hesitation at 3k rpm and no boost

[tom]

I'm glad you are back. I am trying to get my car on the highway but it has problems. The engine stumbles and bogs at around 3k, give or take 200 rpms. There are no codes. I have replaced the afm (after code 31), put in a Walbro fuel pump, changed the fuel filter, taken out the J- pipe restriction, and have checked all vacuum tubes, air inlet and intercooler pipes. I also replaced the rubber gasket at the throttlebody/3k pipe. The needle on my vacuum gage, at a warmed up 600 RPM idle, is a steady 21 inches. The CPS and timing are both set according to TSRM specs. Disconnecting the TPS changes nothing.

Mods: The engine is a JDM 7MGTE transplant into my 87 NA (turbo cpu and harness).
Retained the W58 transmission, using an unsprung 6-puck ACT clutch/pressure plate.
Defcon downpipe, haven't replaced the gutted cat and 2.5" Pacesetter cat back with 3" yet.
The oil filter is relocated on the passenger side inner fender. Puke tank is now in the former battery location, Optima battery is in the back, passenger side. K&N, and the usual basic stuff.

Anyone have any useful advice or abuse?

 

[shaeff]

double, triple and quadrouple check all intercooler pipes, especially the one off the bottom of the turbo. my bet is that it has a crack in it. that one is the most prone to cracking as it is right near the exhaust, my bet is that you have a boost leak.

have you tried checking grounds? one of the most common problems is the small ground wire that goes from the coil packs to the motor. its on the driver's side. give that a look see. also, how old are the spark plugs? are they gapped correctly? how about the sparkplug wires? old? connected all the way?

did you wash the engine bay? if so, did you get water in the sparkplug "valley"? how about oil from leaky valve covers in that same "valley"? check all of your grounds!

do you have any error codes? if so, what are they?

by the way, you're probably going to absolutely destroy that w58 with that clutch

-shaeff

 

[tom]

Shaeff, I just replaced the original hoses with hard pipes, new plugs and wires, have no leaks, and good grounds. No black or white smoke, even at start up. I thought it might be knock sensors or fuel cut, but as I said in my original post, there are no codes. I am stumped.

You may be right about the clutch but it is nice and smooth- no chattering and it engages flawlessly, if immediately. It is not harsh at all, though slipping the clutch to ease forward is not done without focus. I expect the transmission to last until I have to rebuild the motor in a year or two.

 

[shaeff]

perhaps you have a clogged fuel filter, or bad FPR? i'm running out of ideas!

-shaeff

 

[MrBoost]

Kinda sounds like a spark issue to me, but you already did the plugs. Were they factory type? Did you check the gap? How old are the pulg wires; brand?

 

[boost PSSH boost]

I had a similar problem. I had a boost leak, broken coil pack ground wire, and a vac. leak

 

[turboa7mgte]

Any codes?

 

[garrettrowe]

Tom, have you checked the TPS as we suggested on the e-mail list?

 

[tom]

Tom, have you checked the TPS as we suggested on the e-mail list?

I intend to in a few days. I get just a few days a month to work on that !@#$%^&* car and have to go over previous work on some things. It is like the loss of short term memory. I am attempting to accumulate a list or a body of knowledge for reference in my next dive into time-consuming frustration.

Someone left a note in my wiper blade- an offer to purchase (!). But no. Knowing my need to suffer for my wasted youth and many sins I will keep this abominable machine- for scourging my soul- until runs perfectly.