Crossfire 101 (your assistance is welcomed!)

[ironmoo]

My '82 has the bone stock setup. The intake manifold leaks (or hairline crack) on the driver front side as a very small amount of radiator fluid is pooling in one of the depressed areas below where the front bolt is attached.


I bought a 2nd and 3rd crossfire setup off Ebay I wish to rebuild and learn from.



Here is the situation...


I teach college-level Physics, have rebuilt small block engines & build home computers as hobbies…


However I've had this car since 1986 and viewed the Cross-Fire system as something of a mystery and have not been sure what does what and how it does it.



Like what is duel plumping? MAP sensor, voltage checking throttle position voltage off idle, etc etc... lol



More importantly how to tune it myself/maintain and address issues like the current "check engine" light. While it may be a vacuum leak, I did replace both O2 sensor and EGR value, but the light still remains lit.

Reading through the posts have been helpful however it seems the running theme is, while finicky, proper tuning can bring great results from the Crossfire engine.

I do wish to learn to do that tuning!


If someone can provided a source online or simple diagram.../or explanation what all the sensors names are and do in the engine process, that would be of great help get my arms mentally around this engine!


One thought is to buy ALL the sensors/wiring etc and start fresh...The car was paid long ago so cost for parts to diagnose, and to travel a learning curve to master it, is well worth it.



Many thanks in advance!


-Moo

[ex-x-fire]

Crossfire injection is a type of efi that is wet flow, it's considered to be throttle body fuel injection, around 1986 gm introduced a single tbi that became the efi system for its trucks & cars. The early 2 barrel tbi & cfi have the same sensors & connectors. Cfi has an extra idle air control valve. These systems are not much different than port injected engines, the ecm has to drive more injectors & some use mass air flow sensors instead of the map senser found on tbi/cfi. The map senser tells the ecm the engine load by measuring the pressure in the intake(vacuum), the pressure changes w/ how opened or closed the throttle plates are. Throttle post. sensor is bolted to the linkage to tell the ecm how opened or closed the plates are, it also uses a tach reference to help on start up. The tps on earlier (below 1990) is adjustable, a scanner really helps but you can use a volt meter too. These are variable voltage sensers, but some like the o2 sensors make their own voltage through heat & oxygen. And the coolant temp sensor changes resistance as it heats up, cold coolant-lots of resistance, hot coolant- down around 180-200ohms. This tells the ecm how to fuel the engine through pulse widths(time the inj. are on), really the ect sensor is replacing a choke on a carbed engine. Instead of resticting air (when the choke is closed on a carb.) it adds fuel.
You can make ign. timing, tps, & poss. fuel pressure adjustments, but you can't tune it through the ecm. The chips that were once popular are the only way to change anything in the ecm. Later systems are programable.
There is a book by Ben Watson, called 'how to tune & modify chevy fuel injection', I use it to help explain areas that can be tough to figure out .

[geekinavette]

First things first...retrieve the ECM code(s). This can be done with a simple paper clip or by purchasing a OBD1 (On Board Diagnostics, 1st generation) code scanner. To use a paper clip, just use it to jumper pins A and B of the ALDL connector (mounted under the dash to the right of the steering column). Turn the ignition on (do not start!) with the ALDL jumper installed, and the CEL (Check Engine Light) will flash stored codes. The first code will always be 12 (no Distributor Reference Pulse...or in other words the engine is not running). To display a code 12 the CEL will flash once (1), then pause, then flash twice (2), then a longer pause, then repeat this process two more times (every stored code is presented three times). After the last code 12 is presented, it will pause a little longer and display any other codes that are stored in the same manner.

Some definitions...

TBI:
Throttle Body Injection
As ex-x-fire mentioned...a "wet flow" system, which means that fuel AND air flow through the intake manifold (as opposed to a port injection system which injects fuel directly at the cylinder, so only air flows through the intake manifold). The crossfire system uses two Throttle Bodies, each feeding opposing sides of the engine (thus the term "crossfire"). Some TBI systems use a single "dual barrel" throttle body, with two bores and two injectors, but all within one housing. Many consider TBI to be somewhat of a "hybrid" system between a carburetor and modern port fuel injection systems.

ECM:
Electronic Control Module
Also referred to often as the "computer"...which is really what it is, albeit a very slow one.

MAP sensor:
(intake) Manifold Absolute Pressure...reported to the ECM in Kpa (and being a physics professor you already understand the significance of the word "absolute" here. Yes it is just a basic absolute pressure transducer). Manifold pressure is directly proportional to engine load.

