Manifolds are melting my car
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Northstar Engines and System Technical Discussion Discussion, Manifolds are melting my car in Cadillac Engine Technical Discussion; Guys... help.... I haven't got to touch, nor sit in my car for 4 months. Yes, FOUR MONTHS! I took ...
  1. #1
    LacSeville's Avatar
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    Manifolds are melting my car

    Guys... help.... I haven't got to touch, nor sit in my car for 4 months. Yes, FOUR MONTHS! I took it to a local shop trying to save a few bucks over taking it to the Cadillac dealership. I was thinking this was a much more simple problem than it is apparently. My exhaust manifold (both of them) start glowing red after only about 30-40 seconds of running. Both of them are cherry red within 2 minutes of running. I caught the problem early as my plug wires are not melted. I just smelled the firewall melting. This occured on the drive home after having my oil changed at the local quick stop. I have had some problems with heavy knocking right before that. I'd just nail the throttle and I guess the spark knock sensor would compensate or something and it'd quick knocking. I most always use 93 octane, but I filled up with 87 last time. I also have a bad abs sensor and I thought I was needing a TPS. I would hear that thing go nuts after I would shut the car off. The mechanic said the timing is fully retarded. He said he has tried everything that is related to the timing. (I know he's used several new sensors including the knock sensor and put the old parts on after the new ones didn't work) Most recently he took the valve covers off and checked the timing chain marks. Does anybody know of any freak cases like mine. I don't know exactly what he has done, but I assume he's done everything common. He has given up and it writing me a bill for it. He's being very generous on the labor charges. (Since he has had it for 4 months!) I can't help but thinking that I could get it back, get it on the road, and just nail it and it would fix itself. I need HELP! 4 months is a long time to go driving your work pickup everyday! Bbob??? Anyone? Thanks guys, you are always great!

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    davesdeville's Avatar
    davesdeville is offline Banned
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    Re: Manifolds are melting my car

    BBob isn't around anymore. That other smart guy chevelle might be able to shed some insight. I have a question though, have you tried just draining the tank and refilling with 93?

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Manifolds are melting my car

    Glowing manifolds and knocking means you're running lean. Excessively lean. You need to figure out why, here's some things to check.

    Fuel pressure at idle?
    Fuel pressure at WOT?

    Any codes for TPS, MAP or MAF?

  5. #4
    1993 eldorado green1's Avatar
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    Re: Manifolds are melting my car

    i bet its a plugged cat. it will also cause your problem. also, glowing manifolds can be caused by running too rich as well as too lean, how does the car run?

    either way 4 months? take it to a shop that knows how to fix cars before you end up getting screwed at this one..

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    zonie77 is offline Cadillac Owners Connoisseur
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    Re: Manifolds are melting my car

    Lean or retarded timing.

    As suggested, check fuel pressure with a gauge. Check timing with a light. Let us know.

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    Re: Manifolds are melting my car

    I always thought that a glowing manifold was a rich condition. In either case check the FPR, injectors & PCM.

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    Re: Manifolds are melting my car

    replace the O2 sensors too as that could have killed the cat prematurely. just a guess...

    How many miles are on that car?

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    Re: Manifolds are melting my car

    Running to lean....
    I can be your ignition coil. When they are bad fuel are not burn in the chamber but in the exhaust. Correct me if I'm wrong.

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    Re: Manifolds are melting my car

    The guy at the shop said that the timing was fully retarded. The first thing he did was upbolt my exhaust to check for clogged cats. That obviously didn't work. There is a code for a TPS or ISC (ISC out of range, i believe).. .don't recall which one right now. He put 2 bottles of octane boost in the car while working on it. The car ran fine on the way home before I noticed the smell. I don't know if he pursued the lean fuel side of it. I don't know if he's checked the fuel pressure or FPR. I do think he has checked the PCM, because he told me some stuff didn't match up and that the timing was fully retarded. My mechanic is a very popular and reputable one in the area, but I guess I'll just two it to the Cadillac shop.

