is, upon putting the 113 aluminum heads on, and rewiring the entire engine computer system with all new cables, and paying super attention to grounds.....the thing runs like a new car now....perfect, first time in years....that old wiring error caused it to run just 'ok', but not really fine the way it did on first install 12 years ago....this was in '01-02 or so when that occured....money time effort, and so forth...

so watch each and every wire in that harness grounding, do not necessarily accept any harness being totally correct....

oh, btw, computer never did a code....never said anything stupid on the scanner either, went the programming route over chips ad nauseaum....even had a tuner come by the house....no go....

:devil: :devil: :devil: :WTF :cheers:
 

·
Registered
Joined
·
905 Posts
Discussion Starter #3
I've got the socks over my plug wires and am sure they are not grounding on headers. All the plugs are firing as I checked them last night with the wife turning over the engine while I checked the plugs one at a time. I'm going to have her turn the engine over today after work and listen to the injectors to see if I can hear them click open. I'm going to up the fuel pressure to 40 psi and try again. I think I might have been getting the too rich code before cause I didn't have the TV cable to the trans set up properly and was lugging the engine somewhat. I've also got to get a trans cooler today to try to drop the temp in the trans. It runs around 140* -150* on the highway but in town it jumps up to 180*. As far as the fuel mix, is changing the pressure the only way to adjust other than changing injector size?:thud: Art
 

·
Registered
Joined
·
219 Posts
Those socks do not start arcing. I've had them arc right through like the socks weren't even there. That was with POS accel wires.I've found MSD & Taylor to be much better.
 

·
Banned
Joined
·
3,855 Posts
You do have a normal HEI cap don't you?? those 'corrected wiring appearance' caps for for crap caps.....

I still think about those damn plug wires, having been through hell with them like that last summer....

also, yes, running the fuel pressure back up is not bad....what lbs are your injectors?? mine are 24 lb Ford units and only a 355 ci displacement....you should have a MINIMUM of 24s in there,....maybe 28 even....

and yes the pressures need be in the 40 lbs region, that's where the tuners set their chips for....

what computer you using??
 

·
Registered
Joined
·
905 Posts
Discussion Starter #7
The injectors are 24lb. The computer is out of a 90 Camaro with a custom chip burned by the TPI manufacturer. I gave him all my engine specs before ordering.
 

·
Registered
Joined
·
219 Posts
Check with the chip burner to see what pressure the chip is setup for.
My 86 car is setup for 43lbs line off. Each chip burner has their own setup for the chips.
 

·
Registered
Joined
·
905 Posts
Discussion Starter #9
That's what mine is set up for also. I only dropped it because of the oxygen sensor rich code coming on twice. After realizing the adjustment on the TV cable was the problem with the trans and correcting it, I figured the code was brought on by the engine lugging due to early shifting. As soon as I check to make sure the injector for #6 cyl is actually opening, I will test drive again with the higher pressure to check the plugs for correct mixture. I am just worried about that 1 plug looking like it had never been in an engine while all the rest showed signs of use. Prior to starting the engine I tested all the injectors one at a time to make sure they were working and they all fired right open as soon as I hit them with voltage. I'm hoping it is something as simple as it being stuck closed. Also, my dist cap is the stock style.
 

·
Registered
Joined
·
219 Posts
If it's stuck closed it wouldn't be black. Black would be open.
Do you have a nood light to check the injector pulse?
Do you have a fuel gauge on the rail, if so how long does it take to lose pressure once the car is shut off?
Are your injectors used or new?
If they are used, did you have them cleaned and flow matched?

OK I think I had more questions than you did :laughing:
 

·
Registered
Joined
·
905 Posts
Discussion Starter #11
I don't have a nood light but checked with a test light and had proper signal at all injector plugs. The injectors are new. I have a guage in the pressure regulator (Aeromotive) and it takes probably an hour to notice any drop in pressure after car is shut off, and then it is only minimal. Also, if it was stuck open, wouldn't the plug be wet and smell like gas when removed from the car? This one looks like brand new metal. No residue whatsoever! :huh: Art
 

·
Banned
Joined
·
3,855 Posts
I have a anto stesthascope, with a aluminum probe on it for listening....it'e great...even I can hear something with it....I just put that tip on each injector, they all pretty much sound alike....you can hear the fire and decay and fuel flow really easy....

as well as valve trains with wide open headers, etc.....bearings, wheel bearings for smooth operation....tons of crap...one of the primary CHEEEEEEP diagnostic tools you can have...
 

·
Registered
Joined
·
219 Posts
I don't have a nood light but checked with a test light and had proper signal at all plugs. The injectors are new. I have a guage in the pressure regulator (Aeromotive) and it takes probably an hour to notice any drop in pressure after car is shut off, and then it is only minimal. Also, if it was stuck open, wouldn't the plug be wet and smell like gas when removed from the car? This one looks like brand new metal. No residue whatsoever! :huh: Art
Yes it would be wet if it is leaks, check the plug after 2 hours off.
Other than that, bad grounds or a bad harness, bad plug wires.
You can swap the plug wire out to a different cyc and if the problem moves with it.
 

