Sevorg1

so when Im cruising at low speed it seems that the max is stumbling. First thing I think of is that it is missing, but I have done a tune up bout 1 year ago. NGK plugs should last very long right? I have checked for spark at each plug and it seems fine. It never seems to miss when I rev it in park. Seems to only miss or whatever when it is under a load aka moving the car.

It some times stumbles from a start. It is so little though that usualy only I notice it. Only stumbles from 1,000 to 2,000 rpm after that it is fine. So if it were a spark problem wouldn't it miss at higher rpms?

whadda you guys think. btw fuel pressure is good I checked that too. You think maybe an injector going out?

91 max 220,000miles lots of hwy driving

Drockb418

iTrader: (10)

maf?

Josh

iTrader: (5)

Unplug the plugs one by one if it doesn't stumble on one then test that injector to see if it is between 11-14 ohms.

benz-tech

iTrader: (1)

well, since you said it only occurs under load unplugging injectors while its missing isn't a real possibility unless you're on a dyno. BTW when checking for a miss by unplugging an injector, the inj that makes the least difference when unplugging is causing a miss, NOT the one that makes it stumble worse when unplugged.
ohming them out is a good idea since it sounds like injectors are a common issue. more likely is an ignition miss- ohm your wires and inspect the cap and rotor if you didn't replace them during your tune-up. a MAF could cause a miss but you would probably notice your car being down on power long before it was so lean as to cause a misfire. HTH

Josh

iTrader: (5)

sorry I miss stated, if you pull one and the engine DOESN'T change then that is the one to check.

nc90gxe

iTrader: (6)

"inspect the cap and rotor if you didn't replace them during your tune-up"

That's a good point. Did you change the wires, cap, and rotor? If not change those first.

Kountz430

now thats weird my 90 se is the complete opposite,it'll only miss at idle but during normal driving its smooth,no miss no chugging nothing just at idle and it stinks too.I just did a tune up plugs,cap, wires and mobile one

Sevorg1

ok so here is the deal I looked at all of the spark plugs, none of them seem dramatically different from the other. One of them was alittle whiter than the others. It misses at idle as well randomly. Unplugging the wires one by one isnt helping. I looked at the cap and rotor, which was replaced when I did the tune up. It seems that they are worn with white deposits on the contacts. I will probably replace the cap and rotor maybe the plugs as well. I am going to ohm out the one injector for the cylinder that had a whiter plug. thanks for your help

akurtzer57

iTrader: (4)

Have had this problem with many cars and replace the fuel filter and it fixed it. Check out your filter.

benz-tech

iTrader: (1)

not to be contradictory again but fuel filters tend to give up under full load, high fuel-demand situations. but they should be replaced regularaly anyway.
try this: since you are saying it is at low rpm, i will assume you are not using full throttle and that you are experiencing this at normal load. try removing and plugging the vacuum line going to your egr valve. see if the miss or stumble is gone. if so, you may be looking at a lean condition causing the miss - ala maf or poor injector pattern. its a free and easy check to do. if that works it does not mean you have a bad egr valve. you might try putting a delay valve inline with the vac supply to the egr valve.
be careful how far you drive it so as not to set a check engine light due to an egr fault.

Wiking

New cap can be bad already from shop, one year after it will not be any better.

Replace the soot hoses, get real copper wires. Copper is a (symphony) conductor, carbon soot hoses make your horses rock.

Check/replace distr gnd wire.

This is normal, cleaning helps a little bit (see pic). Lacquer spray (not on these) will keep u going for a while...



Check http://www.cardomain.com/ride/748507/12

Sevorg1

new cap (free thanks to orielly's life time warranty), new rotor, new plugs problem is gonzo. I fee like a tool, the cap was cracked on under side in three places.

on another note were is the right up on cleaning iac valve, can I just take some carb cleaner to it. I can prob take apart and clean with common sense. right?

thanks for everyones input! fuel filter was a good suggestion as well as egr valve suggestion, simply ingition problem was culprit.

CapedCadaver

iTrader: (8)

TB cleaner is less harsh on the metals used in the IACV and other things. MAF cleaner is the only thing to use on a MAF. Carb cleaner is slightly different in its formulation.

Wiking

For my VGE it was that +plus+ the TPS. Weird behavior... Check for IACV http://www.cardomain.com/ride/748507/4