1994 Roadmaster Limited: Shaking when accelerating at low speeds (only) please help

[roadmasterfan]

Hello so one of the problems that my '94 Roadmaster has is it shakes/ vibrates when accelerating from 0-10ish mph. But then stops shaking after 10mph. Here are some facts about my RM: it has 117,000 original miles... It has all 4 bad tires... one of the rear tires has camber wear (or bad alignment wear) and has wires sticking out from it... all others have somewhat tread but have several big cracks due to age. Also we recently changed the ATF and found next to no metal shavings on the pan magnet... and no pieces of metal at all. We still have yet to change the rear differential fluid. Also I have not tested to see if the driveshaft is wobbly... but I will soon. Also I'm pretty sure the wheels are not bent or warped as they have next to no curb rash or anything. Any insight on what you guys think might be causing my RM to shake at low speeds would be greatly appreciated. Thank you!

 

[2007LucerneCXL]

I'm going to say all 4 tires to start, but you may want to check the lug nuts. As the worn rear tire isn't in a place where a alignment is possible it probably front end suspension components are worn. The wire means the tire is shot, shouldn't be driven on EVER! The cracks in the others also means they are gone.

 

[roadmasterfan]

I'm going to say all 4 tires to start, but you may want to check the lug nuts. As the worn rear tire isn't in a place where a alignment is possible it probably front end suspension components are worn. The wire means the tire is shot, shouldn't be driven on EVER! The cracks in the others also means they are gone.

Thanks for the reply yeah I'll start with the tires... they're gonna need balance and new tire valves too (as the valves have cracks on them) the cheapest for 255 50 R17 I have found are at Big O Tires... Riken Raptors for $620 including the labor cost, valves, and balance. So it'll be $700ish with alignment. Btw it has 1996 Impala SS wheels

 

[2007LucerneCXL]

It should eliminate one area, unfortunately when it may be a few things it's almost impossible to do over the Internet when you can't feel it, LOL.

 

[roadmasterfan]

So I hadall 4 tires replaced, tire valves replaced, balanced the wheels, and an alignment. Sadly the shaking is still there. I'm gonna start next with replacing all 8 of the spark plugs and wires... also to test the driveshaft for any play. I'm gonna change the plugs because I notice at idle it shakes outta nowhere... every 5 seconds or so. So yeah hopefully it's just the engine that needs a tune up and not a internal problem with the transmission.

Btw I also forgot to mention that it shakes only when giving it half throttle or more

 

[roadmasterfan]

Dangit so I changed all 8 spark plugs with Bosch Iridiums but the shaking is still there... do you guys think maybe the fact that these aren't OEM (or maybe they're just not good plugs?) is the reason why it's still shaking? BTW the plugs that were on the car were OEM AC Delcos... and they were in relatively OK shape for spark plugs that I'm guessing were never changed in 117k miles. Do you guys think I should buy the spark plug wires next? Also... if so... does the brand really matter? (For example: MSD Ignition VS Duralast Gold) thanks for the help and Merry Christmas!!!

 

[ilgoldstein]

Have you ruled out a problem with the Optispark? Ours would stumble under load. Tried several different replacements until finally putting in a rebuilt Delco unit.

 

[2007LucerneCXL]

It probably wouldn't hurt to have replaced the spark plug wires if they are original as the age and milage will be a factor. Stock OEM wires are fine, the other will work but for the most part you're paying for a name and you won't notice any preformance gains. Trying to get to the shake problem may be best to narrow down by replacing worn and/or maintenance parts, cleaning as on a 24 year old vehicle it's probably time. Locating a shop that could you can get a scan might give some codes that could point to a area(s) to look at.

 

[HotZ28]

Unfortunately, the '94 RMS/W was an OBD1 system which may not detect random, or individual cylinder misfire on a scanner. Wires should have been changed along with the plugs! Belden & MSD are the best option for longevity! Been there, done that!

 

[roadmasterfan]

Have you ruled out a problem with the Optispark? Ours would stumble under load. Tried several different replacements until finally putting in a rebuilt Delco unit.

No I haven't changed the optispark yet... I'm pretty sure it has never been changed considering how bad it misfires (it also shakes at idle too... pretty badly) I'll do some research on them and yeah most likely I will buy a Delco one. I'll try and replace it myself... hopefully I can accomplish such a task haha. But before I will take it to a mechanic to find out exactly what it needs. Thanks for the reply

 

[roadmasterfan]

It probably wouldn't hurt to have replaced the spark plug wires if they are original as the age and milage will be a factor. Stock OEM wires are fine, the other will work but for the most part you're paying for a name and you won't notice any preformance gains. Trying to get to the shake problem may be best to narrow down by replacing worn and/or maintenance parts, cleaning as on a 24 year old vehicle it's probably time. Locating a shop that could you can get a scan might give some codes that could point to a area(s) to look at.

Thanks for the reply yeah I will take it to a mechanic for a diagnosis to see what it exactly needs... hopefully its just a ignition problem because I thought it was a internal transmission problem at first lol.

 

[HotZ28]

Ignition misfire can feel like a trans problem, but they are not related. Has the car/engine been exposed to high humidity, rain, fog? If so, suspect the wires first! Years ago, I had a similar misfire with my '96 RMS and was able to to scan the cylinder(s) that were misfiring (4&8) and simply moved the plug wires back & forth on the plugs to make contact and problem solved. I later replaced all wires/plugs and have never had a misfire again!

 

[HotZ28]

Ignition misfire can feel like a trans problem, but they are not related. Has the car/engine been exposed to high humidity, rain, fog? If so, suspect the wires first! Years ago, I had a similar misfire with my '96 RMS and was able to scan the cylinder(s) that were misfiring (4&8) and simply moved the plug wires back & forth on the plugs to make contact and problem solved. I later replaced all wires/plugs and have never had a misfire again!

 

[roadmasterfan]

Ignition misfire can feel like a trans problem, but they are not related. Has the car/engine been exposed to high humidity, rain, fog? If so, suspect the wires first! Years ago, I had a similar misfire with my '96 RMS and was able to to scan the cylinder(s) that were misfiring (4&8) and simply moved the plug wires back & forth on the plugs to make contact and problem solved. I later replaced all wires/plugs and have never had a misfire again!

Hmmm well we live in the desert area of Southern California (Coachella Valley) so we get very few days of rain per year... BUT the car was sitting outside in the sun for 6 months before I bought it... the previous owner decided to decomission it for some reason. So yeah maybe over these 6 months the sun probably dry rotted some of the spark plug wires? And yeah good to know that your RM had a similar problem and you were able to solve it by moving the wires! Hopefully my RM is that easy to fix as well lol. I will try to take it to my local mechanic as soon as possible but I don't think his schedule is on track because of the holidays so it'll probably take a week or two

 

[ilgoldstein]

You really need to check the opti. You might get lucky and have a crapped out cap or rotor. I don't think you can get a Delco reman opti anymore. There are a couple of guys on eBay that claim to be experts at rebuilding optis, but I don't know how good they are. Most aftermarket optis are junk.

 

[G-116719]

My 95 roadmaster shakes on ignition, I have changed the wire,spark plug and opti spark and water pump. It just dint want to start until I gave it some gas and then lots of white smoke Came out and when I turn it turns off