98 Cavalier 5spd manual 134K miles 2.2L I measured the resistance for each injector and they didnt seem right. They were between 3.2ohms -3.4ohms. My Haynes Manual said that normal threshold is between 1.95 -2.4 ohms. My car runs like @!#$ and the injectors are the last things I am willing to replace. I get a strong fuel smell and I get crappy gas milage and pull a CEL with the error code being P0171 or 172. It alternates between those two codes. Which makes me think I have a faulty injector(s) somehome. Ive bought new TPS, plugs, wires, O2 sensors, IAT, Idle air control valve, and checked for vacuum leaks. Any suggestions? If i need new injectors, any of them recommended over other? Thanks

My Chilton manual says resistance of injectors is between 11 - 18 ohms. Take the same meter and check with a new injector at the parts store before you buy new ones. At these low ohm values you have to have a very accurate meter to get the correct reading. Also, the resistance of the test leads comes into play.

There has been a service bulletin for the Cavalier concerning bad and corroded injector terminal connections making for bad operation. Clean up the connections and put some contact lubricant on them. Codes P0171 or 172 are Fuel trim system lean/rich which could mean your injectors screwing around.

Chiltons also recommends checking the wiring from the PCM to the injectors. Unplug the harness at the PCM and check the resistance of the wires going to each injector. The resistance should be less than 5 ohms.

Don't forget the 2.2 had high and low impedence injectors depending on the year.



Gilles
2.3 Ho

I didn't know that. So it makes sense to compare the old injectors with a new one using the same meter. The replacement part number must be the same as the old one. If the circuit is designed for low impedance injectors you cannot fit high impedance ones. Also the other way around. My feeling is that the injectors of Brad's Cavalier are OK.

Thats hilarious, you threw that many parts at the car and it didnt fix it.

Maybe you should get a clue now and take it to a shop, since you have no clue what your doing.

Resistance of the injectors also depends on if you measured them hot or cold.

Before you throw a few hundred bucks at how about having a shop look at it.

This reminds of a funny story about another backyard mechanic like yourself, this guy did a tune up to his car. Used all parts from Junkzone. He brings the thing into my shop says it isnt running right, misfires, CEL is on, loss of power. He mentions he did a tune up, using stuff from Junkzone, gives me a laundry list of stuff he replaced trying to fix the misfiring.

The first think I think of is, this thing doesnt have Nissan genuine parts in it. So I removed the spark plugs to find them fouled over already.

I replaced the spark plugs, cleared the DTCs, made sure the car wasnt running rich and sent the thing up.

The customer came to pay for it, and he flipped out when he found out we replaced the spark plugs. I told him about the condition of the ones I found, and said he needed Nissan ones only.

Well he was very upset but payed for it, swearing he would be right back because the car wasnt fixed.

Well he didnt come back until about two days later.

To apoligize to me and the service advisor because he flipped out and his car was fixed.






- 2004 Cavalier - 124k, owned since new

Maybe we should post our horror stories about so called, "expert qualified mechanics" screwing up our cars. And at dealerships. My due respects to all genuine good auto mechanics. I have personal experience that my one of my cars was screwed up. And I was overcharged for that as well. At a dealership with factory "trained" mechanics.

As I have said, my respects to all good mechanics but I'd rather just fix my car myself.

Well Rob lets put it this way, I have spent far less on the sensors and other parts than what a local shop wanted to charge for just diagnostics. Last time I took any of my vehicles somewhere I was hit with a $600 brake job that I had to replace within a year, costing me only $60 for new pads and $5 for some brake lube. Worked for me for 3 years after that with no problems. This car might be my beater, but we have been through alot. I had a head gasket blow that I fixed without taking to a shop last year and had the head milled flat As far as I see it, I have saved myself money. It needed new plugs and wires at that point anyway as well as a fuel filter, the O2 sensor was a fluke, someone had an extra one so I picked that up for less than a happy meal. And just to justify my spending, normally when you step on the gas pedal the TPS should register that, so I threw $15 at it and the new one works great. I found the Idle air control valve was faulty while looking for a vaccum leak. When I unplugged it and it didn't change the idle at all and the new one does, I figured why not, the new one looks cleaner. So instead of defending myself for working on my car on my time rather than taking it somewhere for them to charge me for thier coffee breaks, I would appreciate you holding back your laughter. I don't mind throwing parts at it. I think she likes it.

And the 98 2.2 is a low impendence injector setup as far as I can tell. If not then the 3.2 - 3.4 ohms is way below the 11-13. I am certain that this is setup with the lower resistance injectors. I will pop a new battery in the multimeter and recheck my readings to ensure accurate readings. I did plan on taking the same meter to the store to check out what a new injector reads. But thanks for reminding me cause I was about to go after work today but my meter is sitting in the garage.

Does anyone know how the resistance changes? What causes it? How it can be avoided, if possible? Its been 11 years since I studied electrical properties. Thanks

Shorted turns would cause low resistance readings. A hot injector will have a higher ohm reading than a cold one because in the case of copper (the coil), resistance goes up with heat. With low impedance coils a hot coil will be a few ohms higher. Higher than normal readings can be caused by bad coil terminations inside the injector. The most common problem with the Cavalier injector system has been bad wiring harness connections. As I've said, there has been a service bulletin to this effect.

