97 Chevy s10 miss under load

[metalman55]

97 Chevy s10 ls
5 spd
2.2l 4 cylinder

Please help!

about 3 weeks ago i put gumout fuel system cleaner into a full tank of gas. it didn't take long for it to start popping here and there, but this has been normal with other vehicles i have added fuel system cleaners to so i didnt think much of it. it slowly got worse and worse, until whenever the engine is under a load it hesitates, pops, and misses (SES light) in only cylinder 1 (had codes read). i added 2 bottles of chevron fuel injector cleaner (recommended by guy at autozone) and still no change. i changed all the spark plugs, spark plug wires, fuel filter, checked the coil packs, and still has the same problem. it now misses when idling as well but sounds better when being revd. i took it to a mechanic and after a 1.5 hour diagnosis he couldn't find the problem. he checked the fuel injectors, coil packs, fuel system, and a bunch of stuff with his big fancy code reader and confirmed that cylinder 1 was the only one missing and everything else checked out. he also did a compression test and it checked out. I'm about to take it back and do "exploratory surgery" on my engine since i can't afford to pay somebody else to. before i do i wanted to see what some other people had to say about it. please help this determined college student out!"

[old_master]

Sounds like it could be a coincidence, but maybe not...

Did the technician tell you if it was a rich misfire or a lean misfire? That alone will give us a head start on where to start looking for a problem. It can be determined if the technician knows how to use his scan tool. With out this information, we've got to start from scratch.

What brand and part # spark plugs?
What brand and part # wires?

[metalman55]

Originally Posted by old_master

Sounds like it could be a coincidence, but maybe not...

Did the technician tell you if it was a rich misfire or a lean misfire? That alone will give us a head start on where to start looking for a problem. It can be determined if the technician knows how to use his scan tool. With out this information, we've got to start from scratch.

What brand and part # spark plugs?
What brand and part # wires?

he didn't say, however the code that came up was p01301. i just picked up the truck and drove it home without much problems. he said to check the valve springs, and if its not that than it could be a bad driver in the computer system and could require it to be flashed or replaced entirely. he also pointed out that it only misses when idling cold or when under a load.

duralast ignition wires (4636)
ACDelco plugs (41-928)

[old_master]

P0301 is in fact a miss on #1 cylinder. Aparently he didn't check O2 voltage in the freeze frame data, (that would indicate a lean or rich mixture when it missed). A lean reading would indicate the injector is not opening. A rich reading could mean the injector is stuck open or an ignition problem.

There are two ignition coil packs on your engine: One coil fires cylinders 1 & 4 and the other coil fires #2 & #3. When a coil fires, it fires both cylinders simultaneously. When one cylinder is firing on the compression stroke, the other is firing on the exhaust stroke. It is entirely possible for half of a coil to fail.

Here are some things to try that will narrow the problem down, but, they must be done in this order:

The first two steps will determine if a spark plug or a plug wire is faulty.

1. Swap #1 & #2 spark plugs, if the miss moves to cylinder #2, the spark plug is faulty.

2. Swap #1 plug wire with #2 plug wire and see if the miss moves to #2 cylinder. If the miss moves, the plug wire is faulty.

This step will determine if the coil is faulty:

Only at the ignition coil, (not the spark plugs) swap #1 & #4 plug wires. If the miss moves to cylinder #4, the coil is faulty.

If the miss stays on cylinder #1 after all this, the problem is with either the injector, the wire harness to the injector, or the ECM.


Post your results.

[metalman55]

Originally Posted by old_master

P0301 is in fact a miss on #1 cylinder. Aparently he didn't check O2 voltage in the freeze frame data, (that would indicate a lean or rich mixture when it missed). A lean reading would indicate the injector is not opening. A rich reading could mean the injector is stuck open or an ignition problem.

There are two ignition coil packs on your engine: One coil fires cylinders 1 & 4 and the other coil fires #2 & #3. When a coil fires, it fires both cylinders simultaneously. When one cylinder is firing on the compression stroke, the other is firing on the exhaust stroke. It is entirely possible for half of a coil to fail.

Here are some things to try that will narrow the problem down, but, they must be done in this order:

The first two steps will determine if a spark plug or a plug wire is faulty.

