erivera788

Hey to all,

I have a 90 SE. When engine is cold it runs fine. Good power and torque. When engine comes to warm operating temp thing go down hill. Idle hovers around 700, just above the 500 RPM mark. The idle starts to hickup or miss slightly. At times it drops guickly then it rises to about 1000rpm and ten settles back to 700RPM but smooth as silk for about 5 seconds then it starts hesitating as before. Unless I out the tranny switch to power setting the engine hesitates more when I give gas. There are times like today that the engine will run smooth without any problems. It coast on the highway with little gas pressure. Acceleration is great. This doesn't happen as often as I would like. It seems the weather helps when it's cool and low Humidty. I have 150k miles. new sparks, wires and Dist cap, rotor. I've been hearing about Knock sensor and Injectors possibly can cause this problem. If correct can I get and Est. as to how much this repair can cost. Also note that Injector sensor connector rubber boots are cracked and when moved causes engine to shake until I find a good position for connector. Are there any repair Kits I can buy to replace these injector electrical connectors?

Thanks in Advance,
Edgar

glowworm_76039

I'd check the sensor right behind the air filter, as well as the plastic and rubber parts of the intake before I go after the injectors. If the filter neck is loose behind that sensor, it will cause the engine to idle roughly, run lean, lose power, choke out, etc. If you're lucky your headache could go away in five minutes?

erivera788

Thanks for the info. I'll checkit out.

Sawby4president

If your car runs well when cold but declines when warmed, you probably have a bad sensor somewhere. I don't know if the VG motor even has a knock sensor (because it doesn't have variable timing control to retard ignition in the event of knocking, like a VE), but it does have an 02 sensor, which may be the culprit. The ECU won't read the O2 sensor signal until it reaches a certain temperature, and if the 02 sensor is malfunctioning, it can cause the car to run like crap once warmed. Good cold operation would indicate that the injectors and other hardware are okay. Rough idle is also often a symptom of a bad oxygen sensor. Hope this helps, take it to a diagnostic shop and have them put it on the computer to see if the O2 sensor is throwing codes.

erivera788

Good to hear It's not that Knock sensor I've been reading so much about. The O2 sensor could be a problem since I have not had the car really checked out since I bought it, except for state emmissions testing which passes. Should the engine light come on if the O2 sensor is giving problems and can I use the ECU diag lights to check it myself?

Thanks

Sawby4president

The Check engine light will not always come on for a bad 02 sensor. I have read that certain codes won't trip the light, but still indicate a problem. I'm not sure about diagnosing it yourself, the only way to know would probably be to replace it. If you watch the repair shops, sometimes they'll run a deal on engine diagnosis, I would just do that if you want to know for sure whether it's bad before you replace it. It's only a guess, but maybe the only codes that indicate a problem that will increase emissions past an acceptable point will trip the light. Also, a physically broken or missing sensor will cause the CEL to come on. My mom just had the 02 sensor in her grand cherokee replaced, and it was only tripping the CEL sporadically.

Pervis Anathema

iTrader: (8)

I am having the EXACT same problem. I just did some fairly extensive fuel injector work and had my exhaust manifold studs fixed. However, that didn't fix my problem. Then I replaced the 02 sensor with a brand new one. Didn't work either. According to the manuals, the VG does have a knock sensor.

I crawled under my car and took a look. Assuming I read the book correctly and am looking in the right place, the wiring harness on mine is covered in gunk and looks corroded. I have checked on prices and it looks like about $150.

I have replaced my plugs, wires, rotor, distributor cap, air filter, fuel filter, and prayed to the Maxima Gods while dancing naked around a roaring fire. Also, I know my injectors, vacuum tubing, 02 sensor, MAF, and TPS are serviceable so I am replacing my knock sensor as soon as I get the funds. I will let you guys know how it goes.

Sawby4president

I was wrong about the VE not having a knock sensor, because the ignition timing would be retarded, not the valve timing (I think)

eric93SE

iTrader: (1)

Yeah the first thing to check is the vacuum lines, look for hard brittle lines, any cracking or spliting in the hoses. And like someone already mentioned the tubing that runs from the mass air flow sensor to the engine.

But like you have already found, the injectors are causing trouble, and if you search you'll find some info on relacing the harnesses, but they can be cleaned along with the injector terminals. The best thing to do would be removing all injector, test their resistance is within spec, clean the filter screen, and use new o-rings (they are know to leak). There is a fuel injection tune up kit that you can get for your VG, beck/arnley makes it and it comes with all the seals, gaskets and o-rings. Carparts.com carries the kit.

erivera788

Guess I'm going to have to find a warm spot to check all this out and find a good place where I can rely ,that the technician is not going to try and milk the diagnosis work. I try doing my own work when I can, that is in warm weather. Now it sound like my front passenger side strut went bad. I hear a soft clonking over rough rode. Thanks for the info guys I let youo know what happens.