android94301

Hi,

I'm a longtime reader of this forum who's a mechanical idiot. I've got a 91 GXE with about 110,000 on it. I recently had a new (rebuilt) tranny put in after the old one died. Now the tranny seems fine, but the engine has a lot of vibration when stopped at a light. It's enough so that it actually is a little nauseating. If I shift into neutral the vibration lessens but doesn't stop. Driving it seems fine, with much less vibration, and seemingly good power.

My local mechanic looked at it and thinks it's a clogged injector. He concluded this by one by one pulling off the spark plug cable, and on most of the cylinders this results in a drop in engine speed, but on one cylinder there is no change in speed when you pull the spark plug cable. He also listened to the suspicious injector with a sound scope, and heard it clicking normally, so he thinks it is clogged not failed, or electrically compromised. He didn't check the resistance. He also checked the compression on the bad cyclinder and it was normal.

He offered to replace it for about $350, saying that he would have to pull off the top of the engine to do so. Or I could pay about $125 to $140 and he would try to clean the injector (which I think is done thru the fuel line, without pulling off the engine top). Of course, if that doesn't work, then I still have the $350 repair.

I tried a little self help. First I ran some injector cleaner thru the gas tank for 2 times (2 tanks of gas). That seemed to improve things somewhat, perhaps back to normal or close to it.

But then I couldn't leave well enough alone and then I replaced the spark plugs with Bosch platinum double gap plugs, and also replaced the spark plug wires with some brand from Kragen. Since then the roughness has returned, and I am a bit puzzled. I'd put back the old wires, but I broke one when switching them.

So here I sit, in my very nice but vibrating 91 GXE, wondering what to do next?

Do I:

1. Replace the spark plugs with NGK's or the old plugs?

2. Get different spark plug wires? (Suggestions?)

3. Check the distributor cap for cracks (How do I do this?)

4. Run another round of injector cleaner thru the engine?

4.5 Check the compression on all the cylinders?

5. Have my mechanic replace the injector? Or should I gamble that the injector cleaning approach he could take would work?

6. All of the above.

7. None of the above (What else should I do?)


Otherwise my car needs new struts, but is in good shape except for that. I don't want to put a ton of money into it, especially after the $1700 for the tranny, so would appreciate some savvy guidance from this forum in fixing the problem for the least $$$.

Thanks for the help!!!

internetautomar

iTrader: (30)

1. go back to NGK plugs. Bosch have a history of running issues
2. go ngk on the wires also
3. pull the distributor cap and look for cracks or lines in the cap that just don't match the rest of the cap
it's very possible and likely that you injector is clogged, so more injector cleaner is a short term fix, as nissan warns against it because it ruins the windings on the injectors IIRC


I sell NGK plugs and wires. I also sell brand new Bosch (OE) injectors not too mention caps and rotors too

subs1000w

1st check resistance of ALL!!!! injectors and replace all that are above or below 10-14ohms (factory spec) if half of them are out of spec i would suggest replacing all the injectors because ive read about several people having to have 1 or 2 injectors replaced every year which ends up costing alot more in labor than the part

your plugs wires shouldnt have anything to do whit the vibration. injector failure is VERY common on these cars. ive had one fail (infinate resistance) and 2 others that were out of ohm spec (18-24ohms) but the new engines injectors were all fine 11-12ohms

Wiking

1. Do as told already, NGK plugs, NGK wires, cap (note: new cap might be dead; buy insulating lacquer and spray). DIY wires are best http://www.cardomain.com/ride/748507/12

2. Clean groundings and wiring connectors, especially the injector plugs.
http://www.cardomain.com/ride/748507/1

3. Check by unplugging wires if the problem is on one cylinder only - if so, points to injector... still ask rplacement price from another shop.

4. Check sensors one by one

5. Compression check is necessary only if constant stutter on one cylinder; still its good to know.

6. Generally do cheap things first: no harm done if electricals are in good shape...

Cap leaks produces intermittent stutter (often on any cylinder); clean, shield electrodes and spray lacquer on both sides:

android94301

Just got off the phone with what I hope will be my new mechanic, and he said that the most likely problem if it's one cylinder, is actually the coil failing. Does this make any sense???? He's going to look at it on Wednesday.

twinkle

iTrader: (1)

yea, but he probly thinks that it s an SE which has the dual overhead cam engine and 6 coil packs, one on each cylender

Wiking

It makes sense, but...

