Help, guys! My 93 'SE Auto has developed a 'miss' over the past week.

Symptoms:
1. Engine misses sporadically at idle.
2. Engine misses/hesitates on takeoff and/or very slow accel rate.
3. Seems to not have a problem if you accelerate at a brisk pace.
4. All three above seem to only start once the car is warmed up fully.

Other stuff:
1. Air cleaner filter is clean (stock intake)
2. Plugs are stock heat range NGK plats (last replaced about 50Kmiles ago). I pulled one plug and it looked fine in color and condition - gap was at ~.042 inches but I can't find any spec on the ideal plug gap!
3. Running 91 octane gas.
4. I checked the EGR valve for 'sticking' by trying to move the plate with my finger - seems OK as it moves fine without any binding.
5. While the engine was idling, I disconnected the 'easy to get to' fuel injector harnesses one at a time while listening for engine speed change. All three caused a slight drop in engine speed when disconnected. I couldn't find the other 3 F.I. connectors - anyone know how to check those?
6. Still have the original muffler, cat & O2 sensor with 149K miles on em.


What should I look at first? I know I should probably replace the plugs and I'll most likely do that today, but what else can I check easily? Is the IAC valve a likely culprit? Should I pull it and clean it? What about the throttle body? None of these things have ever been pulled/cleaned.

Thanks for any input you guys can give me.

 

First off if te o2 is original with 149k its most in need of replacing. Its a good idea to take out the IACV and clean it and to give the car a full tune up, it doesn't hurt, also to check the rear three injector connectors you must take off the Intake Manifold since they sit under it. Your problem sounds like a injector problem, you might want to consider taking out the intake manifold to check the rear injectors by simply checking their resistance with a multi-meter and also by looking at the connector to make sure its not corroded.

 

its proboly an injector but you dont have to take the intake manifold off to test the rear 3. theres a connector to the left of the intake manifold with 4 wires, 3 for the induvidual injectors and 1 common ground. so you can test them all there

 

Good to know the damn mechanic of mine told me that he couldn't test them without removing the manifold. Oh the gasket was just $4.44 not bad and he didn't kill me on labor.

 

Thanks for the info guys. I just got done removing the IAC and cleaning it out. It wasn't the problem cuz it still has the same symptoms. I found that connector for the intake-covered injectors and the resistance checks fine (per the FSM). Also, I'm not sure this points to injectors because the car runs purrrfect until it warms up, then the 'miss' begins. hmmmm I think I'll go ahead and spring for the $10 plugs next. BTW, what's everybody run here as far as plugs? I'm gonna go with the NGK's but should I go a heat range colder or stick with the stock range?

 

Stick with the stock plugs.
check your coolant temp sensor.

 

Red92MaxSE said you should probably check your coil packs for cracks, his was missing at idle and that fixed it.

 

A Mr internetautomar from Chicago, Illinois writes

Dear Rosanna Rosannadanna,

"Stick with the stock plugs.
check your coolant temp sensor. "

Well, Mr Fenner - er Mr internetautomar - you may have nailed the problem. The sensor reads 3.4ohms at outside temperature of about 50F. According to the FSM, it should be 2.1-2.9Kohms at 68F and drop to .3-.33Kohms at 176F. So I'm guessing it should probably be more like 3Kohms at 50F, not 3.4ohms. I haven't bought anything to fix this problem but now I'm likely to at least try buying a new coolant temp sensor. Since internetautomar came up with the suggestion I'll give him first shot at selling me the parts I may want to replace.
How much for 93 VE30DE engine coolant temp sensor and, while you're at it, how about the heated O2 sensor for the same car? Hopefully these aren't dealer only items. BTW, can anyone else run out and check their coolant temp sensor resistance and verify that they should read in the kohm range at ambient?

Thanks for the help

 

Send me an e-mail or PM and I'll give you a price on both tomorrow.
They are both available the o2 is about $60 IIRC (it's on my website)

 

FYI, all: Looks like the problem is solved. New O2 sensor fixed it (replaced the original stocker with 149K miles on it). The new coolant temp sensor, which I installed first, did not fix the problem so I guess that was a red herring to my engine miss problem.

 

Pretty interesting. I will be looking at getting an O2 sensor soon. I have a similar problem and I have ruled out a lot already.

 

lonjuan whose O2 sensor did you use?

 

I used the Bosch sensor, it was only ~$60 compared to ~$80 for the NGK sensor.

 

All depends on where you buy it.