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View Full Version : Major stumble with boost - 3bar setup install



89DaytonaTII
04-10-2006, 03:08 PM
First off the car was running great after I removed it from storage last week. I rowed through a few gears to make sure that there was no issues before I brought it home to install the 3bar cal, map, and +40s I have kicking around.

So I installed the injectors, swapped to the new SMEC, and installed the map sensor - which I notched the stock connection and simply plugged in. Before firing it up I verified that FP was 55psi static.

She fired up like nothing, and idled fine while I let it warm up. Then for the test drive (which I had been waiting for since I ordered the cal 10 months ago!) the car drove great - until I got to an open enough road to put my foot into it a bit. As soon as the car would make any boost the thing would buck and stumble - if I was to compare it to anything it was like the harsh overboost cutout with the stock setup.

I don't get it? I can't find anything that I messed up during the install. And the car is not giving any codes.

The cal, map, and injectors were all purchased straight from TU and brand new upon install. I have messaged Paul to try to discuss this with him, but he hasn't been online for a few days and I'd really like to drive the car.

Can you guy's think of anything other than the cal itself, which I'll leave to discuss with Paul if necessary, that would cause such an issue?

Major thanks to any replies!

turbovanmanČ
04-10-2006, 03:39 PM
Have you check the fuel filter? hows the fuel pressure when it cuts out? did you have an air/fuel guage and if so, what does it do when it starts to cut out?

89DaytonaTII
04-10-2006, 04:13 PM
Have you check the fuel filter? hows the fuel pressure when it cuts out? did you have an air/fuel guage and if so, what does it do when it starts to cut out?
-Fuel filter has less than 2k on it. Fuel pump is a new walbro 255.
-FP guage is in engine bay so I can't see it while driving.
-I have a narrow band A/F, but the stumble comes on so fast as soon as the car makes 1psi, and I only tried it at part throttle so the guage is basically useless at that point.

No more than 2 hours before I test drove the car in it's current state it spooled like nothing and boosted 13psi pulling to redline.

Was I suppose to do anything with the map setup other than notch the connection to fit the 3bar unit?

turbovanmanČ
04-10-2006, 04:59 PM
Nope, just notch it. Sounds like the cal is bad or it could be a faulty MAP. When installed the map, did the vacuum line come off?

89DaytonaTII
04-10-2006, 05:42 PM
It does sound like a map issue, at least that's what I was thinking, just because it's so exact happening as soon as there is positive pressure. But all the vac. lines are attached and they are very secure, I make sure of that. If only it were easy enough to get my hands on another 3bar map, there's so many kicking around :rolleyes:

I hope it's not the cal though :(

89DaytonaTII
04-10-2006, 06:03 PM
Any way to test the map sensor to see if it's faulty with a multimeter?

altered7151
04-10-2006, 06:19 PM
Would it be possible to swap the stock 2-bar back in just to test things out? I know the voltages will be different coming from the sensor, but at least you could take it slowly up to 2-3psi and see if it cuts out, if it does you at least eliminate the map as the problem. If not you should be able to at least read the voltage coming back off the map sensor with the multimeter.

turbovanmanČ
04-10-2006, 06:38 PM
I have tried the 2 bar map on a 3 bar setup, won't run properly. Chugs and pukes out black smoke.

I guess you could backprobe the MAP sensor, middle wire. Set voltage for 5 volts dc and go for a drive, see what happens. Not sure of on the voltage readings on a 3bar, haven't tried mine out.

89DaytonaTII
04-10-2006, 06:52 PM
I thought about watching the multimeter on the fly, but I don't even know what numbers I should be seeing if I tried? lol

I think I have a line on swapping in someone elses 3bar map this weekend and testing it out. But the bastard is trying to throw in a catch - he want's me to get trashed at the bar with him and I have a final on the following monday morning :p Oh what to do, what to do...

turbovanmanČ
04-10-2006, 06:54 PM
Tell him you'll get thrashed NEXT weekend, :thumb:

altered7151
04-10-2006, 09:14 PM
Heres a graph showing you the voltage range for the 2 and 3 bar map sensors. I would hook up the multimeter and see what its reading.
http://hhscott.com/93tmv/3-bar_map.htm

89DaytonaTII
04-10-2006, 09:22 PM
thanks I'll give that a shot if my arangement to swap in someone else's falls through this weekend, I won't have time before than anyway.

BoostMonkey
04-12-2006, 12:44 AM
Hey I had a very similar problem in my 91 RT. Except it was after I installed my MBC. Couldn't figure it out. on the third time under the hood I was triple checking all my vacuum lines (again) and making sure that the connections were tight. there was one connection on a vacuum solenoid that slid on maybe 1/8" tighter than it already was. I hopped in the car thinking that I hadn't even changed anything (that's how little it was off) and the problem disappeared. I just got lucky, but really check all your connections and try pushing them farther onto the barbs. Good Luck!

Michael