Blackpearl

It is true that ECU is the master, but all the inputs comes from sensors that are accessible. I don’t know if anybody tried to trick the sensors.
I only know the so-called "shock sensor" or "vibration sensor" which actually increase the rpm at start to reduce the engine vibration.
If you go downhill and put the gear in neutral, the rpm is going to the idle rpm, but when I was doing that in some dirty roads the vibration produced by the road kept the rpm fluctuating form 650 to 2000 as function of the car vibration. Do you guys know how many sensors actually giving input to the ECU?
Maybe this will help.

gearbox

iTrader: (95)

I'll start checkin sensors if the new plugs don't help. I switched to copper ngk v-power and so far the starts are 100% faster and better. It still cranks 3 times but much faster. And the engine turns over more smoothly. So maybe this will fix it. Just gotta wait til it cools down.

Jrfish007

iTrader: (3)

Well, there a many sensors, I can think of about 10 off the top of my head.

As for a shock sensor, I'm not sure about that. I know that when you start a car, the RPMs are high because the temperature of the engine and catalystic converters are low. The intial 30 second the car is running, it runs at 150% fuel, or fuel rich, this produces more heat which helps to bring the engine and the catalytic converters to operating temperature.

As for changing idle when going down a rough road, that does not seem normal. It can change a little, but 2000 seems a little high and 650 seems a low, but not that low. I go home on some rough roads, normally I have my car in gear, but I will take it out of gear tonight and coast through them and see if I notice a change like that in the RPMs. I'll let you know what happens to my car.

Jrfish007

iTrader: (3)

Hope that's it. I've noticed these cars are very picky about their plugs.

Sick Cycle

I'm 99.9% it's not your plugs fault.

I've noticed that with my d17, my plugs would get loose every 2-3 weeks ... I would have to go back with a torque wrench and re-tighten them. Afterwards, they would feel very responsive, start faster, etc.

same goes with my k20 .. but the plugs in there don't get loose quite as fast.

what are your idle problems? .. do you have an idle that constantly goes up and down?

gearbox

iTrader: (95)

the idle is fine once the car warms up. its only right after the engine turns over that the rpms bog down very low to the point of the car shaking and almost stalling. i just have to try and press the gas and wait a minute for it to level out. only happens when i start it warm, in cold weather. And I'm pretty sure the plugs will fix it. I'll post what happens once the temps go down again.

Sick Cycle

have you tried adjusting the throttle screw thing?

perhaps with your ported head, it's giving the computer some strange readings ... perhaps try subtracting fuel/adding air in the lower rpms?

gearbox

iTrader: (95)

i already advanced the cam to deal with the rough running idle. this is different and only before the car warms up.

gearbox

iTrader: (95)

hmm well so far so good since I put the stock airbox and new plugs. It seemed like it was gonna stall for a couple times right after starting, but the rpm always immediately revs a bit and the idle stays up. I'm not saying for sure cause its only been a couple days...but I think it might be fixed.

Blackpearl

Hmm. I hope I don't have some bad sensors. Any news from rough road drive?

gearbox

iTrader: (95)

my car used to do that idle fluctuation on rough roads, but i had done the tb heater bypass. it went back to normal when i put it back to stock. i have an auto and mine stays at the same rpm unless i let go of the gas.

Blackpearl

There was something bad with your old spark plugs? If I remember corectly, you had iridium.
I replaced my sparkplugs with iridium, and so far is working fine.
Probably we can try to collect some pictures from our old plugs and post them with the problems so people will have some reference.

BTW. Did the sparkplug fix the problem?

Blackpearl

Hmm. I have stock D17.

gearbox

iTrader: (95)

well it didn't happen once i swapped the stock airbox in. seems like it makes the engine rev a bit right after starting that the other intake didn't do. my last plugs were stock double plats. i swapped those for a newer pair i had from someone else, and then checked those and saw a white spot on two of em. looked like lean. so the copper would help out by making a bigger spark and running cooler. but i think the stock intake fixed it or at least made it so that its not happening anymore. copper plugs are starting up better than the plats tho.

gearbox

iTrader: (95)

i just went to start it again after an hour of leaving it in the cold. started right up and drove great. i think problem solved. it was too much restriction with all the mods. and i'd rather have stock intake and aftermarket exhaust since they give the best range of power. when i had other intake and stock exhaust, it was really restrictive with good low end but terrible above 4k rpms. stock intake seems good at hi rpm too.

