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Just finished a 88 shelby z with an 89 T1 2.5 block and the rest T2(including SMEC). Just put in a T2 clutch with T3 pressure plate.

Drove it for about 140 miles with no problems at all. Then while driving it started to "buck" in forth while building boost. So went to fifth and just cruised and it was fine unless i attempted accelerating and vacuum started to drop. Got it home and just went around the block and the bucking happens anytime the vacuum starts to drop and head towards boost.

So I had to swap in my other cluster to pull codes. I got a 22. Went and got a new CTS. Installed it. Checked codes and it was still there. Drove it and still bucked, still has the code. Decided to check the wires for the CTS. Everything seemed good but I took it all the way to the SMEC. While there I changed out my 2.2 for a 89 T1 2.5 and i attempted to push in the wire further into the connector. Put it all together. Check codes and it is gone. I get all excited and it ended up still bucking :bang head. Checked for codes and there is no codes. I'm at a loss as what to check/try now. Suggestions?
 

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You need to check basics...
You are either losing fuel pressure or spark in one or more cylinders.
If the engine was apart you will also want to verify Cam/Ignition Timing are correct.
 

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Discussion Starter #3
You need to check basics...
You are either losing fuel pressure or spark in one or more cylinders.
If the engine was apart you will also want to verify Cam/Ignition Timing are correct.
forgot to mention.

At idle fuel pressure is 48psi..
Plugs/wires/cap are all new.
Cam/ignition timing are good ( set by a friend helping me out and teaching me )
 

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You need to check fuel pressure when the condition is present so you need to connect the fuel pressure gauge to the rail and tee a vacuum gauge inline with the FPR and tape both to the windshield and go for a ride.

Use a spark tester and check for spark under load to see if you can produce 25 KV, you could have a weak coil.

Use a digital voltmeter and sweep the TPS looking for a dead spot or spike in voltage.

Tee a vacuum pressure gauge inline between the Baro Solenoid and Map Sensor and go for a ride and check vacuum/pressure to the Map under the conditions needed for the problem to occur.
 

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Check vacuum line to your fuel pressure regulator. I had a bad vacuum line (would colapse due to vaccuum (cheap hose) and wouldn't operate the fuel pressure regulator properly. So while the car is idling check your vacuum line and your fuel pressure as someone mentioned to make sure your fuel pressure regulator is working properly. Fuel pressure should also increase as boost increases to compensate. Good luck.
 
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