So the rpm's never change, but the car jerks forward at times. It only does it when I'm barely pushing the gas. It doesn't do it in park, or when sitting idle. I used the search tool and found a lot of posts about missing/pinging, but nothing that sounded like my problem.

Gonna try Seafoam tonight in gas, oil, and intake vacuum hose.

Do any of you all have suggestions for possible culprits?

 

fuel filter? timing?

oh, and more info on the ride plz!

you know, year, model, engine type?

 

fuel octane rating or quality, ignition timing, excesssive blowby/worn rings, pcv system, valve stem seals, o2 sensor
many potential causes.

 

Knock sensor any good? Don't know how to test that. Just a thought.

 

to test the knock sensor, just take a 5lb. sledge and beat on the side of the block...

 

Ive had all of those problems and none of my motors ever pinged?

the only time Ive ever had a motor ping on me was when

1. bad fuel/wrong octane, like you said
2. bad fuel filter
3. timing was off
4. overheating

I'm not saying that there not possible culprits, just not likely!

 

any after market peices?

 

I only mentioned them because they technically could cause the problem.

Introduction of aerosolized oil into the combustion chamber can contaminate and lower the actual octane rating of the fuel in the mixture (engine oil can be a fuel).

The O2 can theoretically fail in the direction of reading a 'rich' condition and cause the ECU to lean the mixture abnormally.

Overheating is a possible cause as you've mentioned. But that usually will cause pinging across the entire range of throttle positions, which is why I didn't mention it. Though technically it could cause it to be more pronounced when the fuel mix is at it's leanest- light-throttle/constant engine speed.

I could've, maybe should've, included carbon deposits on the piston crown and combustion chamber and too tight exhaust valve adjustment... just for argument's sake....
but then I could also say spark plugs of the wrong temperature range too, and an improper/malfunctioning thermostat.

edit- the 'too broad' range of culprits was meant to bolster the suggestion that more information was needed. sorry it was too broad and taken the wrong way.

 

hahaha lol.. no need to apologize, its just that my pee sized brain cant handle all that info at once.

 

'pee' sized? lol. guess the longer you hold it, the more 'pee' there is so you're brain would be larger? rofl.

just kidding.

 

so we basically have an engine that pings only under light/part throttle.

now, back to the OP...
... it almost sounds like it's working just fine. pinging under constant vehicle speed and throttle position conditions indicates that the fuel mix is as lean as it can possibly be (in accordance with ecu programming) and timing is near perfectly advanced. Maximum fuel economy at any given engine RPM occurs just before the point where detonation under light throttle occurs. So if it really bothers you, retard the timing a degree and see how it goes.

 

see i told ya.. lol, you gave me to much info!
jk.


to the OP, adjust her back a degree, like abe said.

ohh, and are you getting any codes threw the CEL?... wait, do you even have a CEL??

what type of vehicle are we talking about here??

 

sorry all, I've been slaving away in corporate America.

my car is a '94 4Runner, 3vze, K&N is the only aftermarket part on it.
I replaced the MAF last month (friend unscrewed the 2 screws and pulled for some stupid reason). There is no Check Engine Light, and my friend who owns an AAMCO here ran it through their diag and couldn't find any codes.

I was planning on doing wires, plugs, cap and rotor this weekend and seeing if anythign improves. I'll do the fuel filter while I'm at it. There's no telling how old the wires are, but I know they are definitely a carbon core.

I am getting about 19 miles a gallon on regular fuel, which I know is a little high. Also keep in mind, I live in a really flat state (Florida) and drive 20 miles of 70 mph freeway daily.

 

i work for nissan and just about all the new vehicles have spark knock, the manufacturer sets these vehicles to run as lean as possible to get better mileage ratings as well as emmisions. my 94 22re pings but only when i use cheap gas, if i run chevron it doesnt do it unless im under heavy load

 

So I couldn't take a picture of it, but the wire that runs to the middle plug on the passenger side had come in contact with the EGR and burned completely through it. I'm sure that's what the problem with the pinging was. However, while doing the plugs I found something pretty strange in the the car had 2 different style's of spark plugs (not to fear now, they have NGK's V-Power). The last time it had a tune up was 3 years ago, but my parents had it done at the Toyota dealership. They were all Denso products (Distributor Cap, Rotor, Spark plugs) and all got replaced this morning.

Glad I got this taken care of. thanks for all of the tips guys.

Here's some comparison pictures of new and old plugs.

Plug in the #6 cylinder


Plugs in the rest of the cylinders.

 

whoa.

 

I find it hard to believe... period ....

neither of the two plugs shown resemble anything for a lean mixture condition.

the other 4 plugs, don't know, no pics.

 

the other plugs were in the same condition, except for the on in the #1 cylinder which didn't have as much corrosion on it.

 

Here's some more pics of the work.
By the way, the new plugs are NGK BKR5EYA's and plug wires were NGK TX-50's.

The Engine


Air Intake (removed to get plugs out)


Old Rotor / New Rotor (the old one was like 60 grit sandpaper on the edge)


New Distributor Cap / Old Distributor Cap


U-Joint 12" Extension W/ Spark Plug Tool made quick work of the plugs




Another Shot of Old and New Plugs

 

didn't I mention carbon deposits somewhere up above?

let's see how it goes with the new plugs. also try a gas tank or two of seafoam or berrymans.