Misfire is turning my hair grey!!!! Damn you truck

[DieselDetroit]

Not to insult your intelligence but we need to see the shaded area of the insulator on the plugs but for the most part the plugs look alright so I rather doubt fuel is an issue... So the last thing i can think of is check the color of your spark it should be a nice bright blue to white when using a spark tester. Also disable EGR and run it under conditions that gave you a misfire. The last possibility that comes to mind is a bad cam position sensor or the dizzy is out of phase with the cam. Or its not a misfire at all! (would certainly explain the lack of codes)

Oh dang that's an old pic and the only one I have!!

I don't have a spark tester. Will ask my friend he may have one kicking around.

As I said, the vehicle doesn't miss under load which makes me have a hard time believing it's spark related?

Also, the only 'code' was the blinking check engine light but when I put my reader in(next day) no codes!! It was actually quite difficult to get the check engine like to blink. I have been trying for a week, basically I was going up a hill at 50mph in 3rd and feathered it so maximize the sputtering/missing and then it blinked

I will look into the egr system and unplug the egr and see if that helps.

This thing never missed before so I'm not sure how things go out of time, is there any way to check this with a basic obd2 reader?

Thanks

 

[c1500deathtrap]

There is a way with an OBD 2 reader but i am unsure of how to do it there are however threads on this sight of how to check and fix it. Try searching cam sensor relearn or similar.

 

[cookseyb]

Knock sensor pulling timing won't set codes....

 

[CoolDude1975]

97 Tahoe 2dr 5700/4l60e
315,000 kms


Symptoms:
- misfire consistently under LOW load (lightly pressing accelerator) - makes me suspect fueling, injector, fuel filter, pump, etc
- goes away under high load or when accelerator pedal is completely left alone (coasting downhill or cruising uphill) - makes me suspect same as above
- flat stretches are the worst for misfiring
- I'm losing torque converter lockup because of it.... read somewhere historic misfires prevent tcc lockup
- here's the weird thing, check engine light is off!!! Today it blinked for the first time In 5000 miles..... and it is very rare. No active codes. No stored codes???? Wtf!! It's an OBD2, shouldn't it be stored even after the ignition is turned off
- I thought I saw coolant condensed in the tailpipe (orange crystals), I 'think' I smell coolant but my mechanic friend said it's just fuel.... suspecting lower intake gaskets?

My question is how to verify this without codes? I want to see what these misfire codes are....

Mine shutters off and on around 45-65 and from what I understand is its the tcc solenoid. You have to drop the tranny pan and find the right solenoid and replace. I have yet to try it because I'm afraid I'm going to screw something up more and I don't have the money right now to fix something like that if it does happen

 

[Nathaniel2g]

Newest truck has 477k km and is doing identical thing. Truck quit on me 2 weeks ago Thursday on a back woods trail, after running through some water. Was missing extremely bad after the water at any sort of load. No history codes or current codes. Truck would not fire up and I figured it was due to serious mechanical damage (ie; dropped spring or spun main). Truck was piling up when cranking and would not fire.

After four days the truck finally started up. Runs fine at an idle, and at this point I had not changed any parts. Strong smell of fuel from the exhaust, also cloud of white smoke as it attempted to burn off what I assume was fuel left in the cylinders due to over cranking. Have now discovered it to be a crankshaft position sensor issue! I bought a new motor anyways (excellent compression and only 160k km) so I'm swapping them out anyways.

Good luck on your diagnosis.

 

[c1500deathtrap]

The more i think about it a torque converter issue makes sense.

 

[redfishsc]

Opened the distributor up last year and the cap looked ok

Also, would it make sense with the issues I'm having? Being load related? Going away under throttle?

Also, why doesn't the computer store misfire codes???

Does anyone here have an instance where a bad intake manifold gasket lead to misfiring? I looked at the gaskets and the manifold and find this nearly impossible. Also, surely I would see an external coolant leak or coolant in the oil if this was the case.

I went through a little bit of this recently on my 99 Suburban. I can't say it was the same scenario but very similar. We'd get misfire at idle for about 20 seconds and then it would be OK. Occasional misfire sitting at stoplights (shaking the truck). NO ENGINE LIGHT coming on.

Then. My 4th kid was born. After a good delivery, I made the 20 minute drive back to the house to check on my in-laws and the other 3 kids. Truck misfired horrifically the ENTIRE way, cylinder #5. Swapped the plug, swapped the plug wire, no change.

Was reluctant to dicker with the distributor cap, but when I pulled it off, there was green corrosion all over the brass terminals (Autozone "gold" brand) and it was less than 7 months old!

I returned it for a refund and got the closest thing to OEM I could find--- Delco, aluminum terminals, which are supposed to be lower quality. But that seemed to fix it.

Once in a while I still get a shudder when we crank it but it doesn't feel as shaky as a misfire, and I'm suspecting my old CSFI injectors are getting worn. Truck drives like a dream though.

Long story short, check the dist. cap even if you looked at it recently. Clean the contacts up a little.

 

[DieselDetroit]

Ok guys. Time for an update

For those of you who said it was tranny related, the reason I dismissed this was because it is impossible, in my mind, for a bad torque converter to cause a blinking check engine light

I took the cap off, it was covered with corrosion, cleaned it up with a wire wheel, it actually improved a lot. After a week I ended up just swapping caps with a new one. Again, improved but not perfect

Took the distributor out and noticed lots of rust on the main bolt that holds the rotating assembly to the shaft, and with it, lots of flakes of rust and stuff everywhere

I was also told that thr distributor has two drain holes or vapour holes to allow excess moisture to dissipate. Checked them, not plugged.

Cleaned the distributor out good and reinstalled, further bettered the symptoms

Finally, checked the PCV, did the shake test and checked for vacuum, all good

Now, here is where my brain went 'ooooooooohhhh'. I've noticed the issue is when the vehicle is warm, after about driving an hour. When cold, no stuttering, and when I first hop on the highway, drives like a dream. As it warms up, it worsens drastically. I tried to brainstorm what changes with engine temp, fuel, yes, also EGR!!! The egr is "fully utilized" when the engine load is low, vehicle speed steady, etc, and fully warmed up, so I pulled the plug and checked for continuity across pins 1-5 and 2-4 as outlined in the Haynes manual. 1-5 confirms position sensor and 2-4 confirms the valve (or something like that),

Anyways I got continuity from 1-5 but nothing from 2-4

My next test will be driving and waiting for the problem to re-arise, then unplugging the egr and checking to se if the problem worsens or improves. Called Lordco and they want 320$ for the egr valve. **** me. I can buy a low mileage 5.7 for 400 haha.

Stay tuned

 

[Curt]

Called Lordco and they want 320$ for the egr valve. **** me. I can buy a low mileage 5.7 for 400 haha.

http://www.rockauto.com/en/catalog/chevrolet,1997,tahoe,5.7l+v8,1061367,emission,egr+valve,4968

https://www.partsgeek.com/catalog/1997/chevrolet/tahoe/air_intake/egr_valve.html

 

[c1500deathtrap]

Sweet! Glad you finally have a direction on this issue.