I'm trying to diagnose if one or a couple of my fuel injectors is going bad or if it's just a wiring harness issue.

What happens is when I start the car it will run fairly smooth but when I get on the road and put a load on the engine the check engine light comes on, I lose power and the engine start's idling rough. I'm wondering if it's a wiring issue to the fuel injector because it's intermittent, IE, only if the car is put under a load will the injector not work.

If it is a fuel injector is it possible to have them rebuilt? I'd like to get all of them taken care of while I'm working on it but need to save on money.

Is there an easy way to figure out what injector isn't working. I tried disconnecting the harness to each injector one by one with the engine running but the result's came up inconcluesive. I'd think I had found the culprit but it turns it wasn't it.

Will fuel injector cleaner help at all for something like this? I know some guys say don't even bother with the stuff but I'm grasping for straws at the moment.

 

does your CEL stays ON all the time? my suggestion is to pull the diagnostic codes first.

 

Fuel injector cleaner won't do a darn thing. Don't waste your money on it. Nissan also says not to use injector cleaner, we have a pintless design that does not clog. But the filter screens on the injector does get clogged, they can be cleaned after the injectors are removed. I inverted them in a cup of alcohol and used a gentle paint brush to wash the particulates off (carbon mostly). You need to test the resistance of each injector (11-14 ohms) whatever is out of spec, or out of spec compared to the other's should be replaced. The best thing to do if you have the money is to just replace them all. don't forget to get ALL new seals for them, there are two o-ring per injector and two grommets per injector. Beck/arnley makes a complete o-ring kit for the maxima.

Edit: There is a chance that you do have the pintle design, I forgot that some of the earlier max's (gxe's) have them. there is a color code on the injector (top) its a dot of paint that tells you which one you have.

 

...came up inconcluesive... so maybe its smtg else? Btw, you can listen to injector cliks to verify the electronics and mechanics is ok. Use long screwdriver as a 'scope'.

Loading engine does not burden too much the injectors, so I guess points to other directions, as the intermittent fault decription. 'Pushing gas pedal' gives injectors higher voltage pulses, and they open more rapidly and stay longer open. Rough idle could be because of injector, but so are myriad other reasons...

...save on money...make sure its not smtg else before buying injectors: how many miles on them?

Have u done your maintenance, wires cap rotor plugs, filters, checked all sensors, cleaned all connectors (all=ALL)?

 

Just replaced the cap and rotor, they were shot, I did the plugs earlier and the fuel filter so they are good. The plug wires seem to be in pretty good shape. When I pulled the wires on the injectors a couple of them needed a good wirebrushing because they were pretty corroded. Cleaning the terminals didn't do anything (at least for the problem at hand).

I think I'm at the point of parking the car and just ripping it apart and doing a thorough cleaning and replacing of parts. I need to really get in there and clean all of the wiring because there is a lot of corrosion.

This screw driver method for finding the injector, I don't understand quite how this method is supposed to work? The Chilton's manual says to take the crank angle sensor out and turn it by hand but I don't have a timing gun available at the moment so my dad and I were a little hesitant to do that just yet.

 

Yeah, if you do replace an injector, replace them all. Because, if you have one new one and 5 older ones, the car is not going to run as nicely as it could. Plus, you're tearing your engine apart and the other 5 are practically right there, so you might as well? Just my opinion.

 

The only wires that run smooth are real copper/steel wires [with 1-5k resistor added], all 'soot-tubes' cause problems [scale: minor-major]. Even new carbon dust tubes from shop might have resistance worse than old...

Opening engine should be based on sound diagnosis, well if one lacks hobby...

Clean all (=all) connectors, add minuscle drop of contact grease. Inspect all ctrl rubber hoses, cut brittled ends.

Check all sensors separately.

Distr.: Scrape a line to the distributor/engine side, and you'll get it back in same pos.

Listening mech noises with screwdriver 'scope': one end on engine, ear on the handle... easy to locate all noises.

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see: http://www1.autozone.com/servlet/Ui...&Parameters=004

Sensor tst:
MAF:
Copy from somewhere:
Mass Airflow Sensor malfunction: If the MAF voltage is below the specified value, the ECM senses a mass airflow sensor malfunction. In this case, the throttle position sensor substitutes for the mass airflow sensor. Although the MAF is malfunctioning, it is possible to start the engine and drive. However, engine speed will not rise more than 2200rpm.

Haynes Manual:
Put a DVM probes into MAF pin b (second from left) & gnd
- Ign on, engine stopped 1V
- Idling, temp up 1-1,7V
- 2500 rpm 1.5-2.1V
- Important: linear voltage rise up to 4000rpm.




TPS Throttle pos sensor:
One connector is for the potentiometer. Open, it should be 1kOhm-9kOhm, linear response is important.
Second connector is zero pos switch. Open, as throttle is closed one connector is closed, sw is opened as throttle opens just a little, plus second sw connects for 2/3 throttle postion.

