Irratic Idel/cruise Speed!!!!
10-17-2005, 10:46 PM
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Car: 90 IROC-Z
Engine: LB9
Transmission: M5 5spd
Axle/Gears: 3.42 POSI
Irratic Idel/cruise Speed!!!!
Hears the deal, I have a 305 tpi auto car. While it idels and while it is at cruise speed the tach jumps around and you can feel the car miss or stutter. It does it worse with the torque converter lock up pluged in, so it's un-plugged. Here is a list of things I have replaced. plugs, wires, new msd dist, map sensor, iac valve, o2 sensor, coolent sensor, fuel pump, new venom injectors, new timing chain, and the list goes on!!! I have not replaced the egr valve or fuel pres reg or the computer. Hope some one can help before I start spending money blind!!!! The car has 136,000 on her. Hope I coverd it all.
Thaks Mark
Thaks Mark
10-18-2005, 07:24 PM
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Car: 89' IROCZ
Engine: 5.7 L98
Transmission: 700r4
What did your spark plugs look like when you took them out, any fouling? Hook up your timing light to each cyl. and look for a missfire at idle. Also check for a vac leak, clamp off each hose to the intake one at a time. Any codes from your SES light?
10-19-2005, 01:43 AM
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Car: 90 IROC-Z
Engine: LB9
Transmission: M5 5spd
Axle/Gears: 3.42 POSI
No ses codes, spark plugs looked great all tan in color. I will chek the cyls in the morning, as for the vac hoses all are new.
10-20-2005, 06:27 PM
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Car: 89' IROCZ
Engine: 5.7 L98
Transmission: 700r4
Your vac hoses may be new but the leak might be in what they go to like HVAC or the carbon canister. If you clamp off each line while it's running and the surging stops you have found a leak.
10-21-2005, 01:32 PM
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Car: 90 IROC-Z
Engine: LB9
Transmission: M5 5spd
Axle/Gears: 3.42 POSI
CEP89,
That's gonna be hard to do. It's not a constant thing, it only happens some times, more since I put the timing back to where it runs the best @ 12 deg. 
That's gonna be hard to do. It's not a constant thing, it only happens some times, more since I put the timing back to where it runs the best @ 12 deg.
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