I've got one here that's baffling:

This particular problem is happening on a <COUGH, choke!>Chevrolet, but I don't think it is brand specific. I think I'm right to put it here in general automotive section, even if it can't go in any of the Ford engine sections. I am both interested and totally baffled. I hope I can learn something from this. Whatever this is, I think it could happen on a Ford, Chev, Dodge, etc. I just want answers.

1993 Chevy half ton with 4.2 V6 and 4L60E automatic --- since this is FTE, I'll take just a moment to sneer --- the paint fell off, because it was one of those crappy GM jobs that didn't stick to the primer, it looks like crap; and this thing has the WIMPIEST front drive axle I ever imagined I'd see on a pickup, even a mini-pickup. My wife has a 3/4 ton '96 Suburban, and that's not impressive, but this thing... well, I heard the independent suspended 4x4 Chev half tons have the same live axles as the Citation, which was a crappy small car. I can believe it!

Drove me nuts to work on this half metric, half U.S. abortion. The trick engine-to-trans bolts were worst, with 3/8-16 thread going into the engine, a 9/16 wrench sized "head," then more bolt extending past that, in 8mm x 1.25 thread to take a nut that uses a 13mm wrench. I want my OLD trucks!
Engine pulled for rebuild after it puked a mainseal. Sent out to commercial rebuilder.

Engine came back from rebuilder, sat on my engine stand in my shop for about nine months. Finally got put back into the truck.

Truck would barely start, would not idle at all, would die if put into gear - even at high rpm. We figured Idle Air Control on the Throttle Body Injection. Knowing it needed better timing and a few other checks, we trailered it to Mr. Goodwrench.

Local GMC dealership at first thought IAC and a locked torque converter, but got into it and found the only problem was late valve timing. The rebuild shop had put timing chain and camshaft together wrong. That was fixed, and cost a pile of labor dollars. They assured us the incorrect cam/valve timing was the only problem.

The truck was driven maybe a mile, over the Louis Auto Glass for a windshield, then back the the dealership, then Karen and Joel picked it up the next day, and Joel drove it the 50 miles back to Marblemount.

Joel said it had good power when he left the dealership and got out onto the freeway. He noticed it downshifted twice on a hill about 9 miles short of Marblemount, though he hadn't really changed throttle position. Maybe it was getting weak. He got to my Rental One, a mile above Marblemount, and the truck would not restart. The exhaust manifolds and exhaust system back to the catalytic converter showed red hot.

Joel let the rig cool, beat on the catalytic converter a bit, then drove it the five miles to my shop. We figured plugged catalyst was the only answer.

Last night, I removed the converter, went through three layers of metal, and emptied out the contents. Tonight, I welded our little "door" closed again (two layers, top side of converter), then put the converter back on the truck. Joel and Karen took it for a test drive. I could see some exhaust leak from the bad muffler behind the converter, but nothing seemed obstructed.

They came back soon, Joel saying we had a problem and asking me to come outside and look. I walked out, and I could still see some glow on the right exhaust manifold. I had Karen restart briefly. Exhaust seemed to be coming out of the tailpipe, but it sure seemed hot. Oil pressure is good, and coolant temp has not jumped (and this thing has a ridiculously small radiator, so it wouldn't handle much extra heat). And now there's a pretty good knock that seems to be coming from the right bank.

Now this is professionally rebuilt engine, assembled by a reputable builder. How many things can be screwed up??? Mr. Goodwrench wasn't too surprised about the cam mis-timing, because there was a run of timing chains that was mismarked. Just following the factory manual directions will get you a mis-timed camshaft.

What the H--- can we have that's turning the exhaust manifolds into afterburners? And where did we pick up that knock?

I'm baffled. This thing does not have the AIR system with pump (like my '77 F250), though I believe it does have EGR. Again, it's a '93 with TBI, just rebuilt. I'm open to suggestion here.

Lane

 

I think it's a 4.3L. If metal is glowing, then run open header. Otherwise i've got nothin for ya lol.

 

Yep, you're right, it's a 4.3 liter. Sorry about the typo.

One friend just sent back:

1. Compression test

2. Check spark timing

3. If it's OBD I, see if you can read any codes. Look for lean mixture.

So far, I'm not very impressed, with either the engine or the builder. That's the V6 they made by chopping the front 2 jugs off of a 350. It's close to their original V8, 262 vs 265 cubes. They should never have messed with success, they've been going downhill ever since. The 265 and 283 were good engines. And Ford had a near perfect engine with that 289. Dad still kicks himself for selling his '64 Galaxy 289; it just ran and ran and ran. The '69 Chev 327 he got wasn't nearly as good a car.

For a street rodder of small 4x4 swap, you just won't find a nicer trimmer power package than a 289/302 Ford with C4. It's funny that guys were putting the Ford V8 in the same location as the factory four banger in the early Scouts, but when International decided to put in their massive V8, they had to put it further forward on a rig that was already nose heavy.

I'm baffled on this silly V6. I'm going to make REALLY SURE there's no obstruction anywhere in the exhaust. Maybe I'll take it apart and push an Electrician's fish tape through it. And we'll make what engine checks we can. Short of an obstruction, I just don't know what could be making afterburners out of the exhaust system on that rig.

