OneCrazyCorvette

As you may have guessed from the topic title I made the mistake of purchasing a 84 cross fire injection corvette that was parked for about 1 year. God bless my 78 with no electrical garbage. The symptoms is as followed. The car has a tough time starting when cold this does go away after the motor has warmed up. But this is only the beginning. The car will idle perfect. When you step on the gas the engine will begin to Rev up. While holding the trhottle open the car will begin to cut back fuel and timing to the point that the car will actually stall if you put the pedal to the floor. this symptom does not seem to change when the car is warm or cold. I have already attempted the following.
1) the cars exhaust is open and free flowing- thinking a clogged cat.
2) brand new fuel filter- output from pump seems more then enough.
3) intake gaskets have been replaced under throttle bodies.
4) Brand new map sensor.
5) new engnition module in distributer.
6) new cap, rotor, wires, plugs.
7) new coolant temp switch- this is the one that controls computer not gauge on cluster or coolant fan.
8) new knock sensor.
9) new electronic spark control module- this is the module mounted near the heater fan.
10) cleaned injectors and tested for spray- these are even and run clean there is a neat trick you can perform with your timing light and the injector to check spray pattern.
11) injector firing circuit was tested. The pulse width modulation is working fine to the injector.

the tps switch was tested and appears just fine. I also set the base timing of the car at 8 degrees with the jumper unplugged to the computer.
My thoughts then led me to the computer which indicates no touble codes at all. The stupid thing things the world is ahappy place and its running fine. Imagine that. I then simulated some codes the the computer by unplugging sensors and it acuratly set a code for each sensor I unplugged. So I'm not positive but I think its ok.

At this point I'm not sure what to do. There is a local shop that speciality is corvette's but as we all know these places sometimes can see you coming and I hate that dreaded ooh that's a cross fire system. In reality its nothing more then two TBI units they used on the 4 cylinder fieros but one for each side. The worst part is I cant stand defeat so if you can guys help me out here.
:banghead:
thanks
Jeff

grumpyvette

if your thinking of swapping to carbs or just porting you crossfire intake!
[b] STOP!! DON,T EVEN THINK ABOUT A CROSS RAM STYLE INTAKE MADE FROM A CROSSFIRE EFI INTAKE
heres the crossfire intake GUARANTEED TO RUN OUT OF AIRFLOW BY 4000RPM....your problem is that the stock intake heads and cam all are severly airflow restricted, youll need to change those parts to make serious horsepower!

the EDELBROCK SY1 is no longer in production and must be purchased used and a new custom top plate must be built for either choice from 1/2" thick aluminum plate, the EDELBROCK SY1 does not require the windshield whipper motor be changed for clearance like the OFFY does
your stock heads,intake, displacement and compression ratio and cam are killing performance. the cross fire intake is the worst offender as it only flow about 170cfm-190cfm
swapping to a EDELBROCK SY1 with CUSTOM LID removes that resriction
THE EXTREMELY RESTRICTIVE STOCK INTAKE
THOSE CYLINDER HEADS ARE ALMOST AS BAD (heres L98 heads and THEY FLOW BETTER than those CROSS FIRE HEADS


HERES THE AFR 190cc HEADS



compare the ports, the SY1 flows about 270cfm

unless your rich or hopelessly masochistic get a SY1 with modified lid if you choose to stay with the cfi system

the sy1 flows close to 270cfm out of the box, a cfi flows 170-190cfm (DEPENDS ON WHICH PORT (STOCK) and theres not enought room to port without cutting/welding (EXPENSIVE AND TIME CONSUMEING AND EASILY SCREWED UP)




these are the STOCK CFI INTAKE RUNNERS,THEY WILL NOT SUPPORT A LARGE INCREASI IN HP WITHOUT MASSIVE CUTTING AND REWELDING WORK,WHICH COSTS FAR MORE AND WORK FAR LESS EFFECTIVELY THAN AN SY1 SWAP WITH A CUSTOM LID


this is the port work necessary to get them to flow even as pittifly as a TPI
[b]"A MODIFED EDELBROCK SY1 WITH CUSTOM TOP MATCHED TO 190CC AFR HEADS CRANE 114142 CAM -- AND add a 383 high compression engine kit"

b>
BTW Ill save you the math, youll need to get the 10:1 cpr flat top piston 383 kit for the street, and the 74cc combustion chambers AFR 190cc HEADS with L98 spark plug angles if you intend to run high test gas you find everywhere (some is lousy quality) and get the head gasket as close to .018-.022 as you can for correct quench
fyi DD-2000 and EA pro both guess at OVER a 115 hp improvement at the rear wheels, having done this type mod in the past Im reasonably sure thats UNDERESTIMATED for those listed changes

383 rebuild kit $1000
http://www.strokerkits.com/383.htm
crane cam/lifters $150
AFR heads $1200 http://www.flatlanderracing.com/cylhead_index.html
SY1 with custom lid $500-$600
DOING YOUR OWN WORK>>>>>PRICELESS! :thumbs: :thumbs:











[Modified by grumpyvette, 9:26 PM 8/4/2003]


[Modified by grumpyvette, 9:36 PM 8/4/2003]

CFI-EFI

It sounds like you have done a lot of trouble shooting. You say the TPS has been checked, and it works. Have you SET the TPS voltage? This is a relatively minor item, but it could contribute to the problem. My first guess is fuel pressure. Have you checked it? Volume is one thing, but the injectors need 9-13# in order to function properly. It sounds like you are running out of gas, or at least an adaquate supply. Good luck.

