Misfire at idle in drive and reverse - no park/nuetral - no code

[atrain0007]

The title says about all there is to it so far.

I have a what I think is a misfire on my 2008 v6 sport. It happens at idle when in gear, every 3-7 seconds (not consistent). Watching the tach, the rpms dip from about 600-500 each time (along with a rumble you can feel in the cabin) .

It also happens at low speeds while accelerating. No codes or check engine light so I don't know where to start diagnostics. Even what system to check (fuel vs ignition) is a question mark.

This comes out of nowhere, I lgot the car about a year ago and I replaced plugs and air filter and cleaned the throttle body and MAF.

I don't notice anything once I'm at higher engine speeds. Any tips on where to start looking? Thanks in advance.

 

[atrain0007]

Update

The misfire seems to be present throughout all engine speeds now. Still no codes. All the injectors measured between 14 and 15 ohms. Does this rule out injectors? What else should be done on the fuel side of diagnostics, fuel pressure? If I rule out pressure and injectors, wouldn't that eliminate the fuel system (except bad gas)?

On to ignition - Can someone tell me which posts on the coil pack needs to be touched to test resistance. There's four. I tested 1 and two from the left (holding vertically with the spark side down), and they all came out .034 on the meter. Im having trouble finding the propper resistance spec and I don't know if Im doing this right or how to measure secondary resistance.

I got no reading when I touched the leads to the spring wire inside the spark side of the coil pack and any of the posts on top...

Any experience here specifically on testing spark, or on methodology in general?

Thanks

 

[BrianSD_42]

Two words: compression test

 

[Greydog]

Is the check engine light on? Perhaps go to parts store and check for any stored codes, even if the light is off. It's usually free.

What is the starting rpm when this happens and how low does it dip?

Is it just a low idle issue or alot of vibration that shakes the truk a bit?

Check all the intake air path for loose clamps, etc.

 

[toyo]

You can at least take a little comfort that the CEL is not on. What about any pending codes in the scan tool?

I think you can rule out an ignition problem of any magnitude. A lousy plug will do this at times though. Have you removed each plug for closer inspection? I would at the least throw in a new set and see what happens.

What happens if you power brake/load it up? I'm not meaning spin the rear tires. Brake pedal firmly applied and give it gas slowly. Do you feel the miss? If so, how bad?

When I run into these types of problems I will rule items/systems out before I try to find the problem.

 

[atrain0007]

There are not any codes stored or pending. At least according to my obdII scanner.

I have pulled the spark plugs and they all look similar and ok to me. Compression test is today's activity, I think. Is a fuel pressure test easy on they guys?

Under load, it seems to miss a little less often, but when it does, you definitely feel it in the cabin, it loses momentum for a beat or two. Usually the skips come a few at a time when accelerating.

 

[atrain0007]

compression test looks good to me.

Each cylinder 185-195 after 7 compression strokes.

First stroke brought it up to about 130-140 and it climbed quickly from there...

I replaced the spark plugs while I had them out... I wouldn't think less than a year old plugs Autolite Iridiums would be bad, but I haven't had a chance to test drive yet.

Will update after that. Thanks for the responses.

 

[Ppilar]

I am having the same issues. Especially when the A/C is on. Let me know what you find out because I also have no clue where to start.

 

[toyo]

compression test looks good to me.

Each cylinder 185-195 after 7 compression strokes.

First stroke brought it up to about 130-140 and it climbed quickly from there...

I replaced the spark plugs while I had them out... I wouldn't think less than a year old plugs Autolite Iridiums would be bad, but I haven't had a chance to test drive yet.

Will update after that. Thanks for the responses.

Uh oh. The Toyota Gods are shaking heads with those Autolite plugs!

How bad is this miss???

 

[atrain0007]

Update after test drive. I just ran some errands and the misfire is not showing up at all. After two days of fooling around. It seems like the spark plugs were the culprit.

NGK Iridiums this time. Not autolite.... I don't needs any more punishment from the Toyota gods!

Thanks for the help to everyone. (I hope this isn't a premature celebration)

 

[toyo]

That's great news. I know it might sound crazy but some manufactures of engines are kinda finicky about the plugs. It was either the type of plug or one of the Autolite's had an internal problem that our eyes can't see.

I tuned up a customer's car a few weeks ago and used ND as I always do. It had an ever so slight miss at about 1800 Rpm in neutral. Scan tool was showing cylinder #6 being of a little. Pulled the plugs, inspected them, verified the gap and put them back in. Same miss was showing up. Installed NGK's and now it's gone. 1st time I have ever had a bad ND plug in close to 30 years. This was on Lexus LX570.

 

[Ppilar]

would you recommend the NGK's or Denso plugs?

 

[toyo]

would you recommend the NGK's or Denso plugs?

I have always been a Nd fan. I have never had an issue with them until just recently.

 

[Ask10]

Autolite plugs (in my Autozone experience), are total crap. Wouldn't even put one in my lawnmower to be honest.

 

[Ppilar]

I have always been a Nd fan. I have never had an issue with them until just recently.

So which ones would they be? There is multiple types of the NGK's and I can't figure out which ones are more worth it to buy.

 

[toyo]

So which ones would they be? There is multiple types of the NGK's and I can't figure out which ones are more worth it to buy.

I would use ND SK20HR11.