·
Registered
Joined
·
905 Posts
Discussion Starter #14
The injectors ground through the computer. They have 12 volts all the time and the computer closes ther ground when it recieves the signal from the ign module in the dist. I already checked all the connectors for the injectors one at a time and they were getting proper ground signal like they should. It is a pulse system so one entire bank fires open and then the other instead of sequential where each fires open on a signal from the computer individually. When I checked the plugs yesterday, it was about an hour and a half after returning home. It took that long for the engine to cool down so I could reach around the headers to get to the plugs.:smack (The older I get, the more I feel pain) That one plug just looks like I put it in new and never ran the engine, then took it back out. Not wet, no residue, nothing. I don't get it.:WTF Maybe I'll swap the injector lead with the one next to it and see if that plug comes out looking like the one prevoiusly after installing new plugs.
 

·
Registered
Joined
·
910 Posts
This can be hard to find.

Offhand, it sounds like your injector for the clean sparkplug is clogged. They have fine screens in them that easily get plugged. Try swapping the injector to another cyl and see if that one becomes clean. If it does it MAY be the injector, if it doesn't it is from the wiring back.
I use CHEVRON FUEL INJECTOR CLEANER in as little as 2 gallons of gas to run thru the system to clean. It will smoke a lot, but it cleans the injectors. I hope you are using the proper fuel filter, 10 microns or less.
Set your fuel pressure for what it is supposed to be. Changing it will not cure your problem, probably just diguise it.
Use a stethoscope to listen to the injectors, they should all sound the same and increase with rpm the same.
If you are getting a o2 rich code, then the ecm will continue to lean out your fuel to adjust to efficiency. No need for the noid lites.

The proper way to diagnose, is to test the o2 sensor with a digital volt meter and see what voltages it is putting out.
While your at it, test the voltages for the coolant temp sensor. You should be able to find a flow chart for testing your system.

I have spent as much as 43 hours chasing a miss with FI. It won't necessarilly show up the proper code. If the obvious doesn't work, then you must start with #1 on a flow chart if you don't want to pull your hair out.

You would be amazed at how many dealerships just give up on similar problems.
 

·
Registered
Joined
·
905 Posts
Discussion Starter #16
MRVETTE
Looks like you might have hit the nail on the head. I changed the plugs yesterday and also swapped #6 wire for #8 wire. Took the car out for about 75 or 80 miles and it started to miss a little bit. Drove it in to work today and you can hear a small ticking when the car is idling. Can't tell where it is coming from but sounds like spark plug wire. After I get home and it cools off, I'll check #8 plug and see if it isn't like #6 was day before yesterday. Go figure, as big as the Dallas Ft.Worth area is no one carries a decent set of plug wires in stock! I'm going to have to order some. I found some in the Jegs catalog that have ceramig plug boots. Have you heard anything good or bad or have any experience with them? I have the 8.5mm MSD wires on there now and they're brand new. Sucks to waste $100.00. Oh well. Art
 

·
Banned
Joined
·
3,855 Posts
Art, me age 63 been working on cars all my life, and lemme say this, starting last summer and for about 5 months or so, I fought this damn plug wire problem on and off for till tears.....new wires....ok for a month, back to same thing, added onto that computer wiring error I think/damn sure I made which contributed to ragged assed operation, looking at two problems at once, and then this DAMNED plug wire crap.....like I said, I even hit that POS with windex water in a dark garage, saw absolutely NUTTIN, not one damn glo, not a hiss, not a snap, nuttin.....went inside for the night, scratching my ass and wondering WTF it was.....

what is was was, is is....JACOBS ceramic boots....whole damn set, and hell with it....I recommend using a dap of RTV in each end as you put them on...that locks and seals for water jumping down there....as me how I know THAT too......

Im nearly bald for a damn reason.....

anyway, the damn vette runs/drives like a dream now....

so much so, I have done some 4 other mods to it since figgering out that plug mess, and the computer wiring mess....

I really hate FIXING cars all the time, MODIFICATIONS, FINE, Fixing crap....NO....I FIX crap for a living.....
 

·
Registered
Joined
·
905 Posts
Discussion Starter #18
MRVETTE
I'm not far behind you at 54 and I am bald. I found the problem yesterday. It wasn't 1 plug wire, it was 4!! Brand new MSD crap. I've already made up my mind to get the Jacobs ceramic set. I don't care what they cost. I've spent so much on this car it dosen't matter any more. I replaced with a set of Accell wires (all that was available locally) and till the Jacobs come in it is running like a scalded ass ape!! Thanks for your responses. :cheers: Art
 

·
Registered
Joined
·
45 Posts
If I may ask, how did you determine the 4 wires are bad? Ohm meter? It sounds like they weren't arcing over obviously. I'm chasing some kind of hi-voltage issue on my 454 with a point distributor, and have a set of the MSD 8.5mm wires on it, along with a Accel cap & rotor. In the dark, no obvious light shows. Should be easy, but my diagnostic ventures are shortened by the need to pack up in prep for a move.

TIA

BB NJ Ken

:cheers:
 
1 - 20 of 24 Posts
Top