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Old 07-10-2006, 04:25 PM   #1
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454 engine troubles

I have a serious problem with my 454 engine - HELP! I am very sorry for the length of this, however I wanted to let you see the history in case it gives you clues to what may be going on...

Let me recap events over the last 2 weeks:
Purchased Airstream LY 33, gas Chevy 454 TBI engine on a P30

Unit had been sitting for 11 months, started every 4-5 weeks (unconfirmed) Started after replacing battery, ran rough, temp gauge went right to red after a minute. Mechanics at dealership say gauge is broken & not to worry about temp. Laser thermometer says 205 deg at thermostat during test drive, so I'm not too worried. On the test drive I get it to 70mph on freeway. Good power & acceleration, but runs rough. Bad gas & needs a tune up I think. I purchase the Airstream! Happy Day!

I come back later (at closing) to pick up my new dream machine & give them the final cashiers check. I sign the "as is" paperwork and walk out the door with everyone else. I am the last one to leave the lot. The MH drives the same for about 5 miles, then once I got on the freeway at 70mph started to bog down. Engine started making pinging noise like octane starvation. Tank is between empty & 1/3rd, and I pull into Texaco and fill it to 2/3 with fresh unleaded-plus. Things go downhill from here. I start losing power, engine ping gets worst if I try to give it gas, and my top speed becomes 10-15mph. I turn around and limp it back to the dealership and leave it there for the night. Very sad day.

Next day I return to the lot and inspect the engine very good. I see that a spark plug wire has come off the plug on #2. I put it back on, and wow - the problem is gone and I speed off to take her home, very glad it was only a plug wire that came off!!!! Happy day again!

Once home, It goes on jacks and everything front to rear gets inspected & replaced. I do a complete tuneup (new platimum plugs, new plug wires, new cap & rotor, new PCV valve, new air & fuel filter). I find out it was low on coolant, and later find out the temp gauge works. Don't know if the jiggle made the connection better, or if it really was overheating. I change all the fluids, and for oil go to a 2qt filter and Mobile One extended performance, replacing 1 qt with Lucas oil stabilizer/reconditioner. This all took 3-4 days, and when I crank it up I now have a loud knock on the valve cover!

I pull the cover off, and a rocker arm has come loose and the rod was just sitting there (on #7). There was a slight bend to the rod, so it was replaced. I put everything back together. Start engine and no more knock. Engine runs like crap for about 10 minutes. After 10 minutes the backfiring stops, and the engine seems to smooth out. I do notice a loud sucking noise when the air filter is off. A check of vacuum leaks turns up nothing.

Now for the 1st drive since all the work. Excited, I take her out only to find it acts alot like when I first tried to take it home, only the engine runs smooth now. Seems to do OK at first, then top speed becomes 10-15mph when the bog down hits. I stop and check all the plugs, wires, and traced everything to make sure the firing order was correct - it was. I fill it up with unleaded plus again and limp her home.

All the shade trees in the area whisper catalytic converter, so today I took it out to the muffler shop. It ran better (not much). I drove it about 20 miles through normal traffic and redlights. It sounds good, however has no power and gets to 15mph very, very slowly. It seems to get a little surge of power between 15-20mph, then will loose power and no matter if I floorboard it, or slightly give it gas, it will very slowly increase to a top speed of about 40mph. I can go a little above 40 on a straight-away, however the engine starts pinging like a lack of octaine sound.

The muffler shop opens up the pipe just before the catalytic converter & says that will cure the problem for sure, and that it will be $800 for the new converter to be installed. I told them I would be in touch (charged me $50 for the hole) and I drove home. There was no change at all - converter is ruled out.

I have fixed everything possible that I can think of from my driveway. Any last resort ideas before I take it to the professional shop and need a 2nd mortgage?
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Old 07-10-2006, 04:45 PM   #2
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I've heard of a vehicle sitting for so long that rust builds up in the exhaust pipe and would shake loose and start restricting flow in the muffler. Would start and run fine, but when trying to accelerate would pick up the flakes of rust and start essentially clogging up the muffler. I'd look at at least temporarily removing the converter and muffler to see if the issue clears up. If it was being started and run for just a few minutes and then shut off, that might leave condensation in the pipe, not running long enough to burn off, creating an optimal rust scenario.
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Old 07-10-2006, 06:23 PM   #3
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The TBI system uses a idle air control motor to control idle speed. In English, there is a controlled vacuum leak on the throttle body to regulate idle speed, so the sucking sound is normal.
Your TBI engine should have a somputer with a diagnostic connector (somewhere), see if you can pull any codes out of it. You may have a bad throttle position sensor. This could keep you from getting any acceleration after the engine enters closed loop (about 10 minutes' driving.
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Old 07-10-2006, 06:32 PM   #4
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454 Engine trouble

I think that you may have something Dave. I was going to suggest that you may have a plugged muffler. Also you did not mention how many miles are on the engine. 454 engines are known to have cam timing chains that become loose and the jump time one or two teeth. when this happens the valve timing is off this is why when the engine backfired you lost the pushrod.

