Question: What is causing my '89 to stall?

[DarkRed89Flyer]

Help!! As some of you are aware, I realized my life-long dream of becoming a Corvette owner when I purchased my '89 in March. However, I've started to have issues with it stalling, recently, without any warning.

It started about a month ago when I was driving in-town and ended up behind one of our crazy AZ drivers that didn't know where he/she was going. As a result, I changed lanes to attempt to pass, but when I stepped on the gas pedal, after picking up some speed, I almost got thrown into the steering wheel when the engine went, "Blah!!!" It didn't totally die and I continued down the road as if nothing had happened. Sure did freak me out though!

So, the next day I took it to my mechanic, one that I've used for all my vehicles for the past several years, and was told that I had a really weak spark. Matter-of-fact, when I arrived, the driveability tech couldn't get it started again, and with the help of the other techs, they had to push it back to a service bay.

As a result, and $618 later ad, they performed a major tune-up, replacing the dist. cap & rotor, the ignition coil, the spark plugs & wires, and the fuel filter. Although I'd never been told this before, the technician told me that the previous owner had used a cheaper brand of spark plug, which over time caused the gap on the plugs to widen causing the output of the coil's amperage to increase. Effectively, the cheaper plugs had burned out the ignition coil.

That was about 3 weeks ago. Now, it has developed an outright stalling issue. I haven't driven it in at least a week because last weekend, when I was getting on the freeway and was just about to the end of the on-ramp, it stalled. I was at partial throttle and had reached about 52 mph, then nothing. I had to coast to a stop on the shoulder. After I stopped, it started right up. However, as soon as I put it in gear and went about 15 feet, it stalled again. I managed to ease it off the freeway by going down the shoulder with only the engine idle speed to move me along. If I touched the gas pedal, it would immediately stall.

It's had sort of a rough idle since I bought it and combined with the stalling issue, I thought the EGR Valve was to blame. So, yesterday, I replaced the EGR Valve and checked all of the vacuum lines for leaks. However, whatever is actually causing this seems to have gotten worse. I tried to take the Vette for a test-drive this evening and didn't get 2 blocks away from my home. This time, I was only going about 15 miles an hour. I was accelerating slowly and as I lifted my foot off the gas to step on the brake, at about 1300 rpms, for one of those damned speed humps, it died.

I'm just about at my whits-end with this! What is causing my '89 to stall without any warning? The MIL (Service Engine Soon) warning light has not come on during any of this. One other thing to note: I left it idling the other day, just to charge the battery, and after 15 or 20 minutes, it also died without any warning. No spitting, sputtering, or fanfare. It just stopped!!!

 

[Hib Halverson]

I wouldn't waste any more money on emissions controls parts or fuel system pieces.

Start checking all the wiring for a bad ground.

Start with the engine controls ground right near the oil filter. It's a big bolt with a bunch of black wires going to it. Remove the bolt. Make sure none of the connectors are corroded. If they are, clean them. Then reinstall and tighten the bolt. Check other chassis grounds, too.

 

[DarkRed89Flyer]

I wouldn't waste any more money on emissions controls parts or fuel system pieces.

Start checking all the wiring for a bad ground.

Start with the engine controls ground right near the oil filter. It's a big bolt with a bunch of black wires going to it. Remove the bolt. Make sure none of the connectors are corroded. If they are, clean them. Then reinstall and tighten the bolt. Check other chassis grounds, too.

Thanks for the advice, Hib. I'll give that a try over the next couple of days and keep you posted. I'm sure there are probably at least 10 or 20 ground points to check. Funny how the most obvious things are the ones we forget. That had totally slipped my mind!

 

[WRECKER88]

My 1989 had the same problem 2 years ago. I found that the #7 injector was shorted. To check them you will need a meter and they should be around 16-17 ohms. The #7 was shorted and would shut the engine down. I got new injectors from Fuel Injector Connection and now my car runs like it did when it was new.

 

[boomdriver]

I'd sure stay clear of that shop....they did the "standard fix" but failed to repair anything....that screams of tech school mechanics and not real mechanics...That business about cheap plugs...pure bunk. If that were true, 3/4 of the cars on the streets would be broke down. Everybody outside of performance guys will buy the cheapest plugs available. The Corvette HEI generates up to 40,000 volts at low rpm, and resistance can become a problem but its usually at 5000 rpm where the voltage has dropped to increase the speed of the spark. Modules burn out from shorts, heat or being submerged in water. Not cheap wires or plugs. All thats gonna do is maybe create a knock like it had cheap gas..

