404notfound

Hello everyone,

Recently purchased a 1986 Corvette 4+3 with 9,000 original miles. It drove perfect for a week or two with the only two issues, 1. being a code 32 CEL (EGR) after prolonged cruising on the hwy (no drivability issues) and 2. no OD, it would sometimes engage once during a 45 min drive.

After some research on these forums, I discovered the two relays next to the brake booster on the firewall, with one of them being the OD relay. I read to switch the relays to see if I get OD. After switching them, voila, I had OD! Now the only problem left was the code 32 on the hwy. It was like this for about a week.

Now here is where things go down hill.... was driving back to work from lunch and romped it on the onramp to the freeway pretty good to get up to speed. Once I got back down to cruising speed, 5 min later, the car bucked, and kicked me out of OD and I immediately got a CEL. I tried, pulling over and turning the car off and on again to see if the CEL would go away; it did not and still no OD. Once I traveled for a little while longer (1-2 miles), I pushed the clutch in to switch gears while slowing down and the engine died. The car restarted, but would not idle without me pushing the gas. It remained this way until I got to work when all of a sudden, the CEL disappeared and the car idled fine. Used a paper clip to pull the code, and I only got code 32 again.

On my way home that day, it would drive fine (with OD) for about 15 min, then buck as before (CEL too), kick me out of OD and stall if I let off the gas. After restarting, it would be fine for another 10-15 min and the symptom would repeat.

I have completed the following in an effort to resolve:

1. Re-heatshrinked the wires for the two solenoids. Thought they might be shorting together as some bare wires were exposed.

2. Cleaned and re-installed the EGR.

3. Examined the TB and IAC, both appeared to be clean.

After this, I took it for another test drive. It drove PERFECT for the first 30 min. Then the same exact symptoms appeared, lost OD, CEL, no idle.

Once I limped it back home, I decided to switch the relays back to their original places. Drove it for 20 min with no issues besides not having OD as originally stated (no CEL).

At this point, I thought, bingo I need to get a new OD relay. I purchased two of them and replaced them. SAME ISSUE, except now I immediately get the CEL upon cold start up. It was not this way before. It will idle when cold (1200-1100 rpm), but once it reaches operating temp, it will not. Another item to note is that the CEL will flicker as if there is a loose connection somewhere (it also did this before). When I try to pull the code, the CEL flickers and resets, preventing me from entering diagnostic mode. Thinking that the front most relay is the fuel pump relay, I tried replacing it with my original one, but it did not change the CEL and idle problem.

All the wiring and vacuum hoses appear to be in great condition as it only has 9,000 miles. I suspect the relays as the problem, but after changing them, the problem is the same.

Here are my questions:

- Is there a way to bench test these relays?
- If one of them is the OD relay, what is the other one? Is it the fuel pump relay?
- If the other relay is in fact the fuel pump relay, would a bad fuel pump relay cause these symptoms? Would that cause me to lose OD and get a CEL?
- Which one is the OD relay? I've read posts saying both positions are it.
- Any other areas I should check?

Please help!

404notfound

Also, one other thing I'd like to add. When this problem occurs, the upshift light in the dash is stuck on. The instant fuel economy and range (miles until empty) both read 0 regardless of my mph or fuel tank level.

Cliff Harris

The relay in the back is the fuel pump relay. It has nothing to do with your symptoms.

You bench test the relay by applying 12 volts to the relay coil and checking the NO (Normally Open) contacts to make sure they are connecting together (resistance near zero).

The average MPG and range numbers are calculated by the dash. The ECM sends the fuel injector pulse width to the dash and the dash uses the VSS (Vehicle Speed Sensor) output to calculate these values.

404notfound

Thank you for the response, Cliff.

Since the problem appears to be outside of the relays, should I begin checking the ECM?

AGENT 86

Here is some info on code 32 from my 86 manual

http://members.shaw.ca/corvette86/Code%2032.pdf

Your relays may be just fine.
The ECM will allow OD when all parameters are met, so it is likely that the ECM is not happy and disengaging OD.

404notfound

Thank you for the link, Agent 86.

