c4mo

I have a 85 corvette that runs rich and wont idle, dies when i let off the gas. The car throws no trouble codes. I have two different proms ive tried and they make no difference. I have a otc scanner, multimeter, and injector pulse tool, among other tools to check components on the car. Below is a list of the things ive checked today with no change in the running of the car, any advice is appreciated.
*injectors all ohm at 16.5
* injector pigtails from harness all read 12v
*Injector pulse tool bleeds all injectors from 46 to 40 psi they all bleed the same which eliminate the possibly of leaking injectors???
* timing set at 6 degrees and verified
*fuel pressure set at 46 psi
*tps voltage at .58v at closed throttle
*coolant temperature sensor pigtail reads 5v, cts reads correct resistance for the varying temperatures
*valves adjusted correctly.
*new spark plugs and plug wires
*02 circuit working, always reads .6-.8 volts(rich of course, but does very) cross counts working in scanner
*does go in to closed loop
* less than 2000 mile old oxygen sensor.
*iac pigtail voltage 11.8 (key on)

gkrynick22

Curious about two things

1. What brand O2 sensor. I have read tons of posts about certain brand O2's being junk

2. You tried two different proms or ECM's? I had the same issue you did when I first bought the car. It ended up being a bad ECM. I bought a remanned one from advanced auto parts for $100. Problem solved. The difference between my issue and your issue is my check engine light was on but, when I tried to pull a code nothing would happen.

bjankuski

Is the car stock or have stock injectors or stock rated injectors. If the injectors have been changed to something other than stock a new chip may be needed.

Check to make sure your fuel regulator is not leaking fuel back into the intake through the vacuum line.

c4mo

I tried two different proms not ecms, the car is not stock each prom is for a different engine combination, but still does have the stock 24lb 85 injectors. The oxygen sensor could be bad, however the car runs rough in open loop, before the ECM is using the o2 as a input. Another reason I think its good is the went from running fine to this.

c4mo

Checked the maf by switching it out, no difference. Took the prom out completely and it wont idle but does run cleaner and doesnt smoke. That doesnt make sense because the prom has worked fine in the car for over a year. Im thinking a faulty ecm? Or maybe not, ideas? Thanks

THE 383 admiral

(CTS) Coolant temp sense... will give you that condition.... and is very common....

c4mo

checked afpr just now, no fuel in the line. When i had the prom burned i had the egr deleted out of the program. However the valve is still on the intake i wonder if the diaphragm has gone bad, making me have a internal vaccum leak, making the motor run rough and be constant rich?

Also i checked the coolant sensor already, it reads the correct voltage from the wiring harness. and the sensor reads the correct resistance for the temp its at, although of course it varies with the temp

THE 383 admiral

if your worried about inspections... Grind the EGR flat on the bottom... block off the EGR with a plate... you have it deleted anyway....

ddahlgren

Do whatever you have to do to keep it running I have used a matchbook cover between the idle stop and lever if alone. Pull one injector at a time and see if they all make the same change in rpm. If not the one that does not make a change is a bad cylinder for whatever reason. With a dead cylinder you are pumping air making the ecm think youare lean so it adds fuel to the others and the lambda looks right but is wildly rich.
Dave

R59

Had the same problem......just replace the CTS

84cfi

I had the same problem with my 84 vette, changed thetemp sensor now runs great.

NEVER TRUST A SENSOR.

John A. Marker

Also 46 psi is too high a pressure for your 85. Reduce it to about 39-40.

vader86

From my understanding the ECM mainly looks at TPS, CTS, and its built-in tables with MAF in open loop operation. I'm assuming your injectors are not stuck wide open.

If the TPS reads fine, and you've checked the MAF, then I'd suspect either the BLMs were way off in the programming, or the CTS is toast.

c4mo

Vader,
Your exactly right the blms are 108 way rich from 128, and the injector pulse width is way to much for idling. Wouldnt this be prom related however, or is it internal in the ecm? Maybe the small calpak by the prom? I went ahead and got another cts sensor and remanufactured ecm to try today. I let everyone know how it turns out. Thanks

ddahlgren

I thought you checked or would have brought it up.. If you can read BLM you can read coolant temp what does it read and what do all the other sensors read? Do the readings make sense..
Dave

93Rubie

Do the L98's have a Intake Air Temp. sensor? IF so, check that and check if it is close to CTS before a cold start.

Someone recommended a power balance test, I second that. Will tell you if you have a whole engine issue or one or two cylinders.

Also, explore the idea of vaccum leaks/air leaks in the wrong places. Like in the exhuast before the 02. Fuel pressure regulator is another.

Dirtpoor

ok does anyone know if this fixed the problem. I am having the same issues. Can someone please let me know if this helped. My car has been seating for 3 years because i cant figure it out. It was running great I stop at the store came out and it has ran like crap ever sense.

billschroeder5842

Or anyone over 30 years of age.

Wait.... I'm 55.

Nevermind.....

Rhensonsr

Not sure if this will help but I had the same problem with my 84. TPS and CTS were the problems. I also replaced the injectors, wires, cap, rotor, plugs, O2 sensor, and fuel regulators. Each item made it run better but the TPS and CTS ended the running rich problem. Now I am on to replace the valve seals to get rid of the smoking.

Redneck15racing

Same problem...my injectors open all time key is on do you have 12 volts between two pin on injectors with key on