Engine Shudder

I've read through the posts but can't find one that fits my specific problem concerning engine shudder. Here are the symptoms:

• The truck starts up immediately and idles very smoothly showing 750 rpms on the tack. It continues to do this without problem in either Park or Neutral.
• As soon as I put my foot on the brake and shift it into either Drive or Reverse, the engine shudders for a few seconds and the rpms drop slightly but then returns to normal.
• If I sit there without moving, the engine will idle in gear fine for 15 seconds, then do a single shudder, then idle fine for 15 seconds, then shudder, etc.
• This cycle repeats until I either:
  • Shift back into park or neutral at which point the shudder disappears.

or

• • Leave the truck in park or reverse and take my foot off the brake, at which point the truck begins to crawl but the shudder increases violently. This continues until I give it some gas and reach about 15 mph at which point it smooths out.

While driving the truck operates smoothly until I stop at a light or stop sign and idle in gear, then the 15 second cycle of smooth idle and 1 shudder starts again.

Over the past few weeks I have replaced the spark plugs, plug wires, O2 sensor, cleaned the MAF with special cleaner, and dumped a can of engine cleaner in the gas tank to clear out any carbon deposits. I also cleaned out the throttle body. Also no codes are coming up. I'm running out of patience and cash on this. Any ideas?

1999 Tacoma, Extended Cab, V6, Automatic Transmission, 190,000 miles

Any help is appreciated.

 

Did you clean the IACV when you did the throttle body, MAF, plugs, wires, etc?

 

No I didnt, I mainly focused on cleaning around the valve in the throttle body to make sure I got a good seal when it flapped shut. I didnt think it had to do with the IACV as every post I read that mentioned an IACV problem had to do with high rpms during engine idle. I havent had any high rpms or revving.

 

does not sound "engine" related but transmission.. probably torque converter.

 

^x2

 

^x3

 

Does the RPM drop during the 'shudder' ?
Could it also be an intermittent vacuum leak?

 

Ok seems to be that most people on here think its the torque converter. Now I have to decided if I want to change this out myself or take it somewhere. I hate having other people work on my truck but I live in an apartment so I'm limited in what I can do since I will be working in the parking lot.

Is it possible to replace the torque converter without dropping the transmission? Can I pull the old one off and bolt on a new one or is it more involved than that and require a garage?

 

what i would do (just my opinion) is find a used unit on craigslist. You will most likely find a complete transmission and torque converter. Then you just bolt the entire thing in. I have seen these on my local craigslist for a few hundred bucks. plenty of tacos get totaled and parted out.

OR, you can find a new or used (not as likely) torque converter only and replace that. I have never done this, but it is simiilar to a clutch. i'm someone here has and they might chime in, otherwise search the other boards or consult your factory service manual for a DIY!

 

Ok, I misunderstood. The torque converter bolts inside the transmission housing meaning I would have to drop the tranny down to get it in there right?

Also a guy at work told me that it might just be dirty transmission fluid and I might get away with draining this out and replacing it with new fluid. What are my chances this eliminating the issue?

 

Take it to a local recommended trans specialist and see what they say first. they might be able to identify immediately. Sounds like weak or worn clutches inside the trans. a fluid change might be the fix, or a temp fix till repair.

 

OK,

before going into torque converter

more cheap tricks to look at before dropping crossmember and tranny....

1) snug up all throttle cables and whatnot on throttle body,
take up any slack that has developed

2) clean IAC

3) replace TPS sensor (cheap easy to replace part, it will be worn out if it is original)
an 'almost out of spec' TPS reading can cause flaky tranny

4) clean MAF again, make sure you did it correctly

5) then...reset ECU (disco batt 15 minutes)

6) drive 200 miles varying speeds and roads
so you know you cleared the emissions driving pattern
---------
if issue remains, diagnose/replace shift solenoids next


EDIT: check for any vacuum leaks too...also cheap to remedy before diving into tranny drop

 

I agree with both above posts. No need to spend a bunch of money on something until you know for sure what the problem is. Would suck to replace the TC and find out you didn't fix the problem. I am curious about something myself here. Personally I think a TC that was having problems wouldn't have a cycling vibration like you mentioned. Since I don't know your typical driving style, answer this, could the cycling of the vibration/noise coincide with your AC compressor cycling?

 

Ok, so I took a lot of advice on this forum and did the following: got a transmission fluid and gasket and filter change. Then recleaned the throttle body and MAF, then put in a new air filter, then put in a new TPS, then reset the ECU. Checked all vacuum lines at idle. Then i got ticked off and jammed a block of wood between the front seat and brake pedal, threw the tranny in reverse and rechecked all the vacuum lines. Nothing got rid of the shudder. I called a guy at toyota and he thought it was a sticky valve so I am running another batch of lucas cleaner through the tank. I wanted to see if the problem was in the tranny or engine so I popped the hood and put it in reverse and watched through the small crack under the hood and the problem is coming from the engine and not the tranny. It is doing the shudder that resonates through the truck. Any new engine ideas before I give it over to Toyota?

 

Have you ruled out the brake booster? A bad diaphram could cause a big vacuum leak. The problem does seem to be brake related.

 

Check your engine and tranny mounts. Make sure you have a good clean negative ground on both ends.

Sticky valve? a bad clogged injector nozzle will cause a shudder at loaded idle.

Sticky valve? a engine head valve will make a tap sound eventually,,till crunch crunch CRUNCH!!!!. $$$$$$$

Sticky valve? Lazy fluid pressure on the tranny will cause a studder also,,along with so many other associated bits and parts it will make your head spin.

Unless you know the systems,,your chasing your tail and dumping out very hard earned cash.

If you want to go that route, call around to a few local dealerships and have a 5 min chat with the head mechainka. See how long he has been wrenching, a few basic quick questions will test his skill, be prepared.

 

yeah check for busted motor mounts

 

JL82,

1) Did you clean your idle air control valve?

2) Did you replace your PCV valve?

3) Did your check engine light come on?

Any new developments?

 

Let me get this straight.... You saw the engine shaking, and determined that that is what has to be causing the problem? You do realize that the engine and transmission are bolted together, and that any shaking induced from EITHER unit, will shake both. I am not saying your problem lay in the transmission OR the engine yet. I think it is best to just take the truck to a qualified individual and have them diagnose the problem. There are WAY too many things that can cause exactly what you are describing to just throw parts, or make guesses.

 

Any head way on your shudder problem. Mine does the same thing when waiting at the light. I get the shudder even when in neutral but does not shake the truck and not very noticeable. The rpm's go from 750 then when it shudders it drops down to 500 ish. Doesn't do it in park. Drives absolutely fine. I had all fluids replaced 2000miles ago and changed out spark plugs. No lights come on the dash so I don't think it's misfiring. Just realized this is in the 1st gen but mine is a 2nd gen