ZPEED

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brad11140

iTrader: (3)

Interesting modification. The hesitation is gone. I used a simple jumper in the diagnostic port to bypass the ECu. Ran great. Pulled it out when I got to the gas station and it ran great all the way to work. So I think I fixed it. Will just have to see how it does over the next few weeks.

brad11140

iTrader: (3)

Well I went out to go somewhere this morning and the hesitation was back and this time it was affecting idle which I could see oscillating slightly. When I unplugged the MAF it did nothing to help me this time.

So when I got back I pulled the IAC valve again. This time I stripped it all the way down to the motor. I cycled it by hand and made sure there was 0 carbon deposits. I did not take it apart this far the other night. Put it all back together and its running beautiful. So we will see if it stays.

brad11140

iTrader: (3)

Ill be damned if I didn't start it up and it stared hesitating on me again. Yanked the throttle body and checked the TPS sensor. Was pretty far out on the 60mm setting. Supposed to be infinite, but was showing 0 ohms. Was a PITA to get it adjusted, but I did. Put it back on and now it idles high. So I did another method of loosening the screws in place and turning it till the idle RPM's came down to the 750 +- 50 RPM's. I think ultimately I am going to have to get a new TPS sensor. Hopefully this long rambling thread of me talking to my self will help someone else.

When I pulled the throttle body I also pulled the egr valve out and made sure it wasn't stuck, lubed it up and reinstalled. So at this point I have checked just about everything.

brad11140

iTrader: (3)

Wanted to give an update. I think the fuel pump ECU is the culprit. HAd the chance at work tonight to really try to go through it. Pulled my main O2 sensors and cleaned them. Did not fix and hesitation is back with a vengeance. When MAF is unplugged she works perfect. PLug in the MAF she runs like crap. Tested the MAF and it checks out. I was able to get my TPS calibrated dead on. SO in frustration and on a whim I jumpered Fp and +b. Idle picks up slightly, like it does when I unplug the MAF. Take it for a drive and its perfect. No hesitation whatsoever. So I am theorizing that when I unplug the MAF the limp home map includes setting the fuel pump to high mode, which explains the increased idle. I think my fuel pump ECU is not outputting enough voltage for low speed operation. High speed appears to work fine. At any rate I am going to drive it for awhile jumpered.

If I do this fuel pump ecu mod will I have to deal with a check engine light?

MongooseGA

iTrader: (6)

I want to bump this thread. I am having identical symptoms as the OP was, and am going to try the fuel ECU bypass this weekend. I went through coils, plugs, wires, 4 MAFs, a rebuilt ECU and have not been able to fix the symptoms described in the original post.

If this works, I want to send a beer to Brad.

Trucho

Gonna have to try some of these things out along with adding additional grounds.

lexfreak22

I have the same issue, mine is much worse when its cold. When its warmed up it doesnt really do it. I have a new tps sensor but other than that, i havent checked any other culprits.

there are alot of good ideas on here i might try.