WaryDriver

I hooked up a vacuum gauge to my 98 Civic D16Y7 because cruise control is jerky every other second there's a slight throttle jerk/surge every other second after the SET button is hit and cruising even though it keeps the correct set speed. Vacuum gauge needle wobbles between 20 and 21inHg. What does that mean? Valve adjustments are needed? Needle is supposed to be still and steady when idle. Any ideas or interpretations from the gauge readings are welcome or cruise control advice for fixing. Here's the video:

Tried spraying carb cleaner all around the intake manifold connections and hoses with no audible changes in engine running that i could hear.

And, what is a the optimal reading for an idle D16Y7? How much pressure inHg? I know 20-21 is in the good range but what is optmial, any higher you've seen?

Former User

CC issues are likely a separate issue.

WaryDriver

What would you do to fix the jerkiness when Cruise is engaged and the SET button pressed? Causes passenger heads to go back and forth slightly, because its like its panicing to keep the correct speed so theres a throttle jerk every other second cruising on a flat road. When the ACCEL button is held, it accelerates smoothly. DEACCEL button is held then is deaccelerates smoothly. It's only when cruise is engaged and the SET button is pressed that it is jerky every other second to keep the correct speed on a flat surface. Doesnt matter how fast Im going or what gear. There is a throttle surge every other second then lets off 1 second then surges again 1 second..lets off 1 second then surge again for a second and so on contiuously so passengers heads, water, shifter go backwards one second then forwards another second, backwards one second then forwards another second and so on.

I've played with the servo cable a bunch to the point I can't imagine that being it. Put grease on the entire cable(removed completely), adjusted the cable housing by turning all kinds of ways, had the cable set taunt then with 1/2 deflection and jerky during both. Doesnt seem to be the servo cable leading to throttle or a vacuum leak (see video).

Former User

Your vacuum test indicates that the problem occurs without CC set. Focus there.

WaryDriver

Before gapping (in order left to right as cylinders 4 ,3, 2, then 1st) gaps were 1.25mm to 1.3mm for all of them:


After gapping(same order, 4 3 2 then 1) to 1.1mm:


Cylinder 1's plug, far right in each pic, the cylinder closest to timing belt, its electrode looked like it was missing a piece. I reinstalled every spark plug after gapping in another order 1st cylc -->3rd, 4th ----> 2nd, 2---> 4th, 3rd --> 1st.

Also, cylinder 1's plug seemed almost loose when removing. Wasnt "Loose" but I could remove with one hand on the socket wrench. Unlike the others. Cranked the engine after gapping and was a lot less of a rattling noise than usual. Quieter, guess that was the spark plug loose. Should I replace this spark plug thats missing part of its electrode with a new plug?

Vacuum pressure is now 21-22 and needle floats a bit in between. Shakes back and forth some but not as bad as it was doing.

Removed the MAP sensor in the back of engine. Spray cleaned with MAF cleaner and its hole. Reinstalled, and that did not fix cruise control.

Cruise control is still jerky/bucking/surging/pulsing throttle to keep the correct speed. What should I try next?

Former User

The electrode of the cyl 1 plug looks damaged and the electrode of the cyl 4 plug looks rounded. You probably should install a new set of properly gapped plugs.

WaryDriver

What about cruise control bucking and jerking when cruising at a set speed?
Things I've ruled out:
Throttle cable and housing (Ive turned all sorts of ways, greased cable, etc.)
Throttle pulley
Vacuum leak (hooked up gauge, sprayed carb cleaner everywhere near intake manifold areas and hoses listening for idle changes but no changes when spraying)
MAP sensor (cleaned only and reinstalled)
What else can I try doing to fix CC?

Former User

I'm unable to focus on the CC issue until the engine is running properly. They may be interrelated.

WaryDriver

Why would part of the electrode break off? Seems like that'd be pretty bad for the combustion chamber having something like that in there. Wouldnt that cause some kind of damage?

Former User

Is the broken piece of the electrode loose in the cylinder? Look for it and remove if found. If not, install new plugs, and then check whether you have a rock steady vacuum reading.

Caoboy

How much of a bucking is it? Or is it more of a slight acceleration and deceleration, say 64 to 66 mph when you are setting your cc to 65?

WaryDriver

You cant even see the speedometer change, it stays on the set speed correctly. But does so in a very annoying way. It's every second or so it jerks then lets off, jerks the lets off, and so on. Passengers heads slightly go backwards then forwards, backwards then forwards, over and over and over never stops doing that when cruising on a "set" speed.

ACCEL button hold works perfect. DEACCEL button hold works too perfectly.

Regular holding the gas pedal to maintain a speed not jerky. Its only when CRUISING with cruise control set.

WaryDriver

New spark plugs are in. Wires and distributor are good tested with multimeter. I'm glad I changed the spark plugs, its runs with less rattling noise. The needle is pretty steady on idle just a bit of floating sometimes between 21-22in but not vibrating and shaking like it was. And is higher vacuum pressure. But, still CC doesn't work.

I am going to adjust the intake and exhaust valves this morning. That may fix the needle floating movement which isn't much. I dont know if valves have ever been adjusted. I know in the last 100k they havent.

Besides the CC servo/acctuator, what else could it be that's causing the jerky/bucking/surging/pulsing throttle that cruise control does to keep the correct "set" speed? Ive never driven a car that does this when cruise is set. Passengers notice it after seconds and is not just me. Not smooth when cruising.

Because I'm going to the junkyard this afternoon to pull another actuator, map sensor, and throttle position sensor. And would like to know if theres something else I should pull there or try cleaning before I go to the junkyard again which is a good drive. Can you give me a list of things that would make sense to do like cleaning or parts to replace like sensors?

Things I've tested thoroughly and am continuing to test for being faulty:

• Throttle cable and housing (Ive turned all sorts of ways, straightened cable, greased cable, etc.)
• Throttle pulley (pulls smoothly)
• Vacuum leak (hooked up gauge, sprayed carb cleaner everywhere near intake manifold areas and hoses listening for idle changes but no changes when spraying)
• MAP sensor (cleaned only and reinstalled)

What next should I rule out?

Former User

Replace the distributor cap, rotor, and plug wires if they are old. It's basic maintenance.

Make sure the throttle cable is properly adjusted:




Do the actuator tests in the 3 diagrams below:






Other useful CC diagrams: