My daughter's '97 3.1 Lumina has 90K and has been well taken car of by the previous grandmother who had it from its creation through the time my daughter has had it (the past five years).

Issue:
About three months ago, she noticed a bit of a very slow coolant loss, and the pump was found leaking. Replacing that, about a month ago, it started having a loss of power between 20-40 mph. I took the car and found misfire codes on cylinders 2, 4, 5, and 6. I cleaned the MAS, replaced the spark plugs and wires, checked all the coil-packs with a spark tester (they checked out with strong spark), and checked the fuel pressure at the fuel tube that feeds the injectors . With that done and the problem persisting (especially when the car warmed up to operating temp), I had Cottman transmission (very reputable guys at this local shop) and they checked it out and found the same engine codes, but stated the transmission was working fine. During the next few weeks, another noted very slow coolant leak was detected without anything leaving the engine. During this time, possibly unrelated, I had problem starting the car and found the battery had developed a bad cell, but the alternator checked out, so I replaced the battery. Anyway, knowing the 3.1's storied issue with the complicated factory head gaskets leaking coolant, I took the large task and replaced the head gaskets and had new valves and seats installed in the heads. My daughter stated it is much better, but still noted she felt there was still a lack of power on the hills. She has borrowed my '01 Silverado and she has power to spare and stated that maybe the truck has spoiled her on power, but I don't think that is going to be the issue at all.

I'm getting the car this evening, and need to go back to square one on what could be the issue. I wanted to see if anyone else might be of assistance in a potential issue. These are the fun ones 'eh?

Could it be the control unit for the coils? A fuel injector control issue? IDK.

Thanks so much in advance for any assistance!

Dave

 

Could it be the ECM?

EGR?

CAT?

I have no codes from the above, but...

 

You better check the oil dipstick, these things have an issue with lower intake manifold leaking anti freeze into the oil pan, this isin't head gasket issue. I have a 96 lumina 3.1, I am on my 3rd ECM. Not had an issue with a coil pack, not saying it isn't plug wires ex. as I don't know.

 

Thanks for the idea.
I've changed the oil for her every 3K (was always simply used oil) and I'll certainly check it today. Thanks!
Would the ECM failing throw misfire codes?

 

The lasting. ecm I replaced was due to the engine just stop.., could run 2 days, 2 minutes. The only code I got was (I think ) 102, maf sensor, and that was because there was no air flow through it.

 

I took it for a test drive and here's what she did:
1) Starting it, it had a slightly rough idle but moved easily at low speeds.
2) Upon pulling out of the neighborhood and onto a State road that headed uphill, I pressed the accelerator about 1/2 way as typical. Initially it accelerated as expected, but after about 30 yards it started to run at a lower speed and engine rev as if I reduced the pedal to about 1/4.
3) When the car reached the crest of the hill, even though I didn't alter the pedal position, it began accelerating to a more expected 1/2 pedal acceleration.
4) The above was typical on all uphill slopes... oh, and when I got out with it running, I could smell un-burnt gas.

5) Noting the engine service light was on, I had the code pulled and received the following: PO301 "cylinder misfire detected - cylinder number 1"
6) I pulled the #1 wire (wires and plugs are new) and did a spark test, it was sparking strong and quickly at a separation of 36-38.

I'm going to pull the plug and check it for damage, but that is an extremely remote issue. I don't even understand why 1 cylinder misfire would cause the acceleration issue that she has, it just does't add up. Previously, before the heads were pulled, the misfire codes were intermittent misfire in cylinders 2, 4, 5, and 6.

Ideas? Thanks again in advance to any assistance.

 

Had the code checked again, it is still only "PO300 cylinder misfire detected."

Put the fuel pressure gauge on the fuel-rail tap again and here are the exact numbers:
With the key in and the ignition set to on position, engine not running: 42 psi
With the engine running at idle: 40 psi
With the engine revving at approx 3,000 rpm: 38 psi

I found the fuel leak, which is a very tiny leak at the #1 injector. Must not have gotten it set tight upon re-installation after intake install.

So what do you guys think now? Thanks again for all your assistance!

Dave

 

When you posted 301, and unburnt fuel, only thing it could be is injector leak, good job!

 

Could the leaky injector cause the misfires on multiple cylinders?

Anyway, either way, I tested the fuel pressure again, with the regulator in mind, here are the results:

1. ignition on, motor not running: 40 psi
2. motor running: 40 psi
3. motor running, vacuum line on fuel pressure regulator removed: 46 psi
4. motor running, vacuum line replaced: 38 psi

What does that tell you? Is the fuel pressure regulator bad (seems like it is having something to do with it)? The fuel pump not up to snuff or the fuel filter maybe not flowing perfectly?

Also, there is a small amount of fuel leaking from the base of injector #1, is that simply a bad o-ring or does that mean something is up with the injector/compression off due to leak?

Thanks,

Dave

 

It wouldn't cause multiple misfires. If you are having fuel loose at the injector due to a leak, probably just an o ring. If it were multiple cylinder misfire, you'd get 300 code.