This is a lesson, though. One I learned way back when I was specifying and ordering aid vehicles: Get it all through one shop. If YOU pull the engine, send to rebuilder A, then get the engine back and have problems after installation, then go to Dealership B, you can count on one thing: Nobody will take credit for the problems or stand behind the work on the engine. And it doesn't help when my friends who sent the engine out, let it sit for 9 months or more in my shop. It's all ancient history to the rebuilder; he won't even talk to them.

It may cost more when you take a Ford to the blue oval guys, a Chev to Mr. Goodwrench and a Dodge to the Mopar guys, but the shop generally will back their work.

 

Isn't glowing manifolds normally the result of too much timing?

 

Lane -

Still sounds like valve timing; the exhaust valves letting combustion gasses from the power stroke into the manifolds.

Steve

 

I would agree. Red hot manifolds are almost always timing related.

FWIW, the 4.3 I had was a great motor. But when they're not built right, it doesn't matter whether it's an oval or a bowtie.

 

Good observations, thanks. Someone else also suggested a stuck valve. But this thing gets HOT! I wonder if it's more than one valve -- like maybe Mr. Goodwrench didn't get it right after all.

I'm going downvalley tomorrow. I'll stop by and talk to that Service Manager and see if either of us is smitten by a bolt of inspiration.

 

would the timing have been so far off that maybe a valve (or more than one),
have been bent a little?
I agree, regardless of brand, if they're not put together right, none of em will run right...

 

I'm guessing severely retarded ignition timing. If ignition does not have enough advance, then the burn occurs in the exhaust manifold and heats them rather than producing energy in the motor.

 

Those are sure things to look at. I am really getting tired of this particular truck. But I sure would like to know the answer here.

BTW, the truck seemed to have decent power. Usually a severely retarded spark means overheating and loss of power. Sure makes me wonder. Could stuck EGR valve do all that?

 

I think EGR actually COOLS and dilutes the mixture.

Steve

 

I would definatley say, check the timing. Not to long ago I put a new 5.0 H.O. in my Bronco(some pics in my gallery). When we got it together my dad stood outside while I ed it up. It did not seem to want to keep a very good idle so he had me hold the rpm's at 2k. About 5 min of doing this he yelled, shut it off! I got out and looked and my whole exhaust system was cherry red! Come to find out the timing was way retarded. We fixed it and it still seemed to run a little rough. Well, when the exhaust got cherry red it melted both of my cats. So we took it to the exhaust shop and had them gut one cat and put on a high output one with 3inch pipe and a flowmaster. My truck runs great now! So I would also have to think that it sounds like a timing problem to me.

 

I went downvalley today, and stopped by the dealership to chat. Didn't get a lot of fresh ideas, though a Mechanic suggested using a non-contact thermometer to watch temp on each runner and see if the heat is coming from a particular cylinder. I pointed out my RayTek quits at 750 degrees, but I can use it right after I start up.

Timing was suggested, and I'm definitely going to put a timing light on it soon. I'd expect badly retarded timing to overheat a rig, but not to give good power. I'm told this one drives pretty well -- or did. BTW, the engine doesn't indicate it's overheating, no unusually hot coolant. It's the exhaust that's near meltdown.

I'm going to CONFIRM no blockages in the exhaust. Just because I gutted the cat, doesn't mean that was the only possible restriction. I can see an exhaust leak at bottom center of the muffler. It's pretty rusty looking. Maybe it rusted out inside and partially blocked itself with a lot of rusty pieces.

I'm still concerned about valve timing, though Mr. Goodwrench says he made it right. A compression check is definitely in order.

I didn't like the knock I heard last time it ran. Sounded like it was from the right bank. Can't imagine a rod knocking in a freshly rebuilt engine. Collapsed lifter and piston slap come to mind.

Yep, others have confirmed a stuck EGR will just make it run crappy, not run "normally," but with an "afterburner."

Hey kameronth, how far off was that Bronco? Did it still seem to have decent power, even with the retarded spark and red hot exhaust?

Most of the gas in the tank is about two years old. I'd say seven gallons of it (all I could get in the day we started it, before it overflowed) is new Premium. Also, I added some PRI-G stabilizer for luck, even though I don't really believe their claims about rejuvenating old gas. If this thing started and ran on that old gas, all I'd expect is may diminished octane rating. And the engine does have a knock sensor. I don't THINK the gas is the culprit, but I want to rule out everything I can.

Simple things first: Make SURE the exhaust is open. Check timing. After that, do a compression test.

Does that make sense so far?

 

I was about 15* off. It did not want to keep a very good idle but when I gave it gas it had no problem until the exhaust turned red. Just a tip, on some of the fuel injected Fords such as mine there is a spout that needs to be unplugged to get accurate timing, I am not sure but Chevy could have something like that, just make sure or else you will be getting a false timing read.

 

Hey, thanks! Actually, the Chevy has a plug under a cover on the firewall. Unplug that wire when setting timing. Even timing has more variations than in the old days. Used to be, you just pulled a vacuum line and you were set.