Hesitating and stumbling over 3500 RPMs. Help! **Update**

[SrBigbutt]

I've been trying to get my car running right. I've never felt full boost! :3d_frown: I have fixed a ton of things on this Supra. After I swapped in a 5spd I tried to push it and it just fell on its face. Did a boost leak test and found the intercooler pipes were all busted. Installed a hardpipe kit and it still falls on its face. Did another boost leak test and fixed a bunch of vacuum/boost leaks. (manifold leak, ISCV leak,...) But it still dies after 3500 RPMS. I get no codes. Sometimes it feels like Fuel Cut, but mostly it feels like it just stumbles around 4k and starts to bog.

I feel like a 40yr old virgin that has never felt the exstacy of full boost to redline!! What am I missing??

 

[ben1984j]

Have you checked the timing?

 

[SrBigbutt]

Yes i've checked the timing with the jumpers on. Its set to 10 degrees. I checked the TPS today and adjusted it per the TSRM. Still cutting out at higher RPMS.

 

[SrBigbutt]

I think I'm going to try switching plugs. I'm currently running NGK Platinum BCPR6EP-N8 gapped to .032. I'm going to get some NGK Copper BCPRE6ES and see if that helps. What do yall think?

 

[SrBigbutt]

Swapped plugs to Copper BCPRE6ES gapped to .032 and it still misses at around 3000 RPMs. Damn!! Guess next to check is the AFM?

 

[ben1984j]

Swapped plugs to Copper BCPRE6ES gapped to .032 and it still misses at around 3000 RPMs. Damn!! Guess next to check is the AFM?

No, from here I would say check ignition spark, take a look at the troubleshooting order in the TSRM: http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=FI&P=21. AFM is unlikely (spark plugs too for that matter) according to this.

 

[SrBigbutt]

Yeah i've been reading the TSRM quite a bit lately. Plus doing as much searching on the forums as possible. I'm guessing AFM, ignitor, or coil packs could probably be the culprit. I wish I had just every spare part laying around to test immediately.

 

[SrBigbutt]

Ok, I've been trying to track down this issue for a while and can't seem to figure it out. I've replaced my intercooler pipes, BPV, checked for boost leaks, swapped AFM, Igniters, and coil packs. Checked timing, replaced plugs, new fuel pump, new fuel filter. No codes at all.

I'm starting to lean towards clogged cat. It still has the stock DP and exhaust. I boost gauge stays constant at 6-7psi and I can hear it spooling, but it goes nowhere, then starts to bog. My exhaust is extremely quiet. No funky smell, but I do get a lot of heat coming from the DP area. (maybe normal) But is really hot down there.

 

[SrBigbutt]

Ok. So its not a clogged cat! Installed a BIC DDP downpipe and it still bogs pretty bad. I think I may have finally found the issue! Sripped exhaust studs. I'm guess that would cause the issues I have been having. I guess I'm going to order the Driftmotion 7/16th kit. How difficult is it to do with head in the car? Seems like it would be pretty nerv racking!

 

[stolensupra]

I too am awaiting an answer to your last post. I'm about to do the same thing and install a cometic mls exhaust manifold gasket

 

[ben1984j]

I've never tried it with the head in the car but I can tell you that even with the head out of the car that job is a pain, in my opinion. I was successful with a few of the holes but 4 didn't turn out right and the helicoils wouldn't screw in. Best option would be to pull the head and take it to a machinist; that's what I ended up doing and thought it was well worth it (luckily already had the head off). Wasn't too expensive either; I think they charged me $15/hole.

 

[SrBigbutt]

Guess I will just take it slow. Can't be much worse than it currently is. One is stripped really bad. And two of them keep backing out over time.

 

[SrBigbutt]

Update....finished Helicoiling the threads on the head and got everything back together! Runs a little smoother, no more exhaust ping....but it still BOGS under boost!!!!! :: angry ::

Son of a b#&@h!! Maybe I one of my intercooler pipes is loose and I got a boost leak! Still got no codes. :3d_frown:

 

[stolensupra]

I had a boost leak coming from the hose between the vacuum power brake booster and intake manifold. Check the Interior bends of your hose for cracks that aren't easy to see if you're not looking.

 

[SrBigbutt]

I think what i'm going to do next is replace all the Intake manifold gaskets. Supposedly this car got its Headgasket changed and then never driven for 7 years. But every gasket I take off looks like the original gasket. I'm thinking whoever did the work just reused them.

I'm running out of ideas. I'm guessing this is it and it would be nice to have new gaskets anyway. If that doesn't fix it, then i'm thinking its related to my Fuel Pressure.

 

[SrBigbutt]

Noticed a couple things today. If I sent in traffic for a while it gets worse. As soon as boost starts, it bucks pretty bad. I have to drive like a grandma. Also noticed that it will not rev above 4000 RPMs in Nuetral.

 

[mkiiichip]

So you have never sen boost. what was the condition of the car when you bought the it (apparently not running)? Any mods other than what you have done?

Can you take a pic of the area between the turbo and the air filter (basically the whole exhaust side)? It would help to see pics of your entire setup though.

 

[SrBigbutt]

I've felt it boost. Just not for very long. The highest its ever gone is probably like 4500 RPMs. It has gotten worse recently. Before it would boost and then feel like it falls flat. Now it just bucks and bogs down right when boost starts. Probably gotten worse because the mods i've done have made it spool quicker.

When I got it, it was completely stock. Hadn't run in 7 years. Crappy mechanic must have hastefully changed headgasket. Got it running fairly easily. Just had to fix a lot of old hoses and rubber parts. I've added Apexi Intake, CX Racing hardpipes, Bosch 110 BPV, BIC Recirc DDP, Blitz Nur Exhaust and test pipe as far as mods.

I'll see if I can take a good pic tomorrow. The only one I have are when I first got it and ones that are really dark.

 

[stolensupra]

Your afm could be on its way out as well. A couple months ago I got a little carb cleaner on mine and couldn't get over 3500 or make boost maybe a pound or so but it didn't start throwing a code on the dash just when in diag mode.

 

[SrBigbutt]

I tested someone elses AFM and it didn't change at all. I get no codes on dash or in diagnostic mode.