1. Swap #1 & #2 spark plugs, if the miss moves to cylinder #2, the spark plug is faulty.

2. Swap #1 plug wire with #2 plug wire and see if the miss moves to #2 cylinder. If the miss moves, the plug wire is faulty.

This step will determine if the coil is faulty:

Only at the ignition coil, (not the spark plugs) swap #1 & #4 plug wires. If the miss moves to cylinder #4, the coil is faulty.

If the miss stays on cylinder #1 after all this, the problem is with either the injector, the wire harness to the injector, or the ECM.


Post your results.

the mechanic said that all of the fuel injectors were pulsing correctly, even when it was missing. the miss did not move to cylinder 4 when i switched the wires. i ordered a new ECM today as i have now heard that from multiple sources. I will post results after i replace it.

[old_master]

The ECM fires the injectors sequentially, (no two fire at the same time). If he said they were all pulsing correctly, chances are it's not the ECM. Make sure you can return it if that doesn't fix the problem. (This is the importance of proper diagnosis)

Did you do the first two steps? They make sure the plugs and the wires are good. Swapping #1 & #4 plug wires, and the miss stays on #1, the injector is not firing, BUT, you need to know the plug and wire are ok. If the plug or the wire is faulty on cylinder #1, the miss will stay on cylinder #1. After each of the tests I mentioned in the previous post, you need to re-set the OBDII and drive it until the SES light comes on. The ECM will tell you what cylinder is missing.

[metalman55]

I found a sloution! i should have stuck with my first instincts. i took the truck down to jiffy lube and paid 70 bucks for their fuel system cleaning and the truck has been running better than when i got it! must have been a very stubborn clog in injector 1.

thanks for the help anyways, hopefully these posts help somebody else out. they are usually where i get a lot of my information on things i don't know a lot about. its so great to be able to have people willing to help those who need helping.

[metalman55]

okay, so after a couple days of running fine, it went right back to doing the same thing. total bummer. so i removed the fuel injectors to take them in and have them professionally cleaned, and i couldn't help but notice that my intake manifold was coated in a thin layer of black gunk that seemed to be coming out of cylinder 1 (goes into the other intake pipes progressively less as you go towards #4). not only that, but there are shiny silver metal shavings in the cylinder 1 intake. this combined with the cylinder 1 missfire, and hesitation under load like i mentioned before. what do you think?

[old_master]

The carbon deposits are from EGR... perfectly normal. The metal flakes...hard to say without seeing them but possibly from the injector???

[metalman55]

Originally Posted by old_master

The carbon deposits are from EGR... perfectly normal. The metal flakes...hard to say without seeing them but possibly from the injector???

nevermind, not metal shavings. upon further inspection it was just the poor lighting. chunks of gunk built up to look like metal shavings. i am goingto take the injectors in tomorrow to have them serviced. as far as all of the black crud, how should i go about cleaning it?

[old_master]

You can use a scraper to loosen the big chunks or a wire brush. pick out the big chunks and use a vacuum to clean the rest out. Don't use Mom's good vacuum, she'll get pissed, guaranteed!

[metalman55]

okay, so here is the update.

It no longer misses, it only missed like once or twice in the beginning of the problem but hasn't since. found out the "popping" noise was the engine backfiring. sounds like unburned fuel igniting in the exhaust manifold.

I had the fuel injectors serviced to specs at a specialized shop. didn't help. cleaned the intake plenum and the gunk, didn't help. changed a couple vacuum lines (the ones to the weird black mystery ball attached to the hood) helped for a few days but same problem gradually came back. checked the fuel pressure, its within specs according to my Haynes manual.

I changed the crankshaft position sensor and its been a week and a half (about 15 key cycles of decent trips) and the computer still has not learned it. the code comes back right away after cleared. thinking of replacing TPS next, or even coil packs. probly coil packs first. any other ideas?

[old_master]

What DTC's are in memory and what order are they in, (first to last)?

[metalman55]

the codes? im not sure. the only codes that have come up are the one from cylinder 1 missing from the beginning, and then the crankshaft position sensor not learned, then i just had that cleared at AutoZone and it came up right away again.

[old_master]

If a DTC comes right back after clearing them, the problem is not fixed. DTC's never tell you that a part is faulty, they tell you what circuit a problem has occured in. Find out what the DTC was, then post it here and we can diagnose the problem.