RDS928S

Gents,

My 32V motor runs very strong and smooth except at very low rpm's. When creeping along in traffic around 1000-1200 rpm's it bucks. also in reverse it bucks at slow speed.
Another possible related problem is rough idle when cold. Sometimes it is fine when cold.The bucking is sporadic.
Items I have replaced to correct this are: new Bosch platinum plugs,new Beru spark plug wires, new intake boots and all associated rubber hoses,
new MAF o-rings,new Bosch o2 sensor.
Items not replaced: idle speed control valve,coils,dist. caps and rotors.

Thanks in advance
RDS

John Speake

Did you jusst replace the MAF O rings, or the MAF itself ?

Has MAF been replaced that you know of ?

How many miles on the car ?

Does it buck worse when engine hot, and high ambient temperature ?

H2

Clean engine you have. Did you repaint your manifold pieces? If so, any tips?

Harvey

Thaddeus

Sounds like the engine's missing. I'd do cap and rotors if I were you.

Also, a new MAF is a beautiful thing. My car went from running well (if rich) to running GREAT when I replaced the MAF... picked up some HP too, I do believe. But I suspect the MAF has little to do with the bucking problem you're experiencing.

John Speake

It will buck if MAF is badly aged (car running weak).

jeff jackson

Rich...did you replace the large "boot" from the throttle housing to the large "T" section of the intake...that connects the throttle housing to the large air plenums at each side of the intake port runner tubes ?? All the vacuum is spplied from these individual port runner tubes, to their respective side plenums, and then through the large center "T" pipe to the throttle body. So...replacing the small intake runner boots, and the large boots to the "T" pipe is a great idea...JUST, don't neglect the large boot that connects the "T" pipe to the throttle housing. I think you have vacuum issues, or low idle spped causing your "bucking"

lorenolson888

Surging and dipping idle sounds like the stabilizer...

but my MAF was causing to hardly run at all without opening the throttle and it was running way rich at those speeds.

try to describe the problem as accurately as possible

LO

RDS928S

Thanks responders.

The car has 65k original miles. Autothority chips.
The MAF is original to the car. Jeff, the large intake boot was replaced whith all the other intake boots(I think).
The engine runs very strong and smooth at all speeds except below 1200 rpm's.
Then it starts to buck slightly. The rough idle does not happen all the time?.
Sometimes it takes 3-4 cranks to start then a rough idle until it smooths out.
Mlost of the time it fires up instantly.
These maladies come and go?
Harvey the intake was powder coated silver metallic at Devek.
$400.00 including the intake. You must return your old intake to Devek for a core replacement.

Rich

John Speake

The intermittant nature of the problem suggests ignition or.....maybe flywheel sensor ?

RDS928S

John,

what part of the ignition should I be looking at?

Thanks Rich

lorenolson888

Tough to diagnose as all of the "not new" items you list could cause problem like these if they are beginning to fail.

Do you know someone else with an 85-86? maybe you can check against their parts...

it will help you sort through it all

Good luck...

LO

John Speake

As Thaddeus said, caps and rotors should be inspected and changed if required.

Other possibilities are vac leak.....flywheel sensor....but as Loren says, very difficult to diagnose when internmittant.

jeff jackson

Rich...did you change the 7 way vacuum splitter, and all the rubber "elbows" to the fuel pressure dampers, and regulator ? Reason I ask, is my car did the "bucking at idle", and when at idle in reverse as well...I found a "split" in the side of one of the nipples on the 7 way splitter...and numerous cracks from the inside of the large boot that connects the intake "T" pipe to the throttle body...replaced those things and alls good.

RDS928S

Jeff,

thanks will check. Can I see the 7 way splitter underneath the intake?

Rich

jeff jackson

Only if you have the eyes of a Bird Dog...It is tucked neatly under the air filter box assembly, in the "VEE" under the MAS...easy to find once these things are out of the way...sort of like the Idle Air Control Valve. But anyway...every thing that receives a vacuum signal (fuel management wise...except the thermoswitch for air pump diverter valve, and the HVAC, brake booster, and Cruise Control)...gets its source of vacuum from this 7 way splitter on our 85-86 cars. And the 7 way splitter, is directly fed from the throttle body, which is supplied from the large boot from the center "T" section of the intake that I mentioned in my earlier response to this thread.... check out the vacuum schematic in the WSM and you will see what I mean...or if you want, PM me, and I'll email the pertinent pages to you. Always glad to hear from you Rich...