TPS:
Throttle Position Sensor.
Nothing more than a potentiometer between a fixed 5V and ground with the wiper lead reporting a voltage to the ECM that is directly proportional to throttle position. The adjustment of this is important so that the ECM can detect idle as well as WOT (Wide Open Throttle) conditions (as well as other conditions, but these two are important). The TPS mounts to the driver's side TBI unit, actuated by a lever connected to the throttle shaft.

CTS:
Coolant Temperature Sensor
A simple thermistor used to provide engine temperature information to the ECM. (not to be confused with the temp gauge sending unit...yes they do the same thing but these are two separate sensors).

IAC:
Idle Air Control.
This is a stepper motor mounted to each throttle body with a tapered cone plug attached to a lead screw. There is an air passage that bypasses the throttle bore (kidney-shaped hole on the top of the throttle body base), the IAC motor will extend or retract this "plug" to control how much air is allowed to bypass the throttle bore. This is used to control idle speed mostly, and is also used as a "stall saver" device.

O2 Sensor:
Just that...a device that measures oxygen content in the exhaust stream, used by the ECM (in addition to other sensors, like MAP, CTS...etc) to control fuel flow to the engine.

ESC/EST:
Electronic Spark Control/Electronic Spark Timing. Modern-day equivalents of the old vacuum operated spark advance.

FPR:
Fuel Pressure Regulator
In contrast to a carburetor, fuel injection controls fuel delivery by pulse-width modulating a solenoid inside the fuel injector. How much fuel is delivered is determined by how long the solenoid is engaged in combination with fuel pressure. Obviously higher fuel pressure will deliver more fuel for a given pulse width. You can see here why fuel pressure is very critical in any fuel injection system. When checking fuel pressure it is very important to not only check pressure at idle, but under engine load also. The crossfire system is a serial plumbed system...fuel flows through the first throttle body (passenger's side), then to the second throttle body which contains the fuel pressure regulator. The stock injectors are rated at slightly different flow rates to compensate for the small amount of pressure drop between the two injectors (inherent in any series system), so if the injectors are removed for any reason it is important that they be replaced in the original locations.

The term "dual plumbing" probably was referring to the fact that the crossfire system uses two independent throttle bodies...each with its own fuel feed/return as well as IAC valve (where as the "dual barrel" setup just has one fuel feed and IAC valve). However as with most dual plumbed systems, it is NOT a parallel plumbed system.

There's no mystery to it...all of the laws of physics apply. I would not go the route of just buying stuff and replacing it...all that does is waste money and you won't really learn anything, and likely you won't fix anything either. There are items that wear out that manuals and "normal" repairs aren't going to cover. However with that said...a Factory Service Manual is an invaluable tool.

Again...get those ECM codes! You have to start there.

[geekinavette]

Some other nuances specific to the crossfire system...

As mention in the previous post...fuel pressure! The stock '82 and '84 fuel pumps are notorious for falling short under heavy engine loads...they just can't deliver enough flow to maintain the required 13-14psi of fuel pressure. (yes the FSM states 10-13, but there's enough experience out there that will agree that 13-14 is really what is needed). A common "upgrade" is to swap the stock pump with one for a TPI (Tuned Port Injection) '85-'89 or so Vette. The TPI system requires more pressure, so the pumps are inherently designed to deliver more flow so as to maintain correct pressure. You will not effect pressure by upgrading to a higher flow pump, the Fuel Pressure Regulator takes care of that.

Throttle Body Balance! Being independent throttle bodies, they MUST be balanced! One item that tends to wear out and severely upset this balance is the throttle shaft bores. You can do a quick check by just feeling how much movement there is of the throttle shaft within the throttle shaft bores. This "play" allows the throttle plates to move around, and it takes very little of this movement to upset the balance between the two throttle bodies.

Vacuum Leaks! The intake plenum "lid" is notorious for developing vacuum leaks...not to mention old and cracked vacuum lines.

These are probably the most common ailments of the crossfire system that effect driveability and reliability.

Once again though...before any of this stuff is addressed...

RETRIEVE THOSE ECM CODES! (yes it is important enough to yell)

[ironmoo]

Thanks to you both for the valuable data!!! Awesume!

I'll study up this weekend and see what new questions may come along.

-MoO!

[ironmoo]

Finally had time to pull the codes (thanks for the paperclip idea!)

The CEL comes on within a sec or two of start up and stays on:


Code 24- Vehicle Speed Sensor (The speedo currently not working...any relation to this? Doubtful as the car is in park when the light first comes on.)


