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Old 03-29-2004, 08:43 PM   #15
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Do you have an aftermarket tach? I have seen a bad tach pull the ignition down at high rpm on a racecar.
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Old 03-29-2004, 09:26 PM   #16
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Quote:
Originally Posted by BReed
Steve,

I experienced this problem years ago in a class c motorhome, seems to me the engine was a 454. What we determined was the catalytic converter was plugged. The mechanic drilled two holes in the exhaust pipe preceeding the coverter of course and the problem was temporarily solved. Hope this helps in your trouble shooting efforts. We were stuck in New Hampshire in the White Mtns. and I'm from Michigan.

Bruce
Bruce, steven replaced his exhaust system with headers before he left. I am thinking he, um, eliminated that potential problem.
Steven, you could have a bad ignition pickup, or module. Mid '80's modules on GM were prone to failure, although usually they just stop working altogether, but could be the same problem, it gets hot, and starts sending faulty signals to the coil. If you replace this part, be sure you put dielectric grease on the part that rests on the distributor housing. It is located under the rotor, inside the distributor. The pickup is located in almost the same spot, but removal of the distributor and disassembly are required, probably would be better to replace the whole thing since you have to take it out anyway.
If you are near an AutoZone, or a similar place, why not drive it over and have them perform a free alternator test?
Long-distance diagnosis is kind of like computer tech support...
Only other thing I can think of for you to look at is to remove one of the plug wires from a spark plug, install another plug on the end of the wire, ground the base of the plug, start the engine, and observe the color of the spark. Blue is good, orange is iffy, yellow is not good.
Terry
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Old 03-29-2004, 09:48 PM   #17
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No cats on this rig...pre-converter and your right in that its headers into 2 1/2 inchers all the way back

fangthorpe - your tach comment reminded me that I occasionally get a dead tach or incorrect readings. Like 1200 rpm at 65 mph then it bounces back up. Could be a trouble spot or a short. No tach changes when it's misfiring. I was getting blue when I pulled a wire at the cap but at idle under no load it runs fine.

Terry - I did buy a new pickup so I might try replacing it as well. Thinking I should have just bought a new dist.

This is going to be a fun one.
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Old 03-29-2004, 10:09 PM   #18
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Shot in the dark.

I've been having similar problems on a trip from Texas to Florida. Canít tell you about hill climbing because there were none. Change the carb fuel filter and it ran well for about 300 miles then started acting up. Pulled filler and took you the check valve and replaced filter. Ran good the last 1000 miles. Had it out about a week ago and the problem it back. Read on other forums this was a fix? I'm thinking seriously about converting to a Holley TBI.
Good luck in your hunt.
Bill
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Old 03-30-2004, 06:27 AM   #19
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Quote:
Originally Posted by swebster@myrvadvanta
fangthorpe - your tach comment reminded me that I occasionally get a dead tach or incorrect readings. Like 1200 rpm at 65 mph then it bounces back up. Could be a trouble spot or a short. No tach changes when it's misfiring.
That would be your "blue splice" causing your dead tach. I had similar problems with mine which was how I found where the tach ran to. It merely caused a dead tach, though... no driveability issues. I think I put a new connector on and once the bad connection was cured, it had no more problems.

I have to agree with Terry about the diagnostics... if the simple stuff doesn't fix it, it's probably time to head to someone with diagnostic technology...

Roger
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Old 03-30-2004, 07:22 AM   #20
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thought of another issue--- PeterH had replaced his igniton module awhile back ,and the new one as I recall was bad out of the box, left him low on power also....just another thing to look at.
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Old 03-30-2004, 08:14 AM   #21
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There is two different types of ignition. HEI and ESC. The dristributors from the outside look near identical. ESC "Electronic Spark Control" had a ECM and monitored for detonation and ping. It then adjusted the timing as needed. This was used heavy on the regualr trucks but I don't know if it made it to the P30 or not. They have knock sensor.

Verify that it has HEI nad not ESC. I have heard simular issues when switching from factory manifolds to headers. The change in pitch of the exhaust will trigger the knock sensor.
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Old 03-30-2004, 06:11 PM   #22
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Quote:
Originally Posted by 59toaster
There is two different types of ignition. HEI and ESC. The dristributors from the outside look near identical. ESC "Electronic Spark Control" had a ECM and monitored for detonation and ping. It then adjusted the timing as needed. This was used heavy on the regualr trucks but I don't know if it made it to the P30 or not. They have knock sensor.

