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Thread: Surge and Rough Idle

  1. #1
    Carthago delenda est Lutrova's Avatar
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    Default Surge and Rough Idle

    Around the end of January I was returning from Phoenix in my Town Car. The Smog/AC belt was squealing, but I was surprised when just past the California border my alternator pulley worked itself loose and threw the belt. Got that patched up and continued home, but as I started the engine after getting gas it started to surge, higher and lower until it finally choked itself out and died. I started it up again and it held steady at idle, so I proceeded to drive several hours more down the freeway. As I got off onto a surface road I came to a stop again and noticed the same surge starting again, but not wanting to be stranded at night in the Mojave I didn't wait around to see what happened.

    Fast forward to the present, I've had the car pulled apart for the last couple months as I take my sweet time working on the engine. I've replaced both belts, removed and reinstalled the fan for cleaning, replaced the idler pulley, pulled and reinstalled the ignition coil, cleaned all the plastic intake stuff leading up to the throttle body, and removed the smog pump pulley. So I try starting the car this morning for the first time in ages, and it starts fine but immediately runs quite rough. Not really surging like before but more just sputtery. And the engine is moving a good deal - the whole car is shaking with it. After a few seconds I tried giving it some throttle, but didn't notice any real response from the engine. It sounded like it was going to sputter out and die, but I cut the ignition before that happened. Things smelled pretty rich afterward.

    So I thought about everything I'd done and it seemed the only thing I did that might have this effect was the smog pump. I figured I could throw the pulley and belt back on and see if it made a difference. And the smog pump squeals, which makes me think it was going bad along with the idler above it, but having put it back in service the engine is still idling quite rough. It might be running a little better, but it's hard to say. I only ran it for another 10-15 seconds after reinstalling the pulley and after I cut the ignition again the garage was a little smokey.

    Auto mechanics is pretty new to me and up until now I've only messed with accessories and less critical stuff. But the nearest mechanic is over 35 miles away, and I'd like to take a shot at this before turning it over to someone whose labor costs more than $0. My first thought in January when the issue appeared to be surging at idle was an issue with air intake, like the TPS or IAC or throttle body. And maybe that issue continues to be present, but the engine shake and rich smell made me wonder whether there was also a timing or ignition issue now too. Though I hadn't touched the distributor and I'm pretty sure the coil wire is on as snug as it'll get. The plugs, wires, cap, rotor, and distributor are all new, installed within the last 6 months.

    How might I go about diagnosing this? I have a few thoughts, but with no real personal experience I don't want to jump in blindly and accidentally screw things up more.
    1987 Lincoln Town Car - Signature, "Prudence"

  2. #2
    fomoco panthers !
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    Not answering your question but a little advise, from one who lived and worked in the Ca desert. Get AAA with the 200 mile towing benefit. If you need it towed to a shop, use a AAA shop. Most of the shops in the desert are rip offs.

  3. #3

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    First things first. Air, fuel, spark. Check the vacuum lines and make sure they're correctly routed and not damaged. Check the IAC wiring. Check cap, rotor, wires, plugs. No squirrels in the air cleaner. Decent gas (and enough of it!) in the tank. You may have done all those things, but that covers most of the air and spark. Make especially sure the line to the MAP sensor isn't cracked and that the vacuum lines right off that vacuum fitting are all in good shape.

    From the symptoms, I'd actually guess you have a problem with the EGR valve leaking by and/or the valves in the smog pump piping.

    I'm not sure how handy you are, so I don't want to suggest things that would stick you leaving a tow if you get in too deep; but if you're comfortable with the idea of using a metal plate to block off the EGR valve ports in the intake, you could use that to prove or disprove the EGR valve. Do that only after you've checked the vacuum lines and ignition parts.

    You can also look up how to read the codes and post those here. It doesn't require a code reader on these cars (although a code reader makes it easier if you have one).
    Last edited by bgreywolf; 04-30-2020 at 01:26 AM.