Jrfish007

iTrader: (3)

Yeah, I notices a slight change in idle. Normally my car is around 750-800, which is where it was for most of the time. When hit a relatively large bump, it did jump very quickly to about 1000 RPM and drop very fast. But I think it never got near 2000 RPMs.

With the window down, I can hear the difference between 2000 RPM and 1000 RPM. You may want to try listen to for the difference. The reason I say that is because the tachometer in most cars are terribly inaccurate, they read the engine speed via the voltage (normally the voltage from the alternator). So I generally say tachometer reading are about +- 200 RPMs. It is possible that when you hit a bump, you are grounding or un-grounding something somewhere and causing an electrical spike and hence just messing with your tachometer. I would trust your ear and other senses much more than the tachometer.

So try a different method of measuring RPM's and see how that goes.

Jrfish007

iTrader: (3)

So no more problem.

gearbox

iTrader: (95)

i hope. i'm not gonna say anything for sure cause it might happen again. But I think its over.

gearbox

iTrader: (95)

hmm well i spoke too soon. it happened again after the car sat for 30 mins. it almost stalled but recovered. seems to have gotten milder than before. i think its just too much air with the exhaust so i'll just have to live with it. once the car gets going, it drives great.

Blackpearl

Maybe was lower then 2000. I can't recal. But for sure was high. The road in my case was very bad. At 30 mi/h the car was shaking, because of dirty road humps (like somebody made it with a tank).
BTW, I tought the tachometer geting the read from some of the sensors on the camshaft and not from alternator voltage fluctuation. Hmm. I wondering what people with ScanGauge see on the rmp display compared to the cars tachometer.

Blackpearl

Did you try to reset the ECU and program again the idle speed. I so that there is a procedure to set the idle speed in the service manual.

Jrfish007

iTrader: (3)

Yeah, it comes from voltage on most cars, some read from other places like the cam shaft, generally high performance cars have a more acurate tachometer.

It maybe possible that it was just a rough road, do you travel on this road every day, or was it just a one time thing? How many times have the RPMs shot up? If it only did it once or twice, I wouldn't worry about it.

gearbox

iTrader: (95)

i'm gonna replace iat sensor. do you think the coolant temp sensor is bad? i mean the car seems to warm up super fast according to the temp needle, but the heater still doesn't blow hot air til 5 mins later. this just happened after the timing belt/water pump change.

Jrfish007

iTrader: (3)

Coolant temp sensor? You mean thermostat?

Well, the guage inside the car is reading the coolant temp in the block, this will heat up fast, but the coolant may not start flowing until the thermostat opens up. Once that happens the hot coolant will allow for heat into the heater core hence giving you heat, there could be a time delay between these two points. At least this is how it works in the other cars I've torn appart (except for Dodges, they really are different), I would assume the 7thgens run the same.

What has me a little worried is that you just noticed this after the water pump was changed. Did they use an OEM water pump or some other brand? My first thing would be to test the thermostat and make sure it is opening at proper temperature. My second option would be to test the flow of the coolant, I'm thinking an after market water pump was used and it is not flowing as much as the OEM one. Then my next steps would depend on those things.

As for IAT sensor, that thing is pretty well covered (I work with thermocouples all the time). As long as the black plastic is around it, I wouldn't worry about it. Thermocouples are generally like light bulbs, either they work or they don't. Some times the wires connected to them get loose, but that's about it.

gearbox

iTrader: (95)

i only worry about the iat cause i've dropped it so many times and it has scratches around it. i'd just rather have a new one cause someone's audi was having the exact problem as me and their cel said iat sensor voltage out of range or something even tho the iat was supposedly fine.

the water pump was bought from honda by me and given to the installer.

Sick Cycle

try swapping throttle bodies w/ someone on here to see if there is a difference

Jrfish007

iTrader: (3)

Scratchs on the IAT won't hurt it. For that Audi, I would say there was a loose wire or something, if the IAT was okay (although I'm not sure how they know this) then there was a bad wire some place.

Jrfish007

iTrader: (3)

IF you have a multi meter you can test the connections

gearbox

iTrader: (95)

cold start sensor, rpm sensor, fuel pressure regulator? any of those?

gearbox

iTrader: (95)

dirty IAC valve? should i take it off and clean it?