Code 42- EST Electronic Sensor Timing Problem.


I'll continue to do some research on the forums, any ideas or suggestion on correcting the issues?



Thanks!
-MOo!


PS: She is running and starts up the 1st time. Just a bit rough, & the gas mileage is quite not a good as I recall.

[Buccaneer]

Finally had time to pull the codes (thanks for the paperclip idea!)

The CEL comes on within a sec or two of start up and stays on:


Code 24- Vehicle Speed Sensor (The speedo currently not working...any relation to this? Doubtful as the car is in park when the light first comes on.)


Code 42- EST Electronic Sensor Timing Problem.


I'll continue to do some research on the forums, any ideas or suggestion on correcting the issues?



Thanks!
-MOo!


PS: She is running and starts up the 1st time. Just a bit rough, & the gas mileage is quite not a good as I recall.

This may help you out in finding the issue(s). The speedo must be working properly to provide the ECM with the proper input. Good luck and visit... CrossFire Injection Forum

CODE 24

Trouble Code 24 indicates that the Vehicle Speed Sensor (

VSS) is reporting an abnormally low reading when other sensors indicate it should be higher.

The conditions for setting this code are:
• No Code 33 or 34 (MAF Error) is present, and

• The vehicle speed signal indicates < 4 MPH and

• Engine speed is between 1400 and 4400 RPM, and

• During a low load condition (LV8 between 50 and 99), and

• Transmission not in Park or Neutral, and

• All conditions met for more than 20 seconds

If the code was logged when the vehicle was in motion, the following should be checked:
1) Defective or corroded VSS connections
2) Maladjusted TPS sensor. The TPS should read about 0.525 volts at closed throttle
3) Defective speedometer cable
4) Bad or missing speedometer drive gear(s) in tail shaft housing of the transmission
5) Defective VSS

6) Defective ECM

-----------------------------

CODE 42
Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.
During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit.
An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing.
The conditions for setting this code are:
• System in BYPASS mode but the ignition module is still controlling timing

- or -

• Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 milliseconds.

Typical causes for this code include:
1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
6) Faulty or incorrect ignition module

7) Faulty ECM

[xfirez51]

Besides the Crossfire Injection Forum, I would suggest visiting ThirdGen.org. Tons of info on tuning TBI systems. I had an 84 for 24 years that was modded. It was producing 285rwhp and 347rwtq but it takes work and most is DIY. But it was a fun car to drive on the street. And the Z51 suspension along w C5 brakes and ZF6 trans really changes the character of the car.

[ironmoo]

Thanks for the info. I visited the sites and found them to be a great resource.

I pulled the codes again after clearing them out.

With the car NOT moving, NO code 24. I have the speedo repair job on my list and that should solve it.

Code 42 does pop on again. ;(
I pulled the ECM, checked out the connection/prom etc. All ok.
After blowing some canned air on all the connections and put everything back...still a code 42. Hmmmm.
I'm looking into the ignition module next.

Any ideas?

Thanks again!

-MOo!

[Buccaneer]

Thanks for the info. I visited the sites and found them to be a great resource.

I pulled the codes again after clearing them out.

With the car NOT moving, NO code 24. I have the speedo repair job on my list and that should solve it.

Code 42 does pop on again. ;(
I pulled the ECM, checked out the connection/prom etc. All ok.
After blowing some canned air on all the connections and put everything back...still a code 42. Hmmmm.
I'm looking into the ignition module next.

Any ideas?

Thanks again!

-MOo!

Get your meter and diagrams out and start shooting wires to ensure they are good. Buy a GM Service Manual if you don't have one. Look on eBay.

[cntrhub]

I teach college-level Physics, have rebuilt small block engines & build home computers as hobbies…

I do wish to learn to do that tuning!


If someone can provided .../or explanation what all the sensors names are and do in the engine process, that would be of great help get my arms mentally around this engine!

I'll give you my arm wrapping. No, I am not a teacher of physics. I would rather run a more practical event so as to show how fuel injection uses these components. Once I turn the key on, I more act like a centipede with each leg following a step and no foot crosses over that step to trip itself up on the mental grab hold.

So, I should see a pattern as easy as following OTTO's 4-cycles. Now, I come from the otto-world no matter we run 4 or 2 wheels under us. We have to know our first qualifier question or we are lost and no one is going to hand you any more legs you do not speak the centipede.

