Issues with FWD TT I'm running out of ideas

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09-10-2013, 12:07 PM
Venom13132

Issues with FWD TT I'm running out of ideas

So I have a local guy who bought a 94 SL from a dealer here in Indy. The previous owner had done a TT conversion to the car and I don't think it has ever run correctly.

What is happening. When the car starts to build boost it starts to break apart and is back firing. It runs pretty good under 2500-3000 rpm easy driving. Basically no load driving.

the engine is a 94 SL engine. The wiring harness and Computer are from a 1st gen 9966 ecu the CAS has been rewired for the separate crank/cam sensors
The basics of the swap look to have been done correctly.

What I have checked so far..

The wiring Harness and ECU are correct
I have tried a different ECU with no issues 9966 ecu
It has 360cc injectors
Checked to make sure has TT fuel pump - it does (new with clean strainer)
Swapped the Fuel pressure regulator with one from a TT
Put a jumper in the Fuel Pump Relay to keep full power to the pump
Redid the vacuum lines and deleted the Solenoids

When I try to push through the car breaking apart then let off the blow off valve still releases pressure. Its an HKS bov. It has an aftermarket Boost gauge. It reads like 20 on vacuum at idle (car idles a little high, 1500rpm). It will get to like 1-3psi when I push it while its breaking up.

Thanks for the help
Fred
(yes I know I haven't posted on here in like 2 years)
09-10-2013, 01:14 PM
Uniuno

Sounds like it could be spark escaping the plug wires. It will run fine at low rpm or low load, but then try adding boost and it's too much for the spark to jump so it escapes out the wire. Try changing them out.
09-10-2013, 02:02 PM
dbest671

Have you pressure tested for any boost or vacuum leaks? If you have a NA throttle body, I can guarantee you it's leaking.
09-12-2013, 04:00 PM
Venom13132

I haven't pressure tested it yet. It has an NA TB with the bottom of a TT TB. I have a TT TB that I can swap in there and check. The car has new spark wires on it also. I haven't checked the plugs but I am sure they are dirty.
09-12-2013, 04:09 PM
Uniuno

It's the shaft seals that leak on the NA TB. Wouldn't hurt to throw some cheap copper plugs at it if your old ones weren't replaced with the wires. I change my plugs more than most people I would guess though.
09-12-2013, 08:31 PM
dbest671

Quote:

Originally Posted by Venom13132

I haven't pressure tested it yet. It has an NA TB with the bottom of a TT TB. I have a TT TB that I can swap in there and check. The car has new spark wires on it also. I haven't checked the plugs but I am sure they are dirty.

The bottom part is the same for NA and TT... it's the upper part that's different.

Pressure test before going any further... This is the first thing you should do if you car has ANY issues other than rod knock LOL.
09-19-2013, 07:18 PM
Venom13132

finally got out and messed with the car. I decided to look at the front plugs. took the stupid cover off and the plugs were full of water. the car has a stupid vented hood on it and its been outside. I wondered why there was RTV on the spark cover plate haha. So I am going to change the plugs and valve cover gaskets and put a TT throttle body in there instead of the NA one. Also they had the gasket backwards on the Throttle body.

Ill update tomorrow after I get it back together.
09-20-2013, 12:48 AM
Alan92RTTT

Sounds exactly like what my TT did after I upgraded the fuel pump. Because of and install I was not getting enough fuel pressure.
09-20-2013, 10:01 AM
Bloodlust182

Get some mil-spec shaft seals for the TB you're throwing in just to make sure they are good. I got mine for like $16 shipped and they were easy as cake to install.
09-25-2013, 12:16 PM
Venom13132

Quote:

Originally Posted by Uniuno

Sounds like it could be spark escaping the plug wires. It will run fine at low rpm or low load, but then try adding boost and it's too much for the spark to jump so it escapes out the wire. Try changing them out.

WINNER!!!!

Update

So it was the spark plugs. They were flooded with water. Not good! So I replaced the vented hood with a stock one. Put new plugs and wires in and she runs good. I am sure there are some small boost leaks still but the car has all stock ICs and IC pipes and I am not getting paid to deal with that haha. I used to have spare parts for all this but I got rid of all that stuff 2 years ago when I said I was done working on these things.