In Mesa, call Larry @ 20th auto parts. he will know who to see. He's a parts guy and salvage store for vettes. Their shop is just south of SkyHarbor off the bypass.

have your Fuel Pressure tested. This sounds like a possible filter issue. Works fine then don;t...

 

[DarkRed89Flyer]

I'd sure stay clear of that shop....they did the "standard fix" but failed to repair anything....that screams of tech school mechanics and not real mechanics...That business about cheap plugs...pure bunk. If that were true, 3/4 of the cars on the streets would be broke down. Everybody outside of performance guys will buy the cheapest plugs available. The Corvette HEI generates up to 40,000 volts at low rpm, and resistance can become a problem but its usually at 5000 rpm where the voltage has dropped to increase the speed of the spark. Modules burn out from shorts, heat or being submerged in water. Not cheap wires or plugs. All thats gonna do is maybe create a knock like it had cheap gas..

In Mesa, call Larry @ 20th auto parts. he will know who to see. He's a parts guy and salvage store for vettes. Their shop is just south of SkyHarbor off the bypass.

have your Fuel Pressure tested. This sounds like a possible filter issue. Works fine then don;t...

@Boomdriver - I performed your suggestion from comments in one of my previous threads. The static pressure (key on, engine not running) was 42psi. Dynamic pressure at idle stayed constant at about 40. Bleed-down to zero took a long time, but I can't remember exactly how long. It took hours though.


The thing that confuses me is that once it stalls, I can put it in Neutral and start it right back up, and usually, continue on my way, albeit gingerly then, as not to stall it again. When I purchased the car, the weather was cooler. I didn't seem to have the problem at all. Now that the days are much warmer, the problem seems to be worse. It's almost like the heat is affecting something electronic, but it's an intermittent problem. I'm having a very difficult time diagnosing the issue. And as you said, boomdriver, I won't be taking the car back to THAT shop anytime soon, except maybe to demand my money back for a "faulty" diagnosis and fix!

 

[boomdriver]

@Boomdriver - I performed your suggestion from comments in one of my previous threads. The static pressure (key on, engine not running) was 42psi. Dynamic pressure at idle stayed constant at about 40. Bleed-down to zero took a long time, but I can't remember exactly how long. It took hours though.


The thing that confuses me is that once it stalls, I can put it in Neutral and start it right back up, and usually, continue on my way, albeit gingerly then, as not to stall it again. When I purchased the car, the weather was cooler. I didn't seem to have the problem at all. Now that the days are much warmer, the problem seems to be worse. It's almost like the heat is affecting something electronic, but it's an intermittent problem. I'm having a very difficult time diagnosing the issue. And as you said, boomdriver, I won't be taking the car back to THAT shop anytime soon, except maybe to demand my money back for a "faulty" diagnosis and fix!

well,. if fuel press was up that indicates good flow...so thats not the issue.
ign is all new....
TPS been checked? plug or adjustment?
unmetered air leak around the throttle body? EGR stuck wide open?

last.....CATS clogged up completely? test that at the 02 sensor hole...gauge should NOT get more than 2-3 lbs if it does, CATS clogged.

 

[DarkRed89Flyer]

well,. if fuel press was up that indicates good flow...so thats not the issue.
ign is all new....
TPS been checked? plug or adjustment?
unmetered air leak around the throttle body? EGR stuck wide open?

last.....CATS clogged up completely? test that at the 02 sensor hole...gauge should NOT get more than 2-3 lbs if it does, CATS clogged.

I can tell you that the EGR Valve itself is brand new, I just installed it 2 weeks ago and haven't driven it since then except to run it at idle a few times just to keep the battery charged. However, I have a bigger problem!!!

I replaced the EGR Vacuum Control Solenoid Tuesday night and in the process of re-attaching the vacuum lines, the hard-plastic line broke off right at the soft rubber connector. Now, I can't find a replacement. The local Chevy dealer says it's been discontinued and AutoZone and Napa don't carry it. They don't even have the hard-plastic line so that I could make it form-fitting myself. I even tried contacting DocRebuild and they can't help me either. Anybody have any other suggestions? I'm not that familiar with the vacuum needs of an engine, but I'm sure the lines are hard-plastic instead of rubber for a reason. I bought extra rubber line, probably more than I need, but I don't want to use it, except as a LAST RESORT. :ugh

The TPS hasn't been checked. I've thought of replacing it anyway just because it's probably 22 years old. Also, there is no plug on the back side of the idle stop set screw, but I haven't touched it, so it should be in the same place it was when I bought it, and it ran fine when I picked it up at the dealer.

