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Intermittent Crossfire Miss - HELP!

Z

Zora1

Guest
;help Need some help to isolate a miss on a 84' crossfire that has about 70K miles. While driving on the freeway, the engine will suddenly stumble and basically not run for 3-5 seconds. Then it will catch and run great. At first it would only happen once in a while, but now it does it more frequently, and also does it at slower speeds. It has also happened a few times at idle, and the engine will die, but fires right back up. At first I though it was ignition related. I have recently replaced the wires, distributor cap, rotor, plugs, ignition coil & module. I also replaced the fuel filter. While it seem to run a little better, nothing fixed the miss. Next I thought it might be fuel pressure related or that I might have some water in the tank. However, after replacing the fuel pump and cleaning out the tank, no improvement was seen.

I have also done some other modifications, such as Flowmasters and a 160 thermostat prior to these problems. The car has never thrown a code, and I have searched extensively for a lose or chafed wire through-out the engine.

Does anyone have any ideas of what I should look for, or what parts I should replace next!
 
H

HOWSER

Guest
Sorry for the delay in answering, somebody should have told you about the secret handshake just kidding...I saw your other post). My 82 had the same problem, you should check the setting on your TPS (throttle position sensor). Sorry I can't remember the actua setting but someone will chime in on it soon, or you can check your manual. This little sucker, when not set correctly will make that x-fire do some whacky stuff!

You should also do a search for a crossfire website/forum, it's been so long that I've been there that I can't even remember the address. They are dedicated to the 82/84 engine and can help you alot!

I hope this helps and sorry if I was a bit vague.

Eric
 
L

LarryK 87

Guest
TPS settings ( assuming they are the same for all L98's )

.54v throttle closed +/- .08v
4.5V @ WOT
voltage measured across top two wires @ TPS

at least those are the settings on my L98
BTW the progression from .54v to 4.5v should be smooth with no drop outs / flat spots
 
Z

Zora1

Guest
Larry,

Thanks. I do have a digital multimeter, but am pretty new with it. Will I need to buy a tester unit from one of the vette sites to test the TPS, or can I just rig it myself?
 
L

LarryK 87

Guest
i just use a standard DVM myself( with a fine tipped probe), carefully penetrate the weatherpack, until i get a solid reading.
I have also used standard jumpers to create a quasi-patch cable when the need arose.
BTW you can also use a paper clip to penetrate the weatherpack connector .
 
C

c4ever

Guest
You may want to check your EGR. My slight miss on the 82 was caused by EGR and no codes were set. TPS setting 0.525(+/-.075) ignition on, not running. Use jumper wires between harness and TPS. Meter across terminals A&B (should be two bottom terminals on TPS).

Carlo
 
E

Eagle85C4

Guest
Hello...

Do any of you folks read the previous posts? Read through this thread and you will find that 2 of our members have given the guy 2 completely different sets of info for setting the TPS.

So now which is it...the top 2 wires or the bottom?
And what is the correct voltage? .54 or .525?

Maybe this site should offer a page for these simple fixes and repairs with the correct info and procedures so no one gets bum info when trying to figure out problems. Nothing worse then chasing a ghost through your car only to find out the info was bad and time wasted. my .02¢
 
L

LarryK 87

Guest
hate to be a stinker.... but read the posts
TPS settings ( assuming they are the same for all L98's )

well since mine is a non cross fire ( noted in the post ) i can not vouch for orientation of the wires ( top or bottom ) The manual spells that out. A & B are the terminals needed.

Voltage however is the same .54 +/- .08 and the other post was in line with that .
.54 +/- .08 = .62 to .46 or
.525 +/- .075 = .60 to .45
makeing .54 AND .525 with-in tolerance both are acceptable


i did however neglect to mention ( but C4ever did mention ) that the measurements where with Ignition On, and Engine Off. I would assume no one would attempt to work on the motor or measure any voltage ( or anything else for that matter) on an engine running at WOT in a static condition.
 