  4. #4
    Wagon Addicted Tiggie's Avatar
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    X2 check MAP sensor vacuum hose and other vacuum lines for leaks. It’s a black rectangular thing, top passenger side firewall side with wiring and a vacuum hose to it.

    May also be worth checking out the fuel pressure regulator. It is a round cylinder thing on top of the engine on the fuel rail. About the size of a half dollar, but thicker, and has a red vacuum hose going to it. Check that hose for cracks. They are fragile. And check for fuel smell around the regulator - this would indicate failure.
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  5. #5
    Carthago delenda est Lutrova's Avatar
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    It sounds like I should probably be replacing all vacuum lines anyway. Are they all the same diameter as the ones listed at the top of this forum? And how many feet do you figure I'd need to do all the lines in the engine bay?

    When you say to check the IAC wiring, am I cleaning the electrical connectors, or looking at it with a multimeter? I was figuring I'd pick up a can of throttle body cleaner and clean out the IAC valve, throttle plate, and EGR valve. I've attached a picture of the throttle body from a couple weeks ago. At one point oil was leaking from the breather tube that runs from the valve cover, which I assume is not typical behavior. I replaced the PCV valve and filter since then, which I believe to have relieved whatever pressure may have driven oil through that tube. Or maybe that is normal and I don't understand how it works? Either way, it looks like there might be enough gunk in there to warrant cleaning.

    The smog pump, I had thought, wasn't all that critical to the engine's performance. My shop manual, unfortunately, doesn't seem to say much about it or the emissions equipment in general. Is the smog pump pulley squealing a sign that the whole pump is going bad? And are its valves something I can also hit with throttle body cleaner? (I'm a little confused on the exhaust gas stuff in general. I can't see any piping running off from the exhaust manifolds, and I definitely don't see anything that looks like it could carry exhaust going into the EGR valve. How does that work?)

    On the ignition system, I'm wondering whether it would be worth replacing the coil, as it and the ignition module are the only parts that haven't been replaced in the last six months/1000 miles. The car has a little over 80,000 miles right now, and while I believe the ignition module has been replaced before, I don't know about the coil.

    I'm looking at buying a code reader, though with the way the engine's running I'm not sure it'll run long enough to go through all the codes.

    Regarding towing - my wife and I have USAA roadside assistance, which I've availed myself of once already. I'm fairly confident they'd tow the car to Barstow if needed. But in general I have much more time than money, and particularly on a $1200 car I'm game to spend a lot more of the former if it can save on the latter.
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    1987 Lincoln Town Car - Signature, "Prudence"

  6. #6
    I'm an air-conditioned gypsy gadget73's Avatar
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    map sensor, map vacuum line, or stuck EGR valve sounds pretty likely to me too.

    if the smog pump valves go stupid and keep pumping air into the back of the head, the oxygen sensor will read lean and the ECM will fatten the mix. Pulling the belt will stop it from doing that. Works as a quick and simple diag check. If it runs like garbage with the smog pump belt on but normal with it off, theres something up with that system.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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  7. #7
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    If you are going to change the vacuum lines get a full roll of vacuum line.

  8. #8

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    The smog pump system essentially pumps fresh air into the exhaust stream during startup, to compensate for the rich starting mixture and help prevent catalyst fouling when cold. I believe it does so at extended idle as well, but I can't remember on the '86 and my manuals are at home and I am at work.
    The pump draws in air through a filter on the pump itself, and through a three-way diverter valve. One way pumps air into the the back of the cylinder heads where it mixes with the exhaust. The second route is pumping into the catalytic converters to provide additional oxygen for the catalytic reaction. The third, once the engine is warm and running under load, simply pumps the air back to the atmosphere.
    There is also a check valve (or two, again, I can't remember on the '86 and my manual isn't with me) which prevents the exhaust from getting blasted back toward the smog pump. A failed check valve can wreck the smog pump eventually.
    Smog pumps are noisy when new, but between getting air constantly drawn through the same dusty dry sponge 10" off the ground for 30 years and possibly getting a blast of hot exhaust through a bad check valve, they tend to wear out to be even noisier. So when you said it was squealing, I became worried it might be on its way to locking up from dry bearings and crusty seals.

