3rdgenkindagal

As the title says, my 92 recently has started dying a lot. It starts and runs fine cold but if you try to turn it off and back on while it is warm it struggles and dies. Rpms go up and down then splat. You have to tap the gas then hold it and it then levels out just fine and will stay on. I have already spent too much having multiple people diagnose and replace parts for this problem. I am frustrated as this is my daily driver and I need it to find work since I lost my job due to them sending the work over to memphis. We just replaced the IAC for the third time, o2 sensor twice, distributor cap twice, ignition module, fuel pump, ecm and a bunch of other stuff. Coolant sensor and iac got replaced because they broke again but that was only part of the problem. Sometimes when you do have to tap the gas it doesn't respond almost like it's either not dumping the fuel or not igniting. Anyways, any help would be awesome sauce. I am so frustrated and out of money for a mechanic to keep fixing stuff.

Street Lethal

iTrader: (16)

Really would need some form of a datalog to properly diagnose the sensor feedback, but if the engine is not triggering a malfunction code (check engine light), then chances are it is either fuel related, vacuum related, or you are stuck in Open Loop. Is this a throttle body injection system we're talking about here? Get the basics done first, time the engine again with the EST disconnected to its' proper setting, and tighten down the distributor firmly. Pull each spark plug and check them, and re-gap if necessary. Inspect for broken plug wires, and confirm they are routed properly to their respective location. Then run a quick vacuum test to check for any leaks. I would then have someone confirm fuel pressure (despite the installation of the new pump, as your filter may be clogged). If you can get me a datalog from cold to warm, I can tell you what it is immediately...

- Rob

3rdgenkindagal

I do not have the data log. I am still waiting to hear back from the guy who last worked on it. It's had so many little things wrong we are doing process of elimination. My guess is the ignition module is bad again or something. These after market parts are killing me. I'll update when I get more info.

Oh and no it's not throwing any codes, it's very frustrating. I am updating this as I go. I will say, whatever the issue is it does not happen when the vehicle is cold. When it's cold it runs beautifully. When it's warm is when you have to tap the gas to get it to stabilize. So it seems whatever it is is heat triggered? My dad is going to check spark plugs with me. It seems to be running pretty rich too. It's throttle body, 305 v8

Should I check the TPS? I wonder now if it's related... Sometimes when trying to accelerate it's delayed or weak.

ironwill

I feel your pain, but if you can't work on the vehicle yourself, anything posted here is going to be moot.

That said, when an "OK when cold/not good when hot" problem is mentioned, the first thing that comes to my mind is the ignition control module. Some 'new' ones are worse-quality than a 30-year-old one, and even a 'good' new one will die an early death if it isn't installed correctly.

Here's troubleshooting steps for the ICM: Part 1 -How to Test the GM Distributor Mounted Ignition Module (easyautodiagnostics.com)

Street Lethal

iTrader: (16)

Yes, the lack of O2 correction when warm.,.. and now that you mentioned richness, is why I mentioned possibly being stuck in Open Loop as well. The AFR is much richer in Open Loop, so on a restart, the engine is flooded from the previous shut down, and needs a moment to stabilize itself when warm. This is because the charge is less dense when warm and can't use the additional fuel from Open Loop. Without a datalog it' becomes the process of elimination in which you have already begun. Multiple ignition modules has me steering away from that as a possibility, but then again, parts store could have a bad batch, you never know. Curious, did your dad ever install headers on the engine, as a free floiwing exhaust tends to keep the engine from reaching Closed Loop? Yes, always check the TPS data if you have hesitation off idle...

- Rob

3rdgenkindagal

My dad can help me work on it. We did do a lot of work at home. He was wondering if the ignition control module was bad again. It was just replaced like two months ago. I will check what I can at home with him. We do not have the machines to diagnose these old cars or check codes but we can trial and error it old school. I will keep TPS and ignition control module in mind.

No we didn't install any headers. We have the left the car exactly as we got it besides directly replacing parts.
So the open loop sounds a lot like it. It sounds like TPS as well. It's acceleration can be unresponsive at times. Even when trying to tap the gas to keep it going when it's warm it acts like you aren't hitting the pedal. It only has this issue warm. I appreciate all the ideas! I at least have a general direction to talk with the mechanic about or my father if he helps me.

Edit: the car did act similar to this when the ignition module was bad originally and when it was replaced the issue stopped for a bit.

Street Lethal

iTrader: (16)

Yes, with your dad, check the TPS voltage, run a vacuum leak check, and inspect the fuel injectors. Any kind of richness, or skewed data to the ECM triggering more fuel will cause engine surging/hunting, and that rich exhaust smell. Keep everyone posted. Also make sure your dad gave the ignition control module a generous coating underneath it to keep it happy and cool...

- Rob

3rdgenkindagal

I can tell you what we saw with the fuel injectors yesterday. They were spraying like wild until we replaced the coolant temp sens and bad iac. They aren't as bad now but it still smells rich.

Street Lethal

iTrader: (16)

Yes, these ECM's have a very low threshold with their O2 correction, maybe 6% capability both ways. Once that gets exceeded, you'll surge, and inevitably stall if its' too rich...

- Rob

3rdgenkindagal

I don't know a whole lot but that seems like a bad threshhold xD

southbay08

did you by any chance check the resistance on the injectors? Check them when they are cold and when they are hot.

3rdgenkindagal

So I thought I would update. For some reason my fuel pump is still pumping while the car is off. Not a lot but a few psi, my fuel injectors are damaged and are slowly leaking into the engine when it's off while warm causing it flood which is why I had to feed the pedal when I go turn it back on again if it's hot. My fuel filter was completely obliterated, that one was my fault lol. We are going to replace at least the fuel filter and pump and check the gas tank make sure there are no undesirables in there like bits and pieces. I'm quite pissed because the fuel pump has already been done in the past and it's a 624 dollar fix. I wonder if it's worth it to cut a hole in the trunk and try to work on it myself. I was wondering if Fuel Injectors are a big ordeal to do on your own, do they need to be calibrated or will the computer do that itself?

ironwill

A new Delphi or GM pump is less than $100 on Rock Auto.


Don't do that. You'd actually wind up with more work (and a sketchy outcome) than if you do the job properly.


It can be a bit detailed if you've never replaced injectors before. Have your father help you. Use exact replacement injectors and you'll have no issues. Check with South Bay (above) for more info.

3rdgenkindagal

It's the labor. The part itself is like 34 bucks, mechanics have to resale it at $100. The labor is roughly 4-500. I checked with a few places. Also are you sure about the hole? The one thing I've heard from everyone and their mother is "I cut a hole and it was 10x easier"

ironwill

We're not on the same page here. I'm aware of 'shop' labor rates, but you stated you can get help to do the work yourself.

ETA: I don't recommend installing cheap replacement parts, especially the in-tank fuel pump in a 3rd gen. Doing that job is tough enough the first time; having to do it again in a couple of weeks would be brutal.



There have been numerous posts on this site about this very topic, many with photos. As I recall though, other than maybe one or two of those posts, they were hack jobs, using unreliable methods to reconnect the fuel lines, since they also have to be cut in order to get the pump assembly out of the tank. Remember that those lines carry fuel under pressure.

Like other posters here though, I'll simply remind you it's your car; repair it as you see fit.


GL.