Good luck,
Pat370
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Old 07-10-2006, 06:37 PM   #5
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Something else it could be is the pickup sock in the tank getting clogged with gunk inside the tank. Most TBI GM engines don't have a port to check fuel pressure, but it could be running out of gas, as easily as a computer problem. I am leaning away from the timing chain problem, as you have stated the engine runs good when cold, then progressively worse as it warms up.
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Old 07-10-2006, 08:26 PM   #6
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It has 58,000 miles. Also, it is a very small difference between cold and hot, but just enough to notice.

I opened up the tailpipe before the muffler. No change except now I have a very loud exhaust.

I forgot to add - after the tune up was complete (my neighbor mechanic did the work) we fired it up and it seemed to run good, then after he revved it up it didn't run so good. I killed it, and then it would'nt start. He checked and the firing order was wrong. He fixed it, but it did run and rev up with a bad firing order. Don't know if this makes a difference or not - hate to think my "career mechanic" neighbor caused the problem.

Another strange issue he pointed out - with the air filter off, you have two fuel injectors. They appear to be equal and dropping the same amount of fuel. When you put you hand under the passenger side cutting off the fuel flow, the engine will idle very rough and eventually die. If you do the same thing on the driver side fuel injector, there is not much change in the engine idle - a little rough but never real bad and it will not die.
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Old 07-10-2006, 08:40 PM   #7
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I don't think your neighbor caused the problem. It was already acting up, or you wouldn't have had him tinkering with it. FYI, firing order is 1-8-4-3-6-5-7-2, in case you ever have to take it apart yourself.
The engine will react more to the right side injector being blocked, because that is where that "controlled air leak" is, on the right side of the throttle body, slightly to the rear, so it doesn't mean the left injector is bad. A closer look may be needed, but with an equal-looking amount of fuel coming out of the two injectors, I don't think that is your main problem.
Is the "Service Engine Soon" light on? If so, check the codes, they could be important clues for you. Also, as far as the valve timing having jumped, can your neighbor check the ignition timing? If it is off by "a country mile", it could indicate the timing has jumped, although with only 58,000 on the clock, it would not be the first thing I looked at.
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Old 07-10-2006, 09:38 PM   #8
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The service engine soon light is not on. It comes on with the ignition key like it should, then turns off after the engine starts.

When I first fired it up after the tuneup, the light came on after the first backfire. After the engine smoothed out, the light went back off and has not come back on.

I will call around tomorrow and find a auto shop that can handle it and take her in. I'll have them check the codes in memory first off, then troubleshoot from there. I don't want to keep tinkering with it and keep throwing money at everything that doesn't seem to be the problem. We have a 2000 mile vacation coming up and I would like to get it fixed soon enough to take a few short overnight trips first to work out any other problems before I take my family across the state.
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Old 07-10-2006, 09:46 PM   #9
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OK, this is WAY out there, but I once got an engine 180 degrees out of time and it ran, only had no power and the exhaust was white hot.

See, the cam turns twice for every one turn of the engine, so it is very easy if changing a belt/chain to get the came one turn out of time.

If your engine is out of time like this, it will idle just fine (at least mine did) but it will make virtually no power and it will labor like a dog to get up to highway speed.

This is probably not your situation, but it's worth checking. If the PO or somebody put a new timing chain on it, they might have done this.

Good luck with it!
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Old 07-10-2006, 10:14 PM   #10
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I discounted timing since it had plenty of power and speed when I brought it home. It was only after sitting in my driveway 2 weeks and after the tuneup that the lack of power developed.
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Old 07-10-2006, 10:44 PM   #11
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454 Engine trouble

Sorry to correct you but the cam turns at a rate of one half the speed of the crankshaft. It is very easy to check for a vacuum leak under the throttle body. If there is a leak from a bad gasket between the throttle body and the heat pod or the intake manafold the engine will run rough at idle and will also idel at a faster rpm. to check this out when the engine is running at idle spray WD40 around the base gasket. If the gasket is leaking the idle speed will change when the WD40 hits the hole in the gasket.

Keep looking,
Pat370
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Old 07-10-2006, 11:11 PM   #12
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stop GUESSING and take it to a professional and have it diagnoised--Pieman
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Old 07-10-2006, 11:40 PM   #13
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Quote:
Originally Posted by Mike Lewis
stop GUESSING and take it to a professional and have it diagnoised--Pieman
HERE HERE!
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Old 07-11-2006, 01:15 AM   #14
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454 Engine Problem

Hi, where do we start? First mistake is to accept it running like this. Second mistake, instead of working on it yourself, take it right back to the selling dealer and ask them to fix it. Next lesson, "as is" does not apply to safety items. The selling dealer must repair all safety items. If its not driveable and / or able to pass smog for a certain period of time, this could qualify free repairs from the selling dealer. Check with local DMV or BAR.
Water under the bridge; Pinging can be caused by a number of things, not just bad gas or low octane. Pinging can also be caused by overheating. Not clear on what you said the muffler shop said or did, but putting a hole in front of the catalitic converter, they can test exhaust pressure thus conferming that you have a bad cat. Bad cat won't pass smog; "Take it back to where you bought it. Ask them to fix it [nicely at first], then tell them you will report this illegal action to DMV. DMV has the power to pull their license if they don't do legal business. Also check temperature at more than one place on the engine and parts of the cooling system; A stuck shut thermostat could give you a good reading [205] at the houseing due to lack of flow while actually the rest of the engine is internally boiling.

Just a few other thoughts for your problem. hope you find a cure.

Bob
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