    As Gadget said, pulling the belt is a good diagnostic. Then look on the passenger side of the engine and at the catalytic converters (the 1" lines from the converters to the smog pump, and the lines next to the A/C lines that go from the smog pump and valves to the pipe on the back of the heads) and treat it like you're looking for an exhaust leak, which is what it would be.

    The EGR valve works with internal passages; exhaust is pumped through the heads up to the intake manifold, where the EGR sits; then the EGR lets it pass to the intake air just after the throttle assembly. Blocking the path between the two passages on the EGR valve by clamping a metal plate and a bit of gasket material (I get a new EGR gasket because they often rip; then use a piece of steel shim I made that works on many 70s-90s Fords, place the shim on the old gasket, put the new gasket over the shim, clamp down using the EGR valve body). If it runs much better, the EGR is open when it shouldn't be and troubleshooting can go that way. If it doesn't idle better, the EGR valve isn't the problem.

    For the IAC wiring, a visual check is usually sufficient. It's just in the open at the front of the engine and sometimes gets damaged by overenthusiastic cleaners or clumsy mechanics. I've rarely had issues with the IAC signal, so long as the wiring at the IAC is okay. The physical IAC, on the other hand, often seems to get gummed up (and often responds well to a little cleaning).

    The engine doesn't have to be running to read the codes. Ford built some smarts in the computers; besides being able to read the codes without the reader, you can also perform various tests without anything but the car keys, a test light, and a piece of jumper wire. I'd suggest looking at the EFI "Old Fuel Injection" pages which go into reading the codes better than I could:

    http://www.grandmarq.net/oldfuelinjection/
    and more specifically (at first):
    http://www.grandmarq.net/oldfuelinjection/page13.html

  9. #9
    Carthago delenda est Lutrova's Avatar
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    Thanks, bgreywolf, and everyone else for the help so far. The nice thing about the car breaking down is I end up learning a lot more about how it works.

    Quick update: I took a look around the engine as I was taking the trash out and found the line to the MAP sensor is disconnected at the manifold. So I don't want to call it prematurely, but right now that looks like a strong contender for what's wrong.

    Getting it back on looks like it'll be a trick - facing the firewall and on the underside of the intake plenum. Might need to make friends with someone with very small hands.
    1987 Lincoln Town Car - Signature, "Prudence"

  10. #10

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    If you can get the "5.0 EFI" plate off the top of the manifold, and separate the upper from the lower (2 of the bolts are under that plate, but the 4 small screws in the corners of the plate get pretty stuck...) then it's not too awful to swing the upper manifold out of the way to do all the vacuum lines.
    The downsides are the throttle body (don't want to damage transmission cable or throttle cable) and not damaging the gasket; but if you're doing all the vacuum lines, it's well worth having the extra room.
    If you really want to get in there, undo the throttle body and EGR spacer and just leave them in place as you pull the upper intake off.

    I did the vacuum lines as part of changing to an HO upper manifold and throttle body (and valve cover gaskets, PCV, and screen, while I was in there); getting that intake off makes a lot of the little jobs easier if you do them all at once.

  11. #11
    Carthago delenda est Lutrova's Avatar
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    As it happens I was fixing to replace my valve cover and intake gaskets anyway, as I have a decent leak that's (hopefully just) coming from the lower intake manifold. It looks like a fairly straightforward job, though I'm a little apprehensive about depressurizing/disconnecting the fuel lines and removing the distributor/keeping the right ignition timing. (Does the distributor have to come out, or can I wrestle the lower intake out around it?) Rusted, broken bolts would also be a bummer.

