Hey guys, I cant seem to search and find a specific dealing with my issue.
I have a 97 runner 5vz with 192,000 on the clock. At a cold start up the engine appears to run rough, almost like a single cylinder is misfiring but no codes are being thrown or stored. When you engage into drive it pulses, or jerks a little until it gets warm and then its fine. No problems with engine, just replaced all the plugs based on the plug writeup i found in here, they were ngk double prong and i checked the gaps before installing. My theory is a sensor but i don't quite know where to start. any help is great! I also put on a 1.5 inch body lift just recently and although in my mind the two did not correlate they may be related. I opted not to drop the radiator an inch as it seemed a little pointless, but i might be eating those words shortly.

I'm pretty paranoid when it comes to engine noise. However, I think that's normal. Mine does that too, the engine is a little louder when it's warming up and in park. When I shift to drive, I can feel a little bump when it shifts.

However, if it's getting too loud, it could be dirt in the fuel injection system or perhaps a vacuum leak. I have an "air induction service" at jiffy lube done when I feel the engine is running rough and that solves it most of the time. Just recently I discovered sea foam. I haven't done it yet as both cars are running smooth right now, but it could be a cheap solution.

same thing is currently happening to mine, except it throws a CEL, random misfire is the code. I'm thinking plug wires/coil haven't been done at regular intervel, so i'm guessing that is the culpret. Will do when i can next.

Wow just got a P0303 random misfire in #3 cylinder. But I got that one before and replaced all the plugs and used an injector cleaner. I smelled the exhaust right after I fired up and its got a strong smell of gas. Does that mean its running rich?

Just swung bye the stealership. $60 bucks and one hour to do a top end intake cleaning. They hook it up to some sort of machine and its supposed to clean all of the intake things and valves "to a limited extent" Nothing does as good a job as stripping the motor down and rebuilding it.

Im seafoaming it today. if it doesnt work, looks like im paying $60 for a wash I cant see but will hopefully feel?

Sea foam complete. Problem worse LOL. Now the truck idles a lot rougher when its cold but as usual she firms right up when the engine is warm and runs flawlessly. WTF? So i think the junk in my engine was helping seal something which makes me think its a vacuum leak. I have heard of guys setting up propane tanks with a tube and letting the propane float around the engine and you can see where its going in to identify the vacuum leak as the engine will stall. My question is, we have a mechanical fan that washes air over the engine? Is there another way to check for a vacuum leak?

I used the brake booster line to seafoam the engine, oddly enough i could pull the booster line off the brake booster without having to undo the clamp holding it on. it was tight and didnt appear to be cracked but id rather test the whole engine and replace ALL the leaks.

Anyone know a good way to vacuum check the 5vz?

Mine was doing the same thing. Are you losing coolant, even a little bit? Mine was leaking coolant from the head gasket only when cold and caused it to run rough for the first 10 to 15 seconds of start up after sitting for more than 3 or 4 hours. If your losing coolant, your problem will only get worse until the HG fails.

As far as the shaking goes it sounds like a misfire. I suffered misfire on #3 and it wasn't pretty but in your case it is probably just something simple.


Unrelated to the shaking and misfire code, your truck will still probably start rough in the mornings.

If you haven't already, research the term "IAC" which stands for Idle Air Controller.

But be sure to use the google search bar in top right corner and not the T4R search function because IAC will not show up in T4R's search since it is < 4 characters.

Have you swapped coils to see if will still throw the #3 cylinder CEL? If it stills registers the #3 cylinder, I would imagine it is an injector if you are smelling gas.

I have the same issue when the engine is cold (sits overnight @40 deg F). Runs really rough, like it's misfiring.

After letting the engine warm up for 5-10 minutes, it will run smooth if I shut it off and restart. Have not noticed any smoke.

The Check Engine light came on with these codes:
> P0100 (MAF Circuit Malfunction)
> P0110 (IAT Circuit Malfunction)
> P0304 (Cyl 4 Misfire)

If the weather is warm (>50F), it runs fine, no problem.

I've read posts on the site this morning and many indicate the trouble as a bad ECT sensor, MAF sensor, or O2 sensor.

Before spending more money than necessary, can anyone help narrow down what the trouble is?

Ditto on the IAC.

If you're actually getting a misfire code, then you're getting a misfire. I would check your coil pack, plug wires and plugs. If you've got a multimeter, you can do a lot of testing. The coil packs and ignitor actually have hot and cold values, so your cold resistance might be off the charts. The material properties will change as it warms up.

But that does seem a little unlikely...

How long does it take for it to warm up and run good? If you get a OBDII to USB cable, and run a OBDII program on your laptop, you can see when the ECM switches from a closed to open loop. (Startup has a pre-programmed A/F ratio. Once the vehicle warms up to operating temp, it goes into open loop which gathers data from the sensors). If the problem goes away right when it switches over to open loop, then you've probably got a mechanical failure, which would point to something like the IAC valve, which is controlled by coolant temperature.

While the IAC is usually known for causing slow hot starts, I guess it could cause a motor to cough during a cold start...

I'd also start checking sensors with a multimeter... MAF comes to mind.

Here's one of the best pages from the FSM:
http://ncttora.com/fsm/2003/Repair_M.../ignsy/ovi.pdf

Great - thanks for the ideas & link to the testing page - this will help me isolate the problem and save some $$.
Will try it when it gets cold again.

since mine started i get p0300, and i have changed my plug wires, and also cleaned my maf, no improvement, but i had to add 4l of coolant the other day, wether it be a air lock, or a head gasket, i'll have to check! recently did timing belt so could be air lock.

My truck did this today after sitting for a week. Did you guys resolve the issue?