sjjb7

I'm new to the forum and a new corvette owner but already need some help with my '82 Crossfire. It all started with the check engine light coming on during highway driving at above normal speeds (I'll leave it at that). She had just come out of the shop where I had the AC replaced, fluids changed, brakes repaired, valve cover gaskets replaced and a few other minor repairs. By the time I got home, the car was running very rough leading me to believe it was fuel starvation. I replaced the fuel filter right away which did not help. The next day it would not start and I found Codes 15, 22, and 34. Before taking corrective action, I found the injectors were just continuously dumping fuel after startup (it would not stay running). First, I replaced the MAP sensor and, after a couple of tries, it started up and off I went. I made a round trip of about 10 miles to a gas station and she ran fine. The next day, it starts up but will not stay running. Since then, I've replaced the coolant sensor (original was still in there) and the TPS. Still wouldn't run. A check of the entire fuel system revealed no other problems there (pressure good, everything tight).

Still starts right up but won't stay running. I moved to the ignition system and noticed the spark was not as hot as I thought it should be. I've now replaced the pickup, rotor and coil (cap was good).

I know it needs new plugs and wires but I don't want to replace anything else until I solve this problem. The current plugs are burning fine all the way around.

Could it be a bad ECM? The original is still in the car. The previous owner replaced the original chip with a high performance chip years ago.

Let me say that this car was running great when I got it but it had not been driven much in the last two years.

So, any ideas out there. I've spent hours reading previous threads and have done some of the things suggested to others without success. No comments about replacing the CFI, I won't do that. But it'd look better on the street than in my garage.

...Roger...

Did you check the EGR valve? I replaced one the other day.Also check to see the guys didnt get some wires stuck under the valve covers.Because of the recent repairs I would be looking for something they disturbed.Those damn prof. mech.s cant be trusted.

sjjb7

I did not check this with the car running and now, of course, I can't get it to run long enough to check. It appears to be good (diaphram movement is fine) but is there another way to check it?

sjjb7

Also, to your other point, I have checked everything under the hood since I got her back and nothing seems out of place. Nothing stuck under the valve covers.

...Roger...

If you can get the diaphram to move freely its probably ok.Its pretty easy to remove and check also.

okinawa86vette

I'm in the middle of a business trip right now, so I don't have any of my code books with me. But, using the internet to decifer the codes, I can probably help a little....

code 15 is for low temp/coolant sensor
code 22 is for low throttle position sensor voltage
code 34 is for manifold air pressure voltage

I would start by taking the aircleaner assy off and taking a look at all the wiring. The coolant temp sensor that sends info to the ecm is located at the front of the intake manifold. At least it was on the TBI's, TPI's, and LT1's I've owned. The coolant temp sensor on the head is for the gauge.

I'm not sure where on the manifold the MAP sensor is on a crossfire. The TPS sensor is actuated by the throttle. Bottom line, all of the codes are related to are in the same vicinity.

Check all the wires and connectors around the manifold. Stuff should only be able to be plugged in one way. If the wires have any bare wire exposed, that needs to be fixed. It's very common that the insulation will shrink back.

Check all of the vac lines around the manifold and make sure they match up with the way the lines are run on the underhood diagram. It's likely the mechanic unplugged more than one line to get the valve covers off. There's a good chance he didn't put it all back together correctly.

Get a scan tool and a 1982 vette shop manual. Scan tools, not code readers, are not that expensive anymore. You can pick one up that reads OBDI(pre 1995) GM cars for under 100 bucks at any auto store. With a scan tool, you can see exactly what the temp sensor is reading, what the map sensor is reading and what the tps voltage is. There are specific normal readings for different situations, like open loop(cold), closed loop(warmed up), idle, wot, etc.

Keep in mind that the codes are set when specific conditions are met, which is why you really need the '82 shop manual. So code such and such is set when the voltage of this equals this but that sensor reads this and it's in closed loop or whatever. It is probable, not just possible, that one problem is triggering all of the codes.

For example, I had an injector in a tpi go bad and it threw a mass airflow code and if I remember, a tps sensor code. All because the injector failing made the idle inconsistent, causing eratic sensor readings.

I wish I had my books, I could give you more specific directions to go.

Take a look at the C4 forums. There's a lot of '84 guys there that can help. Sorry for the long post. As you trouble shoot, keep updating. The more info you gather, the easier it'll be to figure out. The nice thing about computer controlled vehicles is that the give extra clues about what's happening.

Chris

sjjb7

Thanks Chris. I do have the manual and that's how I knew to start replacing all those items one at a time. I've replaced the MAP, TPS and coolant sensor. Replacing the MAP sensor corrected the dumping of fuel from the injectors which I noticed was the first problem. Again, it ran fine immediately after replacing the MAP sensor and I thought that was it. After it wouldn't start the next day, I did a complete diagnostic on the fuel system (TBI, fuel pressure, fuel pump, relay, etc) which is all good. When it does start, it runs smooth and clean but only for about 10 seconds. I'm leaning toward the ECM and will look at that next unless you have other thoughts.
Steve

okinawa86vette

Replacing sensors just because the code says that's it is always a bad idea in computer controlled vehicles. Although the sensor can and does go bad, there's procedures to follow that will take you to the usually correct answer. You can go buy a new ecm and keep throwing parts at it, but I don't think you're going to fix it. Normally, after work is done and the car starts running badly, it's because something was disturbed or the work wasn't done correctly.

You have the GM(helms) shop manual, right? A haynes or other generic manual will only identify what the code is. The GM manuals have troubleshooting charts similar to what we used in the military. They have you go one step at a time to come to a conclusion.

