fast idle, hard start (sometimes no hot start at all)

1988 CHEVROLET CAPRICE
90,000 MILES
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88
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My car is a Brougham. 305 V8.

Began with fast idle that could not be adjusted with the throttle set screw.

Now cold start takes longer and after it has been run, may not restart (no hot start). Engine cranks fine, fuel is reaching the four bbl carburetor (I can smell it and fuel pump clicks with key in 'start' position), choke seems to be off, secondary plate is closed. Cranks like it has no spark (does not catch at all) but once cooled down it will start again. Air cleaner is new. I have never changed any of the sensors. When started, the car runs perfectly. It is smooth, quiet, and powerful.
Aug 22, 2016 at 8:44 PM
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HMAC300
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check pick up coil for resistance and broken wires and have ignition module inside distributor checked auto parts can do that. pick up coil resistance should be 500-1500 ohms try a heat gun on it to see if pickup coil goes high or wait until it quits.
Aug 23, 2016 at 8:04 AM
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Thank you. I suspected this might be the problem (or part of it).

What about the fast idle (it is very fast and wont come down, sometimes it backs off a bit after a longer trip but never down to normal)? Would a faulty module have caused that, too? I have sprayed all the appropriate exterior carburetor moving components with penetrating oil to ensure nothing is sticking but it has not helped.

thanks.

Aug 23, 2016 at 10:06 AM
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Just read one of the previous high idle questions below. I will check the vacuum hoses and get back to you. thanks again.
Aug 23, 2016 at 10:14 AM
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HMAC300
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also, you may have to free up the high idle cam on carburetor do not use penetrating oil use choke cleaner instead and move cam with fingers to free up then check to see if a clip has broken/rusted off making it stay on.
Aug 23, 2016 at 12:02 PM
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HMAC300
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one other thing this can be a carburetor problem as well, like due for an overhaul due to alcohol in gas.
Aug 23, 2016 at 12:03 PM
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Thanks. I will try this out but the choke seems to be free. Where is the choke cam, precisely?

The last thing I want is to rebuild the carburetor Is it possible the problem lies in the throttle diaphragm (there is a diaphragm device attached to the throttle on this model that can move the throttle? I do not know if it is temperature controlled or computer controlled or vacuum controlled or what but it overrides the set screw idle adjustment on the throttle mechanism).
Aug 23, 2016 at 12:25 PM
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HMAC300
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the Rochester has a throttle pump not a diaphragm like a holley or older ford carbs. the fast idle cam is on the right side of carb the vacuum motor on side of carb should open choke then linkage opens cam for fast idle we don't have a pic of that. If you go to www. powerblock tv.co m and type in Rochester carb overhaul you may get a video that will show all theparts and actually fix all the problems ever associated with that carb.
Aug 23, 2016 at 3:24 PM
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Thanks very much. I inspected the distributor and noticed the 'coil' looked very different from the old ones. Is that still a coil or a different device used to bump up voltage to the rotor? The center distributor wire goes to it. Could that be burning out? I remember the old ones used to intermittently fail just before burning out completely. What are they worth thee days?
Aug 25, 2016 at 12:48 PM
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HMAC300
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the coil wire could be bad also going to dist. check resistance to it. chec at auto parts for prices
Aug 25, 2016 at 1:00 PM
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The coil wire seems to be fine but I'll check it again. I know automotive wires can cause intermittent problems as they get old. Thanks.

I think I'm going with a distributor tune up (cap, rotor, etc) and see if it starts. If it doesn't start, I think I'll replace the coil because it cranks like it's not getting spark (I've checked to see if any of the wires are loose or disconnected and I couldn't find any). What do you think?

The idle I'll work on after I get this start problem solved. Thanks.
Aug 25, 2016 at 2:10 PM
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HMAC300
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just pull the coil wire from the dist cap put it towards engine block and if you get a good strong spark then it's not the coil or wire. someone will have to turn the engine over while you do this.
Aug 25, 2016 at 3:23 PM
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That's a good tip but I have no one to help.

