Thread: Strange constant speed issue

This is a weird thing that is happening to my vehicle. Taking a 8 hr trip - around hr 3, car starts to miss - something. The car hesitates for a split second. Sometimes it does it a few times one after another in varying degrees, sometimes once. Sometimes it goes 30 seconds between surges, sometimes 10 minutes. This happened the whole way there and the whole way back.
It only happens at a constant velocity. Accellerating and decel are absolutly fine. Idle at a light is fine - It seems to only do it when above 100 km's/hr (uh...60 miles I think?). Oil pressure, oil temp, water temp, volts all check out (gauges I have).

Initially I thought it was a vaccum hose that was disconnected somehow because the neck on the top regulator on the canister was snapped off. I bought a new canister when I was in winnipeg and reattached everything. It didnt help, symptom remains. I changed the plugs, nothing changed. There was a hose that came from the vaccum gallary that went to a plastic coupler, through a rubber grommet, and into my intake tube from my cai, between the tb and the maf that appeared to have split - bought a new grommett, put the vaccum tube in, and siliconed around the tube to ensure a snug and more permanent fit - symptom remains.

I didnt have a multimeter so I couldn't test the tps or maf, but the maf is regrounded.

Ideas?

(rpm's only about 3500 btw)

sounds like it can be your water temp sensor

a faulty ects would cause it to stumble initially at low rpms until it warmed up, but I have never heard of it causing high idle stumble like this before, please explain.

although it has no cel, I yanked the ecu and Pulled the codes (91 nx 2000) and got a 34 - detonation (knock) sensor.

been searching the forums to see the cause, and there's not a lot to go off of. I will test the knock sensor for continuity but it appears there are quite a number of different symptoms, and always has another code associated with it. Mine only has the one code, 34.

Any thoughts as to what the culprit is?

Tested the knock sensor, continuity exists between pin 'a' and ground - knock sensor is therefore in proper working condition according to the fsm. Now, I cleared the codes on the computer and we'll see how she drives. If it drives the same, I have no freaking idea why it's missfiring at high idle like that.
Still looking for an explanation as to why the ects would cause a missfire like that?

it does the same thing, only now it boggs a lot more than it did, and still hesitates at high idle (3k-3500)
ideas?

just cleaned the bpt and egr valves, the bpt was clogged. The car now still hesitates like it did before, but also it now has sparratic rpm, I can't beat this stupid thing!

You know, that could be a lot of things...

Something like that is happening to my GF's parent's car right now and intermittend stuff like that is a bitch to diagnose.

Similar thing was happening to my brother's car recently... Turned out to be a poor connection between the fuel pump and the car's wiring harness. Took 6 months to diagnose because the car would hesitate, or sputter then work fine, or shut off and not work until the next morning when it would be perfectly fine.

I think you might have to see if it gets any worse before being able to track it down...

tested the tps, it's fine, idle is dead on 15-17 degrees, idle is rock at 750-800 with s3 cams, and maf is properly grounded. It's weird, sometimes it drives beautifully, and others it drives like crap. It's now bucking at any constant velocity, regardless of the gear and rpm.

Now I'm really stumped. The fsm says 'hesitation at hot engine' (which it is) plug the canister purge line and fuel regulator line and cruise, see if it fixes it. that will be my next attempt.