Here is how I wrap my world around one number and only one number counts in the OTTO cycle. I am going to ask you the qualifier questions so we are on the same page and when I hear your answer(s), we will continue:

1. If I am sitting in the garage, key fob off, what is the pressure in the exhaust pipe?
2. If I start the car at sea level, the piston is at BDC, intake valve open, what is the pressure inside the cylinder?
3. If the intake, after the BDC and all that closing, what is the pressure now?
4. If I stand outside and just breath in the day, what is the pressure on my skin I look out at the clouds and a storm is heading my way?
5. If I WOT the throttle to the floorboards, what is the pressure for that valve closing?
6. If I Lift on said throttle, what is the pressure inside the engine goings on?
7. If I am skiing and now high up in the mountain air, I turn the key fob, what is that suck into the chamber being all cold starting and such?

This is open book so no cheating!

And do not blame me about me receiving a bulletin about 5 of 5 pages and did one page about choke the chicken? I gots some fuel injection with a manometer you want to blend the bodiesync and low speed screw in some smoothrottle tuning.

Roll that pile out the trailer will you?

[cntrhub]

"The name is literal, ie: a MAF sensor senses the mass of the air flowing into the engine. The signal it generates and sends to the ECM directly relates to the quantity of air taken into the engine."

This is literally rocket science and if you do not get the qualifer not "quantity" taken, you will be taken for a ride you roll that wheel off the trailer, I am telling you right now!

This is big boy talk and Hal is about to get a Hal storm he needs to clean up his act or my name is not the, "HUB" A Bubba 101 Fool Injection Suggestion, "Someone get their acTTogether!

Now, I'll send you on a wild goose chase and waste your minutes. This fool is injected with an A/Fool Ratio and if the digit means anything, I'll upset the car drivers trying to follow my line is, Cross the line to fine tuning.

Dis is how I prepare myself to bore your trailer trash a new hole you all mashed on the floor is to BrinGIT 101!

And may I remind you that the tune you hear is not even close to the throttle body re-tune of that crossfire you might try a tune full. Key strokes and all those caterpillar moves you do not stumble on the throttle.

EDIT: Bud Dougherty Forums Administrator!
Inappropriate UTube Video esp. the CLOSING!!!

Waste your minutes watching me practice some old trick and if you keep wasting your minutes, I use not a rear brake wattsoever. This is a mule full of code speak. It speaks in the absolute so Hal gets it straight.

I'm going to send more air into that MAS and did we qualify the Q yet? I'm asking about that first step if I am in question of Hal's speak in the abstract of the quote/paraphrase I have now presented.

I hide nothing of the Q. The mighty chew of the gulp is waiting for the physicks teacher if I taught myself anything, we are worlds apart we do not see the sick'inn ING way I look at that ECU/ECMmmmmmmmm Due I love speaking in the abstrack is track this practical even down to the _____________ Fill in the blank.


Have you noticed I do not bait your hook and now try to fish I say no more. How about we 3-way the line with a few knots to knot the groupthink. If we are waiting for the physics professor to answer a physics question 7 ways the crap shoot are we 11 up or 7-UP?

I'm more laying out more than 19 fundamental variables if you want to hug the black box any. There are 6 here calling for the answers and where is the principal? Out to lunch?

You're snowed in. I'm rained out. Someone has to be very careful not to hit the link I waste your minutes is that warning banner out we are in RACE Mode and I do not speak any other language.

A smoothing we will go. Upset one car after the other taking line out of lane are the deer eyedoorslammers.

[cntrhub]

Here's a little story for you and you may come to your own conclusions. In college, I tried my hand at 'creative writing' and flunked the course. I took a logic course and of course I failed miserably.

As my body aged into a crippled, limped, old, you get the idea, I was hit on the head one too many times. And now you know how I conditioned myself to learn logic and creative writing my way.

Not my problem we now half a professor at large. I'm about to half bake a fish fillet if someone stands in front of that fish market I use no ice when I sell fool injection.

I more profess to be the fool here. One thing you better not do is point a finger at me I ask the qualifier and Hal has yet to 7-UP. And since this is very-very high tech, it comes down to low tech anyone can comprehend.

Hal, I'm asking you, how can I follow that logic. Are we both on the same page? I'm trying to get the professor on the same page and he knows this is going to blow right UP in his face if not yours, Hal.

Even the fish market has an address and there are 42 websites that more or less were lapped-slapped-rolled that pile UP the ramp they had to come race inn year face.

