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Discussion Starter · #1 ·
Ok today I changed my Plenum pan gasket, dist. rotor, wires, plugs (Autolite), pcv valve, air filter, all hoses, and I changed my T-stat to a 180. The truck is running better, but yet still has some lack of power, especially having trouble keeping 70mph on the flat interstate roads. Would set cruise at 78 and watch it drop to 65 in about a mile. Also while running 70 mph I am turning about 1800 rpm in 4th gear (auto trans) but my rpms are jumping up and down and the truck rides rough with a shake. I have no DTC's coming up, the Ck engine light is not on and there is also a kind of "clunk" sound coming from the motor. It will only do it while crusing at about 70 in 4th gear when the rpms start fluctuating and the truck starts shaking sort of..... I am not quite sure what to do after all of this.... Has anyone had this happen or knows what going on with this motor?

I also did the TSB on the wires which rerouted them to minimize induction.
 

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sounds like torque converter problem to me if it is shaking. just a guess.
 

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The TPS (Throttle Position Sensor) could be the cause of this problem as well.
 

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MeanThree18 said:
I hate saying it, but it sounds exactly like what my old mans truck did before his tranny blew'd up
Yep, I have to agree. What I think happens is the Torque converter starts messing up and takes out the rest of the tranny.
 

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Discussion Starter · #6 ·
well I just recently had the transmisson rebuilt with a new torque converter about 15000 ago
 

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Discussion Starter · #7 ·
It is also now flashing the ck engine light and the dtcs came back up with a misfire on 6 & 8 again! I dont know how this could be? injectors maybe? need [email protected]
 

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Too Big to Sneak
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This is the same problem that everybody seems to be having now that I've reported my symptoms (seriously, there was hardly anyone reporting these issues before).

The 'shaking' is going to be the effect the misfires have on the engine - mine's doing it at idle now sporadically as well.

Something haven't mentioned: Have you checked your catalytic converter and/or O2 sensors? I ask because mine did the exact same thing when the cat failed at speed on the interstate one day. Flashing CE light and no power on anything resembling an incline more than flat horizon.

Seriously - check those out.
 

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I replaced my plenum gasket last nigh and now my truck will not fire up. I didnt mess with the distributor or plug wires. What the HELL? did your truck fire right up?
 

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dhymel1 said:
It is also now flashing the ck engine light and the dtcs came back up with a misfire on 6 & 8 again! I dont know how this could be? injectors maybe? need [email protected]
I tried installing the MSD 8.5mm superconductor wires, thinking that the added insulation would help...but it didn't.
I ended up insulating every other wire in convolute and that fixed the misfire problems.

I agree with Mister 4x4 about the cat possibly being the problem.
If the cat is the problem, you can get a high flow cat & y-pipe from Magnaflow for $150.
I did this rather than pay $275 for a stock replacement.
The next time you drive it, try riding the brake (just enough to make the brake lights come on) this will keep the t/c from locking. See if the shake is still as prevalent.
Try spending $10 on some 1/2" or 5/8" convolute and insulate every other plug wire all the way up to the dist. It's pretty easy and can be done without removing the wires by sliding it up the wire starting at the plug end.
 

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Thanks chizzle1 for the reminder - I'm going to try the convolute/split-loom trick you mention. I have the stock replacement wires, and I've done the TSB re-routing (along with just about everything else I can think of) and my problem still persists as well.

Good call on the brake trick for testing the TC Lockup.
 

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Mister 4x4 said:
Thanks chizzle1 for the reminder - I'm going to try the convolute/split-loom trick you mention. I have the stock replacement wires, and I've done the TSB re-routing (along with just about everything else I can think of) and my problem still persists as well.

Good call on the brake trick for testing the TC Lockup.
No problem.
The convolute should fix the problem.
That TSB is a fancy way of saying keep the wires atelast 1 inch apart...didn't help me either though.
 

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Discussion Starter · #13 ·
Thanks for the info guys, I dont have a converter on the truck, there are just 2 3.5" exhaust pipes and the o2 sensors and installed in thos pipes as they were if I had a converter with the pre cat and post cat sensors, I also insulated all the wires with convolute when I put it back together....
 

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Discussion Starter · #14 ·
ok so I tried the brake check trick and it seems as though the rpms stop fluctuating and the shake is not as noticeable... so iguess I have a torque conv problem, yet I still dont see how I am getting DTC p300, p306 and p308 which is multiple Cylinder misfire, and cylinders 6 & 8 misifire, since I have done the wire insulating and TSB routing, changed plugs, wires, dist cap, rotor, pcv valve etc... is there anything that I am missing that can cause this misfire on these 2 cylinders? THe good thing is that it is not using oil anymore since I replaced the plenum pan gasket. Maybe should I try using different plugs? maybe Bosch +4's? anybody?
 

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Discussion Starter · #15 ·
one other thing I forgot to mention, I am also getting VERY poor gas mileage with these problems... on a 3 hour drive from Baton ROuge to Monroe, LA I usually get about 14 mpg average on the trip, this weekend with the problems I am having I got about 8mpg! THe truck smeels like its running rich since the exhaust smeels a little gassy... BTW I have no catalytic converter and havent had one for about 2 years, I do have 2 high flow mufflers and O2 sensors are installed in the single pipes... I hope htat may help some of yall help me with this money pit.... thanks
 

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first off, if it's still shaking with the brake trick, that means you are getting misfires (probably nothing wrong with the T/C).
The reason it's less severe is with the T/C unlocked, it's not transmitting it directly to the drive-line. The T/C is absorbing some of the misfire shock, so you don't feel it as easily.
If you have done the wire loom, TSB re-routing, and changed all the ignition components...I dunno. The only item left is the coil, but I think that would affect all cylinders, not just 6 & 8.
As for the bosch +4, I ran them for about 3 years with no problems. The do cost about $5 a piece though.
If the ignition has been ruled out, I would look at the fuel injectors on the 6 & 8 cylinders.
You can bring it to a shop and they can hook a dwell tach to it. This will show the dwell time when each cylinder fires.
 

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Discussion Starter · #17 ·
thanks chizzle, I am thinking about swapping the injectors from 6&8 to two other cylinders, then clearing the codes, and then running the truck to see if I get the same misfires on 6&8 or if they move with the injectors. Do you know how much aftermarket injectors run and which ones are the most reliable?> I spoke to the dealrship yesterday about them and they said they were $69 a piece! also if those 2 injectors are my problem, should I change them all or can I get by with just the two troublemakers?
 

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dhymel1 said:
thanks chizzle, I am thinking about swapping the injectors from 6&8 to two other cylinders, then clearing the codes, and then running the truck to see if I get the same misfires on 6&8 or if they move with the injectors. Do you know how much aftermarket injectors run and which ones are the most reliable?> I spoke to the dealrship yesterday about them and they said they were $69 a piece! also if those 2 injectors are my problem, should I change them all or can I get by with just the two troublemakers?
you should be able to change just the 2 bad ones, if it does end up being the injectors causing the fault.
When you change out the 2 injectors, make sure you get the same pound rating and clean the rest of the injectors to ensure you get an even flow rate.
edit: get the same OEM injectors, aftermarket could have slightly more or less flow even with same pound rating.
 

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reset the computer.
 
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