1G: Car misses / bucks under boost

[cybertrip]

So just got this dsm running and have ran into some problems with the car. Here is a video of what it is doing.

https://www.youtube.com/watch?v=CAV-wGPgIL4

If you can't tell from the video (which you probably can't) in first gear it starts missing real bad up top once you build boost, and in second gear it starts bucking real bad. This only happens when you build boost if you feather the throttle and don't build boost you can take it all the way up to red line.

We have checked and verified the following sensors are OK and in spec. Coil pack, tps, iac, igniter, cas, tried multiple ECUs, and maf. We also have done a boost leak test and no leaks either.

Running stock boost off the waste gate. Mods are hard pipes, exhaust and walbro 190.

Any one have any ideas, we've exhausted about everything we could think of.

Edit: sorry half the post is a link, it's doing that automatically.

[WES_393]

Are you certain it's not a boost leak? Not trying to doubt your mechanical abilities, but that's really what it looks like to me. I would test it again for the heck of it but use soapy water in a spray bottle. Any bubbles that appear are a leak. Be sure to spray down the intake manifold and throttle body as well.

If it's not a boost leak, and since you have already replaced nearly the entire ignition system, I would start looking at fuel. Fuel pressure regulators are pretty cheap and it wouldn't hurt to replace the fuel filter. Also, what are your plugs gapped at?

[AQuinonez90]

My old dsm used to do that. When I would drive it and go over a small bump it would buck like a wild horse. I found out it was the postive battery terminal that was loose. Check everything once more. Do the lights blink on and off while its doing that?

[GSLENK]

mine bucked under load. (ie, boost over 0 psi) It was spark plug wires. NGK blue wires fixed that. My coil pack, and igniter was fine also. I re-read you didnt check wires. I bet thats it. or at least try a known good set. if they are old, its probably time...

[cybertrip]

Nope no boost leak, we tested it and held solid till 40+ psi.

Nope no lights flash or anything. This is the first time i have ever encountered this happening with a dsm. I've had it happen before and be a boost leak before, or something stupid like a bad injector. But we've tested pretty much every sensor in the car and all fall well with in spec.

Originally Posted by GSLENK

mine bucked under load. (ie, boost over 0 psi) It was spark plug wires. NGK blue wires fixed that

We are using brand new NGK wires, and have tried BPR6ES and 7ES plugs in this car.

Plugs we have had gapped at .028, .026, .030 nothing changed from them. Brand new fuel filter, and it's using an evo FPR.

[boostront]

I had that problem before with my 2g,or aproblem similar.Make sure the wires on the plug to your maf arent showing any copper,or that its not leaning on the fuse box under the hood if its located in the same spot on a 1g.Mine would do the and it ended up being the plug on the maf touching the harness for the fuse box.I put a small board in between them and it stoped.Just an idea

I had that problem before with my 2g,or aproblem similar.Make sure the wires on the plug to your maf arent showing any copper,or that its not leaning on the fuse box under the hood if its located in the same spot on a 1g.Mine would do the and it ended up being the plug on the maf touching the harness for the fuse box.I put a small board in between them and it stoped.Just an idea

[MichaelSuch]

Originally Posted by cybertrip

Plugs we have had gapped at .028, .026, .030 nothing changed from them. Brand new fuel filter, and it's using an evo FPR.

I believe the stock Evo FPR is 43psi. 1g is 37.5psi, if that's the case your most likely running too rich which is causing the bucking. Can you try swapping on a 1g FPR or an adjustable to help trouble shoot?

[cybertrip]

Tried my SX on it and nothing it hold steady pressure at 38 and same thing.

[And_44]

Having same issue with mine though hasn't been the first dsm I've owned with it. Partial throttle and vacuum driving car runs just great. As soon as it's boosted some times it does exactly what your video did.

Thought it was my GM Maf and translator and gave up tuning it. So went to OEM maf, have 190lph Walbro and boost was set at 10psi, I upped the boost to 12psi and problem seems to of gone away and it's been running a bit better.

So leaning toward a rich running condition or a leak some where.

[waterchppr]

Im new to the dsm world but it seems im having this problem also. I havent found any leaks but it seems exactly like a boost leak. I wonder if all of my lines are run right and whatnot because the intake isnt stock and the bov is also aftermarket. Im not sure if it has anything to do with it, but ive also noticed that sometimes my car will literally like fly out of gear when i pull on the stick. Like it seems like theres pressure built up on the stick. It almost feels like its spring loaded when i pull it sometimes. This could be completely unrelated but i figured id mention it just in case. I recently replaced the plugs and wires and they're properly gaped. i could probably get a pretty good video of what mine does and post it. I also could probably post some pictures of my set up. But ive been messing with this for awhile and im getting tired bc its also eating up my gas

[Gearhead4G63]

Check you're wiring harness, I've had this problem before bare wire exposed, may not be the problem just a thought, but it does look like a boost leak, even though u checked that.

