erratic timing

[esahuque]

what would cause my timing to be erratic like this:

RED is RPMBLUE is timingthis is at idlehttp://www.youtube.com/watch?v=qgqcKrk-mHo

and this is a test drive down the street 15 to 20 mphhttp://www.youtube.com/watch?v=wgmpa40IiYc

this is an s14 and nothing has been modified on the ignition system, its all stock. I've changed the Distributor with a known good one. Also replaced cap, rotor, wires, and plugs.

[esahuque]

also idle is slightly rough and it wont let me adjust the idle any lower then 900 rpm to set my timing.

[esahuque]

and i unplugged the MAFS and it wont idle with it unplugged.

[esahuque]

heres a screen shot of all my sensors at idle.

[eazye2000]

I need to go out and check my car, because I don't know why this is sticking out at me. But I don't think your MAF should be over 1v at idle. I need to go look at this. Some reason I'm dumbfounded at the moment.

Other than that, I don't know.

[motoman399]

i wish i new about tuning... i cant help you. i even have nistune and have never messed with it. but im paying attention to learn all i can! good luck

[DevilMB3017]

What's the scale of the graph in the video?

Is the timing shifting a few degrees or 5-10+? A few degrees is very normal.

The MAFS being unplugged and not idling of course isn't. I would start there, because like Eric said, it should be .98V at idle I think it is?

What ECU are using out of curiosity?

[esahuque]

What's the scale of the graph in the video?

Is the timing shifting a few degrees or 5-10+? A few degrees is very normal.

The MAFS being unplugged and not idling of course isn't. I would start there, because like Eric said, it should be .98V at idle I think it is?

What ECU are using out of curiosity?

its shifting 5-15 deg i've log as low as 4 deg and as high as 26 deg at idle alone.i unplug the maf to see if it idles better and it just dies.i'm using an enthalpy tuned ecu, which has been doing me good for the past 3 years and now nistuned ecu which i haven't put in yet do to the issues i've been having.

i went to do a compression and leakdown test and found #3 and #4 plugs to be oil filed. i changed them and it idled good for a few min then the rough idle came back (3 and 4 filed again). the compression test on a cold motor showed 150 psi across the board dry and 150 across the board with a cap of oil in each cylinder ( rings are good) i just changed the valve seals about 2 months ago do to smoking on start ups, which its doing again along with oil now leaking from where my exhaust meets the head. so the only thing left is either head lift or valve guides. pull the head last night and head gasket looks good and the head is now at the shop getting a overhaul. I'm sure oil getting mix with my fuel along with filing spark plugs would cause a bad idle and erratic timing. hope thats all it was. thanks for the help fellas.

[motoman399]

150 psi is pretty low. they come with about 180 from the factory. i vote that you at least re ring it while you have the head off. new rings, rod bearings, and main bearings, and new seals and gaskets through out the engine. thats my 2 cents.

[esahuque]

*double post*

[esahuque]

150 psi is pretty low. they come with about 180 from the factory. i vote that you at least re ring it while you have the head off. new rings, rod bearings, and main bearings, and new seals and gaskets through out the engine. thats my 2 cents.

the compression test was done on a cold motor which is going to yield lower numbers plus i have 8.6:1 low compression pistons. the leakdown test showed minimal leakage. i just rebuilt the motor about 1500 miles ago. it was a used head, all i did was check for straightness, lapped the valves and replaced the valve seals. i should have sent it to the machine shop to begin with.

[motoman399]

you win. never mind lol

[DevilMB3017]

This sounds like 1 of 2 issues I've had before...

I'd replace your coolant temp sensor right off the bat. It's like $10 and complicated to test. If you have the head out, your coolant is drained anyway. It's well worth the bucks.

The second issue is checking your knock sensor out to make sure it's grounded well, working properly, and that you're not throwing code 34 I think it is. I have my spaced off my block with some rubber washers/spacers/grommets/whatever to cancel out some of the inherent noises from having a loud, forced induction motor.

Now for two more possibilities,

If you start the car with the MAFS unplugged will it stay running? I'd definitely check the wiring for this, per FSM.

I'd also check the sub-harness that goes to your TPS. Your knock sensor will be on this group of wires also. Mine had started to dry out and crack a while back, lead to all sorts of phantom problems.

[esahuque]

yeah, im going to go through the whole wire harness and check the grounds. I know my MAFS is wired correctly because its been wired like that for 4 years and i didnt have this problem before. come to think of it, when i unplugged the mafs i think the TPS was also unplugged because i was trying to set my timing. tps and mafs unplugged along with oil filing plugs? i dont know, it may have trouble holding idle. My machinist call me today and told me that he needs to replace the guides on the head. once i get the head back on and running ill go from there.

PS: I like that rubber garment idea for the knock, im going to go outside right now and do that myself. i run an open wg so it get pretty loud in there.

[DevilMB3017]

PS: I like that rubber garment idea for the knock, im going to go outside right now and do that myself. i run an open wg so it get pretty loud in there.

I'd really make sure you aren't throwing a code then.

I have an Enthalpy ECU and similar things were happening with me - I was also getting a lot of extra fuel/retarded timing in boost, because it was using the knock(safety) map. Super simple to run the scan while you have the consult hooked up.

[esahuque]

im also hooking up a turbosx knock light that i just ordered the other day.