Resolved 4K idle on start and stalls

[Thugmaster1220]

Hello everyone,
Completed an engine swap on my 95 Talon Awd 4g63t, engine came out of another running 95 talon that had real bad cancer. Everything's stock.
Got everything connected back up, put fluids in it, and after adding some fresh gasoline she basically started right up. If only it was that simple! As soon as it turns over the engine goes straight up to 4-5k RPMs then drops down and stalls. If I play with the gas pedal I can keep it running, but the lowest RPMs I've been able to pedal it to is about 2,200.
I can see I'm not the first poster to have this issue and have been reading quite a bit. Seems like everyone's first solution is to go right to the BISS, for me that is the last adjustment I'll make. The engine ran fine a few days ago, the only difference being the chassis. I already checked the throttle plate to make sure it has its full range of motion. Swapped the IAC and TPS, no changes. I feel the most likely culprit is a vacuum leak.
Anyone have suggestions on how to find vacuum leaks without having the car running? Any other solutions to an idle issue besides IAC, TPS and vacuum?

 

[ohlegend]

You could do a boost leak test. If you search on here or go to google and type this: boost leak test site:dsmtuners.com (this searches only dsmtuners.com) you should be able to find out how to do one. Also go over every hose/vacuum line again and make sure everything is connected.

 

[Thugmaster1220]

To my understanding; to perform a boost leak test the engine needs to be running. My engine won't stay running.

I'm probably just going to pull and replace all the vacuum lines. Anyone have a nice imagine of our vacuum diagram? Found a good one for a 97, I'm imagining they're the same but not positive on that.

 

[gdb1039]

To do a boost leak test your engine should not be running. A warmed up engine is preferred but in your case a cold test well work to check for any big leaks. After you fix your idle issues then you can perform the boost leak test again with a warm engine.

 

[Thugmaster1220]

Alright making progress. I had my "e" hose connected where my "p" hose should have been. Fixing that stopped the engine from Reving up to 4K and stalling.

The engine found a stabile idle at 2k for a bit then fell into a 1,700-2,000 lope. Seems like it might be down to finding vacuum leaks now.

 

[19gsx91]

Have you verified your engine timing? I was having an issue with this a few weeks ago, but I was using a dial back light and it was throwing off my actual reading. Beyond that it was all vacuum leaks and BISS adjustment to get the idle from 2k to 850

 

[Thugmaster1220]

I'll have to go make a boost leak tester, but in the mean time since I got the engine running I sprayed it down with soapy water. Couldn't see any leaks on the cold side (I know it doesn't mean they aren't there) but I did find leaks on the exhaust side. A leak from the engine to exhaust manifold, leak from mani to turbo, leak from turbo to down pipe. My question is, would exhaust leaks cause an engine lope? Normally I would think not, but the position of the first O2 sensor makes me wonder.

I have not checked timing. I would think bad timing would cause more severe issues than what I'm getting now. The engine has smoothed quite a bit. Its running strong, now the only issue is lope. I'm gonna keep that one in my back pocket for the time being. Mainly because a timing job is the last thing I want to do.

 

[19gsx91]

I drove around for two days pissed off because my new cams weren't idle as well as everyone said and I had LESS power and way more knock at the same PSI until I rechecked my base timing on a whim and low and behold, I wasn't 5degrees BTDC, I was at 10, and the difference in that alone was huge, not saying that it's your issue but it's an easy thing to check, anything you've checked before and you think is good, double check. once you change the timing the rest of the characteristics change as well.

 

[Thugmaster1220]

19gsx91 if I'm understanding correctly, to verify timing I would line the cam shafts up at 3 o clock and 9 o clock to form a parellel line between their marks and the crankshaft should then line up at "T"?

 

[Boomdeeze]

He is talking about the ignition timing which you have to use a timing light. You are thinking about the mechanical timing which isn't bad to check.

 

[Boomdeeze]

Wait I just saw it was a 95 engine so the CAS is under the intake cam and is non adjustable so that is not your problem.

 

[19gsx91]

Wait I just saw it was a 95 engine so the CAS is under the intake cam and is non adjustable so that is not your problem.

Ohhh damn 2gs. I forget. Then scrap my idea. Thanks for pointing that out Boom.

 

[Thugmaster1220]

Was just able to verify my TPS was incorrectly adjusted. Tomorrow I'll put the throttle body back on with the TPS in the correct position and report back.

Thanks for the help and ideas so far guys. Glad to see the community for cars from two decades ago is still live and well!

 

[dat boi AR]

Like boom said the sensor is behind the intake cam gear, but its only on 95 96 i believe after that it went back to the old ways. Dependimg on whatever happens with the idle problems, ive always liked just riding the bottom half of the throttle body and eliminating the iac and fiav coolant flow. Just set the throttle cable right under a grand and never worry about idle issues. But iutside of that it doesnt change the fact that all tou other guys are right also and those other issues do come into play. Ecu may need some maintaning also giving everythingelse bad signals back and fourth.

Ohhh damn 2gs. I forget. Then scrap my idea. Thanks for pointing that out Boom.

 

[Thugmaster1220]

Found my issue. The seal on the #1 cylinder injector was bad. It was allowing air to sneak in. Surprisingly the car was running really rich. But anyways, got a new seal on there and the car runs and drives