Your post got me thinking. If I'm driving along at 65 mph in 4+OD and all of a sudden it kicks me out of OD and I get a CEL, there's not many things that can cause this. After reviewing the table listed here:

http://www.5speeds.com/43table.htm

It appears that the only time OD will kick out of 4th is 75% or more throttle is applied. I'm guessing the ECU gets information about the throttle through the TPS. Maybe mine is acting up. Also, if the ECU and IAC work off of the TPS voltage, this would explain the failure to idle.

Does this seem logical? Should I go through the TPS test procedure? It isn't helping that I can't pull codes, not even the 12s.

AGENT 86

Code 32 was kicking out OD
I would deal with the exhaust temp switch problem first.
Disconnect the exhaust temp switch and see if the CEL disappears at start up.The switch is at rear of intake manifold where EGR gas tube enters manifold.
Then see if your able to check stored codes.

404notfound

OK, disconnected the exhaust temp switch and turned the car on. Car idles very poorly, maybe 400-500 rpm (engine cold). CEL remained on during idle, will disappear if I give it a little gas to raise the idle to 1100 rpm or so. As soon as I let off the gas, idle returns to 400 rpm, CEL reappears.

Tried pulling codes using a paper clip and this does one of two things:

1. CEL remains on, does not blink.
Or
2. The CEL disappears and does not come on at all.

Some things that I noticed during this test was my range and upshift light in the dash were displaying correctly. My efan was running even though the engine was cold and the AC was off.

As a test, I disconnected the TPS and the behavior was very similar to with it plugged in. Poor or no idle, would run if I kept my foot on the gas.

What should I try next?

404notfound

Update:

Tested the TPS. I get .63 volts at idle, 4.3 volts at WOT. TPS appears to be good. Back to square one....

whalepirot

while differing symptoms, but food for thought:

I fixed a cycling O/D, while on cruise, steady speed, by changing spark plug wires. That's ALL I did to the car.

I reasoned that the partial miss from old wires allowed the O2 sensor to tell the ECM that the car was in open loop, which prevents O/D engagement. the car had a different cam and tune, which was also part of the richness.

If the O/D light cycles along with the disengagement, it is electrical, not fluid, possibly proper operation as the ECM sees things.

Isn't one of those relays for the fan? Tis, on my '84.

404notfound

Update:

Cleaned and reassembled IAC and am trying to set idle. Currently have the IAC disconnected and running the car on the TB set screw to bring car up to normal operating temperature, but it will not run once the engine reaches 145 deg.

Checked fuel pressure and I'm getting ~42 PSI with key ON during fuel system prime. 40 PSI with car running. This pressure holds after the car dies when it reaches 145 degrees.

The problem appears to be ignition related. Replaced the distributor cap and rotor (they looked pretty bad), no difference in behavior. Car runs rough when cold and all dash lights operate normally. Once engine coolant temperature starts reading a number past "LO," upshift light illuminates and fuel economy readouts change to 0. Will stay this way until 145 degrees and the car dies. Unable to keep car running with giving it throttle. There is a CEL while the car is running, but no codes reported when in diag mode.

Cliff, you said:

So the ECM sends the fuel injector pulse width to the dash for the fuel economy numbers. What about the upshift light? Do any of these values on the dash use the Ignition Control Module or pick up coil pulses? My problem appears to be related to this symptom. Trying to narrow the problem down to ignition and/or ECM/prom chip.

404notfound

I also cleaned/inspected the ECM/sensor ground on driver's side of block, no change.

VikingTrad3r

404notfound

Uh oh, popcorn.... did I do something wrong?

DanielRicany

I think the issue is probably a faulty ECM. You should get a scanner on the ECM and watch the data stream as the problems are happening and see if anything looks funny.

404notfound

Thanks for the reply, Daniel. What is a good scanner to try? All I have is a OBD2 scanner.

VikingTrad3r

On the contrary. You are one of the few who come to the table already having tried numerous solutions. I sub'd to see what the resolution is.

Regards,

VT.

confab

^^^^ This sounds familiar with the flickering CEL light and recurrent, incurable code.

Mine had a coolant sensor code and the light would pulse sometimes. Sensor was perfect. Circuit was perfect. Sometimes could not pull codes.

Replaced the ECM, code is gone and the light doesn't flicker.

404notfound

Whew, awesome thank you! I'm trying here!

404notfound

Interesting. Was it your ECM or prom chip or both?