1984 Crossfire problems

I have an 84 Corvette with 130,000 on it. It has run great for the last year, but now is posing some problems. The car starts hard, but then appears to run fine until it reaches the 190 degree range. Then it starts to vary the idle speed from 400 to 800 almost continusly. During this process it sometimes dies, and has an incredible hard time re-starting. Once the temp hits the 220 range it appears to start runnung well again. The only thing I found was the ignition timing was set at 0. Book specs says it should be set at 8bftdc. I made the change, but nothng different excet a higher idle. Any one have any suguestions as where to start?  

do you have access to a scan tool?????

the engine coolant temp sensor is on the front of the intake manifold...  replace it along with the pigtail...    you do have to remove the smog pump to do this...  takes just a few minutes...

the new pigtail  comes with white wire...   replace as much as possible without unwrapping the end of the harness too much...  while you are in there.. swap out the thermostat for a fresh version... 195F please..

the cooling fan switch is on the right cylinder head.. between and just slightly above the number 6 and 8 spark plugs...    examine that pig tail also.   if bad.. replace it...  that is the override switch.. turns on the radiator fan if the ecm fails to do it..  you do want back up...

there are ECM ground wires on the intake somewhere...    either near the thermostat water outlet or on one of the studs that hold the top cover to the intake base...  if these come loose.. you will have problems..

timing is important...  i am almost sure that you have to jump the A and B terminal on the aldl connector to set the timing..

since you will have the air cleaner off... aim the timing light over at the injector spray cones/patterns..  see if they look nice and even..  when the fuel pressure gets weird.. the cone shape will not look right..

you might also want to pull the cap coil cover... examine the coil for powder marks around the outside of the central windings...  circular patterns of dust or white powder... show that the coil is leaking high voltage..  makes a big difference.

many of these have had the timing cover replaced..  they have the 12 o clock timing marks on the damper..     mr gasket makes a special bolt on timing pointer for these...    its really long..


have you replaced the fuel filter??????    was it clogged?????     have you pulled and inspected the fuel pump and strainer .. or just replaced them.. be sure to order a replacement gasket first..  they don't come with just the pumps..

have i found your exact problem???      probably not.. but these are the things that go bad and can cause your problem... it could be one or all...


a few months ago... i got one of these running for a friend..84 XF C4 when he took it for a test drive.. i yelled at him to punch it...  when he did... i could see the smile growing on his face even from behind...  

Thanks for the info. I decided to do some explority surgery, as the intake manifold gasket was leaking. Replaced upper and lower, found the carbs to be extremll dirty, espically the air idle controls(they were completly covered with build-up). All the temp sensors are new. But when I finished I found the rear injector was simply just dribbling fuel out of the injector. I did not notice this before. So I changed the injectors around, yes I know they are different part numbers, and the same thing, the rear injector just dibbled fuel. Therefore, I have to beleive it is somewhere in the fuel line, I don't know, it does not make much sense. The fuel filter and pump have not been touched that I know of, that will be the next step. Just a bit of info to others, I found that every seal and every plastic part under the hood was damaged due to heat, guess that is what happens when it is 25 years old.  

start with this link...

http://www.corvettefever.com/howto/51218/index.html

i wonder if the wiring at the injector has failed at the injector connector.. at the computer connector... somewhere along the route ... i seem to recall the ecm might be behind the seats..

time to break out the ohm meter and ohm it at the ecm connector .. with the injectors connected...

by the way.. did you find Orings for the fuel lines..????    

it could also be the computer failing...  bad solder joints..   the computers can be opened.. and resoldered.. with care...

there is at least one more article.. that shows hot to hop up the crossfire..  and it covers resetting the crossfire linkages as i recall..  

What orings, the ones in the injectors, if so I am still trying to locate new ones. The injector with the problem, the larger oring is swelled up, and will not go back in.  

for the injector seal kits..  you will have to look in the box to verify what you need.. enough for one throttle body or two

here are a few part numbers

delco

FUEL / TBI GASKET KIT
01 219-606 GASKET KIT,TBI ALL MAKES    TUNE-UP KIT     delco tune up kits are like carb kits.. gaskets o rings and seals ...    
   

autozone
Gp-Sorensen / Throttle Body Injector (TBI) Kit
For your 1984 Chevrolet Corvette 5.7L TBI 8cyl
Part Number: 96-629


you might also want one of these dual fuel pressure regulator kit
also at AZ
Gp-Sorensen / Fuel Pressure Regulator Kit
For your 1984 Chevrolet Corvette 5.7L TBI 8cyl
Part Number: 800-261



these are the large fuel line seals in a bag of 10
these should be the large fuel line and filter Orings
Gp-Sorensen / Fuel rail O-Ring
For your 1994 Oldsmobile Cutlass Supreme 3.4L SFI DOHC 6cyl
Part Number: 800-9214

these should be the small return line O rings pack of 10

Gp-Sorensen / Fuel rail O-Ring
Part Number: 800-9215
i actually keep a package of each in one of my parts bin boxes... so i always have some...

be sure to lube the housing with a tiny amount of grease of some kind.. white lithium.. ??    something to let the o rings slide without pinching..

i an still looking for that article on how to clean and assemble them...  and reset them..

http://www.chevyhiperformance.com/techarticles/65138_adjusting_tv_cable/index.html

i found it....  anybody with a crossfire system really needs to book mark this one...

http://www.corvettefever.com/techarticles/4688_chevrolet_corvette_efi_system_tuning/index.html  

Ok, pulled it down to the intake gasket. New intake gasket kit, overhauled carbs including new air idale controls. Runs and starts good. However, when it heats up, I loose power. I have this to ask. I know the injectors are different part #'s, do you know what symptoms it would have if I put the injectors in the wrong carbs?  