[GSTurbo1]

Needs to be tuned... I just had this problem. Look at you wideband, probably too rich of a/f ratio <10 try to lean it out if you know what you are doing.

[Joshky9]

Check the fuel pump in tank o-ring. Also try replacing or checking your fuel filter. What about spark plug gap and plug wires?

[Stew Pidaso]

Mine does this as well if you're dropping a gear and slowing down to turn etc. I also get pretty lean when it does that but if I get into the throttle again the o2 will cycle normally and no more bucking. Weird

[GSTurbo1]

I had this same problem to the T. I'll tell you exactly what I did

1) New plugs
2) Seafoam through tank
3) Checked for boost leak
4) leaned out fuel enrichment on my megasquirt ECU

10psi pushing a little over three hundred HP

[turtlebain]

Originally Posted by Joshky9

Check the fuel pump in tank o-ring. Also try replacing or checking your fuel filter. What about spark plug gap and plug wires?

Anyone know of a good how to on checking the fuel filter? I'm having a similar issue. A/F drops to under 10 when giving heavy throttle, and above 5k. I think checking the fuel filter would be a good start.

[YanDsm]

Take a look on the knock sensor and harness. I had the same problem and it was a broken knock sensor wire. Everything ran just fine until I got into boost, the bad wire sended incorrect detonation signal to my ecu .

[Viva]

Check your ECU for leaking capacitors my dsm did this till i bought a new ecu

[And_44]

If your knock sensor is doing what is discribed above. Would it register anything or I've read a faulty sensor will show 42 or 43 counts all the time as a safety measure to retard timing.

I get counts only when I let off throttle and only see a max or 5 on rare occasion 8. No counts ever during acceleration.

[And_44]

Well, I may of found my reason. Thought I had checked timing when I got car but probably was previous one I checked. My ignition timing was at *10 BDC readjusted to *5 TDC and car runs sooooo much better. Guess being *15 off does effect things.

[snakeyes711]

I'm getting a similar problem, on my 1Gb. Except its not bucking, its straight bogging. No power, only building 5-8 PSI boost. (not even a line running to the Actuator). Car ran fine just started this problem recently. Brand new plugs, NGK wires, fuel filter, pump you name it. Double checked Timing and base timing. No boost leaks. No power at all, before this the boost gauge would try to turn around backwards.

No problems when cruising, no fuel loss (on MPG) WB reads fine.When you go WOT no power, and watching the WB some times it gets up 13-14 or higher, one time it fell on its face, I looked at the A/F gauge it was 18-20. So its like its runnign lean or something. Though the pump is fine, I even swapped pumps same thing. I'm thinking maybe MAF?

[fast420a83]

I just posted this on a previous post that you might wanna read... Check out the symptoms . Six Signs of a Failing Fuel Pump - Yahoo! Voices - voices.yahoo.com also, look at the signs of a clogged fuel filter here... Signs of a Clogged Fuel Filter Save yourself alot of headache, and just do a fuel pressure test, just to rule out any fuel issues. Also, If you do a fuel pressure test, I would manually rev the engine to 4,000 rpms and hold it for a few seconds while you are looking at the gauge, to see if there is any change in presurre. Then you would know.

[snakeyes711]

Maybe FPR? the fuel pump is fine. I swapped it out with same results.

I just tested the coils, I got 2.2 and 14.8K ohms on the first coil, and 1.8 and 14.2K ohms on the second.

[fast420a83]

Originally Posted by snakeyes711

Maybe FPR? the fuel pump is fine. I swapped it out with same results.

I just tested the coils, I got 2.2 and 14.8K ohms on the first coil, and 1.8 and 14.2K ohms on the second.

Yeah, My previous response was geared more towards cybertrip.. In your case you said your running lean, but it isn't the pump... So yeah, it could be your fpr or maybe you have a bad injector....?http://www.ehow.com/facts_4867109_si...-injector.html

[snakeyes711]

Originally Posted by fast420a83

Yeah, My previous response was geared more towards cybertrip.. In your case you said your running lean, but it isn't the pump... So yeah, it could be your fpr or maybe you have a bad injector....?Signs of Bad Fuel Injector | eHow.com

Well I replaced the MAS, and the FPR....Same results.,

:EDIT:

Checked timing, pump, filter, mas,FPR, plugs/wires, coils.

Next turbo swap, check ECU