Brand New D15Z1 - Lean Burn Stutter / Hesitation

[dlb]

finished the input shaft bearing, clutch kit, radiator, and brakes on my VX, so i took it for a big drive yesterday. i have the common complaint of hesitation at times and want to check the TPS and MAP but i can't find any test procedures for them in the FSM. i'd also like to find a test procedure for the o2 sensor. can anyone direct me to what pages to look at, or tell me how to do the tests?

fwiw, here are the symptoms i'm experiencing:

- periodically, while keeping the throttle steady, the car will slightly lose power. this is more noticeable when taking a hill. it usually last for a few seconds, and then while continuing to keep the throttle steady, the power will kick back in. this loss of/return of power is a smooth transition, there is no bucking or jolting.

- often, the throttle does not respond to minimal increases, and will only respond after several of them, but by then it's too much and i need to back off the throttle. so it's like: i'm cruising but need to accelerate slightly so i give it a tad more throttle; no response; i give it a tad more throttle; still no response; i give it a tad more throttle, and the car acts as if i suddenly gave it substantial throttle—which i did, when you add up all the minimal throttle increases—and i need to back off the throttle to get the light acceleration i wanted in the first place.

- lastly, when keeping the throttle steady upon starting climbing a hill, there is a noticeable power increase, as if i just gave it substantial throttle.

thanks gang.

[dlb]

oops, just found a few of the tests. for those interested, they are in the FSM on the following pages:

o2 sensor - page 227
MAP sensor - page 244

unfortunately, i have no CELs and the manual pretty much says "if no CELs, everything's fine right now. look for bad wires or connections." oh, FSMs.

[iveyjh]

Sounds like to me that lean burn is kicking in, at least the symptoms that you are describing are like my car (98 HX) when it is engaging leanburn. Do you have a MPGuino?

[dlb]

no, i do not have an mpguino.

[slownugly]

Yea sounds like normal operation in lean burn. That power increase is it coming out if lean burn= worse mileage. Keep it in that soft low power area for best mpg. Instrumentation helps a lot I have far gauge but you can go with Mpguino for a lot less

[Rusty94cx]

Could be lean burn could be wrong or going bad 02. You can still check for stored codes.

[dlb]

the o2 sensor looks brand new, and the PO mentioned that he installed it recently. i did see some of slownugly's other posts that mention how not all o2's are created equal so i will eventually compare the part #s and go from there. i have a feeling it might be difficult getting the correct sensor since the boxes have the same part # but if it looks like an issue, i'll dig into it.

i remembered today that i checked the timing when i first got the car, and that it was substantially retarded. i advanced it as far as it would go but it is still retarded so next on the to do list is accessing the timing belt and advancing it. i'm familiar with 80s toyotas where you could pull the dizzy to advance it a tooth, which is not possible with these cars. which way should i rotate the crank or cam pulleys to advance the timing by one 'tooth?' i guess that term still applies since the timing belt has teeth on it.

[Rusty94cx]

No you can't put the dizzy in wrong it could be a tOoth off though. You do have to put a jumper wire in a connector when checking timing. If you didn't know. Looks new doesn't always matter look at the wire colors or 02 and look that it has the rubber grommets in slow and uglys post. Good luck.

[dlb]

right, i understand the dizzy cannot be put in wrong. however, the cam and crank pulleys can be aligned inccorectly. that appears to be the case with this car since after jumping the connecter and advancing the timing as far as possible, it is still quite off to the left (looking over from the driver side fender, of course). i guess i will just remove the timing covers, set the crank to TDC on the #1 cylinder, and confirm that the cam and crank pulleys are in fact off. if they are, i guess i'll remove the timing belt, rotate either pulley the small amount required until both are TDC, and then put the belt back on.

what are the correct wire colours for the o2? i haven't seen that mentioned. i have checked the PCV grommet and it appears fine.

[Rusty94cx]

Look at slow and uglys post look at his wire colors. He had a bad stumble with the wrong 02. The harmonic balincet has 3 lines on it make sure you are trying to time it to the correct one. Put the car at top dead center on the crank pull of top timing cover and check the cam.