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

Tiny
88
  • MEMBER
  • 1988 CHEVROLET CAPRICE
  • 90,000 MILES
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.
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Monday, August 22nd, 2016 AT 8:44 PM

22 Replies

Tiny
HMAC300
  • EXPERT
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.
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Tuesday, August 23rd, 2016 AT 8:04 AM
Tiny
88
  • MEMBER
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.
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Tuesday, August 23rd, 2016 AT 10:06 AM
Tiny
88
  • MEMBER
Just read one of the previous high idle questions below. I will check the vacuum hoses and get back to you. Thanks again.
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Tuesday, August 23rd, 2016 AT 10:14 AM
Tiny
HMAC300
  • EXPERT
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.
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Tuesday, August 23rd, 2016 AT 12:02 PM
Tiny
HMAC300
  • EXPERT
One other thing this can be a carburetor problem as well, like due for an overhaul due to alcohol in gas.
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Tuesday, August 23rd, 2016 AT 12:03 PM
Tiny
88
  • MEMBER
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).
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Tuesday, August 23rd, 2016 AT 12:25 PM
Tiny
HMAC300
  • EXPERT
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.
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Tuesday, August 23rd, 2016 AT 3:24 PM
Tiny
88
  • MEMBER
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?
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Thursday, August 25th, 2016 AT 12:48 PM
Tiny
HMAC300
  • EXPERT
The coil wire could be bad also going to dist. Check resistance to it. Chec at auto parts for prices
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Thursday, August 25th, 2016 AT 1:00 PM
Tiny
88
  • MEMBER
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.
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Thursday, August 25th, 2016 AT 2:10 PM
Tiny
HMAC300
  • EXPERT
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.
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Thursday, August 25th, 2016 AT 3:23 PM
Tiny
88
  • MEMBER
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?
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Friday, August 26th, 2016 AT 9:34 PM
Tiny
HMAC300
  • EXPERT
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.
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Saturday, August 27th, 2016 AT 5:42 AM
Tiny
88
  • MEMBER
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?
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Saturday, August 27th, 2016 AT 10:52 AM
Tiny
HMAC300
  • EXPERT
The module is accessible with out pulling dist rotor cap should pull offtry moving one end then other like wiggling it off.
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Saturday, August 27th, 2016 AT 12:03 PM
Tiny
88
  • MEMBER
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?
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Sunday, August 28th, 2016 AT 5:52 PM
Tiny
HMAC300
  • EXPERT
Sometimes they will start but depends on wiring and how messed up it is you have it running so don't worry about it.
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Monday, August 29th, 2016 AT 6:38 AM
Tiny
88
  • MEMBER
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.
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Monday, August 29th, 2016 AT 1:27 PM
Tiny
88
  • MEMBER
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).
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Tuesday, September 6th, 2016 AT 5:52 PM
Tiny
HMAC300
  • EXPERT
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
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Wednesday, September 7th, 2016 AT 6:27 AM

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