Dis is not any skool you want to attend if I have nothing but professors in front of me is one stick that will end up in the revenge counter we do not read every stick of a word comprehension. This is raw data and if Hal or the author of this thread wants to laugh at someone who rolls down car to race, or backs it out the driveway with OTTO inside? Is why I race in my mind all of the time. No offense. It's just that you cannot take the race out of me if I am constantly tuning the injection system. http://i149.photobucket.com/albums/s...me/present.jpg

This is more the underground if I get to clown around witech. Because bottom line, the communication gap is as far away as a side electrode. LOL. "PAzYearazzUP" is the Bandisolay. No offense to the learned. Dis is your language I use for tech. OK, it's called, english.

I'm going to keep paying for body damage we score a tune if I were say to tuneup a double. Here comes your trouble:

1. Say she is old and that floorboard has a nice wear mark. Well, so says the linkage. You need to clear that away so they are anal retentive tight.
a. Say said linkage has to have maybe a roller type cleanup. Whatever it takes; those two linkages will need a spring loader and a screw type setup to run the linkage. You may want that close in increments to tuning.
b. We are talking a tight linkage so we have no lag on the foot drag.
c. Get it? Main linkage is main. Lag-spring is going to catch up on the sustained throttle. When the manometer hits, you will see one merc line lag. That is your slave if it is spring loaded, say. However, they are bone steady at idle.
d. OK, say you don't want to go through all that re-link slop. Then whatever the OEM linkage is designed like and whatever slop you have, check that main to slave linkage on the throttle blip. If they do not match equally... Why did you roll that pile off the trailer or out the garage. You are not even close yet.

2. Before you sync the main to slave, you need the lows set if there is a low to be set. Do we have a pilot screw? Beats me? Do I know said product? No. Then do you know the 7-UP's anyone has yet to answer we have a few eyes looking but no takers.
a. Racing is a hard game with hard core racers; better be on your game even in the tuneup for a simple street tune. Are we on the same page we just want a book tune and key fob away?
b. Then if you want to hit that starter like before you can remove your hand off the fob, she's running. Guess where those are?
c. Those low speeds (if apply) are your smoothers-fast start-screws. They need to be sunk first but you can walk the engineering backwards who cares. The point is to equally find both merc lines all even-up at the low speeds as well.
d. Then if you want to hit the main-slave, you keep thinking one job. So you job the low screws and you look at those tubes as one re-sync. Only way to see it happen is to set your manometer up and have at it to understand the process happen.

And that is how I would setup the slop and now sync the bodies lows and main. Did that make any sense? Only think left now is the engine's telemetry. Pick a sensor.

Bottom line, you pick a sensor, I'll counter a sensor. As far as my posts are concerned... Dis is Classick 101... No nose pickers or you will be the next fillet you step in front of that fish market. Not my fault the tech is tough.

All I want to do is trailer your fill in the blank...

Race, anyone?

[KANE]

Bottom line, you pick a sensor, I'll counter a sensor. As far as my posts are concerned... Dis is Classick 101... No nose pickers or you will be the next fillet you step in front of that fish market. Not my fault the tech is tough.

All I want to do is trailer your fill in the blank...

Race, anyone?

Cntrhub-

I'm not sure where you are going with your posts, so here's a friendly reminder for the CAC's Terms of Service, specifically what I've emboldened below.

Please keep your posts in the appropriate forums and realize there is an audience for your posts, so one-word or nonsense posts are discouraged. Please follow the individual forum guidelines. What is permitted in one forum may not be permitted in another.

Referring to people as nose pickers, advocating street racing, and gambling (racing for titles) are not the types of comments that illustrate an understanding of the CAC's Terms of Service.

Please keep future posts on topic to prevent misunderstandings.



KANE
Corvette Action Center Moderator

[ironmoo]

The cars now is repaired!

Following the diagnostic chart in the shop manual as suggested.

Under wrapped old black tape was a loose wire for smog testing (?) it had become unplugged with signs of repairs of splices. The connection was missing one side of the plug. Cleaned it and taped it tight for now until I get another plug. Found the Oil pressure switch located on the back of the engine under the distributer. Pulled off the wire, blew off the plug and reconnected.

When I put the key to test the car, a series of little whirs and clicks as if the new ECM rebooted itself then the car rolled over on the 1st time.

The car started and sounded just fine. And no code 42.

The combo of the wiring and old ECM acting intermittently was the cause of the problems.

Thanks all for your advise and suggestions as it greatly helped in the process...and I'm more educated for the workings of the Cross-Fire in the process.

PS: I had once one big smiling face taking her out for the 1st time in months....and the fact there was no CEL on at all for a change!