Good knowlegde. I did my readings while the engine was cold. Also it was 30*F outside. Cold there too. Like I said before I am going off what the Haynes manual says the ohms should be and its the low readings. I see your point with the wiring being bad but if the injector itself is not reading normal, wouldnt that be the first troubleshooting step to have them replaced?

Well let me first say something to the one poster specifically and to everyone, than I will try to help you more.

Whenever I do any work on a customers car I treat it just as my own. Use floor and seat covers. I do everything properly, torque down all the bolts to specs. I only recommend parts that need replacing, if it isnt bad I wont replace it.

I take my job very seriously and want customers to be satisfied with my work.

As far as repalcing all those parts, well I didnt mean to rude I just though you tossed all those parts to replace it.

11-14 ohms is normal for injectors. But is GM used low resistance injectors than the other number may be correct.



I have never seen a car with all four injector bad at the same time. That would be almost impossible.

PO171 is system to lean, I know 172 also deals with fuel control.

You would need a scan tool, to read what long term fuel trim is doing, to see the pulse width of the injectors, to see so many things you cant see using a scan tool.







- 2004 Cavalier - 124k, owned since new

As I said, I respect good mechanics who care for the owner's car.

The figures I quoted for injector resistance was from a Chilton manual that covers 1995 - 2000 models. So I would assume that 11 - 18 ohms would be correct for your 1998 Cavalier. Did you buy the car new? If not maybe a previous owner fitted the wrong injectors. Or they have shorted turns. Best is to resistance compare a new injector for you model.

Using higher impedance windings puts less stress on the wiring because the injectors draw less amperage. Also less stress on the driver transistors in the PCM. Low impedance is a virtual dead short when the sharp edged on -off waveform from the driver transistors activates the injector solenoids. Going for higher impedance is an improvement. So I would think that later models would use higher impedance injectors.

I purchased the car used. I hope like hell the previous owners didn't try any repairs on thier own. They bearly took care of the interior needless to say anything mechanical. Going on the readings I have already from the injectors installed, would you look for a low impedence injector?

The readings you are getting suggest low impedance injectors, that is, if they are not high impedance gone bad. Shorted turns on a high impedance injector will give a low ohm reading. Overheating of the injector can cause shorted turns.

My Chilton manual says 11 - 18 ohms for the 1995 - 2000 Cavalier. Those readings are regarded as high impedance. So if it were my car, that is what I would use. Normally, when low impedance injectors are installed, there is a series resistor fitted in the wiring harness to limit current. If resistors are not installed with low impedance injectors they can overheat.

But I would really go to a dealership parts dept. and enquire about the injectors for your model and also compare your ohm readings with a new injector.

Here is a link about injectors.

http://www.sdsefi.com/injectors.htm

I'm sure someone can confirm this...

But I thought 95-99 had low impedence & 2000+ had high impedence...?

Well like I said, the Haynes Manual I have,has the 98 2.2L listed as low impedence but I still am checking with the new ones before I buy them.

Rob S wrote:Thats hilarious, you threw that many parts at the car and it didnt fix it.

Maybe you should get a clue now and take it to a shop, since you have no clue what your doing.

Resistance of the injectors also depends on if you measured them hot or cold.

Before you throw a few hundred bucks at how about having a shop look at it.

This reminds of a funny story about another backyard mechanic like yourself, this guy did a tune up to his car. Used all parts from Junkzone. He brings the thing into my shop says it isnt running right, misfires, CEL is on, loss of power. He mentions he did a tune up, using stuff from Junkzone, gives me a laundry list of stuff he replaced trying to fix the misfiring.

The first think I think of is, this thing doesnt have Nissan genuine parts in it. So I removed the spark plugs to find them fouled over already.

I replaced the spark plugs, cleared the DTCs, made sure the car wasnt running rich and sent the thing up.

The customer came to pay for it, and he flipped out when he found out we replaced the spark plugs. I told him about the condition of the ones I found, and said he needed Nissan ones only.

Well he was very upset but payed for it, swearing he would be right back because the car wasnt fixed.

Well he didnt come back until about two days later.

To apoligize to me and the service advisor because he flipped out and his car was fixed.

yea and mechanics at dealerships arent that great from alot of peoples experiences. at least he tried and learned.

Yea although this post is old, my problem was fixed. New O rings fixed that problem of faulting between lean and rich and the gas smell. So thanks to anyone who supports trying something yourself first and taking a risk of saving a boat load of money. Thats a positive way of looking at it, even though it could have been worse. So for less than what one would spent on a months worth of gas, all I lost was some time and sweat. Plus I gained the knowlegde to take on tasks that most would shy away from. Doing the work yourself can save you money if you have patience. On a car I paided nothing for, spending $200 on cheap sensors and stuff seems like a no-brainer opposed to paying $200 for some shop to tell me I need new blinker fluid or a horn belt or that the air in my tires needs to be changed from summer air to winter air. Thats not for me. Let me cut up my hands or burn the hair off my arms trying to fix something that a "real mechanic" will take their time fixing knowing you have to pay for it anyway.