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    Loose screw is offline Cadillac Owners Fanatic
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    Re: Manifolds are melting my car

    You mentioned "This occured on the drive home after having my oil changed at the local quick stop."
    I have heard plenty of nightmare stories from people you have taken their cars to some sore of quick oil change place. Did they by chance change or look at your air filter? Is it installed upside down which could case the paper folds to colaps on thesleves and largely seal off. (test: remove filter, run engine)

    Could someone of mixed up the wires to the crank sensors, they are very near the oil filter and the guy in the pit who changes the filter and drains the oil may of gotten board and was just playing around and mixed them up (not that he needed to even touch them).

    Check the oil, make sure it looks and smells like engine oil.

    I really don't think any of these are the answer BUT you did say "This occured on the drive home after having my oil changed at the local quick stop." and I have heard them do dumber things. So I would start by carefully checking and ruling any possibilities out that they might of done intentionally or acidentially to your car.

    What does the engine idle at?
    Does it run well otherwise?
    Did you piss anyone off at the lube place?
    Did they try to sell you something extra?
    Check for foreign objects in your tail pipes and the whole intake system.

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    Re: Manifolds are melting my car

    No, the engine ran funny at idle. I had some kind of TPS code and it idled high. The idle speed control motor goes nuts after I turn the car off. No, I haven't pissed anyone off! Nothing extra. No fluid top offs, greasing, or anything. Just an oil and filter change. I will check out the intake stuff. I did check my exhaust though.

    Have not checked the crank position sensor wires. How would that affect the running or timing?

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    Loose screw is offline Cadillac Owners Fanatic
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    Re: Manifolds are melting my car

    The 2 crank position sensors (pickups) record a large rotating carefully multi notched disk in the middle of the crank that tell the computer exactly which piston is at top dead center. It replaces the loobs in a distributor or in new cars the notched front puuly/balancer and sensors. Without them working right the computer doesn't really know what position the crank is in. It can run one crank sensor, I don't remember which one (but the computer goes into a defualt mode) but I don't know what would happen if someone mixed the wires to them, and they were still working, it would certainly throw the timing off.

    I would have to think that pouring in or pumping in cold oil into a hot engine and onto the crank sensors which stick into the engine could cause a thermal shock to the sensor and be hard on them - could possibly crack. Of course the oil does warm up a little as it flows down into the case. But still it's a consideration. Better to change the oil when the engine is cold.

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    Re: Manifolds are melting my car

    Quote Originally Posted by Loose screw
    The 2 crank position sensors (pickups) record a large rotating carefully multi notched disk in the middle of the crank that tell the computer exactly which piston is at top dead center. It replaces the loobs in a distributor or in new cars the notched front puuly/balancer and sensors. Without them working right the computer doesn't really know what position the crank is in. It can run one crank sensor, I don't remember which one (but the computer goes into a defualt mode) but I don't know what would happen if someone mixed the wires to them, and they were still working, it would certainly throw the timing off.

    I would have to think that pouring in or pumping in cold oil into a hot engine and onto the crank sensors which stick into the engine could cause a thermal shock to the sensor and be hard on them - could possibly crack. Of course the oil does warm up a little as it flows down into the case. But still it's a consideration. Better to change the oil when the engine is cold.

    if the crank sensor wires are switched it would not start. the car will run with 1 or the other hooked up backwards. if it was a damaged crank sensor than he would be getting the p083 code when the engine is running.

    all he has to do is unplug the connector on the icm, on the passenger side, closest to the firewall, there is only 4 wires on this plug and there is 2 rubber plugs in the center 2 slots in the plug. then he can check resistance at the plug.

    those wires run down to the crank sensors, you should see about 1.5 resistance on each of the 2 wires.

    on the plug, you will see 2 wires, then 2 rubber plugs, then 2 more wires. those are the crank sensor wires. measure resistance there and you will rule out possible crank sensor problems.

    we can sit and speculate all year whats wrong but atleast this way we know for sure weather there bad or good.

    if there good we can move on to the next test..

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    zonie77 is offline Cadillac Owners Connoisseur
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    Re: Manifolds are melting my car

    Ranger, you are right...running too rich or too lean will cause it to run hot. Too rich is usually more common, I typed ahead of my brain.

  16. #15
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    Re: Manifolds are melting my car

    Look for a big intake leak. Maybe a PCV hose waving around or split.

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