E

Eagle85C4

Guest
Thanks Larry for clearing that up. I knew what was right asI have all the manuals availabe to check. Some are not as lucky, and actually need the info provided. Ken is usually right on time with help and info for folks, and when he does not know he says so, and more times then not goes and finds the info and returns with directions to where it can be found.
I guess what I was pointing out was that all of us need to pay more attention to what info we are passing on.
 

rwd

Well-known member
Joined
Jan 22, 2002
Messages
234
Location
Yes
Corvette
Varies
If the engine is cutting clean, you might try jiggling the ignition switch to see if it catches, or jiggling it when it's running to see if you can interrupt it. I've heard of problems resulting from the switch though I haven't had the problem myself.
 
Z

Zora1

Guest
Thanks for all the replies! Just finished testing the TPS, and it is the bottom two wires. Mine currently reads .477, and operates smoothly hitting 4.46 at WOT. I also played with the ignition switch, and could not make it miss or stumble. I also wiggled every connector & wire I could find to see if anything might be lose or cause it to cut out. Nothing had any effect, and it continues to run perfect in the garage. I ordered a reman ECM unit this week from the dealer, and also ordered two distributor terminal blocks. The Eckler's catalog said the terminal block should be replaced at 75K, though I don't know why. At this point I just want to fix it, and am willing to try any suggestion. I should have the new parts by Friday, and will see if they help. Any more ideas, and how do I check the EGR?
 
C

c4ever

Guest
Zora,
If you need the EGR diagnosis chart shoot me an e-mail.

Carlo
 
C

c4ever

Guest
Eagle,
Regarding discrepencies. I merely augmented Larry's information. As he stated, he does not own the cross-fire. I do. I simply clarified and noted A/B locations. In addition, his measurements were correct and not as you imply as incorrect. I think we all realize the variables when soliciting information.

Carlo
 
E

Eagle85C4

Guest
This I understand. But not all are graced with the necessary abilities to articulate the various processes pertaining to the periodical maintenance and upkeep for the Corvette. At best some of these processes can be trying even for the seasoned veteran. To a complete novice, the difference in suggestions from this particular thread could cause confusion or possibly a non functioning vehicle. Which would be a reflection on all of us here at CAC. I was merely pointing out the we collectivily should take care when submitting information to those seeking help. Not that it is possible or necessary to acertain the level of technical ability of those asking, but for the general issuance of information. I try to help where I can and on subjects I am well versed in. And try to present the information in a technical yet understandable verse. Conflicting information can be very confusing. It was not necessary for me to disect the voltage variables as I can see that .525 volts falls within the variable allowed for the setting. But not all are engineers.
Finally, it was not my desire to demean you or anyone else, just pointing out what possibly could be construed as a discrepency, and that we should be careful not to allow that to happen.
Take care Brother...
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Walking thru the bar room brawl

Was this the first question?

( sticking right foot out, hopping in circle, left index finger in ear.. extending right hand in circular motion )


Since everyone in here is to busy BICKERING..... has the problem been fixed?

and...... if not, how has the problem changed?


Vig!
 
L

LarryK 87

Guest
awww geez... now anyone will be able to find the secret post code..... nice going vig
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Actually

That's the Red Dwarf UK secret hand shake NOT the CAC one



PSYCE!
 
Z

Zora1

Guest
Vig,

Not sure if the problem is fixed, as it takes a couple of days of driving to see if it recurrs. Drove it to work today, and it didn't miss once. I also changed the fuel filter for a second time last night. I had replaced it last year, but since I changed the fuel pump and might have loosened up some junk, replaced it again. Not sure if it's my imagination, but it seem to have more power when I floored it. Anyway, am going on a 2 hour cruise with the corvette club this weekend to Cordele, GA, and well let you'all know if the gremlin is still there.

Zora
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Cap & Rotor

When did you last replace em?

And your plug wires?

Vig!
 

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