If the CATS were clogged, after it stalls, why would I be able to start it right back up and then drive away? I'm thinking it has to be something with either the EGR system, or some other electronics I haven't thought of yet.

 

[boomdriver]

I can tell you that the EGR Valve itself is brand new, I just installed it 2 weeks ago and haven't driven it since then except to run it at idle a few times just to keep the battery charged. However, I have a bigger problem!!!

I replaced the EGR Vacuum Control Solenoid Tuesday night and in the process of re-attaching the vacuum lines, the hard-plastic line broke off right at the soft rubber connector. Now, I can't find a replacement. The local Chevy dealer says it's been discontinued and AutoZone and Napa don't carry it. They don't even have the hard-plastic line so that I could make it form-fitting myself. I even tried contacting DocRebuild and they can't help me either. Anybody have any other suggestions? I'm not that familiar with the vacuum needs of an engine, but I'm sure the lines are hard-plastic instead of rubber for a reason. I bought extra rubber line, probably more than I need, but I don't want to use it, except as a LAST RESORT. :ugh

The TPS hasn't been checked. I've thought of replacing it anyway just because it's probably 22 years old. Also, there is no plug on the back side of the idle stop set screw, but I haven't touched it, so it should be in the same place it was when I bought it, and it ran fine when I picked it up at the dealer.

If the CATS were clogged, after it stalls, why would I be able to start it right back up and then drive away? I'm thinking it has to be something with either the EGR system, or some other electronics I haven't thought of yet.

You're going to have to settle for some rubber vac hose. The hard plastic was d/c because it cracked and broke. 90% of mine is rubber now.

Clogged cats...can allow restart but usually won;t kill the engine completely...just won;t allow it to rev or develope power.

TPS is pretty easy to check with a DVM and to set its base idle then move it thru the range to look for dead spots.

 

[seabee 86]

What kind of transmission, auto or six speed?

I only ask because you mentioned when you throw it in to neutral it comes back to life.

 

[DarkRed89Flyer]

What kind of transmission, auto or six speed?

I only ask because you mentioned when you throw it in to neutral it comes back to life.

It's an AT, but it doesn't come back to life when I put it in neutral. I can re-start it with the key while I'm coasting.

 

[DarkRed89Flyer]

You're going to have to settle for some rubber vac hose. The hard plastic was d/c because it cracked and broke. 90% of mine is rubber now.

Clogged cats...can allow restart but usually won;t kill the engine completely...just won;t allow it to rev or develope power.

TPS is pretty easy to check with a DVM and to set its base idle then move it thru the range to look for dead spots.

OK, I replaced the broken hard-plastic vac line with the rubber hose.

Unfortunately, I don't have the correct gauge to test the back pressure in the exhaust, but I did hook up my DVM to the TPS. With the key on, engine not running, I got a reading of 0.67 at what would be idle. I quickly moved to WOT and got a reading of 4.98. When I tried it again, I went very slowly, and got readings consistent with the movement of the throttle. It never showed any signs of having a "dead spot."

When the shop did the tune-up that doesn't seem to have fixed anything, they didn't replace the ignition module inside the distributor, or the electronic spark control module that mounts to a bracket right next to the windshield washer fluid bottle. Could either of these be the culprit? I inspected the ESC today and it appears to be the original from the assembly line. It still has the barcode on it and with 105K miles on the vehicle, I'm thinking that the innerds might be overheating.

I can't seem to find another reputable shop that I can trust, and you guys/gals have been so helpful, does anyone have any other thoughts?

 

[DarkRed89Flyer]

You're going to have to settle for some rubber vac hose. The hard plastic was d/c because it cracked and broke. 90% of mine is rubber now.

Clogged cats...can allow restart but usually won;t kill the engine completely...just won;t allow it to rev or develope power.

TPS is pretty easy to check with a DVM and to set its base idle then move it thru the range to look for dead spots.

One other thing: I can rev it to 3K RPM's without a problem, while it's parked, but I don't think I'd dare do that while it's moving. The lack of torque/inertia when it stalls would probably throw me through the windshield because it occurs with absolutely no warning.

