timing noise?

[Pasophisto]

I have an '87 3.2 in nice shape.
New high tension wires, distributor cap, rotor, coil. Injectors are clean, SW chip.
Under load at low rpm the motor clatters, like a timing issue. Call it dieseling or tappety or what have you. Like I'm asking too much of the motor with the accelerator pedal.
I understand that timing in these things is completely set by the Motronic chip. My car does the same thing with the stock chip, so it's not the SW. My rotor cap can turn in it's fittings about a sixteenth of an inch (but in another post the consensus is that is not unusual and wouldn't matter). The condition does not change if I rotate the cap that little bit. I've driven other 3.2s and none of them do this.
Anyone have any ideas?
Thanks
SMS

[atc_marty]

Mine makes a noise similar to what you describe, going on three years now. I've had the valves adjusted, changed the cap and the chip like you, but no change. I suspect the noise occurs throughout the entire rev range but above 3000 or so, I just can't hear it over the exhaust. I'd love to get to the bottom of this one! I'm tired of my car sounding like a tin can!

[Flat6pac]

Look for a bad tensioner, some chain slap might be the problem.
Bruce

[Bob Kontak]

Originally Posted by Pasophisto

Under load at low rpm the motor clatters, like a timing issue.

Under load in low RPM's in a higher gear especially, can create a rattly noise from the transmission.

I think it is your transmission making normal noises under load at low RPM. 2nd gear, not too much speed and give it part throttle, transmissions rattle. The best description I pulled from some searches is that the sound is gravely. I experience it in my 915. My pal with a low mileage 89 930 with the G50 five speed, same thing.

As the second quote down states, if it is not scary, relax. Also you have pressure fed tensioners which are far less prone to failure.

Tensioners will sound like a chain being pulled over the edge of a metal garbage can per Bruce Anderson. That is in the scary category. I have never hear the failure noise.

Start in first with higher RPM's and I bet the noise is not there for long.


I suspect this is a normal transmission noise. Trannies make a gravelly sound under load at low engine speeds. If it does not sound scary....that is, if it is not the dreaded chain tensioner noise or something, then just relax.

My G50 makes the same noise you describe under the same types of conditions. It is like a growling-chatter sounding thing that isn't very noticeable. My mechanic said it is completely normal and I haven't really worried about it since.

Ought to hear mine with the LSD and WEVO system - marbles in a muffled can

[Rich Gas]

Bob, you're a wealth of knowledge...for real. Mine does this when cold, but less when warmed up.
Hey, I also have a slight oscillating noise when driving, in gear related...sounds like it's coming from the drivetrain. Probably the tranny too?

Thanks Bob

[Bob Kontak]

Originally Posted by Rich Gas

Hey, I also have a slight oscillating noise when driving, in gear related...sounds like it's coming from the drivetrain. Probably the tranny too?

I can't comment on this from experience or reading.

If a harmonic oscillation is established in the transmission, something is wrong. I would think you would feel it as well as hear it.

Maybe in the CV joints/flanges or bearings?

If you engine is running rich could there be some surging going on? I think you would pick that up, if a cause, only when cruising.

Just talking.

[Rich Gas]

It could also be the fan and pullies...when I first bought the car and after doing extensive work on it, I had Tom Amon come by and give it a spin. He ran it through its paces and gave it a thumbs up.
It makes more noise now that I have Wevo mounts. Damn things are just noisy. Still the slight oscillating noise bugs the crap out of me.

Thanks for your thoughts on the subject.

[Bob Kontak]

Originally Posted by Rich Gas

Still the slight oscillating noise bugs the crap out of me.

On my SC, you can watch the O2 system swing lean/rich/lean/rich etc every second or two using the dwell meter.

I don't know if this could be transmitted through the drive-train, though. And I don't know if Motronic Lambda is more sophisticated than the CIS Lambda.

You could unplug the sensor and take it for a spin just for grins.

[Pasophisto]

Thanks for that input. lots of good comments here. I don't think it's tranny or chain tensioner related, if I understand the mechanism of how those things work because the sound occurs under constant load in gear. Picture putting the transmission in first gear to pull away, rolling off the clutch, and hammering the throttle before you have enough RPM to employ adequate torque- of course this is to elicit the maximum audible symptom, not a good driving technique. It's identical to a bad timing sound. Since ATC Marty is also frustrated with the issue, maybe it's our fresh Canadian air, eh?

[Bob Kontak]

With the gravely transmission noise it would be most audible if you just got rolling in first, shifted to to third then gave it some beans. The noise would last until torque caught up with load demand and then disappear. No dissipation, just gone.

Also the trans noise comes distinctly through the floor pan. There's little question of whether it's the engine or not.

Was the noise present before anything new was installed?

[Pasophisto]

Yeah, not through the floor. definitely engine noise in my case. Don't think anything I did to the motor changed it.
SMS

[Bob Kontak]

Just talking.......

Don't discount some weird rubbing when twisting occurs under load. Set the e-brake and have someone watch the motor to see if it flexes any when you engage the clutch a bit.

[911pcars]

As a suggestion, a long rubber hose next to a suspect area with the other end at your ear can help pinpoint/isolate the source of the noise.

Since this is a noise/vibration that occurs at speed, perhaps the friendly neighborhood smog test center (or equivalent) might allow some roller test time in exchange for a 6-pack or 10.

Sherwood

[Pasophisto]

interesting ideas both. Will try to isolate the sound tomorrow. Are engine mounts usually an issue with these motors?

[Bob Kontak]

Originally Posted by Pasophisto

interesting ideas both. Will try to isolate the sound tomorrow. Are engine mounts usually an issue with these motors?

They get tired but I would not call them an issue. They are not on the list of 3.2 faults. Routine wear parts.

Raise your engine up with a lift and see if it moves much before the car starts to lift.

[Pasophisto]

will do. How much movement should there be?

[Bob Kontak]

There are hefty rubber buffers that get squished a little. Those give the engine a little tiny flex room. High performance metal ones are a direct link.

I would say virtually no real lift of the engine before the car starts to respond. On my old ones, there was a noticeable movement of the engine with zero impact on the car before all connected. I am thinking close to a half inch. They were toast.