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Discussion Starter · #1 · (Edited)
87 Dodge Daytona Shelby Z
Turbo II
15" Vacuum at Idle
Timing marks line up, although I didn't check position of distributor rotor
New Injectors
Vacuum lines have been replaced
Fuel pressure and regulator ok
HEP replaced (Mopar)
FWD Performance Stage 3 Calibration
New distributor cap, rotor and ignition wires (Autozone?)
Distributor shutter is secure and no wobble in shaft
New coil
New coolant temperature sensor
The spark plugs look great (slight pink tint on one side of insulator)

I have a miss in non-boost conditions (vacuum). The miss is most noticeable at cruising speeds. It runs good in boost and will peg a stock (15 psi) gauge. I had the same miss with the stock Logic Module. Starts right up when cold and takes several cranks when hot.

I am not sure where to go next. Any suggestions would be appreciated.

Rob

87 Dodge Daytona Shelby Z
66 Plymouth Barracuda Formula S
70 Ford F250 Camper Special
 

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Hmmm...I have run into a problem not like this before and found it to be a wiring gremlin with the injectors. If you have access to an O-scope I would check the pulse width of each injector and post your results here. Also what impedence are your injectors? I believe they need to be low resistence ~2.4 ohms. Also check your fuel pump wiring to make sure there are is no ground loop which could also cause your problem.
 

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sounds like the cam timing is off a tooth or two but check fuel pressure and compression vac should be closer to 19 should be able to rule out spark since its boosting fine
 

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Discussion Starter · #6 ·
I re-set the cam timing and gained 2 or 3" of vacuum (17-18"). The car ran better especially from a start, although the missing is getting worse. Back to the drawing board.
 

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Can you feel it or actually see the engine running rough at idle?
Does it get worse with the A/C on?
If so have you attempted to isolate the condition to one cylinder?
Have you checked fault codes.
since you have been working on the car if any are present record them, clear them and then drive the car and recheck.
Do you have a spark tester, fuel pressure gauge and cylinder leakdown tester?
 

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Discussion Starter · #8 ·
Can you feel it or actually see the engine running rough at idle?
Does it get worse with the A/C on?
If so have you attempted to isolate the condition to one cylinder?
Have you checked fault codes.
since you have been working on the car if any are present record them, clear them and then drive the car and recheck.
Do you have a spark tester, fuel pressure gauge and cylinder leakdown tester?
NAJ,

I can feel the engine running rough.

A/C is not hooked up.

No difference when removing an ignition wire at a time. Have not checked injectors yet.

I reset the computer and drove the car - no codes except 22.

I have a spark tester, fuel pressure gauge and compression gauge.

Thanks for chiming in, Rob
 

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I ran into this on my CSX, same thing dropped a cylinder. Pulled a wire at a time and narrowd it down to one cylinder. turned out to be a bunk injector. Also just had the same thing happen on the old T1 in my Omni. Turned out the fuel pressure regulator stuck closed and was flooding the motor regardless of duty cycle. have you chacked fuel pressure?
 

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Discussion Starter · #10 ·
Injector Test - Idles at ~ 820 but drops down to 760 during a miss. Pulled each injector connector and the idle dropped down and then it stabilized at 820 with little or no fluctuation. ??? Help!
 

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Discussion Starter · #11 ·
I ran into this on my CSX, same thing dropped a cylinder. Pulled a wire at a time and narrowd it down to one cylinder. turned out to be a bunk injector. Also just had the same thing happen on the old T1 in my Omni. Turned out the fuel pressure regulator stuck closed and was flooding the motor regardless of duty cycle. have you chacked fuel pressure?
Fuel pressure checks out ok, and the plugs look excellent.
 

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If all cylinders dropped RPM equally when removing plug wires and injector connectors the problem is something affecting all cylinders.
You stated that the timing marks lined up but I would re-check cam timing again.
We have seen this numerous times with other members and it turned out the cam timing was 1-2 off.
Verify cam timing again and check/set ignition timing.
Once that is done if the problem persists verify if you are rich/lean by tapping into the
O2 signal line with a digital voltmeter and see what O2 voltage is.
It should be constantly crossing above/below .450 volts.
The prefered range would be .250-.750 volts.

CAM TIMING

http://www.turbododge.com/forums/f4/f14/359212-cam-timing-belt-tension-84-95-a.html
 

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Discussion Starter · #14 ·
Grounds good? There is an important reference ground on the rail I believe.
I checked and cleaned the injector harness ground and the ground from the firewall to the intake manifold, both are good.

Another observation: after it is first started up, it runs perfectly smooth for about 20 second. After that the miss starts and the idle fluctuates.
 

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Discussion Starter · #16 ·
Re-gapped the plugs to 0.0030' and checked the cam timing again (looks ok). Started the car, runs for approx 20 second perfectly smooth with no miss, and then starts missing and the idle starts fluctuating. Checked the codes an have a code 35 - Throttle Position Sensor. I will check it and report back.
 

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TPS code is a Code 24, code 35 is Radiator Fan Relay Circuit.
Incase you made a typo..Code 25 is AIS Driver Circuits

A miss is going to be a basic issue....and you need to start at the beginning and verify all basics are correct.
Engine Mechanical(Compression and Cylinder Leakdown Test)
Engine Vacuum and Vacuum System(Cam/Ignition Timing, Engine Sealing)
Fuel System(Fuel Pressure and Injector Balance Test)
Ignition System(System Capability and Resistance/Insulation)

If you do not Verify all of the basics are correct you will be posting and guessing forever without a solution.
All engine control system decisions are made "assuming" basics are correct.
The controller has no idea if the engine and other supporting systems are ok.
 
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