After I checked the ground wire junction block on the engine today (the one near the oil filter), it started right up. So, I let it idle for awhile since I haven't had it running in a few days. About 20 minutes later, it died. I was able to re-start immediately, but it died again after only about a minute or two.

 

[boomdriver]

One other thing: I can rev it to 3K RPM's without a problem, while it's parked, but I don't think I'd dare do that while it's moving. The lack of torque/inertia when it stalls would probably throw me through the windshield because it occurs with absolutely no warning.

After I checked the ground wire junction block on the engine today (the one near the oil filter), it started right up. So, I let it idle for awhile since I haven't had it running in a few days. About 20 minutes later, it died. I was able to re-start immediately, but it died again after only about a minute or two.

Got MAF relays?

 

[DarkRed89Flyer]

Got MAF relays?

I would assume that it does, boomdriver, but if the MAF sensor wasn't working correctly, it should set a code in the ECM. No fault codes are present. That's one of the first things I checked.

 

[boomdriver]

I would assume that it does, boomdriver, but if the MAF sensor wasn't working correctly, it should set a code in the ECM. No fault codes are present. That's one of the first things I checked.

Try this....

disconnect the MAF and see how it runs open loop. Open loop should be a major improvement, if NOT, then you;re left with a fuel issue and not an electrical or control issue.
When you unplug the MAf thats forces it to run OL and will tell you some things.

 

[vette079]

A long shot here, but check connection to the oil pressure switch and check the fuel pump relay.
It´s a very long shot, but if they start acting up at the same time (not likely) it will kill fuel delivery.
if you have a fuel pressure gauge, try hooking it up and put it on the windshield, start driving slowly and let a passenger keep his eyes on the gauge, when it stalls.
Maybe that way you can determine if it´s fuel delivery related or not.
If not, you really have to look into spark.
You mentioned they didn´t replace the module in the dizzy...

 

[DarkRed89Flyer]

A long shot here, but check connection to the oil pressure switch and check the fuel pump relay.
It´s a very long shot, but if they start acting up at the same time (not likely) it will kill fuel delivery.
if you have a fuel pressure gauge, try hooking it up and put it on the windshield, start driving slowly and let a passenger keep his eyes on the gauge, when it stalls.
Maybe that way you can determine if it´s fuel delivery related or not.
If not, you really have to look into spark.
You mentioned they didn´t replace the module in the dizzy...

Thanks for your reply. I thought it was possibly a fuel delivery issue and checked the pressure with the key on, engine not running, and at idle and higher rpms, while not moving. The static pressure was 42psi, the pressure at idle and throughout the rpm band was just over 40psi.

I replaced the ignition module about 2 weeks ago myself, along with the Electronic Spark Control Module. Neither of these had any affect on the issue.

I have since given in and have had it towed to a repair shop. They've had it almost a week and they can't figure it out either. They verified the fuel pressure readings I got previously, and they were spot on. Plus, they've gone so far as to check all the ignition components including the ignition coil (again) and the pick-up coil, but everything seems to be working correctly. There's just no spark signal to/from the computer. Yesterday, they installed a new computer, just to rule it out, and that didn't work either.

 

[vette079]

Do have a digital voltmeter?Loosen the connectors to the injectors and measure resistance.It's possible that you have some bad injectors in there.Also, check resistance at the CTS, it sits in front and under the TB, slightly to the right.A little sensor that gives info to the ECM.Cold engine should show something like 4000 ohms give or take 500.Do you have an FSM?No, get one.Yes, there should be a list somewhere that shows the temps compared to the ohms you get from the CTS.See what you can find out...

 

[touring turtle]

Hi there, I'm from Holland and facing exactly the same problem with an 1985 C4. I'm sure it isn't the ignition or spark plugs. When cold the Vette runs quite well and can be revved to appr. 2200 rpm. When running, things soon get worse and in the end the engine stalls. It can be restarted again immediately. This is due to a fuel or exhaust problem!! The things I've done are: Change the fuel filter, renewed the fuelpump (and cleaned the tank), renewed the O2 sensor and (just for sure) the spark plugs.
My first tought was that when the ECM comes in "closed loop" things go wrong. (that's why I changed the O2) But that isn't. Also no fault codes are stored in the computer.
I think the ECM is not getting the proper information from the O2 sensor and decreases the amount of fuel given, until the engine stalls.
Next things I'm gonna try: Fuel pressure,measure output of the O2 sensor, check for clogged exhaust pipe or - I hope not- a defective ECM module. I keep you informed.