    I'm also a little unsure on the correct gaskets. I understand Fel-Pro makes good gaskets, and I've identified the proper ones for most conditions, but it looks like there are multiple options for the head to lower intake. Are the FPG 1250's the ones I want? I also see they sell a combo lower/upper set - FPG MS93334 - for about half the price of buying each part separately.
    1987 Lincoln Town Car - Signature, "Prudence"

  12. #12
    I'm an air-conditioned gypsy gadget73's Avatar
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    you really do need the upper off to get all the vac lines. If you're pulling it, do it all in one go. And +1 on the PCV stuff, its much easier. Modern PCV grommets don't tend to fit real well. I've had good luck using heat shrink tubing around the PCV valve to fatten it up. Tape works until oil gets in the adhesive then it comes loose and gets sucked into the valve.

    Also worth changing are the two small coolant lines to the EGR spacer. I want to say its 1/4" or 5/16" fuel hose, can't recall which. One clamps to a fitting at the back corner of the lower intake, the other goes to a coolant pipe on the passenger side. Piece of cake to do with the upper off, absolute bastard to do on the side of the road when the 35 year old hose pops in the middle of nowhere.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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    Quote Originally Posted by phayzer5 View Post
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  13. #13
    Wagon Addicted Tiggie's Avatar
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    It’s 1/4” in the little coolant hoses. Get heater hose not fuel hose. My local parts store gave me fuel hose even though I asked for heater hose. Not the same stuff in terms of material. Fuel hose doesn’t like 200F degrees internally.
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  14. #14
    I'm an air-conditioned gypsy gadget73's Avatar
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    last time I sought out 1/4 coolant hose everyone looked at me like I had 6 heads.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  15. #15
    Wagon Addicted Tiggie's Avatar
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    Quote Originally Posted by gadget73 View Post
    last time I sought out 1/4 coolant hose everyone looked at me like I had 6 heads.
    Yes! RockAuto has it. I am going to order some on my next order. My parts store gave me that expensive high pressure fuel line that’s like $10/ft. I doubt they even carry the right stuff.
    1988 Crown Vic Wagon - daily
    1990 Country Squire - weekend cruiser, former lawn ornament
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  16. #16
    2 decades of DDing Box Panthers, now in a Whale VicCrownVic's Avatar
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    +1, 1/4. I've used 5/16 and may have started that misinformation. The clamp seals it just fine and the 5/16 hose comes off real easy next time.
    Vic

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  17. #17
    Carthago delenda est Lutrova's Avatar
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    Well I've taken the plunge down the rabbit hole of gaskets, vacuum lines, hoses, and generally cleaning things out. Fel-Pro gaskets and a new thermostat are already ordered.

    I discovered another vacuum line coming off the front of the intake that ran up toward the battery and was tucked behind the header panel. The diagram I've found doesn't show any vacuum for the horn, so I assume someone disconnected it long ago and the engine has been running with a vacuum leak for a very long time. It might've gone to something labeled 'CPRV' on the way to 'V REST' and what I assume is the charcoal canister and fuel tank? Not really sure what the implications of that leak might be on the previously vacuum-receiving end.

    I also understand that I should probably replace the lower intake manifold bolts when I put in the new gasket. What is the part number for these? It looks like LMR sells a replacement set, but 45 bucks for 12 bolts seems a little steep. And are there any other bolts on the intake or throttle body that shouldn't be reused?
    1987 Lincoln Town Car - Signature, "Prudence"

  18. #18
    I'm an air-conditioned gypsy gadget73's Avatar
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    That should be the canister purge solenoid, CANP. It hangs in space between the battery and the AC compressor. The other side of that solenoid goes to the charcoal can under the battery. So long as the manifold side is not leaking it won't usually cause major problems but if the manifold side is open it will be unhappy. I've had that hose sliced by the belt from improper routing before. Makes the idle high and stupid.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  19. #19
    Carthago delenda est Lutrova's Avatar
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    I did have an emissions test last fall (just to see where the car was at) and it passed, but nearly failed hydrocarbons at idle. I wonder if the CANP being disconnected would have anything to do with that.
    1987 Lincoln Town Car - Signature, "Prudence"

  20. #20
    I'm an air-conditioned gypsy gadget73's Avatar
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    if the vacuum side was unhooked, probably. Low vacuum to the MAP makes the ECM add fuel.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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