I couldn't remove the rotor. There doesn't appear to be anything holding it (fasteners of any kind). Is there a trick or technique that must be applied to remove it without breaking the board that's beneath it? Do you have a picture of how to install the p.u. coil and the control module?
Aug 26, 2016 at 9:34 PM
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the first reply had a pic of the distributor which has to be removed the gear taken off then shaft pulled out to access pick up coil. the module is held in by screws.
Aug 27, 2016 at 5:42 AM
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How is the rotor removed? The old ones just used to pull out. This one won't come out by pulling and I don't want to risk cracking the board beneath it by prying it with a screw driver. Would some penetrating oil help loosen it up? Or would it contaminate the distributor parts? It's held quite firmly... is there a screw holding it (it feels like it's fastened in place but there's nothing visible)?

The picture doesn't show the module. Is it accessible from the top without removing the distributor?
Aug 27, 2016 at 10:52 AM
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the module is accessible with out pulling dist rotor cap should pull offtry moving one end then other like wiggling it off.
Aug 27, 2016 at 12:03 PM
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Thank you. My car is now home safe in my garage. Lucky I had good weather. It started raining about 2 hours after I got it in the garage.

I could only change the cap and the coil. The rotor would not budge. It started but was missing badly... how many cylinders I don't know... it would barely make the hills. Now the question is, 'why'. The engine always ran smooth as silk once it started even when it was hard starting. I used a squirt of WD40 under the rotor to try to loosen it to no avail. Could the penetrating oil have done any damage to other parts within the distributor or am I just witnessing wire failure from disturbing them? I took the cap on and off twice trying to get the rotor off. Would the wires fail just from taking them on and off? I drew a wiring diagram of the wire pattern before removing them from the cap the first time off. I was careful to put them on exactly like the diagram. Would the car start and run, even badly, if I had crossed the wires?
Aug 28, 2016 at 5:52 PM
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sometimes they will start but depends on wiring and how messed up it is you have it running so don't worry about it.
Aug 29, 2016 at 6:38 AM
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Thank you for your advice. Running like new. Still have to drive it and see if idle comes down but now firing smoothly on all 8 again....

.... for future reference, and if it helps anyone, if you still have the original factory wires, they are numbered (makes it easier to put back in the right place).

I must have gotten a little goofy standing out in the sun for three days.... can't believe she got me all the way home on 4 cylinders.... gotta love it.
Aug 29, 2016 at 1:27 PM
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OK... so here I am again. Drove it for 4 days... smooth as silk, then wouldn't start again. I have new coil and cap (new coil is what solved the problem until it came back). Must change both control module and pick up coil to ensure system will deliver spark I think
1. Must the rotor be removed to change the control module or can I change it with the rotor still in place?
2. Must the distributor be removed to remove the pickup coil? I read somewhere else that 88's had a newer design that allowed p.u. coils to be removed without removing the distributor (which I dread doing).
Sep 6, 2016 at 5:52 PM
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I already sent how to remove pickup coil and dist has to be removed. just try moveing rotor out of way to get to screws
Sep 7, 2016 at 6:27 AM
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Thanks again.
Sep 7, 2016 at 11:49 AM
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Thank you for all your help and good tips. Just for future reference and if it might help anyone else (I've seen several other inquiries on these cars regarding high idle, some that have claimed to have changed just about all related sensors without correcting the problem) After changing the coil, rotor, cap, control module, but not the pick up coil, the car is now starting reliably and running very smoothly. Curiously, the idle seems to have have come back down to or close to normal. Has the system perhaps been trying to compensate for weak or unreliable spark by forcing the engine to idle too high? Prior to the high idle problem, I had to set the idle higher to prevent stalling, then lower it again because it began idling too high. I haven't had the old parts tested yet so I can't be sure which one(s) were failing.

Before changing out the sensors on one of these, it might be wise to test distributor components in high idle situations or if the car is do for a tune up, just do a complete tune up (because it has to be done anyway) before buying new sensors. Unless one has had extensive experience with these systems, it's hard to ascertain what component(s) is/are causing the problem. The systems seem to be so complex it's hard to know if the computer, trying to do its job of keeping the combustion cycle as efficient as possible, is masking the real problem by causing another problem, in this case a high idle.

Just a thought..... Best wishes, 88
Sep 14, 2016 at 3:28 PM