judoant

Started my 99 this morning and had a very rough idle. The truck was in the garage about 40+ degrees. Put in gear and drove off with very poor power and still rough acceleration. I went about a mile and it cleared up.

I drove for about 6 miles. turned the truck off for about 10 min, then re-started. Smooth as silk.

5 days later.............
so I had no issues all week. I did however have to refuel after only 170 miles. Then this morning after about a mile of driving I had another rough idle situation. After about a mile of running terrible it cleared up again. I did notice that if I put the gas pedal to the floor I have no power.

I refueled and put in some fuel injector cleaner and restarted. I now have a check engine light.

AutoZone checked and it was only a P0300 code "Random Multiple Cylinder Misfire". Would plugs and wires be the first thing to replace? It has been about 3-4 years since they were last replaced.

swaycleveland

yes plugs and wires will be a great start

TheDurk

Plugs, sure if that old. Wires should be good, still, if they were Toyota or NGK and not some cut-it-yourself cheapo. Not my first suspect w/P0300 with no P0301-6. How about cleaning MAF sensor, throttle body?--both super cheap and easy to do.

judoant

So after I posted this I went to Valvoline and performed a "fuel system cleaning". This involved cleaning the throtle body and valve, fuel additive and another fluid injected into the combustion chamber to remove carbon. All was good after that.

This morning the problem occured at start up again. Ran down the road about a mile and the problem went away. It is like when the engine gets warm the problem fixes itself.

I guess I will replace plugs and wires. What about ignition coils? Should I replace those as well? They have never been replaced.

mt_goat

Any smoke out the tail pipe when this happens? I would think if its a coil you would get a misfire on specific cylinders rather than a random code. Is this a V6? Has the timing belt been changed recently? Is there a rattling near the front of the engine when this happens? Does the harmonic balancer wobble around?

If the answer to any of the last 3 questions are "yes" read this: http://www.motor.com/MAGAZINE/Articles/012007_04.html

mt_goat

x2...and the MAF cleaning/inspection.

More info on P0300-P0306: http://www.ncttora.com/fsm/1996/SIL/...e/cip0300p.pdf

judoant

There is no smoke when the rough idle occurs. This is a V6 with 140k. I changed the timing belt at 95k. No issues until now. There is no rattle and I am not sure where the harmonic balancer is. I did read that the harmonic balancer issue never goes away and happens under load. My issue is at idle and goes away under load.

I had no issues this morning.

Ironmike4x4

Unfortunately a P0300 isn't going to give you a specific cylinder misfire like P0301-p0306 until you look at a misfire data graph. You might want to go ahead and pull all the spark plugs out and see if any are wet. I had one last week a P0300 code with the data graph showing cylinder 1 misfire. The problem goes away after reving the engine but the misfire is present at idle. Found the #1 spark plug was soaked in fuel, but the other 5 were not. Replaced the #1 injector and no more problems.

Alldata search shows these possibilities for P0300: ECM, injectors, fuel pump, fuel pressure regulator, MAF sensor, ECT sensor, and vacuum leaks. For the cheapest option I would just go ahead and replace the sparkplugs/wires and you've already done the MAF cleaning.

judoant

So I have not got another CEL since running fuel injector cleaner though 2 tanks of gas and another fuel injector cleaner through several other tanks of gas.

However my gas mileage is not good. I get about 180 miles / tank or about 13 miles/ gal

what is up with that?

judoant

I replaced the spark plugs and plug wires this weekend with factory Denso plugs and Toyota wires. WOW I did not realize how bad the performance actually was. Now the throttle response is great and I have no more hesitation when I stomp on the gas.

All symptoms are gone.

TheDurk

I hope you took a good look at the old plugs. That will tell you a lot about WHY you had a problem. If they were fouled as opposed to worn out, the problem may come back.

judoant

I have no idea what would be the difference. i will take pictures and post tonight

DavesToyo

Were you able to find the problem? Mine is having the same issues.

Jomoka

My '99 recently developed the same issue.

First thing to do is try to narrow down which cylinder is misfiring. By disabling once cylinder at a time until it doesn't make a difference. On mine, it was clearly missing on a single cylinder, very regular sound to the misfire.

On the driver's side, you can pull out the spark plug wires one by one. You can't do that on the passenger side because of the way the coils work, but you can reach the injector plugs and undo those.

After doing that on all 6 cylinders, I determined mine was missing on #6. The ECU sometimes has trouble narrowing down which cylinder is missing, perhaps a manual trans makes it worse since I think it watches for the flywheel slowing down over the miss). I had PO300 codes as well, and only one time (I reset them a couple of times) did I get a PO306 in addition to the PO300.

Next up - why is it missing? A cylinder needs 3 things to work. Compression, fuel, and spark.
1) Compression: I used a compression tester to verify it wasn't a serious valve/piston/head/whatever issue. But you can also do a shade tree compression test - disable the EFI (there's a relay in the fuse box you can pull) and crank the motor around. Listen at how the starter labors over each compression. Listen for any pattern of 'fast' cranks over a compression, the starter should all be pretty evenly slowed down on all of them.

2) Next up - spark is easiest to test. Pull the plugs out and look at them. Does the one with a miss look different? Wet with gas? Wet with oil? Fouled? Wet with coolant? If it doesn't look like the others, that's a clue. On mine all 6 plugs looked great, so I started swapping things around to see if it was related to ignition - moved the coils around on the passenger side - the miss stayed with #6. In my case - I 'tested' the spark plug wire leading to #6 by swapping it with one from my wife's '96. But really, just putting an old spark plug on it and cranking, and watching for a nice spark would also work (rest the plug on something metal).

3) That leaves... fuel. And a single cylinder not getting fuel is going to be a problem with the injector. Unfortunately, on a 5VZFE motor, that takes some disassembly to get to the injectors. The throttle body, upper plenum, and lower plenum all have to come off before you have access to the fuel rails sitting on the lower intake. Pulled the fuel rails off, my wife tested the injectors with an ohmmeter and to my surprise, #6 actually tested as significantly different. I was surprised because mine was still running normally when cool, and only running on 5 cylinders when fully warmed up, But, even cold, the injector def. tested bad.

So in any case, long story made short - I first bought some '100% genuine OEM injectors' on eBay. Set of 6 for $217 shipped. Right there I should have stopped, you're not getting 6 genuine injectors for $217. Got them in the mail, and they looked sketchy, in weird little sealed plastic bags, with a red o-ring on the top. I should have stopped there and jsut sent them back. But... the car was apart. So I put them on. And it didn't run right. Ran OK once started, started OK on a warm start, but on a cold start? 10 - 15 seconds of cranking. I emailed the seller, told them they were counterfeits, and I wanted my money back. I guess they're somewhat used to this, agreed for a full refund even though I'd installed them. Then I went to the junkyard and got a set of actual real genuine OEM well used injectors and put them on, and the truck runs like a charm.

DavesToyo

Thanks I was looking at Ebay for injectors. Glad you told me about that. I appreciate all the information.