Switched injectors, no noticible differece, but, I now have backfire out of the carbs with fast onset of the accelerator. Also noted, this blows the egr vaccume line off. I want to beleive this is a timing issue, and that I am not aware on how to time the vehicle. I have jumped the a&b at aldl, unplugged the esc, and some brown wire near the power booster. Also, does anybody know where the grounds fro the emc are? I located one on the manifold, but am unable to locate the second ground.  

i noticed the different injector part numbers also.. but i really don't have an explanation..  perhaps on of the vette history buffs...    perhaps it is to get rid of the lean backfire...

how did the ignition coil look????  

the grounds for the ecm are usually on a stud near the water outlet..  but could be on the upper intake ... i can picture it.. but i don't have a crossfire infront of me...

do you have a scan tool...    to properly work on these cars you really need one...

they are getting cheeper and cheeper ...  as more and more people upgrade to newer cars and don't need the older scan tools...

did you change the coolant temp sensor in the front of the intake below the smog pump..

i almost recall  the last one i worked.. on.. having to take the fan belt off.. and taking the smog pump off so i could get a good look straight down behind the water pump and timing cover..  that as i recall was the only way to see it...

you can start and run the motor for a minute to set the timing with the belt off...  without doing any damage...  a minute is long enough to set the timing..

can you still read the emission label???? the timing instructions are printed on that..

i would bet that replacement emission labels are available for that from restoration houses..    the smog guy gave me a few year old smog handbook.. tells what the timing is on a lot of cars and how to test it..  i just don't know where it is right now.. i will look and post what i find...


you do realize...  that these things idle really slow when they warm up...

got a vacuum gauge??? any chance the cat is plugging up?????  

Well, here is the long of it. I took the engine down to the intake gasket (was leaking). Replaced intake gasket, upper and lower. Rebuilt both tb's with full rebuild kits. Replaced both air idle valves. It was amazing the thing would even run given the condition of the air idle assemblies (one fell apart when I removed it). Figured out how to correctly time the beast. Decided to replace the o2 sensor, there only $19.00. The car runs great, but there is always a but. The only problem I am chasing now is an intermittent check engine light. It only comes on at an idle, about 600 r's. As soon as I reach about 1000 R's it goes away. There is a definite miss in the vehicle when the light is on. When you get on it hard it stumbles, however this problem is not there when the engine light is off. Also, you can hear something click, and the fuel flow change when the light comes on. Oh ya, I guess there are 2 problems. Something I did during this process caused the cooling fan to quit working. For good measure I replaced the sensor, but had to ground the green wire on the relay to get the fan to work. It now is on when the key is on. I checked the circuit, and can not find the problem, but know it is related to the yellow wire that goes to the sensor. If I jump it to a live wire, and compete the circuit with the black ground wire on the sensor it works, however the vehicle runs badly. It did not appear to affect the performance when I grounded out the relay. Does anybody know where the yellow wire goes? Where it would have been connected? I looked into a code reader, but found they only ground out the aldl, so I did that myself, but I am too dim witted to make out the codes. I will try to make it out later. Overall it runs good. Would like to get the cooling system back to factory, and get rid of the engine light and bog. Any suggestions are welcome, and appreciated.  

One problem may be due to the harmonic balancer being broken. The coupling material linking the inner and outer rings deteriorates, allowing the outer ring (with the timing marks) to move relative to the crankshaft-coupled inner ring, making it impossible to time the car until you replace it (got that tee shirt).

Use a scan tool or a paperclip to pull the ECM codes.  This is as essential as the usual basic engine checks (vacuum leaks, good spark and fuel, etc).  Seems you are well versed in them.  You also need a digital VOM (volt-ohm-meter)and basic skills with it to check resistance and voltage readings.

There's some misinformation in the above posts; not interested in discussion of that, I suggest, given your obvious mechanical ability, that you get the factory service manual which has flowcharts for each ECM code.  Much of the trouble attributed to the ECM really lies in deteriorated electrical connections (as you mentioned) whether dirty, corroded or melted, OR with failed sensors and the manual states, then assumes that the basics were checked.  Smart repair guys look to the obvious and simple first, then move to the complicated (throwing part$ at it).

Mileage-based maintenance includes fuel filter and O2 sensor, in addition to other usual items on a non-ECM car. The GM plug wires were excellent on that car but eventually need replacement.