Verify that it has HEI nad not ESC. I have heard simular issues when switching from factory manifolds to headers. The change in pitch of the exhaust will trigger the knock sensor.
The knock sensor, if equipped, is mounted on the left side of the block, just below the line of the freeze plugs. IIRC, unplugging the knock sensor will cut it out of the loop, and the truck will run normally then, just ping.
Terry
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Old 03-30-2004, 07:30 PM   #23
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I installed the new alternator and removed the "extra" line to the dist. This turned out to be the tach feed not the 12V supply. Ran it around town for 30 minutes and it pulled hills well. Took it out on the highway for another 30 and it seemed great.

The trick here is that this problem manifested itself over the course of several hours before so without taking a tour of New England its hard to tell if the problem is solved.

Tomorrow I'll run a new tach wire and investigate installing the new pickup.

BTW - On the knock sensor...what does it look like? I have a screw in style sender on the left head (not the block). Haven't chased the lead but it runs up in the same harness as the ignition.
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Old 03-30-2004, 08:05 PM   #24
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Quote:
Originally Posted by swebster@myrvadvanta
I installed the new alternator and removed the "extra" line to the dist. This turned out to be the tach feed not the 12V supply. Ran it around town for 30 minutes and it pulled hills well. Took it out on the highway for another 30 and it seemed great.

The trick here is that this problem manifested itself over the course of several hours before so without taking a tour of New England its hard to tell if the problem is solved.

Tomorrow I'll run a new tach wire and investigate installing the new pickup.

BTW - On the knock sensor...what does it look like? I have a screw in style sender on the left head (not the block). Haven't chased the lead but it runs up in the same harness as the ignition.
Steven, if you have a knock sensor, it should be in the block, on the left side.
Terry
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Old 03-30-2004, 09:08 PM   #25
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If intervals of running (200 miles) seem to bring the problem on and not just heat, hills or high speed, and then it goes away for a while - how about this...

I had a Suburban with rust in the gas tank. The pickup in the tank was wrapped in screen. After several hours on the freeway it would start to lean out and pop and eventually die. Pump was good and all filters good. After 5 minutes off (all the junk falling off the pickup screen) it would start fine and run normally for several more hours when it would repeat.

Next time it acts up, pull over and shut down for a few minutes and then go again - on the same hill - and see what you get.
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Old 03-31-2004, 08:58 AM   #26
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Quote:
Originally Posted by swebster@myrvadvanta
I installed the new alternator and removed the "extra" line to the dist. This turned out to be the tach feed not the 12V supply. Ran it around town for 30 minutes and it pulled hills well. Took it out on the highway for another 30 and it seemed great.

The trick here is that this problem manifested itself over the course of several hours before so without taking a tour of New England its hard to tell if the problem is solved.

Tomorrow I'll run a new tach wire and investigate installing the new pickup.

BTW - On the knock sensor...what does it look like? I have a screw in style sender on the left head (not the block). Haven't chased the lead but it runs up in the same harness as the ignition.
Left head on most GM's is the gage sender. Right head is for AUX electric cooling fan if so equiped. Most egines have a oil pout in the boss above the oil filter. On my Mark IV block My oil sender is on the driveside of the block at the front right by the harmonic ballancer. The sender that says it has oil pressure that will let the Fuel pump run is also there. On you coach if it has electric choke it will have a simulear oil swithc that will not alow power to the choke if there is no oil pressure.

Now tell me something? Is this a bastard Quadrajet? Does it have any electrical connection on the carb becides the choke and maybe a throttle kicker for the A/C? I didn't think these made it on the P30's but on the regula truck line they had a Quad that ran a mixture solonoid. It adjusted mixture based on coolant temmp. It was very simple deal. You can identify it by taking off the air cleaner assembly. on the passengerside front of the top cover will be a electrical connector with two wires. One wire is tied into the same circuit as the choke and the other goes to a temperature sensor on the intake or water neck. Those solonoides sometimes fail or become intermitant and it will act like it's running out of gas when it does.
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Old 03-31-2004, 04:31 PM   #27
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toaster - no leads on the carb. Terry told me to look for this as well. Looks like I'm lucky that this is not on my setup. I'm thinking it's a voltage issues (either the lack of from the charging system or a short from the tach)

Tomorrow will be a longer test run so I'll keep you posted
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Old 04-02-2004, 07:12 PM   #28
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The coil is suppost to have a ground wire

and can run sometimes without it with no obvious problem. The coil will burn up without it. It's actually a strip of metal. Check to see if it's there. The ignition will act goofy when the coil fails/starts to fail without it.

Otherwise my vote is for the stuck power valve - impacts the entire primary fuel delivery.
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