Thread: Strange constant speed issue

nope, neither worked. I'm going to try cleaning my air filter, and use a can of seafoam. see what happens.

could it possibly be an intermittant fuel pump? if so, why would it work under accel and decel fine and buck only at constant speed?

you know ben, I'd say it's intermittant, but as soon as the engine gets warmed up, it's all the time now. this is really really starting to PISS me off!

have you had your ECU out recently? the plug could be improperly seated. Just a thought.

I have, but the issues happened prior to me taking it out, hence why I pulled it to begin with, but I will tighten it down to make sure. Thanks for the suggestion.

anyone else have anything further to suggest?

Open your Dizzy and check for the presence of oil inside. If found, replace it. Or Swap with a known good dizzy, & go on a test drive.. If the problem disappears, you found your culpret. Also do the same with a known good MAF.

Hiccups like this can come from either 1 of the big 3: Air, Fuel, or Spark. I would start with testing the Spark: Dizzy, wires, plugs. Then Air: Test the MAF voltage at warm engine idle. Then look at the fuel: dirty injectors, fuel filter, fuel pump, fuel regulator.

My money is on the Dizzy or the MAF...

I changed for a good maf on friday - no go
I have a good dizzy as well, I'll see if that fixes it, but my current one I opened up on saturday and it was clean as a whistle. plugs are brand new, gapped, and golden. wires are taken off my wife's 01 sentra, so were verified perfect working.

Mind telling me how to test the maf voltage (or what page it's on in the fsm)? I've been looking in my fsm and can't find the bloody thing anywhere.
*edit* I checked the ground, it's good too. 2mv, well under the 9mv requirement. Just never tested voltage on a maf before.

LOL... Yes, you are like most of us.. We ground the MAF and assume everthing is fine..

Well, Im finding lots of old worn-out MAFs with low signals. Causes all types of intermittant problems. I have found perfectly good grounded MAFs with signals under 1volt. Heres my thread on the subject.. The FSM is very vague on this subject.

UPDATE: HowTo Test MAF
Heres the JWT MAF wiring info.. Just find your MAF in the list to identify your "Signal to ECU" wire.
The MAF Signal wire color is listed in the "0-5V SIGNAL OUT" column in the table.

Then do the following with engine running at operating temps:
1. Insert a straightened paper clip into the hole with the Signal wire on the harness side of MAF plug (while plugged into MAF & Engine running).
2. Connect the Positive DVM lead to the paper clip (using alligator clips).
3. Connect the Negative DVM lead (using alligator clips) to the Intake Mani grounding screws (NOT the battery ground).
4. Turn the DVM to VOLTAGE with 2 decimal points.

You will now have the MAF Signal value at idle. Hopefully its between 1.5v & 2.0v... If not, find another MAF!!

Cleaned the filter - that helped, did the oily blowby gases mod (Vadium) , but most importantly, I forgot I installed a new fuel filter prior to the 16 hr round trip - put the old one in, works just fine.

My question is, do fuel filters take a while to 'break in' or is it a 'works or doesnt work' situation? I will go get a new nissan approved fuel filter ($38!!! :O) and install it, and never look back.

The downside is I wasted 8 hrs on this stupid diagnosis. The good thing is, I have a clean egr, bpt, good vaccum hoses, rerouted oily gasses, cleaned the filter, tested the maf, tested the tps, adjusted the idle, adjusted the rpm, checked the distributor, did the wayne cox rpm trick, checked the aiv valve, tested the knock sensor, changed the plugs, swapped the wires, and changed the canister, and fixed my foglights (though that has nothing to do with it, I decided to look at them since I wanted a break from diagnostics)

The car runs so beautifully, 10x better than it did before the issue happened, so I'm very pleased.

Z32 fuel filter from G-Spec.

LOL... You didnt waste 8 hours..
You performed what everyone should do at least once a year...
Thats called a Complete Tuneup... (Equivalent to a Dealer systems test)
Much better than simply changing the plugs, air filter, oil, dizzy cap/rotor, and calling that your tuneup.

As for the fuel filters, it a good or no-good situation. But all it takes is one bad fillup of dirty gas to clog up the filter. I clogged up a fairly new filter once by filling up my car at a gas station while the gas tanker was there. The tanker stirred up the debris in the station tanks, and I was pumping that debris into my car & clogging up my gas filter. Ive had much better luck with the larger 300zx fuel filters.

Glad to see you are running good..

Just ordered a z32. thanks ben.

Yah DC, it was a bit of a crap shoot, but I feel good that it's all taken care of now. Perhaps next is a new dizzy cap/rotor - and I will have to check the maf voltage again as per your reccommendation, just to make sure, but it seems to be running like a champ