Knock Sensor:
The knock sensor on VG30E engines is located under the rear exhaust manifold.
Just use an ohm meter at the subharness and check each terminal (going to the KS) to ground (battery negative). Resistance should be around 0.5 Meg Ohms (500,000 Ohms). When mine was bad it read 5 Meg Ohms (5,000,000)

This piezo element detects [if any] ping, sends minuscle signal to ECU --> ECU retards ignition timing.
Ping might come from too low octane gas, excess soot causing pre ign in engine. Seldom needed, but maximizes engine life with unaware drivers...

Camshaft pos sensor:
Remove the distributor assembly from the engine.
Disconnect the ignition wires and coil wire from the distributor.The camshaft position sensor electrical harness should remain connected.
Turn the ignition switch ON.
Measure voltage between terminals 3, 4 and ground.
With the engine's distributor shaft rotating slowly, voltage should fluctuate between 0 and 5 volts.


Temp sensor
+20C 2.1kOhm-2.9k
+50C 0.68kOhm-1k
+90C 0.236kOhm-0.250k

Oxygen Sensor, Front
Disconnect the sensor electrical harness.
Measure resistance between the outer terminals of the connector.
Resistance should be 2.3-4.3 ohms @ 77°F (25°C).
Check continuity between the center terminal and each of the outer terminals. Continuity should not exist.
If resistance is not as specified or continuity exists, the oxygen sensor is faulty.
If resistance and continuity are within specification, check and repair the circuits.

Oxygen Sensor, Rear
Disconnect the sensor electrical harness.
On models with a three-terminal connector, measure resistance between the two outer terminals. On models with a four-terminal connector, measure resistance between the two illustrated terminals.
For three-terminal connectors, the resistance should be 5.2-8.2 ohms @ 77°F (25°C). For four-terminal connectors, the resistance should be 2.3-4.3 ohms @ 77°F (25°C).
On models with a four-terminal connector, also check continuity between the various terminal combinations, as illustrated. Continuity should not exist.
If resistance is not as specified or continuity exists, the oxygen sensor is faulty.
If resistance and continuity are within specification, check and repair the circuits.

ECU
-Locate the ECU and take note of the LED and mode switch positions.
-Turn the ignition switch ON.
-Turn the mode switch screw fully clockwise.
-Wait at least 2 seconds.
-Turn the mode switch screw fully counterclockwise.
-Start the engine and allow it to reach operating temperature.
-Run the engine at approximately 2000 rpm for 2 minutes under no load.
-Ensure that the red LED on the ECU or the Malfunction Indicator Lamp (MIL) on the dashboard flash on and off more than 5 times every 10 seconds.
-If the red LED on the ECU or the MIL do not function as specified, check the oxygen sensor circuit back to the ECU for continuity.
-If continuity exists, the oxygen sensor may be faulty

 

Cool, thanks for all of the help guys.

Now I'm trying to figure out if I should replace all of the injectors or just the bad one. I guess because of the amount of work involved it's worth it to do all six if the money is available. I'd like to do all six to avoid having to think about it for a while but only 1 might be in my budget...

I think my dad and I are going to rip apart the engine, take the injectors out and see how bad they are. I think I'll try that cleaning method first and see if that takes care of the problem. I'll of course test the resistance in each one to.

If it's just a simple cleaning that is required then I'll put them all back in, but if they look pretty bad I think I'll go talk to uncle VISA and just replace them all.

Looking online it looks like the Bosch injectors are the cheapest at 85 bucks apiece. Any arguements with these? 120 bucks for injectors is a little rich for my budget... On EBAY there are 6 injectors still on the fuel rail from an old maxima for 100 bucks. I guess the risk is not knowing how bad of shape those things are in so I'm not leaning that way.

I guess there is a difference in the flow rates for the two different color dots. Is it worth buying the higher flowrate injector if I'm buying them anyway, and if so, what color is it?

 

Fuel injectors run by changing the pulse width not the voltage, the solenoid is an on/off device, and can only be moderated by how long it has to stay open or closed (a square wave).

 

check /clean your fuel inj GROUNDS close to where you see the injector wires that plug in to each inj.youll see grounds(off the same wire mass)(rings bolted to engine)(careful when you turn the bolt itll try to turn the ring with it and can break the rings)my friends car went to the shop for this reason after 2 hours of diagnosis the shop guy just cleaned the f .inj. grounds? good luck

 

Solenoid acceleration speed is determined with the voltage level and pulse risetime. Square vawe is theory, seen seldom in cars. Then voltage is gradually dropped to decelerate [not to hit the end too hard].

'Real Life': Direct 1μs spike up, deep downhill from there, the end of the pulse [0V] to 400μs or more.

What the oscilloscope tells: voltage increase along lenght increase; must be the driver FET characteristics, supply voltage variations due to alternator speed change - whatelse...

- Voltage top spike variation: 45-80volt spike (80V ? around 2500rpm)...
- Lenght variation at same speed range: 120μs - 250μs [if zero trigged at 20V level]
- Lenght variation at same speed range: 400μs - 400μs [if zero trigged at 0V level]