Hesitation, sparkknock on the scumbird's 3.1L

[RidgeRunner]

On my way back to campus from Asheville today, I noticed while going up a steep hill a good bit of sparkknock (this car has never sparkknocked that I've ever heard until now), and while trying to duplicate the situation to see if it did it again, the car hesitated badly upon opening the throttle. I assume the two problems are linked, but I don't know that for a fact. No check engine light.

93 3.1L in a Sunbird, has one of Ben's chips and a 62mm TB.

Any ideas?

[Superdave]

the magic 8 ball says...... Replace your CPS...


pull it out and measure the resistance, it should be around 980 ohms...


if it's good then have your ICM tested, and check your coils.. primary's should be between .5 and 1 ohm, the secondaries should be between 5K and 10K ohms..


all this assuming you have good plugs and wires :P


-Dave

[RidgeRunner]

My car hasn't liked me lately.

First, the above issues occur, then it's fine... no problems.

Now, yet another problem has arisen. Related or not, I don't know. It's now got a bad miss under load. I'd check plugs and wires, but that's going to have to wait til I can get ahold of some tools, since mine are all at my parents house right now.

[Superdave]

Git R Done ! :P

[RidgeRunner]

Okiedokie, is it possible that bad/contaminated fuel would cause the sparkknock and hesitation? I drove it the 200 miles home with no problems, and even driving it around some more, stopping/restarting, have been unable to duplicate the problem since it really tried to shit a brick last night.

[RidgeRunner]

It hasn't tried to strand me lately... but it sure doesn't do as usual at idle. Instead of smoothly whirring at idle, it spits and complains a little bit. Not quite a miss, but noticeable. Also still has a bit of hesitation, but not as bad as before. With the previous tank of gas I put in a bottle of Iso-Heet in case it was water in the fuel.

Plugs and wires are new, generic NAPA wires and NGK plugs. I'd have gotten ACD stuff again, but the only parts store open at the time was NAPA.

[RidgeRunner]

OK, for the first time in almost 2 weeks, it didn't want to start. It will crank, but nothing happens unless I mash the gas to the floor. Then it'll sputter and fire off but not want to run at low RPMs for a few seconds. I have to hold around 4k-5k rpm for a bit, then slowly back off. Then it'll run ok.

Help me! What's wrong with this thing?

[bszopi]

Could it be a fuel pump going bad or faulty/clogged injectors?

[RidgeRunner]

You know, after posting last it occured to me that it might be an injector sticking open... can that happen? It would make sense to me, since when it has problems, it won't start at anything but WOT. Given the age and mileage of the thing, and the fact that it's pretty much all original except for obvious things, I probably ought to send the injectors off to Marren or Witchhunter to be serviced. However, that's not going to happen anytime soon, unless I can pick up a spare set of injectors...

I think what I may do is run a bottle of injector cleaner through it on my way back to the mountains at the end of this weekend, and hope for the best. If the problem keeps reoccuring, I'll have to get it back here and park it, then I'll probably be driving my mom's 84 Nissan 720 4x4 Kingcab (complete with faulty fuel pump relays) til the next time I have a lengthy break from school.

[RidgeRunner]

Well, now that I'm back home (again!) I've gotten around to really doing some analysis of what's going on (as opposed to guesses) and the first thing I've come across is fuel pressure issues. The pump seems to only be capable of about 30psi, not even enough to open the regulator to send fuel back on the return line. Flow appears to me to be plenty, I disconnected the pressure line from the regulator and ran the pump momentarily, it shot a steady stream out that line.

[RidgeRunner]

Replaced the pump/sender assembly (old one had issues last time I had it out) and fuel pressure is now exactly what it's supposed to be...

but now it's got a real bad miss. So the fuel pressure might not have been the original problem. Ben, send me those coils & ign mod you said you had! IM me when you get a chance.

[RidgeRunner]

OK, replacing the ignition shizzle did nothing. I'm tempted to throw in another set of injectors to either fix it or rule it out.

What other than ignition or fuel pressure could cause a bad miss?

[RidgeRunner]

The saga ends at last...

The stupid MAP sensor was fucked, throwing it so freaking rich it shook and spat like it had a miss.

Found that out when I gave up and decided to see if a short drive would give any revelations, sure enough it finally triggered a code 33 (and later a 45). Replaced the MAP sensor and it started running right after it ran long enough to un-foul the plugs. I think I'm gonna try to patch up the heater core and drive it back to the mountains tomorrow, instead of the nissan.

Hey, at least I have spare coils and ICM now.