Grumpy,

Now that you've told him why it isn't, and won't be fast, can you help him get it running?
SUSH! Don't let my, origional, factory headed, factory cammed, ported factory Crossfire manifolded, engine hear you. It may stop wanting me to shift it at 6000 rpms.

RACE ON!!!

OneCrazyCorvette

Thanks CFI-EFI that was some valuble information it so happens I pulled the fuel pump out of the tank tonight and found the screen not only clogged but the screen was ripped. I replaced it and the car is running much better. However I do believe now that I have proper fuel pressure that the injectors may infact be clogged because there patterns have changed. I drained the tank completely and wiped out with a rag until bone dry. it is better but I think I will replace the injectors. you are also correct about the TPS it is ooff of the 4.5 volts on the bottom end it is actually at 4.3 not sure if this is enough to cause any issues but I will correct it anyway. I knew someone would have an idea which way to turn. as for Grumpy I appreciate the info and how much a TPI is better but unfortunatly carbs are still better in the long run. Otherwise they would have disappeared from drag racing along time ago. My 84 was never ment to be fast and I would never use Cross fire if I was. My 78 however is fast. It currently is running 12.20's consitant at the local speed strip with a 355. I'm sure you know how heavy that car is the best part is how many guys with stock c5's question what they paid for there car when that old girl goes blowing by. But seriously thanks for the info from both it is much appreciated. I did find it interesting that someone did actually make a high perf. intake for a crossfire.
Thanks
Jeff :steering:

Lionsden

:iagree: My first thoughts were fuel pump or maybe fuel filter or fuel pump strainer. Install a pressure guage and see it the pressure drops off as fuel demand goes up. Mine stays constant from idle to wot.

Was this a problem before the car was parked a year ago?

OneCrazyCorvette

No car ran good when parked. Problem started I believe when it was running but the down time did it in. It is better now but I'm going to look into how to clean injector's next to improve it's running.

oldace84

Time to go to the crossfire forum, http://www.crossfire.webhop.net
You will find alot of info on the crossfire there, and then some.
After you register there.
Good Luck
tony
:chevy :chevy :chevy

frank moran

first off you did not makea mistake and forget the carb stuff, a billion GM cars had TBI on them and they run fine, thought, is the egr valve hanging open?

OneCrazyCorvette

Thanks for the reply's but CFI-EFI hit it right off the bat it was the fuel pump. The car is running ok now. :auto:

CFI-EFI

Been there, Done that. I'm glad if I was a help. I have tested my fuel pressure at the race track. I taped a pressure guage to the outsde of the windshield and made a pass. I purposely over wound 1st and 2nd gears to put the greatest demand on the fuel system. Even at over 6000 rpms, the needle stayed rock steady at the 14 pounds, I have my regulator set at. The toughest pressure leak, I have ever trouble shooted (shot?) was 500 miles away from home at the division finals, one year. It turned out that the output hose from the pump was leaking between the pump and the steel tube, inside the tank. THAT was fun!

The spec, I have, for the TPS, is 0.525v, + or - .075v.

Good luck, and...

RACE ON!!!

corvetteronw

Glad you were able to get it fixed. You might want to contact Ron Kane in Springfield, IL 217-788-5263 or http://www.kaneauto.com He is a Bloomington Gold instructor and loves to fix crossfires. Many folks bring their 82/84 Vettes to his shop, do a couple of days sight seeing and then drive back home. He knows how to make them run as good as they should. He is not cheap but you will love the care after he is done! :seeya

OneCrazyCorvette

I pulled the injectors tonight. I'm not sure which has more dirt in it my atv or the injector housing's This might actually be a good procedure for everyone to check out. I was surprised as to the quantity of stuff that actually got past the fuel filter. All in all the injectors actually were not that bad to clean just be sure you have a new gasket and O ring set for chances are the gaskets will not make it. Mine didn't.

fijidan

[QUOTE= you are also correct about the TPS it is ooff of the 4.5 volts on the bottom end it is actually at 4.3 not sure if this is enough to cause any issues but I will correct it anyway.
Jeff [/QUOTE]

When i was setting my TPS i got a similar reading. Try the middle and lowest wire to get the voltage EFI-TFI posted. Had me confused for a while (testing the middle and top wire giving a similar reading off one decimal point) but once i got it tuned in, made a huge difference in performance.

383vett

9 year old post next month.