4500 rev limit on 4.0 (glowing exhaust)
- Thread starter miksior
- Start date
Again, didn't have time to read everything, but I was referring to mechanical timing by the timing set being a tooth off or the CPS being off. You are correct with factory components timing is not supposed to be adjustable but again, refer to it being a tooth off or maybe an adjustable timing set? Rotating the OPDA should only adjust the injector sync if it's anything like the older distributor equipped version.
My Big Block Chevy 408 could be made to run on regular gas , however it caused more problems than it solved . It had semi - open chamber heads from a 390 h.p. 427 . That head needed 20 - 22 degrees advance because the flame front was so slow . I came from a small block world 12-14 advance worked great in a heavy truck at elevation. When I tried 12-14 Adv. in the 408 it would run Okay , but try to vapor lock idling when stopped. One day after work I got out of the K-20 and heard a loud hissing , I was checking the tires but didn't see a puncture . Then I noticed the noise was loudest between the cab and box it was coming from the passenger side tank vent ! I slowly tried opening the gas cap , a Lot of pressure was bled off , then the fuel in the tank started bubbling and rumbling.
I tightened the cap and the vent started hissing again and the bubbling stopped after a few minutes. I couldn't put my hand on the frame rail it was so hot .
I baby sat my truck for 1 hour , bleeding off pressure and waiting to make sure my truck wouldn't catch fire. Never again.
Afterburning in the 2 1/2 " dual exhaust caused all my issues.
Last edited:
It is pretty simple and you sound like you have a grasp on it so maybe I'm incorrect. It was a non-adjustable timing set I assume? If so, just line the dots up like you said. I guess you could double check it with a timing light gun.
And I know I already said it, but just to be clear turning the OPDA will not change the timing.
Did you rotate the crank around a couple of times and verify the dots still lined up?
Do our engines even have a pointer & timing marks on the harmonic balancer? I don't know that I've ever even looked.
Even if they did I don't see how a timing light is going to verify valve timing??? A timing light is for ignition timing. What am I missing?
Varies by year, but they all have a notch in the crank pulley, and at least a pointer where the timing scale would be on some yrs.
05, 06 just have a pointer on timing cover, no scale. Notch in crank pulley.
It's not, you have to pull the timing cover and verify by the dots on the gears.
My guess is he had slack on the tension side of the chain and didn't rotate the crank around to verify they still lined up. The procedure in my YJ manual has you counting links, the TJ manual just says rotate the crank twice and verify alignment. I never counted links...
Nah, the slack were sefinetly on the bottom part. I rotate the engine without the valve before replacing chain. Even have a photo before changing timing:
The issue was very same before, and after timing replacement.
Well, the PCM controls the ign timing, the cam/crank timing is correct per the photo above.
You can check the MAP sensor by reading it with the ign On, engine off. That is your ambient pressure. Use a barometer app to read the station pressure where you are, not the weather pressure which is normalized to sea level. Compare. They should be about the same. If it is off, it can cause a lean condition. My 06 ate a set of double plat plugs in about 75K mi due to it running lean from a bad MAP sensor.
Have you checked for vacuum leaks?
You can check the MAP sensor by reading it with the ign On, engine off. That is your ambient pressure. Use a barometer app to read the station pressure where you are, not the weather pressure which is normalized to sea level. Compare. They should be about the same. If it is off, it can cause a lean condition. My 06 ate a set of double plat plugs in about 75K mi due to it running lean from a bad MAP sensor.
Have you checked for vacuum leaks?
You said you changed the CPS and I want to confirm; was that the crank position sensor or cam position sensor? Because the crank position sensor also controls timing. Before JTEC could be tuned, people used to use slotted crank position sensors to do the same thing as twisting an old school distributor. Not sure that would be enough to cause the issues though.
I checked map sensor, but i can just replace it i guess
Camshaft, i did not change crankshaft
Sorry, got a little hectic time. I will replace crankshaft sensor and temp map sensor and will upload idle/drive videos
Similar threads