The '84s TBs throttle shafts will erode the bodies.  They may need bushings to stop unmetered air from entering the engine, making it impossible for the ECM to properly control the engine based upon that unknown.  Kits are available to rebush them; but it's been years since I did mine, so I cannot offer a source.

I had to rebuild the injectors due to leaks; a seemingly simple yet tricky job.  Properly synchronizing the two after removal may require the rare specialist.  I never removed mine from the base.  

I have the car working great, except two things. I have a throtle position sensor issue, but the bigest problem is the coolant switch. The sensor will not turn the fans on. I jumped a ground wire to the yellow wire on the sensor, and , bam it works, but the ecm starts to make the car run poorly. So does any one have a schematic specific to the cooling sensor system?  

i went searching... and found this..

http://www.fastbird93.com/Diagnostics.htm

you really want to print the 4 pages... 2 for code 14 and 2 for code 15

be sure to check the lower right corner of the page.. the no start diagnostics..

that page is for TPI... not crossfire.. but most of the diagnostics are the same...


do you have a scan tool????  can you monitor the coolant temp on the scan tool...

the crossfires will not turn on the cooling fans until the coolant temp reaches 228F...

if the ECT reaches 228F and the fans do not come on..  there are more charts.. i will continue searching...

did you change the pigtail and the sensor to the oval connector  instead of the round coaxial connector...     can you measure 5 volts almost exactly on one wire.. when the key is on and the sensor is unplugged..   i have also had other models of GM cars have the insulation fall off inside the wiring harness...  this is a yellow and white twisted pair..  if you don't get a full 5 volts on one wire... or if you get it on two wires...  you have a problem..   its all in the charts for code 14 and code 15...


wait.... i ran into this... the cross fire ecms  do not control the engine cooling fans..

here is the crossfire engine diagram..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/fd/98/large/0900c1528008fd98.gif

the cooling fan switch is in the right cylinder head between the 5 and 7 cylinder..  the wire drops down to the starter harness.. as i recall..

here is the diagram for the cooling fan harness..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/fd/a0/large/0900c1528008fda0.gif

lower right...    see no connection to the ECM...   i work on so many i forget the details sometimes...

Duralast / Cooling Fan Switch - Radiator
Part Number: SW500
http://contentinfo.autozone.com/znetcs/product-info/en/US/wl2/SW500/image/8/

the pig tail is
Duralast / Connector - Coolant Temp Sensor
For your 1984 Chevrolet Corvette 5.7L TBI 8cyl
Part Number: 231
OEM Number: 12102621
http://contentinfo.autozone.com/znetcs/additional-prod-images/en/US/wl2/231/3/image/8/


i looked for delco part numbers...  they have changed their site.. i cannot find them...

i also install a switch that taps into the wiring that goes to the fan switch.. the other side to ground... so when i need to do something on the engine... i open the hood.. turn the key on...  but not the motor.;. flip the switch and run the engine cooling fan for a minute or two... really cools stuff off so you can touch it..  i also label it.. so everybody knows what its for...

the cooling fan switch is not even shown on this component locator..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/fc/a3/large/0900c1528008fca3.gif  

I have that schematic, however I was under the impression that the coolant temp sensor listed was the one on the front of the intake. From what I gather you are saying is the sensor that controls the fans is in the right cylinder head. I was under the impression that was strictly for a temp guage. That could explain the problem, as I have not touched that sensor. However, that leaves me confused, as to what the purpose of the sensor in the manifold is, if the fans are not controlled by the ecm. The other thing is if I ground out the sensor in the manifold(at the pig tail connectin, which is new) the fan kicks on. Also there is no voltage to either of the wires that go to the sensor in the manifold, until I ground it out that is. I also get code 14, 15 and 21. I don't own a scan tool. went to buy one, and found it was a $30.00 paper clip, so I did not buy it. Just figured out I don't have the cooling schematic. That is helpful. It looks as this is a simple system. But again, what is the purpose of the other sensor??  

the sensor in the left head is for the dash board...

the sensor with 2 wires in the front of the intake manifold is the COOLANT TEMP SENSOR... for the ecm...  that sets fuel ratio...

the sensor in the right cylinder head is for the engine cooling fan...

this is only on the 84 crossfire motors...



with a paper clip... you can access trouble codes... if any are set...

with an scan tool that will plug into this system.. you can look at a lot of sensor voltages...

is the sensor in the front of the intake... does it have an oval connector??? with 2 pins in the end of the sensor...

or does it have the circular connector that looks like a lap top power connector..

with the coolant temp sensor unplugged and the key on...   you should get 4.95 ro 5.0 volts on one of the wires...  when the other test lead is grounded to the upper intake manifold..


when you open the links over at the firebird page...  you can drag the images to MS Word.. and enlarge them so you can read them...  you have 6 pages to print...

on the coolant temp sensor..  with the sensor connector unplugged  the yellow wire should have really close to 5 volts DC...  the other side should have ground... it also hooks to the Throttle position sensor.. black wire..

print the 6 diagrams.. follow them.. post what you find..

i will be back on tomorrow..