As twinkle says, no coilpacks in u machine. Distributor & wires instead: if one wire and/or plug is dead, then no fire on that cyl.

FSM tells to take distributor off, turn ign on, rotate distibutor: injectors will all click if theyre electrically ok. Still might be some other problem.

You may yourself verify the injectors click very easily: take a long screwdriver, place it on a injector, ear on its handle and listen. Repeat x6. All should sound the same.

android94301

Thanks for all the recommendations.

I took it in to another shop that was recommended and they looked at it and said that the number 5 injector is clicking okay, and seems electrically okay, but doesn't seem to be getting full flow. He recommended I replace it.

What's weird is that he accidentally left the spark plug wire off when I drove it off, and it ran MUCH worse until I stopped, opened the hood, and replaced the wire on the number 5 plug. So apparently the injector must be at least delivering partial gas flow to the cyclinder.

Does this mean there is hope that the injector could clear, maybe with another round of injector cleaner? Or does it mean that it would be worth letting my mechanic do a professional injector cleaning, which as I understand it, means they remove the fuel lines, and run cleaner right into the injectors. He would charge about $140 to do that, but can't guarantee it would work.

This other mechanic wants even more for replacing the injector, like $383 parts and labor for 3 hours labor and the part which he said was $113 for the OEM nissan injector.

Here's my dilemma. Since removing the plenum is the expensive part of the job, would it make sense to do all six injectors, which of course would cost almost $900, or should I just do the one? I'd like to keep the car for another couple of years, but probably will get something else then. Am I likely to squeeze out another 2 years on the five older injectors?

Does anyone know a cheaper shop that is any good in the Palo Alto, CA area???

internetautomar

iTrader: (30)

if you can afford it, do all 6. you'll save in the long run

android94301

I can afford it, just not sure it's really worth it. Strangely enough, the car seems to be running a little better. I think I'll step thru changing the plugs back to NGK's and checking the distributor cap, and then re-evaluate how she's running. Maybe there's a poltergist in my injector!!!

Wiking

If the choice is to replace all 900$, what happens to the current injectors does not matter. Then I'd go for chapter 4 with overcharge - relatively cheap if it works as u now indicate:

"4. Run another round of injector cleaner thru the engine?"

Gasolin has this tar gum that descends gradually to bottom if the car stands for a long period, it may reach the injector. The cleaner could be able to dissolve it in repeated runs. Cannot really guess which would work best: overadministration and/or repeated cleanup, drive more or drive less during cleanup.

internetautomar

iTrader: (30)

nah, no poltergeist.
but as other's have stated when one goes, another one or 2 is not usually far behind, and labor is mostly in pulling the plenum so it makes sense economically to do them all at one shot.

aksansai

iTrader: (2)

The government mandates that fuels must have some level of clean already in the gas you buy at the pump. Adding fuel injector cleaner can provide a boost, but in my experience not even of a difference to remove sludge or carbon baked onto the end of an injector.

This is true - there is no guarantee that it will correct the problem. But, honestly - if you're a good sport, you can DIY to save you some money. A novice with a good tech manual can probably accomplish the feat in a day. Remove the snorkel and intake plenum, then you can get to the fuel rails (which have all the injectors attached). Use an allen-type wrench to remove the bolts holding the rails in - then lift them straight out. Make sure you have new intake gaskets and high-temp gasket sealer available when you go to put them back on.

When you remove the fuel rails (please get a Chiltons or FSM) - inspect the ends of the injectors for carbon or sludge deposits. You can use intake/carb cleaner to remove collected debris. If that does not correct the problem, just replace the injectors. They've come down a TON in price since 3rd gens are going into retirement faster.

You can save yourself the $270 labor if you DIY. It's really not that hard. And unfortunately, if you have an early VG you might as well teach yourself how to do it if you're only going to replace them one at a time. 92+ through 04 VG injectors are a superior design (4 nozzle) than the early 92 down to 89 VG (1 nozzle). You can buy and use those injectors to replace the injectors that are in your car (if you had the older style injectors).

It really depends. I agree with another post that the condition of the injector (if it is not electrical) is probably nearly shared by all six. I've seen quite a few injectors that have been brought back to life if carbon/sludge is located on the tip of the nozzle. You can attempt to clean the internals of the injector with carb/intake cleaner (low pressure) by removing the injectors the rails.