Rattling Noise, Especially When Under Load Like Climbing a Hill

[SFBayQ45]

I hear a very faint rattling noise coming from, I believe, the engine whenever I climb a hill from a full or semi-stop. Other than that, it doesn't make any noise at any other time. What do you suspect is the problem?

Vehicle = 1991 Q

[squeefoo]

Hope it's not preignition or detonation. Arghh !!

Can you repeat it in the garage? (by torqueing it up ?)

[szh]

Bad gas perhaps (sound of engine knock perhaps)? Are you using at least 91 RON?

Z

[Q_SHIP]

What gear and what RPM's would this be at? Could even be a converter cover or somthing.

It could be Knock but could you describe better? Does it sound hollow or tingy? ETC....

[MY92Q]

It might be the accelerator cables ratteling in their mounts on the firewall. I zip tied mine and all rattles went away.

[sijoko]

What kind of gas are you using? What was the ambient temp.? Does it happen when the weather is cooler? Also, when was the cooling system last serviced?

-sijoko

[AZhitman]

Sounds like knock.

Check base timing and go to 91+ octane...

[Jeff Williams]

It might be the accelerator cables ratteling in their mounts on the firewall. I zip tied mine and all rattles went away.

There was a TSB in this issue. The zip-tie is the fix!

[elwesso]

Yeah i had the same issue.. Just put the cables back in their holders and check everytime you check the oil

[SFBayQ45]

It might be the accelerator cables ratteling in their mounts on the firewall. I zip tied mine and all rattles went away.

MY92Q - Do you have any pictures to illustrate the cables you're referring to. I have no idea where that is located at.

squeefoo - Don't have a garage to try this...

szhosain - I've been religiously filling it up with 91 all the way, in fact I just used 2 cans of BG 44K on a 1000-mile-trip, with regular intervals of Chevron's injector cleaners...

Q_SHIP - I didn't take notice of what RPM, but the noise is noticable only from a stop and go situation so my guess is it's around 2K. The sound isn't hollow or tingy, but it sounds more like a rattling noise similar to what you would hear coming from a rattle snake. Does that make sense?

sijoko - This happens regardless of weather temperature. The cooling system was last service December 2004 in preparation for this long trip, including new OEM radiator, water pump, hoses, radiator cap, 50/50 distilled water concentration, etc. (I might have overdone it, but I didn't want to get stranded on the highway).

AZhitman - How do I check the base timing? Again, I've been using only 91 octane @ close to $3/gal in the SF Bay Area...the price of keeping the Q!

Jeff Williams - "There was a TSB in this issue"? Where can I find this? Can you provide a link? Again, where can I zip-tie this thing?

elwesso - Put what cable back onto it's holders? Can you provide some pics?

[Q_SHIP]

So does it sound like a rattle around the motor or does it sound internal in the engine?

[maxnix]

If it sounds like someone is shaking BBs in a can rapidly, it is predetonation.

Go get a tank of good gas (Premium, new station, natiional brand) and run some ISOheet in it.

If it still knocks, time to look at the KS sensors.

[gniknave]

SFBAY, what city do you live in again? Maybe 2 Q heads can figure it out. I'm pretty good at detecting noises and where they're coming from. Worst case scenatio you can visit the shop I'm at in Palo Alto and I can guarantee you an answer.

[Q45tech]

One problem is 91 average octane can be created by using MORE of the cheaper to make components that have higher RESEARCH octane and less of the expensive MOTOR octane components and still get close to 90.500001 average test octane.

http://www.zeltex.com/eval.html

you see that typical RON ~~98 and typical MON is ~~88 yielding ~~93

http://www.refiningonline.com/...9.htm

Note that aromatic have the desirable HIGHEST MON and California regulations have forced a dramitic reduction in AROMATICS

[Q45tech]

"Improving the RON of FCC gasoline as discussed is for the most part well understood. The same cannot be said for MON. Although it is true that increasing the RON of gasoline does increase its MON, the incremental increase in MON is typically only 33-50% of the RON. Referring to Table 1, MON values (either actual or blending) are always less than RON except for highly branched paraffins. Increasing the weight fraction of isoparaffins in the gasoline should result in an increased MON/RON ratio although overall R+M/2 could in fact decrease. This is due to the fact that although isoparaffins have higher MON values than RON, their absolute values are generally less than their olefin counterparts.

Another approach to increase the MON / RON ratio of gasoline may result from increasing the weight fraction of those hydrocarbons having blending MON's nearly equivalent to the blending RON's. Examples include propyl or isopropyl-benzene, C-5 and substituted C-5 naphthenes and highly branched olefins like 4-methyl 2 pentene. The ability to selectively increase the concentration of these hydrocarbons may be more a feedstock property than anything that current catalyst technology can do.

If motor octane is to be increased to a greater extent than research octane it appears that the specific hydrocarbon types must be selectively produced or concentrated. Directionally, the degree of highly branched isomers, either paraffinic or olefinic, must be increased with emphasis on the degree of internal branching. Although aromatics have a large effect on both RON and MON, alkylbenzenes such as propyl or isopropyl benzene may effect MON to a greater extent than RON. To fully understand the factors effecting MON, detailed chemical characterizations of a variety of gasolines should be studied."

About all one can do easily is to blend in 10% more single chemical aromatics: toluenes and or xylenes [note the 3 types and how much better p-xylene is than the others] from the above chart.

What would be done at the refinery if they didn't have to account for the cost of ethanol downstream.

[Jeff Williams]

Here is the first page:

[Jeff Williams]

Here is the second page:

[guadofreak]

I had that issue. Turned out to be a loose catalytic converter heat shield.

[Q45tech]

Rattle in park/in drive vs just rattle under light load.

More about your friend p-xylene:http://academic.scranton.edu/f....html

See how it is produced...........Decatur Alabama plant, maybe our Alabama members could found out where what how much 55 gallons costs out the back door. Obviously the blended ortho, m and p xylene mixture would work well and be much cheaper...........what one can get at Homedepot in paint department.[purity and other added things?]...............don't pour it directly into tank preblend 1 gallon with 4 gallons of gasoline then add to tank gasoline..........10% [0.9 x 91 + 0.1 x 127] = 94.6 maybe, maybe less or maybe more depends on base gasoline.

Texasoil might chime in here.

Homeland defense/EPA/your insurance company/Fire Department might not like you have 55 gallon drums at home.