The $80 you're going to spend on the ecm would be much better spent on a simple scan tool that shows sensor readings.

I think it would be wise to check your vac lines, not just for proper routing but that they hold vacuum. It's entirely possible that the mechanic cracked a line or fitting while messing with the valve covers.

Right now, you're throwing your money away and getting frustrated when you should check the simple and free stuff first. Trust me, I lived and breathed OBDI since I started driving Vettes.

Actually, the first thing you should do is reset the computer and see what codes come back. With all the stuff you replaced, that may be all it needs. Pull the battery cable and let it sit for a couple minutes. Re-connect and start it up. It may be hard to start, since it defaults bcak to the default program and has to re-learn.

Chris

...Roger...

One question-when you replaced the TPS you adjusted to .525 volts

MN-Brent

There is a freeware program called WinALDL. It can be used with a simple wire harness to hookup a laptop to your 82s ALDL connection and give you real time readings of sensors. Do a google search and youll find it.

This may be your ace in the hole if you cant follow anything to fruition with the GM 82 Corvette shop manual -which can be had on Ebay or a forum Vette parts sponsor. Dont bother with a Haynes or Chiltons book-they not hardley worth the paper.

Brent...

copter

It is getting harder to find someone that still knows how to work on older cars.Most shops get people that have been trained on the newer stuff.You have to remember that our cars are older than there training.You need to find someplace that has at least one employee that is over fifty.Find a place like that and get to know them on a personal bases and then keep them happy.I supply my shop with all kinds of stuff I get from work that they are going to scrap.You know,keep them happy and they will keep you happy.I'm saying this because it looks like you might have to take this one in for what seems to be a fuel problem. I hope some one on here can pippoint whats wrong and maybe you can fix it.I also have an 82.Mines a collector Edition and I'm keeping my crossfire too so this thread is of interested to me.Sorry I don't have any answers.I'm still kinda new to the crossfire and some day I might be in the same boat as you.

sjjb7

Thanks Gents, it's exactly what I needed...someone to slow me down and get back to hoping for the simple fix. I studied up on the WinALDL software and am working toward putting a cable together but does it work when the car won't run longer than 10 seconds? If so, how reliable will the readings be? I trusted the shop because it's owned by a 50+ y/o friend of mine and he put his best mechanic on it. This guy has worked on various older makes/models and I was happy when I saw him working on a C1. A lot under the hood of my '82 is original which makes some of Chris' remarks even more critical. Those hoses/lines are probably in need of replacement. The TPS was set correctly when replaced. I've got the GM assembly manual but not the GM shop (helms) shop manual. I was using an off-brand. I'll pick one up before I try anything else and get back to you.

Steve

okinawa86vette

The nice thing about the helms manuals is that they have t/s charts for all the codes. It also gives a break down of what to look for when it comes to multiple codes and intermittents.

For now, while you're looking for a book, reset the computer and see how it runs after that. If it throws the codes again, they're not bogus.

Again, check your vac lines. Since you replaced the sensors yourself recently, I'm going to assume everything's plugged in properly. There's only one way and place each plug can go. I imagine you didn't leave anything unplugged.

People forget that while there's a computer, deep down, computer controlled vehicles are still cars underneath, especially C3 and C4s, with their maze of vac lines. Any break in a line can cause codes. The computer is just a tool to help t/s.

Again, post a message over at the C4 tech forum and see what they have to say. They're pretty good at t/s problems that throw codes.

Good luck
Chris

FASTAZU

How’s your fuel pressure? 82’s have a small rubber connector with no clamps from the pump to the hard line on the sending unit assemble that comes lose or swells up and you lose pressure.

Eds82

Is The coolant sensor you replaced the one on the front of the intake manifold? There are two sensors. The one on the intake gives data to the ECM and the one on the block is just for the gauge. A bad CTS will dump alot of fuel through the injectors as you described.

jdp6000

Sounds like a bad connection. Code 15 and 22 diagnostic in book indicate the wires all go to the black connector on the ecm. The CTS and TPS share the same ground.

Code 34(MapSensor). Two wires go to the white connector. The signal wire goes to the black connector.

I would check the black connector at he ECM. Also follow the wires around from the TPS and CTS...they appear to go through a box on the firewall but there are 3 or 4 connectors inside that box.

Take a close look at your EGR solenoid. Its plastic. The mechanic broke mine.

Jim

sjjb7

1) Fuel pressure reading was fine at 9-12 psi when I checked it after this problem started
2) Coolant sensor replaced was the one on the manifold and the original was still in there when I replaced it
3) After replacing the MAP sensor, the fuel problem quit and the injectors worked fine. Again, I drove the car and it ran fine for the 10 miles or so I had it out.

I have not done anything yet with the ECM and plan on checking all the wires before considering replacing anything else. Will update if I ever get time to get back on it. Thanks everyone.

jugmeister

My '82 crossfire is doing the same thing--runs for 5 to 10 seconds and quits. Although I get no codes when I check the computer! So, I'll be checking this thread often, to see what you do to solve the problem. If I get my fixed first, I'll let you know what fixed it!!
Good Luck,
jugmeister

jdp6000

How does it quit. Does it just stop or does it bog out.

Jim

bluesilver82

Where did you test the fuel pressure at? Mine was bogging down and then would only run for a few seconds at start up. I changed the fuel filter and fuel pump and now no more problems. If it turns out that you do need and ECM, I have two used spares. I would be willing to part with one of them. I have not tested them so I do not know the working condition but I was told both were working when they were removed.